Interplay between the distribution of nitrogen and hydrogen and mineral inclusions in E-type diamonds from Yakutia, Siberian craton

Interplay between the distribution of nitrogen and hydrogen and mineral inclusions in E-type diamonds from Yakutia, Siberian craton | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Interplay between the distribution of nitrogen and hydrogen and mineral inclusions in E-type diamonds from Yakutia, Siberian craton Angellotti A., Barni L., Morana M., Cinque G., Lu Y., Tao R., and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9020643/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Diamonds in nature are known to have formed by redox-assisted precipitation of carbon from oxidized fluids containing also hydrogen and nitrogen, both of which are hosted in the diamond lattice. Minerals entrapped during the growth of diamonds might have played a role in nitrogen and hydrogen incorporation and abundance although, so far, no evidence has been reported. We used synchrotron micro-FTIR mapping to investigate the interplay between the distribution of nitrogen and hydrogen and mineral inclusions (graphite, sulfide and garnet) in four eclogitic diamonds from the Yakutian kimberlite field, Siberian craton. Combined mapping of nitrogen and hydrogen-related infrared bands reveals heterogeneities near minerals. In particular, a marked absorbance of N- and H-related peaks observed in correspondence with sulfide inclusions supports their incorporation in the host mineral, while near graphite and garnet inclusions, only the H peak absorbance of peaks at 3107 cm − 1 , 1405 cm − 1, and 3236 cm − 1 increases. These zones can extend to tens of micrometers from the inclusion-diamond interfaces and provide insight into the potential control that entrapped minerals exert on the distribution and abundance of N and H in the diamond lattice during and after its formation at mantle depths. diamond eclogite redox IR mapping methane sulfides Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Introduction Diamonds in nature record unique information about local physical and chemical processes that occurred at the inaccessible depths of the Earth where they have formed due to their exceptional chemical inertness that prevents any reaction with the encapsulated minerals and fluids inclusions so that pressure, temperature, and oxygen fugacity conditions at the time of encapsulation can be retrieved through application of oxy-thermobarometry (Daniels and Gurney 1991 ; Deines et al. 2001 ) and elastic barometry techniques (Angel et al. 2015 ). Two main paragenetic assemblages are recognized in lithospheric diamonds, peridotitic (P-type with frequent inclusions of olivine, pyroxene, spinel) and eclogitic (E-type with frequent inclusions of pyroxene, garnet and sulfides) (Sobolev 1977 ; Meyer 1987 ; Stachel and Harris 2008 ). Furthermore, the intrinsic chemical properties of the diamond provide insights into growth and post-growth processes. In fact, diamonds contain a variety of impurities such as nitrogen (N) and hydrogen (H). Nitrogen commonly occurs at concentrations of 200–300 ppm (Mikhail and Howell 2016 ), while H generally reaches ~ 50 ppm (Sweeney et al. 1999 ; Ashfold et al. 2020 ). These impurities can influence the optical (Green et al. 2022 ; Zaitsev 2013 ) and physical (Field et al. 2012) properties of diamonds and provide key information on their geological history. Nitrogen, for instance, is incorporated mainly by substitution forming a series of so-called N centers (Smith et al. 1959 ; Boyd et al. 1994 , 1995 ), whose aggregation state depends on temperature and residence time within the mantle (Taylor et al. 1990 ). Fourier Transform infrared (FTIR) spectroscopy remains the most used method for quantifying N concentration, aggregation and mantle residence temperatures (Kohn et al. 2016 ). However, discrepancies between calculated temperatures and geological constraints indicate that N aggregation alone cannot fully account for the diamond thermal history (Angellotti et al. 2025a , b ). Hydrogen, the second most abundant impurity in diamond is likely hosted in the structure during formation from carbonated aqueous fluids and diffuses under mantle conditions (Lang et al. 2007 ; Chevallier et al. 1998 ; Hartland 2014 ). The heterogeneous distribution of N centers and H-N clusters in diamonds has been extensively documented on sub-millimeter to millimeter scales and explained as a result of differences in crystal growth rate, local redox conditions, and fluid composition during formation (Chen et al. 2000 ; Howell et al. 2012b ; Spetsius et al. 2015 ; Kohn et al. 2016 ; Eaton-Magaña et al. 2017 ). Stress fields generated by inclusions, dislocations, voidites, and platelets can also locally distort the diamond lattice, influencing defect formation and optical properties (Evans and Woods 1987 ; Kanda and Watanabe 1997 ; Speich et al. 2017 ; Laidlaw et al. 2021 ). As minerals are also trapped during the diamond growth, it is unknown whether they control N and H incorporation and diffusion. Synchrotron-based infrared microspectroscopy has enabled mapping at resolutions of ~ 10 µm 2 , far exceeding the ~ 50 x 50 µm 2 scale of conventional FTIR (Howell et al. 2012a , 2012b ; Cinque et al. 2017 ). Such advances have enabled the investigation of rim zones and inclusion halos where localized heterogeneities can provide key insights into defect formation mechanisms. In fact, higher spatial precision reveals microscale differences in N and H distributions that were previously undetectable (Angellotti et al. 2025a ). Eclogitic diamonds are ideal samples for this approach, as their inclusions frequently record fluid-rich environments, as indicated by H 2 O contents higher than those of their peridotitic counterparts (Logvinova et al. 2015 ; Nimis et al. 2016 ; Curtolo et al. 2025 ). Following the dataset by Stachel et al. ( 2022 ) (Figs. 1 a - b), about 32% of eclogitic diamonds exhibit total N concentrations ≤ 100 ppm, while only 2.8% exceed 1000 ppm. The distribution of B% [(N B−center /N Total ] indicates a predominance of Type IaA diamonds (N mainly in A-centers) relative to Type IaB diamonds (N aggregated as B-centers). Approximately 25% of the samples analyzed display B% ≤10%. The dataset also includes N-free Type IIa diamonds. Among the regional subsets (Figs. S1 and S2), all Russian eclogitic diamonds exhibit higher average N contents (~ 600 ppm), which may reflect either sampling bias or a compositional anomaly. All Russian (eclogitic) diamonds also show a distinct B% distribution relative to the global dataset, with the samples dominated by the Type IaAB. This trend may similarly reflect sampling effects, yet it is consistent with the pattern observed in the African subset, which is supported by robust statistics based on more than 1000 analyzed samples. By contrast, producing comparable statistics for H remains challenging due to data scarcity. In this study, we investigated E-type diamonds from the Udachnaya kimberlite pipe to better understand the interaction between mineral inclusions and N and H, and the possible effects on their distribution and abundance. Materials and Methods Sample Description We characterized four lithospheric eclogitic diamonds from the Udachnaya kimberlite pipe in the Daldyn-Alakit kimberlite field, Yakutia Province (Siberian Craton), namely DIA4 , DIA5 , LGM12 and LGM15 , respectively. All samples originally presented an octahedral shape and were characterized by having mineral inclusions visible and distinguishable under the stereoscope. These were double-polished parallel to the (110) planes to produce plates suitable for FTIR analyses. The images of the four diamonds (Fig. 2 a - d) and their inclusions were acquired using the AmScope stereoscope under reflected and transmitted light along with images collected under polarized light with a Leica DM750 microscope. Both microscopes, available at the Department of Earth Sciences of Sapienza University (Rome, Italy) are equipped with high-resolution cameras, and images are acquired using integrated software. All four diamonds exhibit greenish and light-orange inclusions of clinopyroxene and garnet, respectively. Additionally, some inclusions appear dark and/or with metallic luster easily identified by eye as graphite and sulfides, respectively. Raman spectroscopy Raman spectroscopy analyses were performed to identify mineral inclusions occurring within the areas selected for IR mapping. A confocal Raman microscope (WITec alpha 300R system, WITec GmbH, Ulm, Germany) was used at the High-Pressure Science and Technology Advanced Research Center (HPSTAR) in Beijing, China. A laser with an excitation wavelength of 532 nm was employed for all the measurements. The optical system included a 20× long working-distance objective lens (Mitutoyo BD Plan Apo SL 20× /0.28, NA = 0.28), coupled with a 50 µm confocal pinhole to enhance spatial resolution and reduce background interference. Two diffraction gratings were used in the spectrometer: a 600 g/mm grating, which provided a spectral resolution of approximately ~ 3 cm − 1 , and a high-resolution 1800 g/mm grating, which achieved a resolution of ~ 1 cm − 1 . The laser power at the source was maintained at approximately 50 mW. Calibration of the Raman system was conducted using the characteristic Raman peak of pure silicon at 520.7 cm − 1 . A higher-magnification Zeiss LD EC Epiplan-Neofluar Dic 50×/0.55 objective lens was employed to analyze small inclusions, yielding a focal spot size of approximately 1.5 µm. Each Raman spectrum was acquired with at least 10 accumulations, each with an integration time of 10 seconds, ensuring a high signal-to-noise ratio and reproducibility of spectral features. Micro-FTIR Data Acquisition and Processing The micro-Fourier transform infrared spectroscopy (micro-FTIR) data were collected in transmission mode at the MIRIAM beamline B22 of the Diamond Light Source facility (UK) using a Bruker Hyperion 3000 IR microscope coupled to a Vertex 80V FTIR spectrometer (Cinque et al. 2011 ). A 36× objective and equivalent condenser optics were used, with a knife-edge aperture positioned in the detection beam path and a high-sensitivity MCT detector with a 50 µm pitch cooled by liquid nitrogen. Background measurements were conducted with 512 scans per analysis on the underlying BaF 2 plate. Spectra were collected over the wavenumber range 4000 − 500 cm − 1 , with a spectral resolution of 2 cm − 1 and 256 scans per spectrum (~ 1 min per point for optimal spectral quality). High-resolution maps covering areas of ~ 100 × 100 µm 2 were generated using a 10 × 10 µm 2 knife-edge aperture and a 7 µm stage step size, yielding 3-µm point overlap. Line-scan transects (30 spots, 10 × 10 µm 2 aperture, 10 µm step size) were used to survey diamond surfaces and assess N and H variability in proximity of and at mineral inclusions as shown in Fig. 2 a - d. Spectra acquisition and visualization were performed using Bruker OPUS v8.7.41. Spectra exhibiting saturation effects, inclusion interference, or surface irregularities were excluded. The analytical workflow follows Angellotti et al. ( 2025a ; Fig. S3). For data processing, a custom baseline removal script was developed to correct mid-infrared FTIR spectra of the diamond samples. Baseline distortions were removed using a tailored asymmetric least squares (AsLS) approach. The region 3550 − 1050 cm − 1 was divided into four contiguous intervals (3550 − 2670 cm − 1 , 2670 − 1700 cm − 1 , 1700 − 1395 cm − 1 and 1395 − 1050 cm − 1 ), each processed independently. The baseline for each spectral interval was subtracted using the AsLS algorithm. The smoothing parameter ( λ ) controlled baseline stiffness, while the asymmetric parameter ( p ) ensured the fitted baseline remained below the absorbance signal. To avoid discontinuities between spectral regions, tapering functions were applied over 5–20 data points at block edges. Corrected blocks were, then, recombined into a continuous spectrum. Finally, spectra were extended to 4000 − 500 cm − 1 with zero-padding to meet the input requirements for N quantification software. Nitrogen concentration and residence temperature (T res ) were determined using QUIDDIT software (Speich and Kohn 2020 ), which supports batch data processing. Spectra previously flagged for saturation were masked prior to map generation like in Angellotti et al. ( 2025a ). Estimates of T res require a formation age for the diamonds, which has not been uniquely determined for Udachnaya. Consequently, we employed two different ages: 2.00 and 2.733 Gy. The first value was employed by Morana et al. ( 2025 ) for geobarometric calculations, after deriving the T res for three ages (i.e., 1, 2 and 2.8 Ga), covering the range of existing hypotheses for Udachnaya. For comparison, a second model was used with age of 2.733 Gy following Pearson et al. ( 1999 ). This age is obtained by subtracting the age of the kimberlitic eruption at Udachnaya (estimated at 367 Ma) from the diamond residence age used (3.1 Gy). The estimates obtained from the two models differ by 7.5°C. Subsequently, a dedicated workflow was applied to determine the absorbance of H-related peaks. Three diagnostic peaks like 3236 cm − 1 , 3107 cm − 1 and 1405 cm − 1 were selected. For each peak, a ± 20 cm − 1 window was chosen for a better resolution, and a local AsLS baseline correction was applied. Within narrow search windows (± 2 cm − 1 at 3236 cm − 1 ; ±1 cm − 1 at 3107 cm − 1 and ± 1.5 cm − 1 at 1405 cm − 1 ), local maxima were identified to precisely determine peak position and height. The same workflow was applied for the platelet peak at 1365 cm − 1 . Each spectrum was processed individually with diagnostic plots generated for visual quality control. Results summarizing peak metrics for all analyzed spectra were exported to Excel. To allow a smooth comparison between the investigated samples and literature data, spectra were normalized according to Speich and Kohn ( 2020 ). The 2700 − 1700 cm − 1 range, including the 2nd -order diamond phonon band, was baseline-corrected with AsLS. The absorbance value at 1992 cm − 1 was extracted, and a normalization factor was calculated to scale it to 12.3, as defined in the reference protocol (Speich and Kohn 2020 ). The collected spectra were further processed to obtain 3D color-coded maps as a function of distance from the geometric (2D) center of the inclusions. Only in the case of DIA5 Map2 , the distance was referred to the inclusion rims. The methodology of this procedure is illustrated in Fig. S3 of the Supplementary Material. Vectorial measurements were derived and integrated with 2D maps, producing 3D maps in which color encodes distance, and the z-axis corresponds to absorbance. During data processing and map construction, a comparison between the absorbance at 3107 cm − 1 with the normalization factors obtained following Speich and Kohn ( 2020 ) (Fig. S4) allowed us to assess whether variations in defect-related absorbance (e.g., the 3107 cm − 1 peak) reflected genuine heterogeneities in defect distribution or simply general changes in sample absorbance. In addition, the normalized versus raw absorbance values at 3107 cm − 1 (Fig. S5) result in a correlation factor (R 2 ≈ 0.70 for the entire dataset, slightly higher when evaluated separately by diamond) that demonstrates a degree of propagated error, indicating that part of the scatter observed in normalized plots might derive from this normalization uncertainty. This aspect is taken into consideration when interpreting trends in normalized scatter plots. Finally, maps of N sumq values were also used to assess spectral quality according to Angellotti et al. ( 2025a ) (Fig. S6). Results Spectroscopic characterization of the investigated diamonds A summary of the acquired data for each diamond (e.g., maps, transects, spot analyses and grid sizes) is listed in Table S1. Table S2 reports the presence and relative intensities of the main H-related bands in each dataset acquired from the investigated diamonds with peak assignments based primarily on the extensive review by Day et al. ( 2024 ) and supported by previous experimental and theoretical studies (Davies et al. 1984 ). Diamonds DIA4 , DIA5 , and LGM15 show very similar spectral shapes (Figs. 3 a - d), whereas LGM12 displays little variations in the N region (~ 1332 − 400 cm − 1 ), likely caused by a different aggregation state. All diamonds can be classified as type IaAB. A distinct absorption at 3107 cm − 1 is visible in the spectra collected from all diamonds (Figs. 4 a - d) that is indicative of the incorporation of H-related defects (Goss et al. 2014 ), a feature of VN 3 H (N 3 VH 0 ) defects. This peak, attributed to C-H stretching vibrations (De Weerdt and Kupriyanov 2002 ), is accompanied by the bending mode at ~ 1405 cm − 1 (Figs. 5 a - d), characteristic of VN 3 H defects (Goss et al., 2014 ), in all samples, although their intensity varies significantly with the position of the analytical point. The absorptions at 3107 cm − 1 and 1405 cm − 1 are listed for all acquisition types (i.e., map, line and spot) along with additional features such as those at 3236 cm − 1 (Figs. 4 a - d), 2786 cm − 1 , 1560 cm − 1 , 1540 cm − 1 , 1430 cm − 1 , 1420 cm − 1 (Figs. 5 a - d). The 3236 cm − 1 refers to VN 4 H defects. Weak bands at 2786 cm − 1 , occasionally detected with low absorbance near the background level, correspond to the 2 x 1405 cm − 1 overtone of the VN 3 H 0 defect (Goss et al. 2014 ). Importantly, since the intensity of 3107 cm − 1 is lower than the intensity of the general lattice absorption near 2158 cm − 1 , none of the samples can be classified as H-rich diamonds (Fritsch and Scarratt 1993 ). The 2nd phonon region (2700 − 1800 cm − 1 ) displays the IR absorption spectrum typical of diamond (Type IIa), consistent with the general C lattice vibrations (Figs. 3 a - d). A particularly distinctive feature is represented by the variable intensity of the band at ~ 1365 cm − 1 , often referred to as N B−centers (Sobolev et al. 1969 ), that arises from extended planar defects-aggregates of C interstitials and N atoms known as platelets (Woods 1986 ; Goss et al. 2003 ; Figs. 5 a - d). The main absorption assigned to A-centers (N-N pairs) occurs at 1282 cm − 1 , and N concentrations can be determined from the absorption coefficient in this spectral region (Woods et al., 1990 ). A distinct shoulder near 1175 cm − 1 , attributed to B-centers (four N-vacancy aggregates) is also evident. These peaks are clearly visible, and their relative intensities indicate a lower contribution from B-centers in diamond LGM12 . A minor feature near 1332 cm − 1 is also related to B-centers, while the band at 1096 cm − 1 corresponds to common N-related absorptions (Fritsch et al. 2007 ; Breeding and Shigley 2009 ; Green et al. 2022 ). N Center distribution and mantle residence temperatures The analysis of N concentration provides an overview of the distribution of N A−center , N B−center and N Total as well as the corresponding mantle T res (°C) and B% derived from N B−center divided for the N Total concentrations as summarized in Table 1 and shown in Figs. 6 and 7 . The mean N Total across the four diamonds is 137 ± 60 ppm with average concentrations of 91 ± 38 ppm for N A−center and 41 ± 32 ppm for N B−center . In detail, LGM15 contains the highest N Total concentration (330 ± 101 ppm), whereas LGM12 exhibits the lowest B% (8 ± 4%), compared with ~ 35–51% (± 10%) in the other investigated diamonds. Estimated T res range from 1112 to 1180°C (± 13–14°C), which is in agreement with Morana et al. ( 2025 ). The standard deviations of the N-related parameters are consistent with those reported in previous studies (Howell et al. 2012a ; Kohn et al. 2016 ; Afanasiev et al. 2022 ; Angellotti et al. 2025a ). LGM12 is the only diamond among those studied here with a B% below 35% as inferred by its distinct B -defect spectral features (Fig. 5 c). The other three diamonds display broadly homogeneous N A−center and N B−center distributions and, therefore, B% . DIA4 and LGM15 , in particular, exhibit closely comparable general N-defect aggregation state (51 ± 10% and 50 ± 2%). Nevertheless, as illustrated in Fig. 6 , diamonds sourced from the same locality (e.g., DIA4 and DIA5 or LGM12 and LGM15 ) can exhibit significant differences in both N abundance and aggregation state, yet remain within the most representative classes on the global scale (Fig. 1 a-b). Table 1 Summary of N centers and estimated temperature. Sample N A−center N B−center N Tot B% T (°C) DIA4 58 (30) 57 (36) 122 (63) 51 (10) 1180 (14) DIA5 90 (34) 50 (24) 144 (53) 35 (10) 1155 (12) LGM12 104 (39) 9 (7) 114 (45) 8 (4) 1112 (14) LGM15 169 (50) 159 (56) 330 (101) 50 (2) 1149 (8) *Statistics are calculated on the central 85% of the data observations, excluding data tails to provide robust averages. N and H distribution at the mineral inclusion - diamond interface Infrared maps of the distribution and concentration of N and H were collected over areas that included or surrounded inclusions to evaluate potential interplay. Figures 8 and 9 present two representative cases, and the remaining datasets are provided in Figures S7-S13 of the Supplementary Materials. These nine panels show a) the optical micrograph of the analyzed area along with the spatial distributions of b) N A−center , c) N B−center , d) N Total , e) the calculated T (°C), f) the B% and the absorbance maps of the H-related peaks like g) 3107 cm − 1 , h) 1405 cm − 1 , and i) 3236 cm − 1 . DIA5 Map2 in Fig. 8 is characterized by the presence of a large inclusion (~ 150 × 100 µm 2 ) of covellite identified by Raman spectroscopy (Fig. S14a), while LGM12 Map2 in Fig. 9 includes a smaller (~ 20 × 20 µm 2 ) inclusion of graphite easily identifiable by eye. The highest H and N absorbance signals follow the inclusion boundary and partially extend beyond the inclusion area, indicating a correlation with higher absorbance along the possible interface regions. Figure 8 b shows higher concentrations of N A−center (100–120 ppm) and N B−center (45–60 ppm) in the area overlapping the rim of sulfide inclusion than in the proximity of the rim, as reported in Fig. 8 c (40–60 ppm and 10–20 ppm, respectively). The lower-central portion of the map (Fig. 8 d) corresponds to a region directly over a thicker section of the inclusion resulting in lower N Total (40 ppm), which is more likely due to an artifact of spectral attenuation rather than true depletion. Despite this, the spectra were not masked, as the data remained of high quality. Figures 8 e and 8 f do not exhibit significant variations of T and B% at the map scale except for the isolated outliers attributable to local spectral saturation effects rather than to genuine features of the chemical distribution. Hydrogen-related defects in DIA5 Map 2 (Fig. 8 g - i) show significant increases in absorbance, with the 3107 cm − 1 peak height varying from 0.02–0.06 to 0.14–0.18. Similar, though less intense, variations are observed for the 1405 cm − 1 and 3236 cm − 1 peaks. LGM12 Map2 reveals a different relationship between the H-related defects and N. As shown in Fig. 9 b - d, N is lower near the defect, with N Total content of 60–80 ppm and 110–130 ppm in graphite-free regions. The calculated T and B% (Fig. 9 e and f) closely follow these trends. Hydrogen-related defects (Fig. 9 g - i) exhibit markedly higher absorbance over the inclusion and along its oblong outline. Peak heights at 3107 cm − 1 range from 0.06 to 0.08 over the inclusion, compared with 0.01 to 0.03 in the surrounding diamond. A comparable trend is observed at 1405 cm − 1 . By contrast, the 3236 cm − 1 band is generally weak or absent in the LGM12 Map2 area, making it unsuitable for any significant spatial trend in this sample. Similar relationships, in which H and N concentrations correlate with the presence of sulfide inclusions or with silicate inclusions such as garnets, are also observed in additional maps reported in the Supplementary Materials and summarized below. In DIA4 Map1 (Fig. S7a), analysed in the vicinity of an aggregate of covellite and chalcopyrite (~ 150 × 150 µm 2 ; Fig. S14b), N concentrations increase sharply along the inclusion, with N Total rising from ~ 50 to ~ 250 ppm (Fig. S7b - d). Calculated T and B% (Fig. S7e - f) display a consistent pattern with spectra collected directly over the inclusion, yielding lower T estimates (1110–1130°C), whereas inclusion-free regions show higher values (1170–1190°C). This behavior reflects the corresponding variation in B% , which is very low (10–20%) within the inclusion area and increases to 40–50% in the surrounding diamond. Hydrogen-related defects (Fig. S7g - i) show a parallel trend to N with the 3107 cm − 1 absorbance increasing from 0.02–0.03 to 0.05–0.06 along the inclusion, accompanied by similar rises in the 1405 cm − 1 and 3236 cm − 1 bands, implying a coupled N-H enrichment associated with sulfide. DIA4 Map2 (Fig. S8a) is, instead, characterized by the presence of a small garnet inclusion (~ 50 × 50 µm 2 ) and widespread graphite (Fig. S14c). Nitrogen contents, together with the calculated T and B% (Fig. S 8b - f), do not exhibit a consistent spatial trend related to the inclusion or to the distribution of graphite. The H-related defects (Fig. S8g - i) increase in the lower part of the map where both garnet and graphite inclusions are present. The overlapping effects arising from the spatial proximity of graphite and garnet inclusions make it difficult to disentangle individual contributions. UDA5 Map1 (Fig. S9a) also exhibits complex patterns due to pronounced graphitization and the inclusion of covellite (150 × 150 µm 2 ), as already described in UDA5 Map2 . Here, N Total concentrations (Fig. S9b - d) are high (300–400 ppm) relative to areas where inclusions occur (50–150 ppm). No general trend is observed for T or B% , whose distributions appear quite homogeneous (Fig. S9e - f). Hydrogen-related defects show slightly higher absorbance in graphite-rich rather than graphite-free regions (0.15 − 0.13 against 0.10–0.11). In LGM12 Map1 (Fig. S10a), N and H-related defects increase and are observed in the region surrounding an inclusion (~ 50 × 50 µm²) of sulfide as inferred by the metallic luster. N Total (Fig. S10b - d) shows a moderate increase near the inclusion, rising from 100–200 ppm in the surrounding diamond to 300–350 ppm over the inclusion. In contrast, B% and T (Fig. S10e - f) do not display any discernible spatial trends and appear relatively uniform across the entire map. The H-related defects (Fig. S10g - i) exhibit greater absorbance in the presence of the inclusion. The 3107 cm − 1 band increases from 0.08–0.15 in inclusion-free areas to 0.20–0.25 in correspondence with the inclusion, accompanied by similar increases in the 1405 cm − 1 band and, where detectable, by a corresponding increase in the 3236 cm − 1 band. The results described above are strengthened by the acquisition of two additional maps in regions free of inclusion. The first map is DIA5 Map 3 (Fig. S11a) chosen since this is a diamond where various localized graphitization occurs. An area with no visible graphite was mapped to evaluate whether graphitization influenced the defect distribution. In this region, N concentrations are consistently 220–240 ppm across the map, except along the upper and lower margins (Fig. S11b - d). T and B% (Fig. S11e and f) show no spatial trend and broadly match the uniform N distribution. Hydrogen absorption is very low (Fig. S11g - i) with 3107 cm -1 peak heights not exceeding ~ 0.03. This contrasts with what was described for DIA5 Map2 where both sulfide and graphite appeared to exert control on the N and H defects distribution. The second quality-control mosaic was collected for LGM15 Map1 (Fig. S12a). This diamond is characterized by irregular morphology (Morana et al. 2025 ), and only a limited number of spectra were acquired; therefore, the dataset available for this sample is smaller than those from the other diamonds. The N Total values are generally 350 − 300 ppm (Fig. S12b - d), and both T and B% (Fig. S12e and f) show no clear spatial variability, mirroring the N distribution. Hydrogen absorbance is extremely low (Fig. S12g - i), with the 3107 cm -1 band reaching a maximum of ~ 0.03. As a result, any apparent trend in the H maps is likely driven by noise measurement rather than by real variations in H-defect, particularly in an area free of inclusions. For completeness, a separate analysis was performed on the platelet-related absorption peak B′ at 1365 cm -1 (Fig. S13), and dedicated maps were generated to assess potential spatial correlations and similarities with the defect distribution. Interestingly, despite the marked B′ intensities and the significant variation observed in several of the most interesting maps, for instance DIA5 Map1 (absorbance varying from 0.625 to 0.425), DIA5 Map2 (absorbance varying from 0.375 to 0.175), and LGM12 Map2 (absorbance varying from 0.26 to 0.16), the resulting spatial patterns do not align with those documented previously for N or H-related defects suggesting, therefore, a different mechanism of distribution. Discussion Chemical relation between diamond and inclusions Graphite is among the most common phases found as inclusions in natural diamonds, and its formation results from various processes, including epigenetic origin by T and P variations, deformation-induced mechanisms, or crystallization along with diamonds from a carbon-saturated fluid (Harris and Vance 1972 ; Evans 1979 ; Nechaev and Khokhryakov 2013 ; Mikhailenko et al. 2016 ). Graphite typically appears as disks or rosettes surrounding mineral or fluid inclusions, or as centrally located hexagonal platelets oriented relative to the diamond lattice (Bulanova 1995 ; Nasdala et al. 2005 ). In diamonds from Marange, highly ordered graphite inclusions have been identified, without evidence of fracturing or graphitization halos in the surrounding diamond matrix, and they exhibit spatial correlations with CH 4 -rich fluid inclusions (Eaton-Maganà et al., 2017; Smit et al., 2016 , 2018 ). Experimental studies conducted at high pressure and temperature confirmed that graphite and diamond can nucleate and grow simultaneously in carbon-saturated systems (Sokol and Palyanov 2004 ; Palyanov et al. 2005 ). Moreover, graphitization can also occur during heating outside the diamond stability field, particularly during ascent (Korsakov et al. 2016). Sulfides are incorporated into diamond as high-temperature monosulfide solid solution and later exsolve into Fe-, Ni-, and Cu-rich end members during cooling associated with exhumation (Kullerud et al. 1969 ; Pamato et al. 2021 ). Both of these inclusions are found in the four diamonds investigated here and, in the case of LGM15 , are described in detail by Morana et al. ( 2025 ). In this study, synchrotron-assisted micro-FTIR mapping reveals that areas containing graphite and sulfides inclusions consistently display stronger absorption at 3107 cm − 1 than inclusion-free regions of the same crystals suggesting that the 3107 cm − 1 band is a potential tracer of C-H chemical interaction within the parental growth medium. Because graphite is known to incorporate low concentrations of hydrogen (Atsumi and Tauchi 2003 ), their strong affinity can be explained by the formation of adsorbed or chemisorbed species (Zecho et al. 2002 ; Rougeau et al., 2006 ). The presence of circulating (aqueous) fluids can promote graphitization by catalyzing the process (Harris and Vance 1972 ). For this reason, enrichments in the absorbances of the VN 3 H defect in the area characterized by graphite inclusions might be taken as proof of a fluid-mediated H-enrichment heterogeneously distributed in the diamond to reflect the spatial and temporal variation of the growth medium. Several reactions might be written to represent the chemical equilibrium between C and H at the time of diamond formation, such as, CH 4 + O 2 = C + 2H 2 O Eq. 1, CO 2 + 2H 2 = C + 2H 2 O Eq. 2, CH 4 = C + 2H 2 Eq. 3, It can be seen that the precipitation of C to diamond via oxidizing/reducing agents such as O 2 and H 2 would favor the formation of H 2 O (Sokol et al. 2019 ). However, the formation of diamonds appears incompatible with H 2 O-saturated conditions in eclogitic environments (Stagno and Fei 2020; Stagno and Aulbach 2021). In contrast, methane-bearing fluids have been proposed as a source of diamonds through high-P/T experiments (Matjuschkin et al. 2020), via isotopic geochemistry (Thomassot et al. 2007 ), and thermodynamically (Mikhailenko et al. 2020; Aulbach et al. 2022). Reaction Eq. (3) would imply H formation and, hence, sequestration that can occur by elemental carbon itself, other than coexisting silicate minerals. Again, the finding of H, mostly hosted by trapped silicates (Curtolo et al. 2025 ), suggests that H in diamonds must have been inherited by the diamond growth medium itself, a mechanism that is consistent with the positive correlation between graphite and H reported in our study. Similarly, the affinity of H for sulfide has been demonstrated experimentally (Errea et al. 2015; Abeykoon et al. 2023) and recently reported in sulfides of meteorite samples (Barrett et al. 2025 ) as result of fast diffusion-driven processes. In addition, under mantle f o 2 conditions at which diamonds form from methane, N would also be stable in several forms, such as NH 4 + and N 3− , or even in Fe-nitride (Li 2024 ), supporting possible mechanisms of incorporation into sulfides. Our IR maps suggest that either N or H is incorporated into sulfides, and quantification of these species might provide useful insights into the chemical composition of the parental fluid growth medium (Thomassot et al. 2025 ). In fact, water is an important component that lowers the temperature of diamond crystallization by 200–300°C (Wang et al. 2021 ). On the other hand, possible post-entrapment mechanisms of diffusion from the diamond matrix to the sulfides cannot be ruled out. This relationship is shown in Fig. 10 and Fig. 11 , where the z-axis represents the absorbance intensity at 3107 cm − 1 . Elevated regions (i.e., high z-axis) spatially coincide with disk-like graphite inclusions and large sulfide inclusions, respectively. The highest absorbance occurs directly above the inclusion zones, gradually decreasing with distance, consistent with localized hydrogen diffusion or with hydrogen being trapped along residual fluid films at the inclusion-diamond interface (Harris and Vance 1972 ). In particular, in LGM12 Map2 ( Fig. 10 ), the 3107 cm − 1 peak absorbance decreases almost radially away from the inclusion, reflecting the small size of the graphite inclusions and the efficient spatial H diffusion. In contrast, in UDA5 Map2 (Fig. 11 ), the main sulfide inclusion is 150 µm across, preventing clear detection of gradients in the surrounding area. The variability of the absorbance intensity observed across the inclusion zone would reflect the (polycrystalline) morphology of the inclusion, due to destabilization of the monosulfide solid solution (Pamato et al. 2021 ; Morana et al. 2025 ). Even if the two maps represent distinct diamond-forming environments, it is possible to observe a general trend in which higher 3107 cm − 1 absorbances occur where inclusions are present. Comparable relationships have been noted for Mg-chromite inclusion in P-type diamonds by Angellotti et al. ( 2025b ), who reported a correlation between the 3107 cm − 1 absorption and N A−center and explained it as due to stress-assisted diffusion or fluid-mediated H enrichment. It is largely established that H interacts with nitrogen-vacancy centers to form stable complexes such as NVH, N 3 VH, and N 4 VH (Day et al. 2025 ). Hydrogen-related defects are also identified by IR-active C-H stretching and bending modes (Kaminsky et al. 2024 ), with typical absorptions at ~ 3107 and ~ 1405 cm − 1 attributed to the VN 3 H (or N 3 VH 0 ) defect (Fritsch et al. 2007 ; Goss et al. 2014 ). Figure 12 a-b shows an interesting correlation between the 3107 cm − 1 and 1405 cm − 1 bands, as well as the effect of distance from the inclusion. In Fig. 12 a ( LGM12 Map2 ), points near the graphite inclusion exhibit an enriched trend with significantly higher absorbance values, whereas more distal regions exhibit a deficient trend, serving as the background. Notably, these observed trends suggest that the IR sensitivity for detecting H distribution in response to environmental variations is achieved within areas as small as 10 µm 2 . A similar pattern is observed in Fig. 12 b for UDA5 Map2 , where only an enriched-type trend is present. Once again, spectra collected near or directly on the inclusion show systematically higher absorbance than those measured far away, confirming the inclusion’s influence on the local hydrogen-related defect concentration. Noteworthy, local stress and strain around inclusions could also contribute to H-defect enrichment (Kanda and Watanabe 1997 ). However, the consistent correlations observed across different maps and the spatial correspondence with enrichments and inclusions indicate that H-rich fluids could be the dominant control factor, whereas stress-driven processes could be secondary enhancers. Conclusions High-resolution synchrotron micro-FTIR mapping was used to investigate the spatial distribution of nitrogen- and hydrogen-related lattice defects in four eclogitic diamonds from the Udachnaya kimberlite, with particular focus on their relationship to mineral inclusions. The results demonstrate that hydrogen-related infrared absorption bands, most notably those at ~ 3107 and ~ 1405 cm − 1 attributed to VN3H defects, show systematic spatial enrichments in proximity to graphite and sulfide inclusions. These enrichments commonly extend over distances of several to tens of micrometers from the inclusion–diamond interface, whereas inclusion-free regions within the same crystals display comparatively homogeneous and low hydrogen-related absorbance. Nitrogen systematics exhibit more variable behavior. Sulfide inclusions are frequently associated with locally elevated concentrations of both N and H, whereas graphite inclusions are characterized primarily by H enrichment with weaker, absent, or locally negative correlations with nitrogen concentration and aggregation state. Garnet inclusions show less systematic effects, suggesting that the influence of inclusions on lattice-bound impurities depends on both mineral chemistry and local growth or post-growth conditions. The spatial coincidence between inclusions and enhanced H-related absorbance indicates that mineral inclusions represent zones of localized perturbation in the diamond lattice, capable of influencing the distribution and stabilization of H-bearing defects. These perturbations may reflect interaction with residual growth media, localized fluid films, or enhanced diffusion and trapping of H in the vicinity of inclusions. While the present data clearly document spatial correlations, they do not uniquely discriminate between chemical control by the parental fluid, stress- or strain-assisted defect stabilization, or a combination of both processes. Importantly, H-related defects appear to be more sensitive tracers of such localized perturbations than N aggregation state or calculated mantle residence temperatures, which remain largely homogeneous at the scale of the FTIR maps. This highlights the utility of micro-scale H defect mapping as a complementary tool to conventional N-based thermo-chronometry in assessing diamond growth environments and post-growth modification. Although based on a limited number of samples from a single locality, the investigated diamonds span N concentrations and aggregation states that are representative of global eclogitic diamond populations. The phenomena documented here therefore may not be unique to Udachnaya diamonds, but broader applicability will require investigation of additional samples from diverse cratonic settings and parageneses. Overall, this study demonstrates that mineral inclusions can be associated with localized heterogeneities in hydrogen- and, in some cases, nitrogen-related lattice defects in natural diamonds. These observations provide new constraints on the micro-scale complexity of diamond formation and modification processes and underscore the need to integrate high-resolution spectroscopic mapping with independent geochemical and structural constraints to fully resolve the mechanisms governing impurity incorporation in diamond. Declarations Acknowledgements The authors gratefully acknowledge Diamond Light Source for funding the experiment proposal SM35052. CRediT authorship contribution statement A. Angellotti: Writing – original draft, Software, Investigation, Formal analysis, Data curation, Conceptualization. L. Barni: Writing – original draft, Formal analysis, Data curation, Investigation. M. Morana: Writing – review & editing, Investigation. G. Cinque: Writing – review & editing, Validation, Methodology, Software, Investigation. Y. Lu: Investigation. R. Tao: Writing – review & editing, Investigation. G. Marras: Writing – review & editing. A. Logvinova: Writing – review & editing, Resources. L. Bindi: Writing – review & editing, Formal analysis, Resources. D. Mikhailenko: Writing – review & editing, Validation, Resources. V. Stagno: Writing – review & editing, Supervision, Resources, Investigation, Formal analysis, Data curation, Conceptualization. Funding VS acknowledges financial support from the HERMES project (PRIN 2022, grant no. 2022R35×8Z). A.L. acknowledges financial support of the CAS PIFI project n. 2025PVA0073. D.S. acknowledges financial support of IGG UB RAS (124020400013-1). Conflict of interest The authors have no competing interests to declare that are relevant to the content of this article. 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13:21:50","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-9020643/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9020643/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103880423,"identity":"b5b89be8-a56d-44ed-a65f-cf6d582c0b87","added_by":"auto","created_at":"2026-03-04 05:10:27","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":42294,"visible":true,"origin":"","legend":"\u003cp\u003eGlobal frequency distribution of \u003cstrong\u003ea)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e and \u003cstrong\u003eb)\u003c/strong\u003e N aggregation state (\u003cem\u003e%B\u003c/em\u003e) in eclogitic diamonds (dataset by Stachel et al. 2022).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/c8426af3cbc3c9ed4332f496.png"},{"id":104401130,"identity":"5090a5a2-832a-4bcb-945c-7264912e5a2b","added_by":"auto","created_at":"2026-03-11 12:11:57","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1068669,"visible":true,"origin":"","legend":"\u003cp\u003eOptical images of diamonds \u003cstrong\u003ea)\u003c/strong\u003e \u003cem\u003eDIA4\u003c/em\u003e, \u003cstrong\u003eb)\u003c/strong\u003e \u003cem\u003eDIA5\u003c/em\u003e, \u003cstrong\u003ec)\u003c/strong\u003e \u003cem\u003eLGM12\u003c/em\u003e and \u003cstrong\u003ed)\u003c/strong\u003e \u003cem\u003eLGM15\u003c/em\u003e. Red squares indicate the areas where the FTIR maps were collected.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/fb7c3f8ea4b9e4b3ad01c889.png"},{"id":103880431,"identity":"f0b7c0ae-35a5-4cf9-9833-14cf0bfbe245","added_by":"auto","created_at":"2026-03-04 05:10:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":241739,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra collected in the 3500 - 1050 cm\u003csup\u003e-1\u003c/sup\u003e range for \u003cstrong\u003e(a)\u003c/strong\u003e \u003cem\u003eDIA4\u003c/em\u003e, \u003cstrong\u003e(b)\u003c/strong\u003e \u003cem\u003eDIA5\u003c/em\u003e, \u003cstrong\u003e(c)\u003c/strong\u003e \u003cem\u003eLGM12\u003c/em\u003e, and \u003cstrong\u003e(d)\u003c/strong\u003e \u003cem\u003eLGM15\u003c/em\u003e. The black line represents the mean spectrum, and the shaded region shows the minimum and maximum absorbance values.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/fe776a3fba044f666326ff2e.png"},{"id":103880434,"identity":"890d81a7-48b6-46af-af36-92420576df87","added_by":"auto","created_at":"2026-03-04 05:10:33","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":165894,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra collected in the 3500 - 3000 cm\u003csup\u003e-1\u003c/sup\u003e range for \u003cstrong\u003e(a)\u003c/strong\u003e \u003cem\u003eDIA4\u003c/em\u003e, \u003cstrong\u003e(b)\u003c/strong\u003e \u003cem\u003eDIA5\u003c/em\u003e, \u003cstrong\u003e(c)\u003c/strong\u003e \u003cem\u003eLGM12\u003c/em\u003e, and \u003cstrong\u003e(d)\u003c/strong\u003e \u003cem\u003eLGM15\u003c/em\u003e. The black line represents the mean spectrum, and the shaded region shows the minimum and maximum absorbance values. Key spectral features are indicated by black arrows.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/3af9124ebeaeb4e03b53ce8c.png"},{"id":104401447,"identity":"a3d717d7-5600-40d4-af2a-f50b33ae0690","added_by":"auto","created_at":"2026-03-11 12:12:44","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":290530,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra collected in the 1500 - 1050 cm\u003csup\u003e-1\u003c/sup\u003e range for \u003cstrong\u003e(a)\u003c/strong\u003e \u003cem\u003eDIA4\u003c/em\u003e, \u003cstrong\u003e(b)\u003c/strong\u003e \u003cem\u003eDIA5\u003c/em\u003e, \u003cstrong\u003e(c)\u003c/strong\u003e \u003cem\u003eLGM12\u003c/em\u003e, and \u003cstrong\u003e(d)\u003c/strong\u003e \u003cem\u003eLGM15\u003c/em\u003e. The black line represents the mean spectrum, and the shaded region shows the minimum and maximum absorbance values. Key spectral features are indicated by black arrows.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/f5e82b41d38d0b4084a12370.png"},{"id":103880429,"identity":"9af3f678-f320-439e-99ba-bbf6749dfbc1","added_by":"auto","created_at":"2026-03-04 05:10:31","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":90469,"visible":true,"origin":"","legend":"\u003cp\u003eHistograms showing the numerical distribution of \u003cstrong\u003ea)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e (total nitrogen in ppm), \u003cstrong\u003eb)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA-center\u003c/em\u003e\u003c/sub\u003e, and \u003cstrong\u003ec)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB-center\u003c/em\u003e\u003c/sub\u003e (ppm) measured from all the spectra collected on \u003cem\u003eDIA4, DIA5, LGM12, \u003c/em\u003eand\u003cem\u003e LGM15\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/fb61139ee1fafed8bfd27225.png"},{"id":103880425,"identity":"bbbedca1-6484-4f79-b16a-1fb3c9b7b3c4","added_by":"auto","created_at":"2026-03-04 05:10:31","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":81974,"visible":true,"origin":"","legend":"\u003cp\u003eHistograms showing the frequency distribution of the \u003cem\u003eT\u003c/em\u003e\u003csub\u003e\u003cem\u003eres\u003c/em\u003e\u003c/sub\u003e (°C) (left panel) and \u003cem\u003e%B\u003c/em\u003e (right panel) calculated from all the spectra collected on \u003cem\u003eDIA4, DIA5, LGM12, \u003c/em\u003eand\u003cem\u003e LGM15\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/4b12b9ed896c84724f94d41d.png"},{"id":103880428,"identity":"b96346e2-7df9-4320-9f1f-7f50851ef025","added_by":"auto","created_at":"2026-03-04 05:10:31","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":259399,"visible":true,"origin":"","legend":"\u003cp\u003eNine mosaic maps of sample \u003cem\u003eDIA5 Map2\u003c/em\u003e including a sulphides inclusion shows \u003cstrong\u003e(a)\u003c/strong\u003e optical micrograph of the measured area, the spatial distribution of \u003cstrong\u003e(b)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA-center\u003c/em\u003e\u003c/sub\u003e, \u003cstrong\u003e(c)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB-center\u003c/em\u003e\u003c/sub\u003e, \u003cstrong\u003e(d)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e, \u003cstrong\u003e(e)\u003c/strong\u003e T (°C), \u003cstrong\u003e(f)\u003c/strong\u003e B%, (\u003cstrong\u003eg - i\u003c/strong\u003e) absorbance at 3107 cm\u003csup\u003e-1\u003c/sup\u003e, 1405 cm\u003csup\u003e-1\u003c/sup\u003eand 3236 cm\u003csup\u003e-1\u003c/sup\u003e. Masks (white pixels) were applied to exclude saturated spectra.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/d8cb73755fc993533dbf3423.png"},{"id":103880435,"identity":"83c6ec52-2960-4eab-a10a-e12d312495fb","added_by":"auto","created_at":"2026-03-04 05:10:33","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":257779,"visible":true,"origin":"","legend":"\u003cp\u003eMaps of sample \u003cem\u003eLGM12 Map2\u003c/em\u003e showing \u003cstrong\u003e(a)\u003c/strong\u003e optical micrograph of the measured area, the spatial distribution of \u003cstrong\u003e(b)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA-center\u003c/em\u003e\u003c/sub\u003e, \u003cstrong\u003e(c)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB-center\u003c/em\u003e\u003c/sub\u003e, \u003cstrong\u003e(d)\u003c/strong\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e, \u003cstrong\u003e(e)\u003c/strong\u003e T (°C), \u003cstrong\u003e(f)\u003c/strong\u003e B%, (\u003cstrong\u003eg - i\u003c/strong\u003e) absorbance at 3107 cm\u003csup\u003e-1\u003c/sup\u003e, 1405 cm\u003csup\u003e-1 \u003c/sup\u003eand 3236 cm\u003csup\u003e-1 \u003c/sup\u003ein the vicinity of a graphite inclusion. White masks have been applied to exclude saturated spectra.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/c54e8c3b71f73832fa67c072.png"},{"id":103880430,"identity":"ad402f75-6857-4f77-aab6-925ca12926a4","added_by":"auto","created_at":"2026-03-04 05:10:32","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":433642,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eLGM12 Map2 data presented as a 3D map \u003c/em\u003ecolor-coded by distance from the center of the graphite inclusion, with elevation corresponding to the absorbance of the 3107 cm\u003csup\u003e-1\u003c/sup\u003e peak. An inset shows the sampling position on the \u003cem\u003eLGM12\u003c/em\u003e diamond.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/61f8d3ebeecb37bf8599719c.png"},{"id":103880432,"identity":"1f488232-67fa-434f-8812-c684693acd65","added_by":"auto","created_at":"2026-03-04 05:10:32","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":410572,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDIA5 Map2\u003c/em\u003e data presented as a 3D map color-coded by distance from the rim of the sulfide inclusion, with elevation corresponding to the absorbance of the 3107 cm\u003csup\u003e-1\u003c/sup\u003e peak. An inset shows the acquisition area on the \u003cem\u003eDIA5 Map2\u003c/em\u003e. The point corresponding to the positions of the inclusion have distance of zero.\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/d66e2c23d3c259df87389f27.png"},{"id":103880426,"identity":"ed317c90-0d2f-4e1a-83f7-6f510efc7241","added_by":"auto","created_at":"2026-03-04 05:10:31","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":190516,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e Scatter plot from \u003cem\u003eLGM12 Map2\u003c/em\u003e and \u003cstrong\u003e(b)\u003c/strong\u003e from \u003cem\u003eDIA5 Map2\u003c/em\u003e showing the absorbance at 3107 cm\u003csup\u003e-1\u003c/sup\u003e plotted against the peak at 1405 cm\u003csup\u003e-1\u003c/sup\u003e, color-coded by the distance from the center of the inclusion. Two trend lines are shown in the case of (a) to illustrate the overall relationships, with the corresponding R\u003csup\u003e2\u003c/sup\u003e values for the enriched and deficient trends. A single trend line is fitted in (b) to highlight the general relationship, with the associated R\u003csup\u003e2\u003c/sup\u003e value indicated.\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/b754d8b35a1be2be794c2d72.png"},{"id":104408089,"identity":"887715ed-cdfb-4765-9bfa-7d0402dfb3cd","added_by":"auto","created_at":"2026-03-11 12:41:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4904750,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9020643/v1/6206230e-b5b1-47c6-8bae-f23392da70cc.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eInterplay between the distribution of nitrogen and hydrogen and mineral inclusions in E-type diamonds from Yakutia, Siberian craton\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eDiamonds in nature record unique information about local physical and chemical processes that occurred at the inaccessible depths of the Earth where they have formed due to their exceptional chemical inertness that prevents any reaction with the encapsulated minerals and fluids inclusions so that pressure, temperature, and oxygen fugacity conditions at the time of encapsulation can be retrieved through application of oxy-thermobarometry (Daniels and Gurney \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Deines et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) and elastic barometry techniques (Angel et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Two main paragenetic assemblages are recognized in lithospheric diamonds, peridotitic (P-type with frequent inclusions of olivine, pyroxene, spinel) and eclogitic (E-type with frequent inclusions of pyroxene, garnet and sulfides) (Sobolev \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e1977\u003c/span\u003e; Meyer \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Stachel and Harris \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Furthermore, the intrinsic chemical properties of the diamond provide insights into growth and post-growth processes. In fact, diamonds contain a variety of impurities such as nitrogen (N) and hydrogen (H). Nitrogen commonly occurs at concentrations of 200\u0026ndash;300 ppm (Mikhail and Howell \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), while H generally reaches\u0026thinsp;~\u0026thinsp;50 ppm (Sweeney et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Ashfold et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These impurities can influence the optical (Green et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Zaitsev \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and physical (Field et al. 2012) properties of diamonds and provide key information on their geological history. Nitrogen, for instance, is incorporated mainly by substitution forming a series of so-called N centers (Smith et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1959\u003c/span\u003e; Boyd et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1994\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1995\u003c/span\u003e), whose aggregation state depends on temperature and residence time within the mantle (Taylor et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). Fourier Transform infrared (FTIR) spectroscopy remains the most used method for quantifying N concentration, aggregation and mantle residence temperatures (Kohn et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). However, discrepancies between calculated temperatures and geological constraints indicate that N aggregation alone cannot fully account for the diamond thermal history (Angellotti et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003eb\u003c/span\u003e). Hydrogen, the second most abundant impurity in diamond is likely hosted in the structure during formation from carbonated aqueous fluids and diffuses under mantle conditions (Lang et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Chevallier et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Hartland \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The heterogeneous distribution of N centers and H-N clusters in diamonds has been extensively documented on sub-millimeter to millimeter scales and explained as a result of differences in crystal growth rate, local redox conditions, and fluid composition during formation (Chen et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Howell et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2012b\u003c/span\u003e; Spetsius et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Kohn et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Eaton-Maga\u0026ntilde;a et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Stress fields generated by inclusions, dislocations, voidites, and platelets can also locally distort the diamond lattice, influencing defect formation and optical properties (Evans and Woods \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Kanda and Watanabe \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Speich et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Laidlaw et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). As minerals are also trapped during the diamond growth, it is unknown whether they control N and H incorporation and diffusion.\u003c/p\u003e \u003cp\u003eSynchrotron-based infrared microspectroscopy has enabled mapping at resolutions of ~\u0026thinsp;10 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, far exceeding the ~\u0026thinsp;50 x 50 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e scale of conventional FTIR (Howell et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2012a\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2012b\u003c/span\u003e; Cinque et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Such advances have enabled the investigation of rim zones and inclusion halos where localized heterogeneities can provide key insights into defect formation mechanisms. In fact, higher spatial precision reveals microscale differences in N and H distributions that were previously undetectable (Angellotti et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e). Eclogitic diamonds are ideal samples for this approach, as their inclusions frequently record fluid-rich environments, as indicated by H\u003csub\u003e2\u003c/sub\u003eO contents higher than those of their peridotitic counterparts (Logvinova et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Nimis et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Curtolo et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFollowing the dataset by Stachel et al. (\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea - b), about 32% of eclogitic diamonds exhibit total N concentrations\u0026thinsp;\u0026le;\u0026thinsp;100 ppm, while only 2.8% exceed 1000 ppm. The distribution of B% [(N\u003csub\u003eB\u0026minus;center\u003c/sub\u003e/N\u003csub\u003eTotal\u003c/sub\u003e] indicates a predominance of Type IaA diamonds (N mainly in A-centers) relative to Type IaB diamonds (N aggregated as B-centers). Approximately 25% of the samples analyzed display B% \u0026le;10%. The dataset also includes N-free Type IIa diamonds. Among the regional subsets (Figs. S1 and S2), all Russian eclogitic diamonds exhibit higher average N contents (~\u0026thinsp;600 ppm), which may reflect either sampling bias or a compositional anomaly. All Russian (eclogitic) diamonds also show a distinct B% distribution relative to the global dataset, with the samples dominated by the Type IaAB. This trend may similarly reflect sampling effects, yet it is consistent with the pattern observed in the African subset, which is supported by robust statistics based on more than 1000 analyzed samples.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBy contrast, producing comparable statistics for H remains challenging due to data scarcity. In this study, we investigated E-type diamonds from the Udachnaya kimberlite pipe to better understand the interaction between mineral inclusions and N and H, and the possible effects on their distribution and abundance.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSample Description\u003c/h2\u003e \u003cp\u003eWe characterized four lithospheric eclogitic diamonds from the Udachnaya kimberlite pipe in the Daldyn-Alakit kimberlite field, Yakutia Province (Siberian Craton), namely \u003cem\u003eDIA4\u003c/em\u003e, \u003cem\u003eDIA5\u003c/em\u003e, \u003cem\u003eLGM12\u003c/em\u003e and \u003cem\u003eLGM15\u003c/em\u003e, respectively. All samples originally presented an octahedral shape and were characterized by having mineral inclusions visible and distinguishable under the stereoscope. These were double-polished parallel to the (110) planes to produce plates suitable for FTIR analyses. The images of the four diamonds (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea - d) and their inclusions were acquired using the AmScope stereoscope under reflected and transmitted light along with images collected under polarized light with a Leica DM750 microscope. Both microscopes, available at the Department of Earth Sciences of Sapienza University (Rome, Italy) are equipped with high-resolution cameras, and images are acquired using integrated software. All four diamonds exhibit greenish and light-orange inclusions of clinopyroxene and garnet, respectively. Additionally, some inclusions appear dark and/or with metallic luster easily identified by eye as graphite and sulfides, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eRaman spectroscopy\u003c/h3\u003e\n\u003cp\u003eRaman spectroscopy analyses were performed to identify mineral inclusions occurring within the areas selected for IR mapping. A confocal Raman microscope (WITec alpha 300R system, WITec GmbH, Ulm, Germany) was used at the High-Pressure Science and Technology Advanced Research Center (HPSTAR) in Beijing, China. A laser with an excitation wavelength of 532 nm was employed for all the measurements. The optical system included a 20\u0026times; long working-distance objective lens (Mitutoyo BD Plan Apo SL 20\u0026times; /0.28, NA\u0026thinsp;=\u0026thinsp;0.28), coupled with a 50 \u0026micro;m confocal pinhole to enhance spatial resolution and reduce background interference. Two diffraction gratings were used in the spectrometer: a 600 g/mm grating, which provided a spectral resolution of approximately\u0026thinsp;~\u0026thinsp;3 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and a high-resolution 1800 g/mm grating, which achieved a resolution of ~\u0026thinsp;1 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The laser power at the source was maintained at approximately 50 mW. Calibration of the Raman system was conducted using the characteristic Raman peak of pure silicon at 520.7 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. A higher-magnification Zeiss LD EC Epiplan-Neofluar Dic 50\u0026times;/0.55 objective lens was employed to analyze small inclusions, yielding a focal spot size of approximately 1.5 \u0026micro;m. Each Raman spectrum was acquired with at least 10 accumulations, each with an integration time of 10 seconds, ensuring a high signal-to-noise ratio and reproducibility of spectral features.\u003c/p\u003e\n\u003ch3\u003eMicro-FTIR Data Acquisition and Processing\u003c/h3\u003e\n\u003cp\u003eThe micro-Fourier transform infrared spectroscopy (micro-FTIR) data were collected in transmission mode at the MIRIAM beamline B22 of the Diamond Light Source facility (UK) using a Bruker Hyperion 3000 IR microscope coupled to a Vertex 80V FTIR spectrometer (Cinque et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). A 36\u0026times; objective and equivalent condenser optics were used, with a knife-edge aperture positioned in the detection beam path and a high-sensitivity MCT detector with a 50 \u0026micro;m pitch cooled by liquid nitrogen. Background measurements were conducted with 512 scans per analysis on the underlying BaF\u003csub\u003e2\u003c/sub\u003e plate. Spectra were collected over the wavenumber range 4000\u0026thinsp;\u0026minus;\u0026thinsp;500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with a spectral resolution of 2 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 256 scans per spectrum (~\u0026thinsp;1 min per point for optimal spectral quality). High-resolution maps covering areas of ~\u0026thinsp;100 \u0026times; 100 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e were generated using a 10 \u0026times; 10 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e knife-edge aperture and a 7 \u0026micro;m stage step size, yielding 3-\u0026micro;m point overlap. Line-scan transects (30 spots, 10 \u0026times; 10 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e aperture, 10 \u0026micro;m step size) were used to survey diamond surfaces and assess N and H variability in proximity of and at mineral inclusions as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea - d.\u003c/p\u003e \u003cp\u003eSpectra acquisition and visualization were performed using Bruker OPUS v8.7.41. Spectra exhibiting saturation effects, inclusion interference, or surface irregularities were excluded. The analytical workflow follows Angellotti et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e; Fig. S3). For data processing, a custom baseline removal script was developed to correct mid-infrared FTIR spectra of the diamond samples. Baseline distortions were removed using a tailored asymmetric least squares (AsLS) approach. The region 3550\u0026thinsp;\u0026minus;\u0026thinsp;1050 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was divided into four contiguous intervals (3550\u0026thinsp;\u0026minus;\u0026thinsp;2670 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 2670\u0026thinsp;\u0026minus;\u0026thinsp;1700 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1700\u0026thinsp;\u0026minus;\u0026thinsp;1395 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1395\u0026thinsp;\u0026minus;\u0026thinsp;1050 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), each processed independently. The baseline for each spectral interval was subtracted using the AsLS algorithm. The smoothing parameter (\u003cem\u003eλ\u003c/em\u003e) controlled baseline stiffness, while the asymmetric parameter (\u003cem\u003ep\u003c/em\u003e) ensured the fitted baseline remained below the absorbance signal. To avoid discontinuities between spectral regions, tapering functions were applied over 5\u0026ndash;20 data points at block edges. Corrected blocks were, then, recombined into a continuous spectrum. Finally, spectra were extended to 4000\u0026thinsp;\u0026minus;\u0026thinsp;500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with zero-padding to meet the input requirements for N quantification software.\u003c/p\u003e \u003cp\u003eNitrogen concentration and residence temperature (T\u003csub\u003eres\u003c/sub\u003e) were determined using QUIDDIT software (Speich and Kohn \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), which supports batch data processing. Spectra previously flagged for saturation were masked prior to map generation like in Angellotti et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e). Estimates of T\u003csub\u003eres\u003c/sub\u003e require a formation age for the diamonds, which has not been uniquely determined for Udachnaya. Consequently, we employed two different ages: 2.00 and 2.733 Gy. The first value was employed by Morana et al. (\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) for geobarometric calculations, after deriving the T\u003csub\u003eres\u003c/sub\u003e for three ages (i.e., 1, 2 and 2.8 Ga), covering the range of existing hypotheses for Udachnaya. For comparison, a second model was used with age of 2.733 Gy following Pearson et al. (\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). This age is obtained by subtracting the age of the kimberlitic eruption at Udachnaya (estimated at 367 Ma) from the diamond residence age used (3.1 Gy). The estimates obtained from the two models differ by 7.5\u0026deg;C. Subsequently, a dedicated workflow was applied to determine the absorbance of H-related peaks. Three diagnostic peaks like 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were selected. For each peak, a\u0026thinsp;\u0026plusmn;\u0026thinsp;20 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e window was chosen for a better resolution, and a local AsLS baseline correction was applied. Within narrow search windows (\u0026plusmn;\u0026thinsp;2 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; \u0026plusmn;1 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and \u0026plusmn;\u0026thinsp;1.5 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), local maxima were identified to precisely determine peak position and height. The same workflow was applied for the platelet peak at 1365 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Each spectrum was processed individually with diagnostic plots generated for visual quality control. Results summarizing peak metrics for all analyzed spectra were exported to Excel. To allow a smooth comparison between the investigated samples and literature data, spectra were normalized according to Speich and Kohn (\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The 2700\u0026thinsp;\u0026minus;\u0026thinsp;1700 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range, including the 2nd -order diamond phonon band, was baseline-corrected with AsLS. The absorbance value at 1992 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was extracted, and a normalization factor was calculated to scale it to 12.3, as defined in the reference protocol (Speich and Kohn \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe collected spectra were further processed to obtain 3D color-coded maps as a function of distance from the geometric (2D) center of the inclusions. Only in the case of \u003cem\u003eDIA5 Map2\u003c/em\u003e, the distance was referred to the inclusion rims. The methodology of this procedure is illustrated in Fig. S3 of the Supplementary Material. Vectorial measurements were derived and integrated with 2D maps, producing 3D maps in which color encodes distance, and the z-axis corresponds to absorbance.\u003c/p\u003e \u003cp\u003eDuring data processing and map construction, a comparison between the absorbance at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with the normalization factors obtained following Speich and Kohn (\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) (Fig. S4) allowed us to assess whether variations in defect-related absorbance (e.g., the 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peak) reflected genuine heterogeneities in defect distribution or simply general changes in sample absorbance. In addition, the normalized versus raw absorbance values at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig. S5) result in a correlation factor (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;\u0026asymp;\u0026thinsp;0.70 for the entire dataset, slightly higher when evaluated separately by diamond) that demonstrates a degree of propagated error, indicating that part of the scatter observed in normalized plots might derive from this normalization uncertainty. This aspect is taken into consideration when interpreting trends in normalized scatter plots. Finally, maps of N\u003csub\u003esumq\u003c/sub\u003e values were also used to assess spectral quality according to Angellotti et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e) (Fig. S6).\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eSpectroscopic characterization of the investigated diamonds\u003c/h2\u003e \u003cp\u003eA summary of the acquired data for each diamond (e.g., maps, transects, spot analyses and grid sizes) is listed in Table S1. Table S2 reports the presence and relative intensities of the main H-related bands in each dataset acquired from the investigated diamonds with peak assignments based primarily on the extensive review by Day et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) and supported by previous experimental and theoretical studies (Davies et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). Diamonds \u003cem\u003eDIA4\u003c/em\u003e, \u003cem\u003eDIA5\u003c/em\u003e, and \u003cem\u003eLGM15\u003c/em\u003e show very similar spectral shapes (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea - d), whereas \u003cem\u003eLGM12\u003c/em\u003e displays little variations in the N region (~\u0026thinsp;1332\u0026thinsp;\u0026minus;\u0026thinsp;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), likely caused by a different aggregation state. All diamonds can be classified as type IaAB.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA distinct absorption at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is visible in the spectra collected from all diamonds (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea - d) that is indicative of the incorporation of H-related defects (Goss et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), a feature of VN\u003csub\u003e3\u003c/sub\u003eH (N\u003csub\u003e3\u003c/sub\u003eVH\u003csup\u003e0\u003c/sup\u003e) defects. This peak, attributed to C-H stretching vibrations (De Weerdt and Kupriyanov \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2002\u003c/span\u003e), is accompanied by the bending mode at ~\u0026thinsp;1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea - d), characteristic of VN\u003csub\u003e3\u003c/sub\u003eH defects (Goss et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), in all samples, although their intensity varies significantly with the position of the analytical point. The absorptions at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are listed for all acquisition types (i.e., map, line and spot) along with additional features such as those at 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea - d), 2786 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1560 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1540 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1430 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1420 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea - d). The 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e refers to VN\u003csub\u003e4\u003c/sub\u003eH defects. Weak bands at 2786 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, occasionally detected with low absorbance near the background level, correspond to the 2 x 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e overtone of the VN\u003csub\u003e3\u003c/sub\u003eH\u003csup\u003e0\u003c/sup\u003e defect (Goss et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eImportantly, since the intensity of 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is lower than the intensity of the general lattice absorption near 2158 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, none of the samples can be classified as H-rich diamonds (Fritsch and Scarratt \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1993\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe 2nd phonon region (2700\u0026thinsp;\u0026minus;\u0026thinsp;1800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) displays the IR absorption spectrum typical of diamond (Type IIa), consistent with the general C lattice vibrations (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea - d). A particularly distinctive feature is represented by the variable intensity of the band at ~\u0026thinsp;1365 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, often referred to as N\u003csub\u003eB\u0026minus;centers\u003c/sub\u003e (Sobolev et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e1969\u003c/span\u003e), that arises from extended planar defects-aggregates of C interstitials and N atoms known as platelets (Woods \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Goss et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea - d). The main absorption assigned to A-centers (N-N pairs) occurs at 1282 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and N concentrations can be determined from the absorption coefficient in this spectral region (Woods et al., \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). A distinct shoulder near 1175 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, attributed to B-centers (four N-vacancy aggregates) is also evident. These peaks are clearly visible, and their relative intensities indicate a lower contribution from B-centers in diamond \u003cem\u003eLGM12\u003c/em\u003e. A minor feature near 1332 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is also related to B-centers, while the band at 1096 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to common N-related absorptions (Fritsch et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Breeding and Shigley \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Green et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eN\u003csub\u003eCenter\u003c/sub\u003e distribution and mantle residence temperatures\u003c/h2\u003e \u003cp\u003eThe analysis of N concentration provides an overview of the distribution of \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA\u0026minus;center\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB\u0026minus;center\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e as well as the corresponding mantle \u003cem\u003eT\u003c/em\u003e\u003csub\u003e\u003cem\u003eres\u003c/em\u003e\u003c/sub\u003e (\u0026deg;C) and B% derived from N\u003csub\u003eB\u0026minus;center\u003c/sub\u003e divided for the N\u003csub\u003eTotal\u003c/sub\u003e concentrations as summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The mean \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e across the four diamonds is 137\u0026thinsp;\u0026plusmn;\u0026thinsp;60 ppm with average concentrations of 91\u0026thinsp;\u0026plusmn;\u0026thinsp;38 ppm for \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA\u0026minus;center\u003c/em\u003e\u003c/sub\u003e and 41\u0026thinsp;\u0026plusmn;\u0026thinsp;32 ppm for \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB\u0026minus;center\u003c/em\u003e\u003c/sub\u003e. In detail, \u003cem\u003eLGM15\u003c/em\u003e contains the highest \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e concentration (330\u0026thinsp;\u0026plusmn;\u0026thinsp;101 ppm), whereas \u003cem\u003eLGM12\u003c/em\u003e exhibits the lowest \u003cem\u003eB%\u003c/em\u003e (8\u0026thinsp;\u0026plusmn;\u0026thinsp;4%), compared with ~\u0026thinsp;35\u0026ndash;51% (\u0026plusmn;\u0026thinsp;10%) in the other investigated diamonds. Estimated T\u003csub\u003eres\u003c/sub\u003e range from 1112 to 1180\u0026deg;C (\u0026plusmn;\u0026thinsp;13\u0026ndash;14\u0026deg;C), which is in agreement with Morana et al. (\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The standard deviations of the N-related parameters are consistent with those reported in previous studies (Howell et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2012a\u003c/span\u003e; Kohn et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Afanasiev et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Angellotti et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e). \u003cem\u003eLGM12\u003c/em\u003e is the only diamond among those studied here with a \u003cem\u003eB%\u003c/em\u003e below 35% as inferred by its distinct \u003cem\u003eB\u003c/em\u003e-defect spectral features (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec). The other three diamonds display broadly homogeneous \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA\u0026minus;center\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB\u0026minus;center\u003c/em\u003e\u003c/sub\u003e distributions and, therefore, \u003cem\u003eB%\u003c/em\u003e. \u003cem\u003eDIA4\u003c/em\u003e and \u003cem\u003eLGM15\u003c/em\u003e, in particular, exhibit closely comparable general N-defect aggregation state (51\u0026thinsp;\u0026plusmn;\u0026thinsp;10% and 50\u0026thinsp;\u0026plusmn;\u0026thinsp;2%). Nevertheless, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, diamonds sourced from the same locality (e.g., \u003cem\u003eDIA4\u003c/em\u003e and \u003cem\u003eDIA5\u003c/em\u003e or \u003cem\u003eLGM12\u003c/em\u003e and \u003cem\u003eLGM15\u003c/em\u003e) can exhibit significant differences in both N abundance and aggregation state, yet remain within the most representative classes on the global scale (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea-b).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of N centers and estimated temperature.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u003csub\u003eA\u0026minus;center\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u003csub\u003eB\u0026minus;center\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u003csub\u003eTot\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eB%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eT (\u0026deg;C)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDIA4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e58 (30)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e57 (36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e122 (63)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e51 (10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1180 (14)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDIA5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e90 (34)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50 (24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e144 (53)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e35 (10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1155 (12)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLGM12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e104 (39)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e114 (45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8 (4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1112 (14)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLGM15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e169 (50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e159 (56)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e330 (101)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e50 (2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1149 (8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u003cem\u003e*Statistics are calculated on the central 85% of the data observations, excluding data tails to provide robust averages.\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eN and H distribution at the mineral inclusion - diamond interface\u003c/h3\u003e\n\u003cp\u003eInfrared maps of the distribution and concentration of N and H were collected over areas that included or surrounded inclusions to evaluate potential interplay. Figures\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e present two representative cases, and the remaining datasets are provided in Figures S7-S13 of the Supplementary Materials. These nine panels show a) the optical micrograph of the analyzed area along with the spatial distributions of b) \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA\u0026minus;center\u003c/em\u003e\u003c/sub\u003e, c) \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB\u0026minus;center\u003c/em\u003e\u003c/sub\u003e, d) \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e, e) the calculated T (\u0026deg;C), f) the \u003cem\u003eB%\u003c/em\u003e and the absorbance maps of the H-related peaks like g) 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, h) 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and i) 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. \u003cem\u003eDIA5 Map2\u003c/em\u003e in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e is characterized by the presence of a large inclusion (~\u0026thinsp;150 \u0026times; 100 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e) of covellite identified by Raman spectroscopy (Fig. S14a), while \u003cem\u003eLGM12 Map2\u003c/em\u003e in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e includes a smaller (~\u0026thinsp;20 \u0026times; 20 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e) inclusion of graphite easily identifiable by eye. The highest H and N absorbance signals follow the inclusion boundary and partially extend beyond the inclusion area, indicating a correlation with higher absorbance along the possible interface regions. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb shows higher concentrations of \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA\u0026minus;center\u003c/em\u003e\u003c/sub\u003e (100\u0026ndash;120 ppm) and \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eB\u0026minus;center\u003c/em\u003e\u003c/sub\u003e (45\u0026ndash;60 ppm) in the area overlapping the rim of sulfide inclusion than in the proximity of the rim, as reported in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec (40\u0026ndash;60 ppm and 10\u0026ndash;20 ppm, respectively). The lower-central portion of the map (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed) corresponds to a region directly over a thicker section of the inclusion resulting in lower \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e (40 ppm), which is more likely due to an artifact of spectral attenuation rather than true depletion. Despite this, the spectra were not masked, as the data remained of high quality. Figures\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ee and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ef do not exhibit significant variations of \u003cem\u003eT\u003c/em\u003e and \u003cem\u003eB%\u003c/em\u003e at the map scale except for the isolated outliers attributable to local spectral saturation effects rather than to genuine features of the chemical distribution. Hydrogen-related defects in \u003cem\u003eDIA5 Map 2\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eg - i) show significant increases in absorbance, with the 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peak height varying from 0.02\u0026ndash;0.06 to 0.14\u0026ndash;0.18. Similar, though less intense, variations are observed for the 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peaks.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eLGM12 Map2\u003c/em\u003e reveals a different relationship between the H-related defects and N. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb - d, N is lower near the defect, with \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e content of 60\u0026ndash;80 ppm and 110\u0026ndash;130 ppm in graphite-free regions. The calculated \u003cem\u003eT\u003c/em\u003e and \u003cem\u003eB%\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ee and f) closely follow these trends. Hydrogen-related defects (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eg - i) exhibit markedly higher absorbance over the inclusion and along its oblong outline. Peak heights at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range from 0.06 to 0.08 over the inclusion, compared with 0.01 to 0.03 in the surrounding diamond. A comparable trend is observed at 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. By contrast, the 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e band is generally weak or absent in the \u003cem\u003eLGM12 Map2\u003c/em\u003e area, making it unsuitable for any significant spatial trend in this sample.\u003c/p\u003e \u003cp\u003eSimilar relationships, in which H and N concentrations correlate with the presence of sulfide inclusions or with silicate inclusions such as garnets, are also observed in additional maps reported in the Supplementary Materials and summarized below. In \u003cem\u003eDIA4 Map1\u003c/em\u003e (Fig. S7a), analysed in the vicinity of an aggregate of covellite and chalcopyrite (~\u0026thinsp;150 \u0026times; 150 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e; Fig. S14b), N concentrations increase sharply along the inclusion, with N\u003csub\u003eTotal\u003c/sub\u003e rising from ~\u0026thinsp;50 to ~\u0026thinsp;250 ppm (Fig. S7b - d). Calculated \u003cem\u003eT\u003c/em\u003e and \u003cem\u003eB%\u003c/em\u003e (Fig. S7e - f) display a consistent pattern with spectra collected directly over the inclusion, yielding lower T estimates (1110\u0026ndash;1130\u0026deg;C), whereas inclusion-free regions show higher values (1170\u0026ndash;1190\u0026deg;C). This behavior reflects the corresponding variation in \u003cem\u003eB%\u003c/em\u003e, which is very low (10\u0026ndash;20%) within the inclusion area and increases to 40\u0026ndash;50% in the surrounding diamond. Hydrogen-related defects (Fig. S7g - i) show a parallel trend to N with the 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e absorbance increasing from 0.02\u0026ndash;0.03 to 0.05\u0026ndash;0.06 along the inclusion, accompanied by similar rises in the 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e bands, implying a coupled N-H enrichment associated with sulfide.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eDIA4 Map2\u003c/em\u003e (Fig. S8a) is, instead, characterized by the presence of a small garnet inclusion (~\u0026thinsp;50 \u0026times; 50 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e) and widespread graphite (Fig. S14c). Nitrogen contents, together with the calculated \u003cem\u003eT\u003c/em\u003e and \u003cem\u003eB%\u003c/em\u003e (Fig. S 8b - f), do not exhibit a consistent spatial trend related to the inclusion or to the distribution of graphite. The H-related defects (Fig. S8g - i) increase in the lower part of the map where both garnet and graphite inclusions are present. The overlapping effects arising from the spatial proximity of graphite and garnet inclusions make it difficult to disentangle individual contributions. \u003cem\u003eUDA5 Map1\u003c/em\u003e (Fig. S9a) also exhibits complex patterns due to pronounced graphitization and the inclusion of covellite (150 \u0026times; 150 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e), as already described in \u003cem\u003eUDA5 Map2\u003c/em\u003e. Here, \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e concentrations (Fig. S9b - d) are high (300\u0026ndash;400 ppm) relative to areas where inclusions occur (50\u0026ndash;150 ppm). No general trend is observed for \u003cem\u003eT\u003c/em\u003e or \u003cem\u003eB%\u003c/em\u003e, whose distributions appear quite homogeneous (Fig. S9e - f). Hydrogen-related defects show slightly higher absorbance in graphite-rich rather than graphite-free regions (0.15\u0026thinsp;\u0026minus;\u0026thinsp;0.13 against 0.10\u0026ndash;0.11). In \u003cem\u003eLGM12 Map1\u003c/em\u003e (Fig. S10a), N and H-related defects increase and are observed in the region surrounding an inclusion (~\u0026thinsp;50 \u0026times; 50 \u0026micro;m\u0026sup2;) of sulfide as inferred by the metallic luster. \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e (Fig. S10b - d) shows a moderate increase near the inclusion, rising from 100\u0026ndash;200 ppm in the surrounding diamond to 300\u0026ndash;350 ppm over the inclusion. In contrast, \u003cem\u003eB%\u003c/em\u003e and \u003cem\u003eT\u003c/em\u003e (Fig. S10e - f) do not display any discernible spatial trends and appear relatively uniform across the entire map. The H-related defects (Fig. S10g - i) exhibit greater absorbance in the presence of the inclusion. The 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e band increases from 0.08\u0026ndash;0.15 in inclusion-free areas to 0.20\u0026ndash;0.25 in correspondence with the inclusion, accompanied by similar increases in the 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e band and, where detectable, by a corresponding increase in the 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e band.\u003c/p\u003e \u003cp\u003eThe results described above are strengthened by the acquisition of two additional maps in regions free of inclusion. The first map is \u003cem\u003eDIA5 Map 3\u003c/em\u003e (Fig. S11a) chosen since this is a diamond where various localized graphitization occurs. An area with no visible graphite was mapped to evaluate whether graphitization influenced the defect distribution. In this region, N concentrations are consistently 220\u0026ndash;240 ppm across the map, except along the upper and lower margins (Fig. S11b - d). \u003cem\u003eT\u003c/em\u003e and \u003cem\u003eB%\u003c/em\u003e (Fig. S11e and f) show no spatial trend and broadly match the uniform N distribution. Hydrogen absorption is very low (Fig. S11g - i) with 3107 cm\u003csup\u003e-1\u003c/sup\u003e peak heights not exceeding\u0026thinsp;~\u0026thinsp;0.03. This contrasts with what was described for \u003cem\u003eDIA5 Map2\u003c/em\u003e where both sulfide and graphite appeared to exert control on the N and H defects distribution. The second quality-control mosaic was collected for \u003cem\u003eLGM15 Map1\u003c/em\u003e (Fig. S12a). This diamond is characterized by irregular morphology (Morana et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), and only a limited number of spectra were acquired; therefore, the dataset available for this sample is smaller than those from the other diamonds. The \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eTotal\u003c/em\u003e\u003c/sub\u003e values are generally 350\u0026thinsp;\u0026minus;\u0026thinsp;300 ppm (Fig. S12b - d), and both \u003cem\u003eT\u003c/em\u003e and \u003cem\u003eB%\u003c/em\u003e (Fig. S12e and f) show no clear spatial variability, mirroring the N distribution. Hydrogen absorbance is extremely low (Fig. S12g - i), with the 3107 cm\u003csup\u003e-1\u003c/sup\u003e band reaching a maximum of ~\u0026thinsp;0.03. As a result, any apparent trend in the H maps is likely driven by noise measurement rather than by real variations in H-defect, particularly in an area free of inclusions. For completeness, a separate analysis was performed on the platelet-related absorption peak \u003cem\u003eB\u0026prime;\u003c/em\u003e at 1365 cm\u003csup\u003e-1\u003c/sup\u003e (Fig. S13), and dedicated maps were generated to assess potential spatial correlations and similarities with the defect distribution. Interestingly, despite the marked \u003cem\u003eB\u0026prime;\u003c/em\u003e intensities and the significant variation observed in several of the most interesting maps, for instance \u003cem\u003eDIA5 Map1\u003c/em\u003e (absorbance varying from 0.625 to 0.425), \u003cem\u003eDIA5 Map2\u003c/em\u003e (absorbance varying from 0.375 to 0.175), and \u003cem\u003eLGM12 Map2\u003c/em\u003e (absorbance varying from 0.26 to 0.16), the resulting spatial patterns do not align with those documented previously for N or H-related defects suggesting, therefore, a different mechanism of distribution.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eChemical relation between diamond and inclusions\u003c/h2\u003e \u003cp\u003eGraphite is among the most common phases found as inclusions in natural diamonds, and its formation results from various processes, including epigenetic origin by T and P variations, deformation-induced mechanisms, or crystallization along with diamonds from a carbon-saturated fluid (Harris and Vance \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1972\u003c/span\u003e; Evans \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1979\u003c/span\u003e; Nechaev and Khokhryakov \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Mikhailenko et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Graphite typically appears as disks or rosettes surrounding mineral or fluid inclusions, or as centrally located hexagonal platelets oriented relative to the diamond lattice (Bulanova \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Nasdala et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). In diamonds from Marange, highly ordered graphite inclusions have been identified, without evidence of fracturing or graphitization halos in the surrounding diamond matrix, and they exhibit spatial correlations with CH\u003csub\u003e4\u003c/sub\u003e-rich fluid inclusions (Eaton-Magan\u0026agrave; et al., 2017; Smit et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Experimental studies conducted at high pressure and temperature confirmed that graphite and diamond can nucleate and grow simultaneously in carbon-saturated systems (Sokol and Palyanov \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Palyanov et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Moreover, graphitization can also occur during heating outside the diamond stability field, particularly during ascent (Korsakov et al. 2016). Sulfides are incorporated into diamond as high-temperature monosulfide solid solution and later exsolve into Fe-, Ni-, and Cu-rich end members during cooling associated with exhumation (Kullerud et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1969\u003c/span\u003e; Pamato et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Both of these inclusions are found in the four diamonds investigated here and, in the case of \u003cem\u003eLGM15\u003c/em\u003e, are described in detail by Morana et al. (\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). In this study, synchrotron-assisted micro-FTIR mapping reveals that areas containing graphite and sulfides inclusions consistently display stronger absorption at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e than inclusion-free regions of the same crystals suggesting that the 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e band is a potential tracer of C-H chemical interaction within the parental growth medium. Because graphite is known to incorporate low concentrations of hydrogen (Atsumi and Tauchi \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), their strong affinity can be explained by the formation of adsorbed or chemisorbed species (Zecho et al. \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Rougeau et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). The presence of circulating (aqueous) fluids can promote graphitization by catalyzing the process (Harris and Vance \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1972\u003c/span\u003e). For this reason, enrichments in the absorbances of the VN\u003csub\u003e3\u003c/sub\u003eH defect in the area characterized by graphite inclusions might be taken as proof of a fluid-mediated H-enrichment heterogeneously distributed in the diamond to reflect the spatial and temporal variation of the growth medium. Several reactions might be written to represent the chemical equilibrium between C and H at the time of diamond formation, such as,\u003c/p\u003e \u003cp\u003eCH\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;O\u003csub\u003e2\u003c/sub\u003e = C + 2H\u003csub\u003e2\u003c/sub\u003eO Eq.\u0026nbsp;1,\u003c/p\u003e \u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;C + 2H\u003csub\u003e2\u003c/sub\u003eO Eq.\u0026nbsp;2,\u003c/p\u003e \u003cp\u003eCH\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;C + 2H\u003csub\u003e2\u003c/sub\u003e Eq.\u0026nbsp;3,\u003c/p\u003e \u003cp\u003eIt can be seen that the precipitation of C to diamond via oxidizing/reducing agents such as O\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003e would favor the formation of H\u003csub\u003e2\u003c/sub\u003eO (Sokol et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). However, the formation of diamonds appears incompatible with H\u003csub\u003e2\u003c/sub\u003eO-saturated conditions in eclogitic environments (Stagno and Fei 2020; Stagno and Aulbach 2021). In contrast, methane-bearing fluids have been proposed as a source of diamonds through high-P/T experiments (Matjuschkin et al. 2020), via isotopic geochemistry (Thomassot et al. \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), and thermodynamically (Mikhailenko et al. 2020; Aulbach et al. 2022). Reaction Eq.\u0026nbsp;(3) would imply H formation and, hence, sequestration that can occur by elemental carbon itself, other than coexisting silicate minerals. Again, the finding of H, mostly hosted by trapped silicates (Curtolo et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), suggests that H in diamonds must have been inherited by the diamond growth medium itself, a mechanism that is consistent with the positive correlation between graphite and H reported in our study. Similarly, the affinity of H for sulfide has been demonstrated experimentally (Errea et al. 2015; Abeykoon et al. 2023) and recently reported in sulfides of meteorite samples (Barrett et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) as result of fast diffusion-driven processes. In addition, under mantle \u003cem\u003ef\u003c/em\u003eo\u003csub\u003e2\u003c/sub\u003e conditions at which diamonds form from methane, N would also be stable in several forms, such as NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e and N\u003csup\u003e3\u0026minus;\u003c/sup\u003e, or even in Fe-nitride (Li \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), supporting possible mechanisms of incorporation into sulfides. Our IR maps suggest that either N or H is incorporated into sulfides, and quantification of these species might provide useful insights into the chemical composition of the parental fluid growth medium (Thomassot et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). In fact, water is an important component that lowers the temperature of diamond crystallization by 200\u0026ndash;300\u0026deg;C (Wang et al. \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). On the other hand, possible post-entrapment mechanisms of diffusion from the diamond matrix to the sulfides cannot be ruled out. This relationship is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e, where the z-axis represents the absorbance intensity at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Elevated regions (i.e., high z-axis) spatially coincide with disk-like graphite inclusions and large sulfide inclusions, respectively. The highest absorbance occurs directly above the inclusion zones, gradually decreasing with distance, consistent with localized hydrogen diffusion or with hydrogen being trapped along residual fluid films at the inclusion-diamond interface (Harris and Vance \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1972\u003c/span\u003e). In particular, in \u003cem\u003eLGM12 Map2 (\u003c/em\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e), the 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peak absorbance decreases almost radially away from the inclusion, reflecting the small size of the graphite inclusions and the efficient spatial H diffusion. In contrast, in \u003cem\u003eUDA5 Map2\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e), the main sulfide inclusion is 150 \u0026micro;m across, preventing clear detection of gradients in the surrounding area. The variability of the absorbance intensity observed across the inclusion zone would reflect the (polycrystalline) morphology of the inclusion, due to destabilization of the monosulfide solid solution (Pamato et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Morana et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Even if the two maps represent distinct diamond-forming environments, it is possible to observe a general trend in which higher 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e absorbances occur where inclusions are present. Comparable relationships have been noted for Mg-chromite inclusion in P-type diamonds by Angellotti et al. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2025b\u003c/span\u003e), who reported a correlation between the 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e absorption and \u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003eA\u0026minus;center\u003c/em\u003e\u003c/sub\u003e and explained it as due to stress-assisted diffusion or fluid-mediated H enrichment.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIt is largely established that H interacts with nitrogen-vacancy centers to form stable complexes such as NVH, N\u003csub\u003e3\u003c/sub\u003eVH, and N\u003csub\u003e4\u003c/sub\u003eVH (Day et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Hydrogen-related defects are also identified by IR-active C-H stretching and bending modes (Kaminsky et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), with typical absorptions at ~\u0026thinsp;3107 and ~\u0026thinsp;1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attributed to the VN\u003csub\u003e3\u003c/sub\u003eH (or N\u003csub\u003e3\u003c/sub\u003eVH\u003csup\u003e0\u003c/sup\u003e) defect (Fritsch et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Goss et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea-b shows an interesting correlation between the 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e bands, as well as the effect of distance from the inclusion. In Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea (\u003cem\u003eLGM12 Map2\u003c/em\u003e), points near the graphite inclusion exhibit an enriched trend with significantly higher absorbance values, whereas more distal regions exhibit a deficient trend, serving as the background. Notably, these observed trends suggest that the IR sensitivity for detecting H distribution in response to environmental variations is achieved within areas as small as 10 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e. A similar pattern is observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003eb for \u003cem\u003eUDA5 Map2\u003c/em\u003e, where only an enriched-type trend is present. Once again, spectra collected near or directly on the inclusion show systematically higher absorbance than those measured far away, confirming the inclusion\u0026rsquo;s influence on the local hydrogen-related defect concentration. Noteworthy, local stress and strain around inclusions could also contribute to H-defect enrichment (Kanda and Watanabe \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). However, the consistent correlations observed across different maps and the spatial correspondence with enrichments and inclusions indicate that H-rich fluids could be the dominant control factor, whereas stress-driven processes could be secondary enhancers.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eHigh-resolution synchrotron micro-FTIR mapping was used to investigate the spatial distribution of nitrogen- and hydrogen-related lattice defects in four eclogitic diamonds from the Udachnaya kimberlite, with particular focus on their relationship to mineral inclusions. The results demonstrate that hydrogen-related infrared absorption bands, most notably those at ~\u0026thinsp;3107 and ~\u0026thinsp;1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attributed to VN3H defects, show systematic spatial enrichments in proximity to graphite and sulfide inclusions. These enrichments commonly extend over distances of several to tens of micrometers from the inclusion\u0026ndash;diamond interface, whereas inclusion-free regions within the same crystals display comparatively homogeneous and low hydrogen-related absorbance.\u003c/p\u003e \u003cp\u003eNitrogen systematics exhibit more variable behavior. Sulfide inclusions are frequently associated with locally elevated concentrations of both N and H, whereas graphite inclusions are characterized primarily by H enrichment with weaker, absent, or locally negative correlations with nitrogen concentration and aggregation state. Garnet inclusions show less systematic effects, suggesting that the influence of inclusions on lattice-bound impurities depends on both mineral chemistry and local growth or post-growth conditions.\u003c/p\u003e \u003cp\u003eThe spatial coincidence between inclusions and enhanced H-related absorbance indicates that mineral inclusions represent zones of localized perturbation in the diamond lattice, capable of influencing the distribution and stabilization of H-bearing defects. These perturbations may reflect interaction with residual growth media, localized fluid films, or enhanced diffusion and trapping of H in the vicinity of inclusions. While the present data clearly document spatial correlations, they do not uniquely discriminate between chemical control by the parental fluid, stress- or strain-assisted defect stabilization, or a combination of both processes.\u003c/p\u003e \u003cp\u003eImportantly, H-related defects appear to be more sensitive tracers of such localized perturbations than N aggregation state or calculated mantle residence temperatures, which remain largely homogeneous at the scale of the FTIR maps. This highlights the utility of micro-scale H defect mapping as a complementary tool to conventional N-based thermo-chronometry in assessing diamond growth environments and post-growth modification.\u003c/p\u003e \u003cp\u003eAlthough based on a limited number of samples from a single locality, the investigated diamonds span N concentrations and aggregation states that are representative of global eclogitic diamond populations. The phenomena documented here therefore may not be unique to Udachnaya diamonds, but broader applicability will require investigation of additional samples from diverse cratonic settings and parageneses.\u003c/p\u003e \u003cp\u003eOverall, this study demonstrates that mineral inclusions can be associated with localized heterogeneities in hydrogen- and, in some cases, nitrogen-related lattice defects in natural diamonds. These observations provide new constraints on the micro-scale complexity of diamond formation and modification processes and underscore the need to integrate high-resolution spectroscopic mapping with independent geochemical and structural constraints to fully resolve the mechanisms governing impurity incorporation in diamond.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge Diamond Light Source for funding the experiment proposal SM35052.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA. Angellotti:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; original draft, Software, Investigation, Formal analysis, Data curation, Conceptualization. \u003cstrong\u003eL. Barni:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; original draft, Formal analysis, Data curation, Investigation. \u003cstrong\u003eM. Morana:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing, Investigation. \u003cstrong\u003eG. Cinque:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing, Validation, Methodology, Software, Investigation. \u003cstrong\u003eY. Lu:\u0026nbsp;\u003c/strong\u003eInvestigation. \u003cstrong\u003eR. Tao:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing, Investigation. \u003cstrong\u003eG. Marras:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing. \u003cstrong\u003eA. Logvinova:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing, Resources. \u003cstrong\u003eL. Bindi:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing, Formal analysis, Resources. \u003cstrong\u003eD. Mikhailenko:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing, Validation, Resources. \u003cstrong\u003eV. Stagno:\u0026nbsp;\u003c/strong\u003eWriting \u0026ndash; review \u0026amp; editing, Supervision, Resources, Investigation, Formal analysis, Data curation, Conceptualization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVS acknowledges financial support from the HERMES project (PRIN 2022, grant no. 2022R35\u0026times;8Z). A.L. acknowledges financial support of the CAS PIFI project n. 2025PVA0073. D.S. acknowledges financial support of IGG UB RAS (124020400013-1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no competing interests to declare that are relevant to the content of this article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAfanasiev V, Ugapeva S, Babich Y, Sonin V, Logvinova A, Yelisseyev A, Ivanova O (2022) Growth Story of One Diamond: A Window to the Lithospheric Mantle. Minerals 12(8):1048\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAngel RJ, Alvaro M, Nestola F, Mazzucchelli ML (2015) Diamond thermoelastic properties and implications for determining the pressure of formation of diamond- inclusion systems. 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J Chem Phys 117(18):8486\u0026ndash;8492\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Sapienza University of Rome","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"diamond, eclogite, redox, IR mapping, methane, sulfides","lastPublishedDoi":"10.21203/rs.3.rs-9020643/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9020643/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDiamonds in nature are known to have formed by redox-assisted precipitation of carbon from oxidized fluids containing also hydrogen and nitrogen, both of which are hosted in the diamond lattice. Minerals entrapped during the growth of diamonds might have played a role in nitrogen and hydrogen incorporation and abundance although, so far, no evidence has been reported. We used synchrotron micro-FTIR mapping to investigate the interplay between the distribution of nitrogen and hydrogen and mineral inclusions (graphite, sulfide and garnet) in four eclogitic diamonds from the Yakutian kimberlite field, Siberian craton. Combined mapping of nitrogen and hydrogen-related infrared bands reveals heterogeneities near minerals. In particular, a marked absorbance of N- and H-related peaks observed in correspondence with sulfide inclusions supports their incorporation in the host mineral, while near graphite and garnet inclusions, only the H peak absorbance of peaks at 3107 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1405 cm\u003csup\u003e\u0026minus;\u0026thinsp;1,\u003c/sup\u003e and 3236 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e increases. These zones can extend to tens of micrometers from the inclusion-diamond interfaces and provide insight into the potential control that entrapped minerals exert on the distribution and abundance of N and H in the diamond lattice during and after its formation at mantle depths.\u003c/p\u003e","manuscriptTitle":"Interplay between the distribution of nitrogen and hydrogen and mineral inclusions in E-type diamonds from Yakutia, Siberian craton","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-04 05:10:04","doi":"10.21203/rs.3.rs-9020643/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9089b43e-d796-4880-aa09-037e1293a780","owner":[],"postedDate":"March 4th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-04T05:10:04+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-04 05:10:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9020643","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9020643","identity":"rs-9020643","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}