Brittle Deformation of Carbonated Peridotite—Insights From Listvenites of the Samail Ophiolite (Oman Drilling Project Hole BT1B). Issue 10 (26th October 2020)

• Record Type: Journal Article
• Authors: Menzel, Manuel D.; Urai, Janos L.; de Obeso, Juan Carlos; Kotowski, Alissa; Manning, Craig E.; Kelemen, Peter B.; Kettermann, Michael; Jesus, Ana P.; Harigane, Yumiko
• Is Part Of: Journal of geophysical research. Volume 125:Issue 10(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-10-26
• Subjects: Oman Drilling Project -- peridotite carbonation -- ophiolite obduction -- cataclasite; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2020JB020199
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: Hole BT1B of the Oman Drilling Project provides a continuous sampling from listvenite into the metamorphic sole that preserves the deformation, hydration, and carbonation processes of oceanic mantle peridotite at the base of the Samail ophiolite, Oman. We present evidence of multistage brittle deformation in listvenites and serpentinites based on field observations, visual core logging and petrography. About 10 vol% of listvenite and serpentinite in Hole BT1B is composed of cataclasite bands. Cataclasites contain lithic clasts of listvenite with spheroidal, zoned magnesite and quartz, and fragments of chalcedony‐carbonate veins that elsewhere crosscut listvenite—showing that cataclasis postdates listvenite formation. Locally the cataclasites are reworked and cut by thin, sharp faults, pointing to repeated reactivation of brittle structures. SEM‐EDS mapping shows that cataclasis was related to dissolution of carbonate and/or silica cementation. Dolomite veins crosscut cataclasites and breccias, suggesting that part of the Ca gain in BT1B is related to late fluids after listvenite formation. These results indicate a multistage tectonic overprint after peridotite carbonation and listvenite formation, which may be related to the tectonic history of the deformed continental margin under the ophiolite. These relatively late brittle structures should be excluded when trying to understand the carbonation of peridotite to listvenite. Key Points: Abundant cataclasites overprint previously formed listvenite in the Oman Drilling Hole BT1B Cataclasis was related to fluid flow, which caused Mg loss and/or Si enrichment, and local redistribution of Cr The multistage tectonic overprint after peridotite carbonation in the Oman ophiolite should be excluded when analyzing early structures