The Assembly of UHP Terranes: Was the Western Gneiss Region Built By Sequential or Repeated (Ultra)High-Pressure Events?

了解超高压岩石的形成和折返仍然是我们这个时代突出的构造问题之一，因为这些过程对地壳和地幔之间的物质交换，山脉的产生和坍塌，大陆地壳的形成和加工以及构造板块运动产生了影响。一个重大的进步将是了解超高压造山带是如何构造的：通过大陆边缘的俯冲，微大陆的俯冲，陆内俯冲或其他过程？该项目通过检查一个具体的例子-挪威西部片麻岩区，检验超高压造山带是通过同一构造单元的反复俯冲还是通过不同单元的相继俯冲形成的。经过仔细的岩石学，锆石成因进行了评估，光学和背散射电子岩相学，阴极发光，微量元素丰度，和拉曼光谱。单颗粒和颗粒碎片进行了分析，热电离质谱，选择人口的化学磨损热电离质谱，和继承的核心，激光烧蚀多收集器电感耦合等离子体质谱。独居石成因是通过解卷积记录的主要和微量元素分带的硅酸盐和磷酸盐矿物在不同的结构设置。在侦察性二次离子质谱测年之后，将通过热电离质谱法分析单个颗粒和颗粒碎片。这种方法的优势在于它使用了最先进的锆石和独居石地质年代学和岩石学，与尖端设施的研究人员合作，以及我们对其他超高压造山带的熟悉。这项研究的影响应该是相当大的，广泛适用，因为挪威超高压的原型性质。

Understanding the formation and exhumation of ultrahigh-pressure rocks continues to be one of the outstanding tectonic questions of our time because of the impact such processes have had on the exchange of material between the crust and mantle, the generation and collapse of mountain belts, the formation and processing of continental crust, and tectonic plate motions. A major step forward will be to understand how ultrahigh-pressure orogens are constructed: by subduction of continental margins, subduction of microcontinents, intracontinental subduction or another process?This project tests whether ultrahigh-pressure orogens form through repeated subduction of the same tectonic unit or through sequential subduction of different units, by examining a specific example, the Western Gneiss Region of Norway. Following careful petrology, zircon genesis is assessed by optical and back-scattered electron petrography, cathodoluminescence, trace-element abundances, and Raman spectroscopy. Single grains and grain fragments are analyzed by thermal-ionization mass spectrometry, select populations by chemical abrasion thermal-ionization mass spectrometry, and inherited cores by laser-ablation multiple-collector inductively-coupled-plasma mass spectrometry. Monazite genesis is determined by deconvolving the record of major- and trace-element zoning in silicate and phosphate minerals in different textural settings. Following reconnaissance secondary-ion mass spectrometry dating, single grains and grain fragments will be analyzed by thermal-ionization mass spectrometry.The strength of this approach lies in its use of state-of-the-art zircon and monazite geochronology and petrology, collaboration with researchers at cutting-edge facilities, and our familiarity with other ultrahigh-pressure orogens. The impact of this research should be considerable and broadly applicable because of the archetypal nature of the Norwegian ultrahigh-pressure terrane.