SGER: A New Method for Determining the Paleoelevation of Orogens

这笔用于探索性研究的小额赠款正在研究一种新的方法，利用变形过程中与大气降水相互作用和平衡的糜棱岩石英岩的稳定同位素组成来确定坍塌或侵蚀造山带的古海拔。在造山带的伸展坍塌过程中，气象水渗入上地壳，并与滑脱糜棱岩中重结晶的白云母彻底相互作用。大气水的同位素组成可以从用白色云母测量的同位素比率中恢复，从而使深部岩石的化学和结构演化与地貌和气候的演化之间建立了直接联系。用40Ar/39Ar方法测定了石英岩中同位移白色云母的年龄，以确定变形的时间和与流体的相互作用。在云母中测得的重氢比提供了使用现有气候模型与海拔高度之间的联系。来自Shuswap核心复合体(不列颠哥伦比亚省)的初步结果表明，大约4900万年前，该地区的海拔至少为4000米。新方法正被应用于科迪勒拉其他核心杂岩(Okanogan-Kettle杂岩、Albion-RAFT River-Grous Creek杂岩)中暴露的糜棱岩石英岩，以测试该方法的重现性。糜棱岩化的年龄从5000万年到1500万年不等。因此，该方法被用来解释始新世至中新世科迪勒拉的构造和古海拔。这项技术可移植到其他造山带，并增强了对造山过程中地壳动力学、地貌演变和气候之间相互作用的理解。

This small grant for exploratory research is investigating a new approach to determining paleoelevation of collapsed or eroded orogens using the stable isotope composition of mylonitic quartzite that interacted and equilibrated with meteoric water during deformation. During extensional collapse of the orogen, mateoric water penetrates the upper crust and interacts thoroughly with recrystallizing white mica in detachment mylonites. The isotopic composition of the meteoric water can be retrieved from the isotopic ratios measured in white micas, permitting a direct link to be made between the chemical and structural evolution of rocks at depth and the evolution of landscape and climate. Syn-kinematic white mica in the quartzite is dated using 40Ar/39Ar methods to determine the timing of deformation and interaction with fluids. Deuterium-hydrogen ratios measured in mica provide the link to elevation using existing climate models. Preliminary Results from the Shuswap core complex (British Columbia) indicate that the region was at an elevation of at least 4000 meters about 49 million years ago. The new method is being applied to mylonitic quartzite exposed in other core complexes in the Cordillera (Okanogan-Kettle Complex, Albion-Raft River-Grouse Creek Complex ) as a test of the reproducabilty of the method. The age of mylonitization varies from 50 to 15 million years old. Therefore, the method is being used to interpret the tectonics and paleoelevation of the Cordillera from Eocene to Miocene time. This technique is portable to other orogens and enhances understanding of the interaction among crustal dynamics, landscape evolution, and climate during orogeny.