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，因为这种过程对地壳和地幔之间的物质交换、山带的生成和坍塌、陆壳的形成和加工以及构造板块运动产生了影响。向前迈进的一大步将是理解超高压造山带是如何构成的：通过大陆边缘的俯冲、微大陆的俯冲、陆内俯冲还是其他过程？这个项目通过研究一个具体的例子，挪威西片麻岩地区，测试超高压造山带是通过同一构造单元的反复俯冲形成的，还是通过不同单元的连续俯冲形成的。经过仔细的岩石学研究，通过光学和背散射电子岩石学、阴极发光、微量元素丰度和拉曼光谱对锆石成因进行了评估。单颗粒和颗粒碎片用热电离质谱仪分析，群体用化学磨损热电离质谱仪分析，遗传岩芯用激光烧蚀多集电极电感耦合等离子体质谱分析。独居石的成因是通过解卷解不同结构背景下硅酸盐和磷酸盐矿物中主量元素和微量元素分带的记录来确定的。在侦察二次离子质谱仪测年之后，单颗粒和颗粒碎片将被热电离质谱学分析。这种方法的优势在于它使用了最先进的锆石和独居石年代学和岩石学，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。由于挪威超高压地体的原型性质，这项研究的影响应该是相当大和广泛适用的。

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.