An Integrated Investigation of Ultrahigh-Pressure (?) Metamorphism, North Qaidam, China

中国柴北缘超高压（？）变质作用的综合研究

• 批准号: 0337191
• 负责人: An Yin
• 金额: $ 26.03万
• 依托单位: University of California-Los Angeles
• 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: 2004-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337191&HistoricalAwards=false
• 关键词: Integrated; Investigation; Ultrahigh; Pressure; Metamorphism

A recent discovery by geologists is that continental crust could be buried as deep as 90 km. This is a rather astonishing revelation because continental crust is typically about 30-35 km thick, and to have it buried below a depth of 90 km would require the continental crust to be surrounded by denser and fluid upper mantle rocks. This is rather difficult in physics because it requires the lighter continental crust to be dragged into the denser mantle materials. Exactly what forces have made the occurrence of this unusual process possible remains an active debate. A team of geologists from the University of California is currently investigating this problem. Because there are a variety of likely processes that may have induced continental rocks to decent to great depths, it is important to examine the rocks that bear the record of such deep burial in as many places on earth as possible. Another reason for geologists to examine as many cases of rock records of deep burial is that individual areas may not preserve a complete record of the burial process. Therefore, geologists as detectives, must use as many cases as possible to piece the complete history together. The study area that is currently under investigation is located in North Qaidam of the northern Tibetan plateau. This is a desert region exhibiting excellent exposure of rocks. Their research includes the following components. (1) Making a detailed geologic map of rocks that record deep-burial processes. The geologic map allows the naturally occurred geologic elements to be placed into a rigorous spatial context. As a result, the geometrical relationships among the different types of rocks can be systematically examined. (2) Sampling and petrologic analysis. Numerous samples collected from the field area are currently being analyzed for their mineralogical and chemical compositions using a variety of the state-of-the-art techniques and instruments. This analysis determines the exact depth that the rocks were buried and the temperature history associated with the rock burial. (3) Determination of age, duration, and rate of rock burial. This task is being carried out using the ion-microprobe and noble gas analyses. The main purpose of this investigation is to determine how fast the rock burial took place and how long it has taken to bring the rocks back to Earth's surface. The final completion of this research project will allow geologists to determine the forces that caused the down plunging of the light continental crust into the denser upper mantle, which in turn will reveal the fundamental aspects of physics and chemistry for the formation and evolution of Earth's crust that is central to Human's day-to-day livelihood.

地质学家最近发现的是，大陆地壳可以埋葬到90公里的深处。这是一个相当惊人的启示，因为大陆壳通常厚30-35 km，并且将其埋在90公里的深度以下将需要大陆地壳被浓密和液体上层地幔岩所包围。这在物理学中很困难，因为它需要将较轻的大陆壳拖入密集的地幔材料中。正是什么力量使这种异常过程的发生仍然是一个积极的争论。来自加利福尼亚大学的地质学家团队目前正在调查此问题。因为可能有多种可能导致大陆岩石的过程变得不错，因此重要的是要检查在地球上尽可能多地埋葬的岩石。地质学家检查岩石记录的许多案例的另一个原因是，各个地区可能无法保留埋葬过程的完整记录。因此，地质学家作为侦探，必须使用尽可能多的案例将完整的历史拼凑在一起。 目前正在调查的研究区域位于藏族北部高原的北基地室。这是一个沙漠地区，表现出极好的岩石曝光。他们的研究包括以下组件。 （1）制作记录深层过程的岩石的详细地质图。地质图允许将自然发生的地质元素置于严格的空间环境中。结果，可以系统地检查不同类型的岩石之间的几何关系。 （2）采样和岩石学分析。目前，正在使用各种最先进的技术和仪器分析从现场区域收集的许多样品，以分析其矿物学和化学成分。该分析确定了岩石被埋葬以及与岩石埋葬相关的温度历史的确切深度。 （3）确定年龄，持续时间和岩石埋葬率。该任务是使用离子微探针和贵重气体分析进行的。这项调查的主要目的是确定岩石埋葬发生的速度以及将岩石带回地球表面花费了多长时间。该研究项目的最终完成将使地质学家能够确定导致光线大陆壳向密度浓密的上地幔坠落的力，这反过来又揭示了物理学和化学的基本方面，而化学的基本方面是地球地壳的形成和进化，这是人类日常薪水的核心。