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

海洋地壳通过俯冲作用再循环进入地幔，最终导致了弧岩浆作用形成大陆地壳。这些岩浆过程的起源被认为是火山弧下地幔岩石的融化，这是由俯冲的海洋板块释放的流体引发的。导致这种岩浆活动的流体组成是许多研究的主题，包括对偶尔返回地表的俯冲作用的变质副产物的研究。这些含石榴石的变质岩（榴辉岩）是唯一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的流体记录，但很难确定这些岩石中保存的流体记录是来自俯冲带深处，还是它们被发掘出来的结果。这项由该基金资助的研究将把俯冲期间生长的石榴石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，生成这些岩石的综合构造和流体记录。化学分带的石榴石和在其生长过程中被包裹的矿物包裹体已被证明保存了来自洋壳俯冲和榴辉岩挖掘的压力和温度信息。在石榴石中，氧在粒内的缓慢扩散表明，这些石榴石将保存18O的流体在这些路径上与石榴石保持平衡。离子探针技术的新进展现在允许&amp；#948；18O的石榴石可在原位测量，精度高。通过就地集成&amp；#948；利用现有的和新的定量的正反行P-T-fO2信息和构造指导的地质年代学，对石榴石进行18O分析，将为形成于俯冲带的榴辉岩及相关岩石提供第一个详细的P-T-t-f路径。这些历史将使榴辉岩样品成为弧前构造和流体条件以及化石俯冲带俯冲通道环境的探测器。这些数据的综合性质将把关于流体的信息直接与这些岩石的构造演化联系起来，并允许它们被用来测试一些关于被发掘出的俯冲带变质岩保存的流体记录的性质和时间的假设。比较在msamuange带和连贯断层边界块中发现的沉积岩和火成岩原岩的数据集，将提供对它们并列时间的洞察，并将使现有的地球化学研究与共同的构造和热框架联系起来。

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.