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

RUI：俯冲带飞行记录仪：通过石榴石及其包裹体的微分析，整合榴辉岩俯冲和折返的 P-T-t-f 历史

• 批准号: 1249778
• 负责人: F. Zeb Page
• 金额: $ 17.48万
• 依托单位: Oberlin College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-01 至 2018-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1249778&HistoricalAwards=false
• 关键词: RUI; Subduction; Zone; Flight; Recorders

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.

洋壳通过俯冲作用再循环到地幔中，最终通过弧岩浆作用形成了地球的陆壳。这些岩浆过程的起源被认为是地幔岩石在火山弧下的熔融，由俯冲洋板释放的流体触发。最终导致岩浆活动的流体成分是许多研究的主题，包括研究偶尔返回地表的俯冲变质副产品。这些含石榴子石的变质岩（榴辉岩）是俯冲到很深的物质的唯一样本，但可用于研究。虽然榴辉岩可以保存俯冲带的流体记录，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，还是折返的结果。由该基金资助的研究将把在俯冲过程中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的化学组成记录的压力和温度条件联系起来，化学环带的石榴石和在其生长过程中捕获的矿物包裹体已被证明可以保存来自岩石的压力和温度信息，洋壳俯冲和榴辉岩折返。石榴石中氧的缓慢粒内扩散表明，这些石榴石将保持流体中的#948; 18 O与石榴石沿着这些路径平衡。离子探针技术的新进展使石榴石中的~（948; 18）O能高精度地原位测量。通过就地整合δ石榴石的18 O分析与现有的和新的定量的P-T-fO 2信息和结构指导的地质年代学，这项研究将产生第一个详细的P-T-t-f路径的榴辉岩和相关岩石形成于俯冲带。 这些历史将允许榴辉岩样品作为探针的构造和流体条件的弧前和俯冲通道环境的化石俯冲带。这些数据的综合性质将联系信息的流体直接构造演化的这些岩石，并允许他们被用来测试一些假设的性质和时间的流体记录保存的折返俯冲带变质岩。在混杂岩带和连贯的断层边界块中发现的具有沉积和火成岩原岩的岩石之间的数据集的比较将提供对它们并置的时间的深入了解，并将使现有的地球化学研究与共同的构造和热框架相联系。