United States-China Scientific Cooperative Project: A Petrotectonic Study of Precambrian Blueschist and Eclogite Belts in Central China

中美科学合作项目：中国中部前寒武纪蓝片岩和榴辉岩带岩石构造研究

• 批准号: 8917319
• 负责人: W. Gary Ernst
• 金额: $ 14.35万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-04-01 至 1992-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8917319&HistoricalAwards=false
• 关键词: United; States; China; Scientific; Cooperative

This proposal described a United States - Peoples Republic of China multidisciplinary cooperative project in earth science. The study involves three investigators from Stanford, two from Japan and 8 from China. We wish to continue to conduct coordinated field-petrological-geochronological-tectonic investigations of Precambrian blueschist and eclogite belts in central China in order to constrain the genesis of these intracratonal blueschist belts. Recent reports of many pre- Mesozoic-- even Precambrian -- blueschist belts in the PRC provide an excellent opportunity to test various hypotheses for blueschist facies metamorphism by establishing the tectonic and age relations of these occurrences. Chinese colleagues have identified 4 probable Precambrian occurrences including a discontinuous, coherent blueschist belt more than 2000 km long in central China and suggested its origin is related to deep fault systems. Eclogites are abundant and some are associated with blueschists: other lie within Archean gneiss terranes and contain relict coesite -- a high pressure polymorph of SiO2. Except for reconnaissance surveys, little is known about the phase petrology and mineral parageneses of Chinese blueschists and eclogites; available radiometric dating from Precambrian blueschist and eclogite metamorphism is ambiguous. The proposed U.S. China project will remedy these problems; it will involve systematic field observation, microprobe analyses of coexisting minerals + P-T-ometry, bulk XRF analyses of rocks and K-Ar, U-Pb, Nd-Sm and Ar39/Ar40 age determinations. Primary objectives are: (1) to map the distribution and structural setting of blueschist facies rocks and eclogites; (2) to determine mineralogical and chemical compositions of the metamorphic rocks; (3) to compare and contrast various types of eclogites; (4) to delineate mineral paragenesis and P-T-time paths for blueschist and eclogite metamorphism; (5) to establish the ages of blueschist and eclogite metamorphism through radiometric dating; and (6) to elucidate the genetic relationship between recognized metamorphic, igneous and tectonic features. The program should contribute to a much improved understanding of the genesis of intracratonal blueschists and eclogites and the complex geologic- tectonic assembly of central China. Our previous cooperative exchanges with Chinese geologists have been highly productive. Accelerated progress is anticipated because of the detailed groundwork and many preliminary petrological and field studies that have already been completed.

本提案描述了一个美国和中华人民共和国在地球科学领域的多学科合作项目。这项研究包括来自斯坦福大学的三名研究人员，两名来自日本，八名来自中国。我们希望继续对中国中部地区前寒武纪蓝片岩和榴辉岩带进行野外岩石学、地质年代学和构造学的协调研究，以限制这些克拉通内蓝片岩带的成因。最近关于中国前中生代—甚至前寒武纪—蓝片岩带的报道，通过建立这些产状的构造和时代关系，为检验蓝片岩相变质作用的各种假设提供了极好的机会。中国同事已经确定了4个可能的前寒武纪地层，包括中国中部一个长达2000多公里的不连续、连贯的蓝片岩带，并提出其起源与深部断裂系统有关。榴辉岩丰富，部分与蓝片岩伴生；其他榴辉岩位于太古代片麻岩地体内，含有残余榴辉岩——一种SiO2的高压多晶岩。除勘测外，对中国蓝片岩和榴辉岩的相岩学和矿物共生特征了解甚少；可用的前寒武纪蓝片岩和榴辉岩变质的放射性测年是不明确的。拟议中的美中项目将弥补这些问题；它将包括系统的现场观测、共存矿物的微探针分析+ p - t测定、岩石的大量XRF分析以及K-Ar、U-Pb、Nd-Sm和Ar39/Ar40年龄测定。主要目的是：(1)确定蓝片岩相岩和榴辉岩的分布和构造背景；(2)确定变质岩的矿物学和化学成分；(3)对各类榴辉岩进行比较对比；(4)圈定蓝片岩和榴辉岩变质作用的矿物共生和p -t -时间路径；(5)通过放射性测年确定蓝片岩和榴辉岩变质的年龄；(6)阐明已识别的变质、火成岩与构造特征之间的成因关系。该项目将有助于更好地了解克拉通内蓝片岩和榴辉岩的成因以及中国中部复杂的地质构造组合。我们以往与中国地质学家的合作交流卓有成效。由于已经完成了详细的基础工作和许多初步的岩石学和实地研究，预计工作进展会加快。