RUI: Subduction Zone Flight Recorders: Integrating P-T-t-f Histories of Subduction and Exhumation of Eclogite through Microanalysis of Garnet and its Inclusions

洋壳通过俯冲作用循环进入地幔，是地球大陆地壳通过弧形岩浆作用形成的最终原因。这些岩浆作用的起源被认为是火山弧下的地幔岩石在俯冲的大洋板块释放流体时引发的熔融。对这种岩浆作用负有最终责任的流体的组成是许多研究的主题，包括对俯冲作用的变质副产品的研究，这些副产品偶尔会返回地表。这些含石榴石的变质岩(榴辉岩)是仅有的被俯冲到很深的物质样本，但可供研究。虽然榴辉岩可以保存俯冲带流体的记录，但很难确定保存在这些岩石中的流体记录是来自俯冲带深处，还是它们折返的结果。由这笔资金资助的研究将把俯冲期间生长的石榴石的氧同位素组成中保存的流体记录与石榴石化学成分记录的压力和温度条件联系起来，产生这些岩石的完整构造和流体记录。在它们生长过程中捕获的化学分带石榴石和矿物包裹体被证明保存了洋壳俯冲和榴辉岩折返的压力和温度信息。氧在石榴石中缓慢的粒内扩散表明，这些石榴石也将沿着这些路径与石榴石保持平衡的流体的18O。离子微探针技术的新进展现在可以高精度地原位测量石榴石的18O。通过将石榴石的原位分析与现有的和新的定量的进退P-T-fO2信息和结构引导的年代学相结合，这项研究将首次生成形成于俯冲带的榴辉岩和相关岩石的详细P-T-t-f轨迹。这些历史将允许榴辉岩样本作为探测古俯冲带弧前和俯冲通道环境的构造和流体条件。这些数据的综合性质将把有关流体的信息直接与这些岩石的构造演化联系在一起，并允许它们被用来检验一些关于折返俯冲带变质岩保存的流体记录的性质和时间的假说。对混杂岩带和一致的断层边界地块中发现的沉积原岩和火成岩原岩之间的数据集进行比较，将有助于深入了解它们并置的时间，并使现有的地球化学研究能够与共同的构造和热框架联系在一起。

The recycling of oceanic crust into the mantle through subduction is ultimately responsible for the formation of the Earth's continental crust through arc magmatism. The origin of these magmatic processes is thought to be the melting of mantle rocks under volcanic arcs triggered by the release of fluids from the subducting oceanic slab. The composition of the fluids ultimately responsible for this magmatism is the subject of much research, including the study of the metamorphic byproducts of subduction that are occasionally returned to the surface. These garnet-bearing metamorphic rocks (eclogite) are the only samples of material that have been subducted to great depth, but are available for study. Although eclogite can preserve a record of fluids from subduction zones, it is difficult to determine whether the fluid record preserved in these rocks comes from deep in the subduction zone, or is a result of their exhumation. The research funded by this grant will tie the record of fluids preserved in the oxygen isotope composition of garnets that grew during subduction with the pressure and temperature conditions recorded by the chemical composition of the garnets, generating an integrated tectonic and fluid record for these rocks.Chemically zoned garnets and mineral inclusions entrapped during their growth have been shown to preserve pressure and temperature information from both the subduction of ocean crust and exhumation of eclogite. Slow intragranular diffusion of oxygen in garnet suggests that these garnets will preserve the δ18O of fluids in equilibrium with the garnet along these paths as well. New advances in ion microprobe technique now allow the δ18O of garnet to be measured in situ with high precision. By integrating in situ δ18O analysis of garnet with existing and new quantitative prograde and retrograde P-T-fO2 information and texturally guided geochronology, this study will generate the first detailed P-T-t-f paths for eclogite and related rocks formed in subduction zones. These histories will allow samples of eclogite to serve as probes into the tectonic and fluid conditions of the fore-arc and subduction channel environment of fossil subduction zones. The integrated nature of these data will tie information on fluids directly to the tectonic evolution of these rocks, and allow them to be used to test a number of hypotheses regarding the nature and timing of the fluid record preserved by exhumed subduction-zone metamorphic rocks. Comparison of data sets between rocks with sedimentary and igneous protoliths found in mélange zones and in coherent fault bounded blocks will offer insight into the timing of their juxtaposition, and will allow existing geochemical studies to be tied to a common tectonic and thermal framework.