Listvenite Formation During Mass Transfer into the Leading Edge of the Mantle Wedge: Initial Results from Oman Drilling Project Hole BT1B
Listvenite Formation During Mass Transfer into the Leading Edge of the Mantle Wedge: Initial Results from Oman Drilling Project Hole BT1B
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DOI：
10.1029/2021jb022352
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发表时间：
2022-01
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通讯作者：
P. Kelemen;Juan Carlos de Obeso;J. Leong;M. Godard;K. Okazaki;A. Kotowski;C. Manning;E. Ellison;M. Menzel;J. Urai;G. Hirth;M. Rioux;D. Stockli;Romain Lafay;A. Beinlich;J. Coggon;N. Warsi;J. Matter;D. Teagle;M. Harris;K. Michibayashi;E. Takazawa;Zaher Al Sulaimani
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作者：
P. Kelemen;Juan Carlos de Obeso;J. Leong;M. Godard;K. Okazaki;A. Kotowski;C. Manning;E. Ellison;M. Menzel;J. Urai;G. Hirth;M. Rioux;D. Stockli;Romain Lafay;A. Beinlich;J. Coggon;N. Warsi;J. Matter;D. Teagle;M. Harris;K. Michibayashi;E. Takazawa;Zaher Al Sulaimani
本文概述了阿曼钻探项目BT 1B孔及周边地区岩心的研究情况，以及Samail蛇绿岩下特提斯俯冲带的新数据和计算结果。该地区的下方是轻微倾斜，广泛折叠层的异地Hawasina远洋沉积物，变质的唯一的Samail蛇绿岩，带状单位橄榄岩的基础上Samail地幔部分。尽管一些断层在杰贝勒阿克达尔和赛哈塔特穹丘隆起期间重新活动，但该地区保留了白垩纪俯冲带的构造“地层学”。平缓倾斜的橄榄岩带，平行于橄榄岩带和橄榄岩与变质鞋底之间的接触，取代橄榄岩和附近的基底冲断。李斯特文岩形成于低于200°C和（限制性较差）25-40 km深度，通过与从更深处迁移的富含CO2的含水流体反应形成，这些流体来自于400°-500°的俯冲沉积物的脱挥发分作用，类似于Hawasina地层中的碎屑沉积物。这些过程可能形成俯冲CO2的重要储层。李斯特文岩的形成伴随着蛇纹岩和李斯特文岩的韧性变形-可能是由流体-岩石反应促进的-在一个过程中，可能导致在某些地区的俯冲。此外，H2O和CO2的地幔楔，形成蛇纹岩和listvenites，造成大幅度增加的固体质量和体积的岩石。这可能是由于体积变化而形成的裂缝所适应的，主要是在蛇纹化前缘。
This paper provides an overview of research on core from Oman Drilling Project Hole BT1B and the surrounding area, plus new data and calculations, constraining processes in the Tethyan subduction zone beneath the Samail ophiolite. The area is underlain by gently dipping, broadly folded layers of allochthonous Hawasina pelagic sediments, the metamorphic sole of the Samail ophiolite, and Banded Unit peridotites at the base of the Samail mantle section. Despite reactivation of some faults during uplift of the Jebel Akdar and Saih Hatat domes, the area preserves the tectonic “stratigraphy” of the Cretaceous subduction zone. Gently dipping listvenite bands, parallel to peridotite banding and to contacts between the peridotite and the metamorphic sole, replace peridotite at and near the basal thrust. Listvenites formed at less than 200°C and (poorly constrained) depths of 25–40 km by reaction with CO2‐rich, aqueous fluids migrating from greater depths, derived from devolatilization of subducting sediments analogous to clastic sediments in the Hawasina Formation, at 400°–500°. Such processes could form important reservoirs for subducted CO2. Listvenite formation was accompanied by ductile deformation of serpentinites and listvenites—perhaps facilitated by fluid‐rock reaction—in a process that could lead to aseismic subduction in some regions. Addition of H2O and CO2 to the mantle wedge, forming serpentinites and listvenites, caused large increases in the solid mass and volume of the rocks. This may have been accommodated by fractures formed as a result of volume changes, mainly at a serpentinization front.