Tectonic and Metamorphic Implications for High Cl-Contents in Serpentinites

EAR-0309794SharpOcean蛇纹岩含有高浓度的水溶性氯化物，作为俯冲带高盐度流体的来源，应该是负责从外圈清除氯的重要载体。提出了四个目标：1)通过表征ODP型岩芯和遮蔽的等价物，更好地约束蛇纹岩的氯含量及其丰度；2)利用电子微束和透射电子显微镜技术，表征蛇纹岩中氯的矿物学位置；3)研究弱变质和高度变质的蛇纹岩岩体和伴生围岩，寻找高盐度流体及其变质/交代作用的证据；4)测量蛇纹岩的氯同位素比值和相关岩性，以确定氯的来源。这项工作将包括直接测量阴离子浓度、测定流体包裹体的盐度、H、O和Cl同位素比值，以及评估矿脉和剪切带中的交代作用，以此作为高盐度流体通过期间元素迁移的间接证据。更广泛的影响--本提案中概述的综合方法将有助于更好地理解高盐度流体在与深俯冲有关的变质作用中的重要性，以及这种流体的来源。这项工作将由三名PI进行，一名博士生和本科生(荣誉论文)和高中生(NASA夏令营实习)。该项目将包括大量各级学生，包括将受益于真正的科学探究实践经验的少数民族高中生。

EAR-0309794SharpOcean serpentinites contain a high concentration of water-soluble chlorides, and should be an important carrier responsible for removal of Cl from the exosphere as a source for high-salinity fluids in subduction zones. Four goals are proposed: 1) to better constrain the Cl content of serpentinites and their abundance by characterizing ODP cores and obducted equivalents, 2) to characterize the mineralogical siting of Cl - in serpentine using electron microbeam and TEM techniques, 3) to examine weakly and more highly-metamorphosed serpentinite bodies and associated wallrocks for evidence of high salinity fluids and their metamorphic/metasomatic effects and 4) measure chlorine isotope ratios of serpentinite and related lithologies in order to identify the origin of Cl. This work will include direct measurements of anion concentrations, salinity determinations of fluid inclusions, H, O and Cl isotope ratios, and evaluation of metasomatism in veins and shear zones as indirect evidence for element migration during passage of high-salinity fluids. Broader impacts - The integrated approach outlined in this proposal will lead to a better understanding of the importance of high-salinity fluids in deep subduction-related metamorphism, and the source of such fluids. The work will be carried out by the three PIs, a Ph.D. student and undergraduate (honor's thesis) and high school students (NASA SHARP summer internship). The project will include a large number of students at all levels, including minority high school students who will benefit from hands-on experience of a real scientific inquiry.