Gneiss Dome architecture: Investigation of Form and Process in the Fosdick Mountains, W. Antarctica

片麻岩圆顶建筑：南极洲西部福斯迪克山脉的形式和过程调查

• 批准号: 0338279
• 负责人: Christine Siddoway
• 金额: $ 15.8万
• 依托单位: Colorado College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0338279&HistoricalAwards=false
• 关键词: Gneiss; Dome; architecture; Investigation; Form

This project will study migmatite domes found in the Fosdick Mountains of the Ford Ranges, western Marie Byrd Land, Antarctica. This area offers unique, three-dimensional exposures that may offer new insight into dome formation, which is a fundamental process of mountain building. These domes are derived from sedimentary and plutonic protoliths that are complexly interfolded at decimeter to kilometer scales. Preliminary findings from geobarometry and U-Pb monazite dating of anatexite suggest that peak metamorphism was underway at 105 Ma at crustal depths of ~25 km, followed by decompression as the Fosdick dome was emplaced to 16-17 km, or possibly as low as 8.5 km, in the crust by 99 Ma. Near-isothermal conditions were maintained during ascent, favorable for producing substantial volumes of melt through biotite-dehydration melting. This dome has been interpreted as a product of extensional exhumation. This is a viable interpretation from the regional standpoint, because the dome was emplaced in mid-Cretaceous time during the rapid onset of divergent tectonics along the proto- Pacific margin of Gondwana. However, the complex internal structures of the Fosdick Mountains have yet to be considered and may be more consistent with alternative intepretations such as upward extrusion within a contractional setting or lateral flow within a transcurrent attachment zone. This proposal is for detailed structural analysis, paired with geothermobarometry and geochronology, to determine the flow behavior and structural style that produced the internal architecture of the Fosdick dome. The results will improve our general understanding of the role of gneiss domes in transferring material and heat during mountain-building, and will characterize the behavior of the middle crust during a time of rapid transition from divergent to convergent tectonics along the active margin of Gondwana. In terms of broader impacts, this work will train undergraduate and graduate students, and involve them as collaborators in the development of curricular materials. It will also foster mentoring relationships between graduate and undergraduate students.

该项目将研究在南极洲西部玛丽·伯德（Western Marie Byrd Land）的福特山脉（Fosdick Mountains）中发现的Migmatite Domes。该区域提供了独特的三维暴露，可以为圆顶地层提供新的见解，这是山区建筑的基本过程。这些圆顶源自沉积物和丘脑原岩，它们在十分表至公里尺度上复杂地连接起来。在地壳深度约25 km的地壳深度为105 mA的峰值变质峰的初步发现表明，峰值变质性在105 MA处进行，然后进行减压，因为fosdick圆顶将fosdick Dome扩展到16-17 km，或可能低至8.5 km，在99 Ma colust by 99 km中低至8.5 km。在上升期间维持近乎温度的条件，有利于通过生物岩含水融化产生大量熔体。该圆顶已被解释为伸展发掘的产物。从区域的角度来看，这是一个可行的解释，因为在冈瓦纳原始缘沿发散构造的快速发作中，圆顶是在白垩纪中期的中期。但是，Fosdick山脉的复杂内部结构尚未考虑，并且可能与替代性直肠（例如在收缩环境中的向上挤出或跨膜附件内的侧向流动）更一致。该建议用于详细的结构分析，并与地球测量学和年代学配对，以确定产生Fosdick Dome内部体系结构的流动行为和结构样式。结果将提高我们对片麻岩圆顶在山区建设过程中转移材料和热量中的作用的一般理解，并将表征从冈瓦纳（Gondwana）活跃边缘的迅速过渡到融合构造的过程中中壳的行为。在更广泛的影响方面，这项工作将培训本科生和研究生，并将他们作为合作者参与课程材料的开发。它还将促进研究生和本科生之间的关系。