LISTVEIN: Multiscale structure evolution during peridotite carbonation and hydration in an oceanic subduction zone: a case study of listvenite in the Oman Ophiolite

阿曼蛇绿岩中的Listvenites形成于俯冲带上盘含碳酸盐沉积物之上的洋幔橄榄岩逆冲。在这个大规模橄榄岩水化和碳酸化过程的例子中，ICDP阿曼钻井项目（OmDP）的BT 1岩心提供了一个独特的样本。尽管listvenites记录了海洋俯冲带的碳通量，并且是通过矿化作用捕获和储存碳的可能天然类似物，但这种碳酸化发生的过程还没有得到很好的理解，需要努力了解这种天然例子的演变。我们提出了一个微观和宏观结构的变形和反应结构的研究，在钛铁矿和蛇纹橄榄岩在BT 1核心。使用光学和电子显微镜（ViP、CL、BIB-SEM、EDX、EBSD、QEMSCAN）与我们的岩心描述数据和最先进的图像数据相结合根据OmDP采集的岩心扫描、X射线CT、高光谱、XRF等数据，我们将重点关注（i）不同世代的断层、碎裂岩、断裂和脉状结构对硬脉岩显微结构的改造，分析叠加关系和变形机制，（ii）碳酸盐岩的显微结构，测试碳酸盐化过程中韧性剪切带的存在，（iii）原岩蛇纹岩和部分蚀变橄榄岩的显微结构，（iv）同轴和反轴脉中的显微结构，以区分反应引起的断裂和构造和孔隙压力引起的断裂，以及最后（v）关于微米和纳米孔隙度及其连接性以约束基质中潜在的流体路径。我们的目标是更好地理解结晶力的相互作用，构造应力和孔隙压力在BT 1大规模水化和碳酸化过程中，并测试在这个系统的驱动力，构造演化和流体传输路径的假设。更一般地说，我们希望有助于一个面向过程的角度来研究俯冲带的质量转移和元素的“回收”，并了解质量转移和矿物学转化对板块边界变形的影响。

Listvenites in the Oman Ophiolite formed from oceanic mantle peridotite thrust over carbonate-bearing sediments in the hanging wall of a subduction zone. In this example of large scale peridotite hydration and carbonation processes, core BT1 of the ICDP Oman Drilling Project (OmDP) provides a unique sample. Although listvenites record carbon fluxes in oceanic subduction zones and are a possible natural analogue for carbon capture and storage via mineralization, the processes by which this carbonation occurs are not well understood, calling for work to understand the evolution of this natural example. We propose a micro- and macrostructural study of deformation and reaction structures in listvenite and serpentinized peridotite in Core BT1. Using optical and electron microscopy (ViP, CL, BIB-SEM, EDX, EBSD, QEMSCAN) integrated with our core description data and with the state of the art image data (core scans, X-ray CT, hyperspectral, XRF) collected by OmDP, we will focus on (i) the different generations of fault, cataclasite and fracture and vein structures modifying the listvenite microstructure, analyzing overprinting relationships and deformation mechanisms, (ii) the microstructure of listvenite, testing the presence of a ductile shear zone during carbonation, (iii) the microstructure of protolith serpentinites and partially altered peridotites, (iv) microstructures in syntaxial and antitaxial veins to distinguish reaction-induced- from tectonically and pore pressure-induced fracturing, and finally (v) on micro- and nano-porosity and its connectivity to constrain potential fluid pathways in the matrix.We aim to better understand the interplay of force of crystallization, tectonic stress and pore pressure during large scale hydration and carbonation processes in BT1 and test hypotheses on driving forces, structural evolution and fluid transport pathways in this system. More generally, we hope to contribute a process-oriented perspective to studies of mass transfer and element “recycling” in subduction zones, and to understand the effect of mass transfer and mineralogical transformation on plate-boundary deformation.