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: 1040980
• 负责人: Donna Whitney
• 金额: $ 2.65万
• 依托单位: University of Minnesota-Twin Cities
• 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 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1040980&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.

俯冲大陆地壳可以达到高于许多地壳岩性的固相线的压力-温度条件，但深地壳熔融的条件，时间和后果在很大程度上是未知的。虽然已经有超高压（UHP）熔融的实验研究，有很少的自然实例的实地研究，现有的工作主要集中在年龄和化学特征的花岗岩类机构，与超高压地形，而不是混合岩，通常主机超高压岩石。俯冲过程中大量部分熔融地壳的产生对地幔向地壳的质量和热量转移、深部部分熔融物质的增加导致的造山带增长以及造山带景观的演变（例如高原的发展）都有影响。此外，部分熔融的地壳的作用，必须考虑在了解机制（U）高压岩石在折返和随后的造山过程中叠加。这个提议的探索性研究早期资助（EAGER）项目旨在从与榴辉岩空间相关的岩浆体（无色体，伟晶岩）中获得锆石U/Pb年龄，以确定锆石是否结晶，从而在超高压条件下发生熔融。如果这项探索性研究成功，它将为一个更大规模的项目建立背景画布，最终目标是检验这样一个假设，即在某些造山带，大陆地壳的部分熔融发生在大陆俯冲期间，并与造山带的热-机械演化和超高压岩石的折返有动态联系。将在西部片麻岩区（挪威）寻找足够的样品材料，因为该区域是一个可接近的地点，有大量由混合岩承载的超高压岩石暴露;一些榴辉岩体本身就是混合岩。