Layered Intrusion-Footwall Hydrothermal Interactions - An Analog For Subduction Zone Hydrothermal Sytems

层状侵入-下盘热液相互作用 - 俯冲带热液系统的模拟

基本信息

批准号：
1647727
负责人：
A. Boudreau
金额：
$ 25.04万
依托单位：
Duke University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-06-01 至 2022-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1647727&HistoricalAwards=false
关键词：
Layered Intrusion Footwall Hydrothermal Interactions

项目摘要

Subduction zones are formed where lithospheric plates that make up the rigid, outer shell of the Earth are recycled back into the Earth's mantle. When that happens, the rigid plate is heated and releases water and other volatiles into the overlying mantle. This induces melting in the mantle and expresses itself in explosive surface volcanism, such as those around the Pacific Ocean basin (the so-called 'Ring of Fire'). Volcanism associated with subduction zones is closely linked to the formation of economic mineral deposits. Unfortunately, the nature of fluid movement from the descending slab into the overlying mantle cannot be directly observed. This project will test if large igneous bodies that intruded into the shallow continental crust and dehydrated underlying rocks can serve as proxies to processes operation at depth in subduction zone hydrothermal systems. The study will be centered on the intrusion of the 2.7 billion year old Stillwater Complex in Montana, and which has since been exposed by erosion. Specifically, it is planned to investigate mechanisms (fractures, veins, etc.) by which fluids liberated from the underlying rocks and moved into the overlying igneous rocks and the degree that these were modified during this process. The study has broader applications to the study of the explosive volcanism that occurs at subduction zones as well as understanding the ultimate source of fluids involved in ore deposits in both the subduction zone environment and in unique magmatic intrusions that are the main sources of critical materials for our modern industry. Copper, chromium and the platinum-group elements are examples of critical resources with great importance for the national economy. The funding also will help support advanced training for a graduate student and senior thesis projects for undergraduate students. More specifically, the work entails mapping and characterization of hydrothermal features (high temperature veins and pegmatoidal bodies) of the lower part of the Stillwater Complex and its 2-3 km thick metamorphic aureole. This will include comparing the stable (particularly carbon) and radiogenic (Nd, Sr, and Pb) isotopic composition of veins pegmatoidal bodies in the Stillwater Complex with the surrounding host rock to test the degree country fluids were involved in their formation. The composition of these hydrothermal features will be compared with bulk rock major and trace element composition of the Stillwater Complex up to the Middle Banded series, for which there currently is no comprehensive coverage of the complex. These field data can be used to constrain theoretic models of fluid channelization in both subduction zone and layered intrusion settings. It can also lead to insights toward understanding the transition from magmatic to country fluid migration in three-phase crystal-liquid-gas mushes, and has consequences for ore deposit formation models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

俯冲带是形成的，其中构成刚性，地球外壳的岩石圈板被回收回到地球的地幔中。发生这种情况时，将刚性板加热，并将水和其他挥发物释放到上覆的地幔中。这会引起地幔融化，并在爆炸性的地表火山中表达自己，例如太平洋盆地（所谓的“火环”）周围的火山融化。与俯冲带相关的火山主义与经济矿藏的形成密切相关。不幸的是，无法直接观察到从降板到上覆披风的流体运动的性质。该项目将测试侵入浅层大陆壳和脱水的基础岩石的大火成岩是否可以用作处理俯冲带水热系统深度操作的代理。这项研究将集中在蒙大拿州27亿年历史的斯蒂尔沃特综合体的入侵中，此后已通过侵蚀暴露。具体而言，计划研究机制（裂缝，静脉等），通过这些机制从基础岩石中解放出来并进入上覆的火成岩岩石，并在此过程中修改了这些岩石。这项研究在俯冲区域发生的爆炸性火山爆发方面具有更广泛的应用，并了解俯冲带环境中矿石沉积物和独特的岩浆入侵中涉及的流体的最终来源，这是我们现代工业的关键材料的主要来源。铜，铬和铂群元素是重要资源的例子，对国民经济非常重要。这项资金还将有助于支持研究生和高级论文项目的高级培训。更具体地说，该作品需要绘制和表征静水络合物下部的水热特征（高温静脉和甲状腺体体）及其2-3 km厚的变质金黄色的映射和表征。这将包括将静脉配合物中静脉的静脉pegmatoidal体的稳定（尤其是碳）和放射原（ND，SR和PB）与周围的宿主岩与测试乡村流体涉及其形成。这些水热特征的组成将与散装岩石专业和痕量元素组成进行比较，直到中间带状系列，目前尚无对复合物的全面覆盖。这些现场数据可用于约束俯冲区和分层入侵设置中流体通道化的理论模型。它还可以带来深入的见解，以了解三相晶体液体 - 液体糊状中从岩浆到国家流体迁移的过渡，并对矿石存款形成模型产生后果。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力和更广泛影响的评估来通过评估来支持的，这是值得的。