SGER: A New Method for Determining the Paleoelevation of Orogens

SGER：确定造山带古海拔的新方法

• 批准号: 0412509
• 负责人: Christian Teyssier
• 金额: $ 5.04万
• 依托单位: University of Minnesota-Twin Cities
• 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: 2004-03-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0412509&HistoricalAwards=false
• 关键词: SGER; New; Method; Determining; Paleoelevation

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.

这项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崩塌或侵蚀造山带的古高程。在造山带伸展塌陷过程中，岩浆水侵入上地壳，与拆离糜棱岩中的重结晶白色云母发生了彻底的相互作用。从白色云母中测得的同位素比值可以得到大气降水的同位素组成，从而可以将深部岩石的化学和结构演化与景观和气候的演化直接联系起来。石英岩中的同运动白色云母用40 Ar/39 Ar方法测定年龄，以确定变形和与流体相互作用的时间。在云母中测量的氘氢比提供了使用现有气候模型与海拔的联系。从Shuswap核心复杂（不列颠哥伦比亚省）的初步结果表明，该地区是在海拔至少4000米约4900万年前。新方法正被应用于其他核心复杂的科迪勒拉（Okanogan-Kettle复杂，Albion-筏河-松鸡溪复杂）作为测试方法的可重复性暴露的糜棱岩石英岩。糜棱岩化的年龄从5000万年到1500万年不等。因此，该方法被用来解释从始新世到中新世的科迪勒拉的构造和古海拔。该技术可移植到其他造山带，增强了对造山运动期间地壳动力学、景观演化和气候之间相互作用的理解。