EAGER: Collaborative Research: Continental Subduction and Deep Crustal Melting

EAGER：合作研究：大陆俯冲和深部地壳融化

• 批准号: 1041257
• 负责人: Stacia Gordon
• 金额: $ 2.89万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2010-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1041257&HistoricalAwards=false
• 关键词: EAGER; Collaborative; Research; Continental; Subduction

Subducted continental crust can attain pressure-temperature conditions that are above the solidus for many crustal lithologies, but the conditions, timing, and consequences of deep crustal melting are largely unexplored. Although there have been experimental investigations of ultrahigh-pressure (UHP) melting, there are very few field-based studies of natural examples; existing work has focused largely on the age and chemical characteristics of granitoid bodies that are associated with UHP terrains and not on migmatites that commonly host UHP rocks. The generation of large amounts of partially molten crust during subduction has implications for mass and heat transfer from the mantle to the crust, orogenic growth by the addition of partially molten material generated at depth, and evolution of orogenic landscapes (e.g. development of plateaux). Moreover, the role of partially molten crust must be considered in understanding the mechanisms by which (U)HP rocks are overprinted during exhumation and subsequent orogenic processes. This proposed Early Grant for Exploratory Research (EAGER) project is designed to obtain U/Pb zircon ages from magma bodies (leucosomes, pegmatites) spatially associated with eclogite to determine if zircon crystallized and thus melting occurred at UHP conditions. If this exploratory study is successful, it will set up the background canvas for a larger scale project with the ultimate goal of testing the hypothesis that, in some orogens, partial melting of continental crust occurs during continental subduction and is dynamically linked to the thermal-mechanical evolution of orogens and the exhumation of UHP rocks. The pursuit for adequate sample material will take place in the Western Gneiss Region (Norway) because it is an accessible locale with abundant exposure of UHP rocks that are hosted by migmatite; some eclogite bodies are themselves migmatitic.

对于许多地壳岩性而言，俯冲大陆地壳可以达到高于固相线的压力-温度条件，但深层地壳熔融的条件、时间和后果在很大程度上尚未被探索。尽管已有超高压（UHP）熔化的实验研究，但针对自然实例的现场研究却很少；现有工作主要集中于与超高压地形相关的花岗岩体的年龄和化学特征，而不是通常含有超高压岩石的混合岩。俯冲过程中产生大量部分熔融的地壳对从地幔到地壳的质量和热量传递、通过添加深部产生的部分熔融物质的造山生长以及造山地貌的演化（例如高原的发展）具有影响。此外，在理解（U）HP岩石在折返和随后的造山过程中叠印的机制时，必须考虑部分熔融地壳的作用。这项拟议的探索性研究早期拨款 (EAGER) 项目旨在从与榴辉岩空间相关的岩浆体（无色体、伟晶岩）中获取 U/Pb 锆石年龄，以确定锆石是否在超高压条件下结晶并因此发生熔化。如果这项探索性研究成功，它将为更大规模的项目奠定基础，最终目标是检验以下假设：在某些造山带中，大陆地壳的部分熔融发生在大陆俯冲过程中，并且与造山带的热机械演化和超高压岩石的折返动态相关。寻找足够样本材料的工作将在西部片麻岩地区（挪威）进行，因为该地区交通便利，暴露出大量以混合岩为主的超高压岩石；一些榴辉岩体本身就是混合岩。