Petrologic and Chronologic Evaluation of Himalayan Tectonic Models in Southern Bhutan

在这个项目中，正在研究不丹南部出露的变质岩的压力-温度-时间演化，以检验碰撞造山作用的模型。在喜马拉雅的大部分地区，低等级特提斯岩石与高等级大喜马拉雅岩石沿着一个韧性伸展构造-南藏支拆离-并列在一起。然而，在不丹的申冈地区，最近的一项研究提出了一个从大喜马拉雅到特提斯岩石的完整地层剖面。如果正确，这个模型强烈限制了碰撞造山过程中两种地壳变形行为模型的重要性，并进一步暗示了大喜马拉雅-特提斯接触的正常年代学、热梯度和气压梯度。关于含石榴石岩石的压力-温度条件和含独居石岩石的变质年龄的新数据正在收集中。新的数据将确定该剖面是否确实在年代学和变质方面是完整的，测试地层模型，并为喜马拉雅变质作用和变形行为提供关键的新约束。这项研究解决了大陆地壳在碰撞期间的基本问题：它是(在管流意义上)弱地流向集中侵蚀的区域，还是以更强、更刚性的方式表现？虽然这场争论起源于喜马拉雅山脉，并在那里得到了积极的研究，但它已经被广泛应用于其他碰撞山带。因此，新的结果引起了地质界的广泛兴趣。研究变质岩的新的年代学和岩石学方法正在得到更普遍的发展，扩大了对其他岩石类型和造山带的应用。该项目支持对一名新近获得博士学位的女性进行博士后培训，提高妇女在地球科学领域的代表性。

In this project, the pressure-temperature-time evolution of metamorphic rocks exposed in southern Bhutan is being investigated to test models of collisional orogenesis. In most areas of the Himalaya, low-grade Tethyan rocks are juxtaposed with high-grade Greater Himalayan rocks along a ductile extensional structure, the South Tibetan Detachment. In the Shemgang region of Bhutan, however, a recent study instead proposes an intact stratigraphic section from Greater Himalayan to Tethyan rocks. If correct, this model strongly limits the importance of two models of crustal deformation behavior during collisional orogenesis, and further implies a normal chronologic, thermal and baric gradient across the Greater Himalayan - Tethyan contact. New data are being collected on pressure-temperature conditions from garnet-bearing rocks, and on metamorphic ages from monazite-bearing rocks. The new data will identify whether the section is indeed chronologically and metamorphically intact, testing the stratigraphic model, and provide crucial new constraints on Himalayan metamorphism and deformation behavior.This research addresses the fundamental problem of how continental crust behaves during collisions: does it flow (in a pipe-flow sense) weakly towards areas of focused erosion, or does it behave in a stronger more rigid fashion? While this debate originated in the Himalaya and is actively studied there, it has been widely applied to other collisional mountain belts. Thus new results are of broad interest to the geologic community. New chronologic and petrologic methods of investigating metamorphic rocks are being more generally developed, expanding applications to other rock types and orogens. This project supports the post-doctoral training of a recent female PhD, improving representation of women in the geosciences.