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Hydrothermal Alteration of the Ocean Crust and Patterns in Mineralization With Depth as Measured by Micro-Imaging Infrared Spectroscopy

Greenberger, Rebecca N. and Harris, Michelle and Ehlmann, Bethany L. and Crotteau, Molly A. and Kelemen, Peter B. and Manning, Craig E. and Teagle, Damon A. H. (2021) Hydrothermal Alteration of the Ocean Crust and Patterns in Mineralization With Depth as Measured by Micro-Imaging Infrared Spectroscopy. Journal of Geophysical Research. Solid Earth, 126 (8). Art. No. e2021JB021976. ISSN 2169-9313. doi:10.1029/2021jb021976.

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Processes for formation, cooling, and altering Earth's ocean crust are not yet completely understood due to challenges in access and sampling. Here, we use contiguous micro-imaging infrared spectroscopy to develop complete-core maps of mineral occurrence and investigate spatial patterns in the hydrothermal alteration of 1.2 km of oceanic crust recovered from Oman Drilling Project Holes GT1A, GT2A, and GT3A drilled in the Samail Ophiolite, Oman. The imaging spectrometer shortwave infrared sensor measured reflectance of light at wavelengths 1.0–2.6 μm at 250–260 μm/pixel, resulting in >1 billion independent measurements. We map distributions of nine key primary and secondary minerals/mineral groups—clinopyroxene, amphibole, calcite, chlorite, epidote, gypsum, kaolinite/montmorillonite, prehnite, and zeolite—and find differences in their spatial occurrences and pervasiveness. Accuracy of spectral mapping of occurrence is 68%–100%, established using X-ray diffraction measurements from the core description. The sheeted dikes and gabbros of upper oceanic crust Hole GT3A show more pervasive alteration and alteration dominated by chlorite, amphibole, and epidote. The foliated/layered gabbros of GT2A from intermediate crustal depths have similarly widespread chlorite but more zeolite and little amphibole and epidote. The layered gabbros of the lower oceanic crust (GT1A) have remnant pyroxene and 2X less chlorite, but alteration is extensive within and surrounding major fault zones with widespread occurrences of amphibole. The results indicate greater distribution of higher temperature alteration minerals in the upper oceanic crust relative to deeper gabbros and highlight the importance of fault zones in hydrothermal convection in the lower ocean crust.

Item Type:Article
Related URLs:
URLURL TypeDescription
Greenberger, Rebecca N.0000-0003-1583-0261
Harris, Michelle0000-0001-9618-2862
Ehlmann, Bethany L.0000-0002-2745-3240
Crotteau, Molly A.0000-0001-7888-0093
Kelemen, Peter B.0000-0003-4757-0855
Manning, Craig E.0000-0002-1463-3701
Teagle, Damon A. H.0000-0002-4416-8409
Additional Information:© 2021. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Issue Online: 24 August 2021; Version of Record online: 24 August 2021; Accepted manuscript online: 15 July 2021; Manuscript accepted: 11 July 2021; Manuscript revised: 24 June 2021; Manuscript received: 28 February 2021. The authors gratefully acknowledge use of samples and data provided by the ICDP Oman Drilling Project. The Oman Drilling Project has been possible through co-mingled funds from the International Continental Scientific Drilling Project (ICDP; Kelemen, Matter, Teagle Lead PIs), the Sloan Foundation – Deep Carbon Observatory (Grant 2014-3-01, Kelemen PI), the National Science Foundation (NSF-EAR-1516300, Kelemen lead PI), NASA—Astrobiology Institute (NNA15BB02A, Templeton PI), the German Research Foundation (DFG: KO 1723/21-1, Koepke PI), the Japanese Society for the Promotion of Science (JSPS no:16H06347, Michibayashi PI; and KAKENHI 16H02742, Takazawa PI), the European Research Council (Adv: no.669972; Jamveit PI), the Swiss National Science Foundation (SNF:20FI21_163073, Früh-Green PI), JAMSTEC, the TAMU-JR Science Operator, and contributions from the Sultanate of Oman Ministry of Regional Municipalities and Water Resources, the Oman Public Authority of Mining, Sultan Qaboos University, CRNS-Univ. Montpellier II, Columbia University of New York, and the University of Southampton. BLE thanks a grant from the Rose Hills Foundation for supporting acquisition of the imaging spectroscopy data. MAC thanks a George R. Rossman SURF fellowship for stipend support. The authors also thank the technicians on the JAMSTEC drilling vessel Chikyu for enabling the imaging spectroscopy measurements and the ChikyuOman2017 core description teams whose visual and laboratory analyses of the core were critical for validation of the imaging spectroscopy data. Finally, the authors are grateful for the helpful and constructive comments by Reviewers Wolfgang Bach and Andrew McCaig, the Associate Editor, and Editor Mark Dekkers. Data Availability Statement: All XRD measurements were published in Kelemen et al. (2020), and data are available from ICDP. Thin sections shown here were produced as part of Kelemen et al. (2020) and descriptions are available there. No new samples were analyzed in this work beyond the 1.2 km of OmanDP core, and samples can be requested through ICDP. The imaging spectroscopy data set are available through CaltechDATA: (Greenberger, Ehlmann, & the Oman Drilling Project Science Party, 2021). Mineral occurrence maps (Files S2–S4) are part of the supplement of this study but are available through CaltechDATA due to their large size:
Funding AgencyGrant Number
International Continental Scientific Drilling ProjectUNSPECIFIED
Alfred P. Sloan Foundation2014-3-01
Deutsche Forschungsgemeinschaft (DFG)KO 1723/21-1
Japan Society for the Promotion of Science (JSPS)16H06347
Japan Society for the Promotion of Science (JSPS)16H02742
European Research Council (ERC)669972
Swiss National Science Foundation (SNSF)20FI21_163073
Japan Agency for Marine-Earth Science and Technology (JAMSTEC)UNSPECIFIED
Texas A&M UniversityUNSPECIFIED
Oman Ministry of Regional Municipalities and Water ResourcesUNSPECIFIED
Oman Public Authority of MiningUNSPECIFIED
Sultan Qaboos UniversityUNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Universidad de Montpellier 2UNSPECIFIED
Columbia UniversityUNSPECIFIED
University of SouthamptonUNSPECIFIED
Rose Hills FoundationUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords:imaging spectroscopy; hyperspectral imaging; Oman drilling project; oceanic crust; hydrothermal alteration; infrared spectroscopy
Issue or Number:8
Record Number:CaltechAUTHORS:20210729-172352683
Persistent URL:
Official Citation:Greenberger, R. N., Harris, M., Ehlmann, B. L., Crotteau, M. A., Kelemen, P. B., Manning, C. E., et al. (2021). Hydrothermal alteration of the ocean crust and patterns in mineralization with depth as measured by micro-imaging infrared spectroscopy. Journal of Geophysical Research: Solid Earth, 126, e2021JB021976.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110069
Deposited By: Tony Diaz
Deposited On:02 Aug 2021 18:48
Last Modified:31 Aug 2021 20:12

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