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

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...

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Veröffentlicht in:Journal of geophysical research. Solid earth 2021-08, Vol.126 (8), p.e2021JB021976-n/a
Hauptverfasser: Greenberger, Rebecca N., Harris, Michelle, Ehlmann, Bethany L., Crotteau, Molly A., Kelemen, Peter B., Manning, Craig E., Teagle, Damon A. H.
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container_end_page n/a
container_issue 8
container_start_page e2021JB021976
container_title Journal of geophysical research. Solid earth
container_volume 126
creator Greenberger, Rebecca N.
Harris, Michelle
Ehlmann, Bethany L.
Crotteau, Molly A.
Kelemen, Peter B.
Manning, Craig E.
Teagle, Damon A. H.
description 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. Plain Language Summary The oceanic crust, the rock from the ocean floor to the mantle, forms much of Earth's solid crust, yet it is difficult to access, drill into, or collect samples from. This kilometers‐thick crust forms from cooling of molten rock, but we do not entirely understand how it forms, cools, and changes by chemical reactions with water. Ophiolites are places where rock from the ocean crust and uppermost portion of the mantle have been pushed upward and exposed on continents. One such location is in Oman, where the Oman Drilling Project drilled into continuous sections of ocean crust. We measured this drill core with imaging spectroscopy, a technique where we measure how infrared light at hundreds of wa
doi_str_mv 10.1029/2021JB021976
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H.</creator><creatorcontrib>Greenberger, Rebecca N. ; Harris, Michelle ; Ehlmann, Bethany L. ; Crotteau, Molly A. ; Kelemen, Peter B. ; Manning, Craig E. ; Teagle, Damon A. H. ; Oman Drilling Project Science Team ; the Oman Drilling Project Science Team</creatorcontrib><description>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 &gt;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. Plain Language Summary The oceanic crust, the rock from the ocean floor to the mantle, forms much of Earth's solid crust, yet it is difficult to access, drill into, or collect samples from. This kilometers‐thick crust forms from cooling of molten rock, but we do not entirely understand how it forms, cools, and changes by chemical reactions with water. Ophiolites are places where rock from the ocean crust and uppermost portion of the mantle have been pushed upward and exposed on continents. One such location is in Oman, where the Oman Drilling Project drilled into continuous sections of ocean crust. We measured this drill core with imaging spectroscopy, a technique where we measure how infrared light at hundreds of wavelengths reflects off the rock. We use the characteristic infrared fingerprints of minerals to map them at sub‐millimeter scale, producing over one billion measurements. We find that much of the rocks closer to the ocean reacted with water at high temperatures to form new minerals. Some rocks deep within the ocean crust also interacted with large volumes of water, but intense fluid flow was concentrated in fractures and smaller areas, leaving less reacted rock. Key Points Imaging spectroscopy efficiently and effectively mapped spatial patterns in hydrothermal alteration mineral occurrence in ocean crust core Samail ophiolite upper ocean crust cores are dominated by chlorite, amphibole, and epidote, while deeper cores have more zeolite/prehnite Hydrothermal alteration largely decreases with depth in the ocean crust but is locally intense in major fault zones, even in lower crust</description><identifier>ISSN: 2169-9313</identifier><identifier>EISSN: 2169-9356</identifier><identifier>DOI: 10.1029/2021JB021976</identifier><identifier>PMID: 34595085</identifier><language>eng</language><publisher>United States: Blackwell Publishing Ltd</publisher><subject>Access ; Amphiboles ; Analytical methods ; Biogeosciences ; Calcite ; Chemical reactions ; Chlorite ; Composition of the Oceanic Crust ; Cooling ; Coring ; Dikes ; Drilling ; Drills ; Earth crust ; Earth mantle ; Embankments ; Fault zones ; Fluid dynamics ; Fluid flow ; Fractures ; Gabbros ; General or Miscellaneous ; Geochemistry ; Geological faults ; Gypsum ; High temperature ; Hydrothermal alteration ; Hydrothermal Systems ; hyperspectral imaging ; imaging spectroscopy ; Infrared detectors ; Infrared spectrometers ; Infrared spectroscopy ; Instruments Useful in Three or More Fields ; Kaolinite ; Lava ; Marine Geology and Geophysics ; Mineral Physics ; Mineralization ; Mineralogy and Petrology ; Minerals ; Montmorillonite ; Montmorillonites ; Ocean floor ; Oceanic convection ; Oceanic crust ; Oceanography: Biological and Chemical ; Oceans ; Oman drilling project ; Ophiolites ; Ophiolites and Oceanic Lithosphere, with a focus on the Samail ophiolite in Oman ; Optical, infrared, and Raman spectroscopy ; Reflectance ; Rock ; Rocks ; Short wave radiation ; Spectroscopic analysis ; Spectrum analysis ; Tectonophysics ; Volcanology ; Wavelengths ; Zeolites</subject><ispartof>Journal of geophysical research. 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H.</creatorcontrib><creatorcontrib>Oman Drilling Project Science Team</creatorcontrib><creatorcontrib>the Oman Drilling Project Science Team</creatorcontrib><title>Hydrothermal Alteration of the Ocean Crust and Patterns in Mineralization With Depth as Measured by Micro‐Imaging Infrared Spectroscopy</title><title>Journal of geophysical research. Solid earth</title><addtitle>J Geophys Res Solid Earth</addtitle><description>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 &gt;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. Plain Language Summary The oceanic crust, the rock from the ocean floor to the mantle, forms much of Earth's solid crust, yet it is difficult to access, drill into, or collect samples from. This kilometers‐thick crust forms from cooling of molten rock, but we do not entirely understand how it forms, cools, and changes by chemical reactions with water. Ophiolites are places where rock from the ocean crust and uppermost portion of the mantle have been pushed upward and exposed on continents. One such location is in Oman, where the Oman Drilling Project drilled into continuous sections of ocean crust. We measured this drill core with imaging spectroscopy, a technique where we measure how infrared light at hundreds of wavelengths reflects off the rock. We use the characteristic infrared fingerprints of minerals to map them at sub‐millimeter scale, producing over one billion measurements. We find that much of the rocks closer to the ocean reacted with water at high temperatures to form new minerals. Some rocks deep within the ocean crust also interacted with large volumes of water, but intense fluid flow was concentrated in fractures and smaller areas, leaving less reacted rock. Key Points Imaging spectroscopy efficiently and effectively mapped spatial patterns in hydrothermal alteration mineral occurrence in ocean crust core Samail ophiolite upper ocean crust cores are dominated by chlorite, amphibole, and epidote, while deeper cores have more zeolite/prehnite Hydrothermal alteration largely decreases with depth in the ocean crust but is locally intense in major fault zones, even in lower crust</description><subject>Access</subject><subject>Amphiboles</subject><subject>Analytical methods</subject><subject>Biogeosciences</subject><subject>Calcite</subject><subject>Chemical reactions</subject><subject>Chlorite</subject><subject>Composition of the Oceanic Crust</subject><subject>Cooling</subject><subject>Coring</subject><subject>Dikes</subject><subject>Drilling</subject><subject>Drills</subject><subject>Earth crust</subject><subject>Earth mantle</subject><subject>Embankments</subject><subject>Fault zones</subject><subject>Fluid dynamics</subject><subject>Fluid flow</subject><subject>Fractures</subject><subject>Gabbros</subject><subject>General or Miscellaneous</subject><subject>Geochemistry</subject><subject>Geological faults</subject><subject>Gypsum</subject><subject>High temperature</subject><subject>Hydrothermal alteration</subject><subject>Hydrothermal Systems</subject><subject>hyperspectral imaging</subject><subject>imaging spectroscopy</subject><subject>Infrared detectors</subject><subject>Infrared spectrometers</subject><subject>Infrared spectroscopy</subject><subject>Instruments Useful in Three or More Fields</subject><subject>Kaolinite</subject><subject>Lava</subject><subject>Marine Geology and Geophysics</subject><subject>Mineral Physics</subject><subject>Mineralization</subject><subject>Mineralogy and Petrology</subject><subject>Minerals</subject><subject>Montmorillonite</subject><subject>Montmorillonites</subject><subject>Ocean floor</subject><subject>Oceanic convection</subject><subject>Oceanic crust</subject><subject>Oceanography: Biological and Chemical</subject><subject>Oceans</subject><subject>Oman drilling project</subject><subject>Ophiolites</subject><subject>Ophiolites and Oceanic Lithosphere, with a focus on the Samail ophiolite in Oman</subject><subject>Optical, infrared, and Raman spectroscopy</subject><subject>Reflectance</subject><subject>Rock</subject><subject>Rocks</subject><subject>Short wave radiation</subject><subject>Spectroscopic analysis</subject><subject>Spectrum analysis</subject><subject>Tectonophysics</subject><subject>Volcanology</subject><subject>Wavelengths</subject><subject>Zeolites</subject><issn>2169-9313</issn><issn>2169-9356</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2021</creationdate><recordtype>article</recordtype><sourceid>24P</sourceid><sourceid>WIN</sourceid><recordid>eNp9kU1v1DAQhiMEolXpjTOyxIUDS2M7TuILUrtAu1WrIj7E0Zq1nV1XiZ3aCSicuHLjN_JLOqstq8IBH2asmcevPPNm2VOav6I5k0csZ_T8BIOsygfZPqOlnEkuyoe7O-V72WFK1zmeGku0eJzt8UJIkddiP_t5NpkYhrWNHbTkuB1shMEFT0JDsEqutAVP5nFMAwFvyHsYEPGJOE8unUe6dd-3L764YU3e2B4jJHJpIY3RGrKcENQx_P7xa9HByvkVWfgmwqb3sbd6iCHp0E9PskcNtMke3uWD7PO7t5_mZ7OLq9PF_PhiBkUl6ayxDQOwEijGigmuKy6NxtRwKbVopKT5smgKqChUzNCSmcIwCULYpak1P8heb3X7cdlZo60fcAjVR9dBnFQAp_7ueLdWq_BV1bg0xmsUeHEnEMPNaNOgOpe0bVvwNoxJMVHVVZVTxhF9_g96HcbocTykyqKQyG0EX24p3FJK0Ta7z9BcbWxW921G_Nn9AXbwH1MR4Fvgm2vt9F8xdX764USIvKT8FhaqtNk</recordid><startdate>202108</startdate><enddate>202108</enddate><creator>Greenberger, Rebecca N.</creator><creator>Harris, Michelle</creator><creator>Ehlmann, Bethany L.</creator><creator>Crotteau, Molly A.</creator><creator>Kelemen, Peter B.</creator><creator>Manning, Craig E.</creator><creator>Teagle, Damon A. 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Solid earth</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Greenberger, Rebecca N.</au><au>Harris, Michelle</au><au>Ehlmann, Bethany L.</au><au>Crotteau, Molly A.</au><au>Kelemen, Peter B.</au><au>Manning, Craig E.</au><au>Teagle, Damon A. H.</au><aucorp>Oman Drilling Project Science Team</aucorp><aucorp>the Oman Drilling Project Science Team</aucorp><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Hydrothermal Alteration of the Ocean Crust and Patterns in Mineralization With Depth as Measured by Micro‐Imaging Infrared Spectroscopy</atitle><jtitle>Journal of geophysical research. Solid earth</jtitle><addtitle>J Geophys Res Solid Earth</addtitle><date>2021-08</date><risdate>2021</risdate><volume>126</volume><issue>8</issue><spage>e2021JB021976</spage><epage>n/a</epage><pages>e2021JB021976-n/a</pages><issn>2169-9313</issn><eissn>2169-9356</eissn><abstract>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 &gt;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. Plain Language Summary The oceanic crust, the rock from the ocean floor to the mantle, forms much of Earth's solid crust, yet it is difficult to access, drill into, or collect samples from. This kilometers‐thick crust forms from cooling of molten rock, but we do not entirely understand how it forms, cools, and changes by chemical reactions with water. Ophiolites are places where rock from the ocean crust and uppermost portion of the mantle have been pushed upward and exposed on continents. One such location is in Oman, where the Oman Drilling Project drilled into continuous sections of ocean crust. We measured this drill core with imaging spectroscopy, a technique where we measure how infrared light at hundreds of wavelengths reflects off the rock. We use the characteristic infrared fingerprints of minerals to map them at sub‐millimeter scale, producing over one billion measurements. We find that much of the rocks closer to the ocean reacted with water at high temperatures to form new minerals. Some rocks deep within the ocean crust also interacted with large volumes of water, but intense fluid flow was concentrated in fractures and smaller areas, leaving less reacted rock. Key Points Imaging spectroscopy efficiently and effectively mapped spatial patterns in hydrothermal alteration mineral occurrence in ocean crust core Samail ophiolite upper ocean crust cores are dominated by chlorite, amphibole, and epidote, while deeper cores have more zeolite/prehnite Hydrothermal alteration largely decreases with depth in the ocean crust but is locally intense in major fault zones, even in lower crust</abstract><cop>United States</cop><pub>Blackwell Publishing Ltd</pub><pmid>34595085</pmid><doi>10.1029/2021JB021976</doi><tpages>29</tpages><orcidid>https://orcid.org/0000-0002-4416-8409</orcidid><orcidid>https://orcid.org/0000-0003-1583-0261</orcidid><orcidid>https://orcid.org/0000-0002-2745-3240</orcidid><orcidid>https://orcid.org/0000-0001-9618-2862</orcidid><orcidid>https://orcid.org/0000-0001-7888-0093</orcidid><orcidid>https://orcid.org/0000-0003-4757-0855</orcidid><orcidid>https://orcid.org/0000-0002-1463-3701</orcidid><oa>free_for_read</oa></addata></record>
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identifier ISSN: 2169-9313
ispartof Journal of geophysical research. Solid earth, 2021-08, Vol.126 (8), p.e2021JB021976-n/a
issn 2169-9313
2169-9356
language eng
recordid cdi_pubmedcentral_primary_oai_pubmedcentral_nih_gov_8459238
source Wiley Online Library Free Content; Access via Wiley Online Library
subjects Access
Amphiboles
Analytical methods
Biogeosciences
Calcite
Chemical reactions
Chlorite
Composition of the Oceanic Crust
Cooling
Coring
Dikes
Drilling
Drills
Earth crust
Earth mantle
Embankments
Fault zones
Fluid dynamics
Fluid flow
Fractures
Gabbros
General or Miscellaneous
Geochemistry
Geological faults
Gypsum
High temperature
Hydrothermal alteration
Hydrothermal Systems
hyperspectral imaging
imaging spectroscopy
Infrared detectors
Infrared spectrometers
Infrared spectroscopy
Instruments Useful in Three or More Fields
Kaolinite
Lava
Marine Geology and Geophysics
Mineral Physics
Mineralization
Mineralogy and Petrology
Minerals
Montmorillonite
Montmorillonites
Ocean floor
Oceanic convection
Oceanic crust
Oceanography: Biological and Chemical
Oceans
Oman drilling project
Ophiolites
Ophiolites and Oceanic Lithosphere, with a focus on the Samail ophiolite in Oman
Optical, infrared, and Raman spectroscopy
Reflectance
Rock
Rocks
Short wave radiation
Spectroscopic analysis
Spectrum analysis
Tectonophysics
Volcanology
Wavelengths
Zeolites
title Hydrothermal Alteration of the Ocean Crust and Patterns in Mineralization With Depth as Measured by Micro‐Imaging Infrared Spectroscopy
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