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.

通过俯冲将海洋壳回收到地幔中，最终是通过弧形岩浆形成地球连续地壳的原因。这些岩浆过程的起源被认为是在火山弧下通过从俯冲的海洋板上释放笛子触发的地幔岩石的融化。笛子的组成最终导致了这种岩浆作用，这是许多研究的主题，包括研究偶尔会返回表面的俯冲的变质副产品的研究。这些具有石榴石的变质岩石（Eclogite）是唯一已俯冲到深度但可用于研究的材料样品。尽管Eclogite可以保留俯冲带的流体记录，但很难确定这些岩石中保存的流体记录是否来自俯冲带的深处，还是由于它们的挖掘结果。这项赠款资助的研究将把保存在俯冲过程中氧气同位素组成中保存的记录与石榴石化学成分记录的压力和温度条件一起生长的石榴石的记录，从而产生了这些岩石的综合构造和流体记录，对这些岩石的整体构造和流体记录。在其化学上，在其生长过程中，在其生长过程中均散发出了海洋和矿物质的灌输。 eclogite。石榴石中氧气的慢速扩散表明，这些石榴石也将在同等灌木丛中与沿这些路径的石榴石相同的灌木丛中保存＆＃948; 18o。现在，离子微探针技术的新进展允许石榴石的18o以高精度原位测量。通过将石榴石的原位分析与现有的和新的定量程序以及逆行P-T-FO2信息以及质地指导的地年代学分析，这项研究将生成第一个详细的eclogite和相关岩石的P-t-t-f路径。这些历史将使叶绿石样品成为化石俯冲带的前弧和俯冲通道环境的构造和流体条件的问题。这些数据的综合性质将有关流体的信息直接与这些岩石的构造演化联系起来，并允许它们用于测试有关流体记录的性质和时机的许多假设，这些假设由发散的俯冲区域变质岩石保存。比较在混合区域和连贯的断层块中发现的带有沉积和火成岩原石的岩石之间的数据集将提供对它们并置的时机的见解，并将允许现有的地球化学研究与常见的构造和热框架联系在一起。