Ancient Anorthosites on Mars: Widespread in the Lower Crust

Ancient Anorthosites on Mars: Widespread in the Lower Crust | 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 Article Ancient Anorthosites on Mars: Widespread in the Lower Crust Michael Phillips, Christina Viviano, A. Deanne Rogers, Linae Larson, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6823461/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 22 Nov, 2025 Read the published version in Communications Earth & Environment → Version 1 posted You are reading this latest preprint version Abstract We report extensive detections of feldspathic, likely anorthositic, lithologies within outcrops uplifted by the Argyre basin-forming impact on Mars. The radial position of feldspathic outcrops from the basin center indicates that they are stratigraphically above olivine-bearing material and below low-calcium pyroxene-bearing rocks, and the inferred depths suggest that feldspathic lithologies are present in the lower martian crust in the circum-Argyre region. This stratigraphy bears striking resemblance to that observed at the Hellas basin rim and indicates that feldspathic rocks could be a pervasive component of the lower crust across the entire southern highlands of Mars. These results are consistent with evidence from geophysical data suggesting a lower-density lower crust, but likely not sufficient to fully account for the discrepancy in density. Importantly, these feldspathic rocks are present alongside pyroxene- and olivine-bearing units, a suite of compositions commonly associated with layered mafic intrusions (LMI). We suggest that a process early in Mars' history produced large volumes of melt that cooled slowly to form LMI-like complexes and that these complexes represent an aspect of primary martian crust. The melt-producing process ostensibly affected the whole southern hemisphere, and possibly the globe. These observations offer direct evidence to support and refine existing models of early crust formation, addressing key questions regarding crustal density variations and formation mechanisms that have previously lacked widespread observational constraints. Earth and environmental sciences/Planetary science/Mineralogy Earth and environmental sciences/Planetary science/Petrology Full Text Additional Declarations There is NO Competing Interest. Supplementary Files EDTable1categorizedsummary.csv Extended Data Table 1 EDTable2themiscategorycounts.csv Extended Data Table 2 EDTable3GeologicUnits.xlsx Extended Data Table 3 extendeddata.pdf Extended Data Figures Cite Share Download PDF Status: Published Journal Publication published 22 Nov, 2025 Read the published version in Communications Earth & Environment → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6823461","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":468549294,"identity":"abcaa7f0-fb82-4326-a154-ce7a34eaa03b","order_by":0,"name":"Michael Phillips","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5UlEQVRIiWNgGAWjYDACCcbGAw8MgAz2BgaGBJggAS0NBxJAWngOEK2FgeEAWKVEAoogbmAu3Qy0peCOve7Mx88+PPhjk8ffwHzwNg8eLZZzDoIc9ixx2+004xkJPGnFEgfYkq3xaTG4kQjScjjB7HaCMUOCxGEgl8dMmhgt9mY3j39mADIS5x/g/0aUFsZtN3iAtiQcTtxwgIcNrxbLGYlQv5zJKWZIOJCWuPEwm7HlHDxazCXSHz748OeOvdnx45sZf/yxSZx3vPnhjTf4HAahDiAJMeNRjkPLKBgFo2AUjAI0AADsfljDkBb9dQAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-8873-2238","institution":"The University of Arizona","correspondingAuthor":true,"prefix":"","firstName":"Michael","middleName":"","lastName":"Phillips","suffix":""},{"id":468549295,"identity":"81a31a69-6a70-4d00-b2ca-234e8b0db01b","order_by":1,"name":"Christina Viviano","email":"","orcid":"https://orcid.org/0000-0003-1601-2105","institution":"Johns Hopkins University Applied Physics Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Christina","middleName":"","lastName":"Viviano","suffix":""},{"id":468549296,"identity":"6c878122-0ed5-466a-b820-25805e411cff","order_by":2,"name":"A. 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