Collaborative Research: Preserving Evidence of Extreme Metamorphism in the Rhodope Complex

合作研究：保存罗多彼杂岩极端变质作用的证据

• 批准号: 1650266
• 负责人: Michael Williams
• 金额: $ 17.62万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650266&HistoricalAwards=false
• 关键词: Collaborative; Research; Preserving; Evidence; Extreme

Plate tectonic processes on Earth control the location and timing of major volcanic eruptions and earthquakes, and over longer time scales, the location of mountain belts. Some of the most active tectonic regions occur where plates converge, typically with one plate moving ('subducting') under another, such as the Himalayan Mountains where the Indo-Australian Plate is currently subducting under the Eurasian plate. Subduction zones are important regions of mixing. For example, surface materials and fluids are commonly pulled or dragged into Earth's deep mantle and mantle materials can be brought to the surface. In order to better understand the mechanics of critical processes that occur at subduction zones, it is important to recognize and investigate ancient subduction zones. In particular, it is essential to recognize rocks and fluids that were present at the Earth's surface, were carried hundreds of kilometers into the mantle, and then were returned to the surface. The goal of this research is to develop tools to identify and characterize rocks and fluids (or melts) that were once brought to great depth in subduction zones, and to ultimately use these far-traveled materials as recorders or indicators of the processes that occur in major subduction zones today. This project is co-funded by the Petrology & Geochemistry and the EPSCoR (Experimental Program to Stimulate Competitive Research) programs and represents a collaboration between Bowdoin College, Maine and the University of Massachusetts. The study will provide an opportunity for undergraduate students from Bowdoin College to interact with graduate students from UMass and for students from both institutions to carry out high-level research using modern analytical instruments. Although it is widely accepted that surface materials were subducted to high- and ultrahigh- pressures in many plate tectonic collisions, especially in Phanerozoic time ( 500 million years before present), the actual evidence of ultrahigh-pressure metamorphism ('UHP metamorphism') is commonly obscured by younger events. The primary objective of the proposed research is to determine what factors favor the preservation of evidence of extreme metamorphism. The ultimate goal is to unravel the effects of overprinting on UHP rocks, gain insight about the mechanics of UHP tectonism, and potentially develop new methods to identify rocks that were metamorphosed at UHP conditions, but now retain little to no evidence of this transformation. This insight may improve our ability to identify evidence of UHP metamorphism in older tectonic settings. Five relatively accessible localities within the Rhodope Metamorphic Complex, Bulgaria and Greece, have been chosen for detailed study. The five localities have all experienced UHP metamorphism, but the geologic evidence has been overprinted and obscured to varying degrees. Through fieldwork, a 10-week summer research institute, and collaborative research over the next two years, student and faculty researchers from Bowdoin College and UMass will characterize the petrologic, microstructural, and geochronological evidence for high- and ultrahigh-pressure metamorphism and highlight the structural and petrologic processes that overprint and obscure this record.

地球上的板块构造过程控制着主要火山喷发和地震的位置和时间，并在较长的时间尺度上控制着山脉的位置。一些最活跃的构造区域发生在板块汇聚的地方，通常一个板块移动（“俯冲”）到另一个板块之下，例如喜马拉雅山脉，印度-澳大利亚板块目前正在欧亚板块之下俯冲。俯冲带是重要的混合区域。例如，表面材料和流体通常被拉或拖入地球深处的地幔，并且地幔材料可以被带到地表。为了更好地了解俯冲带发生的关键过程的机制，识别和研究古代俯冲带非常重要。特别是，必须认识到地球表面存在的岩石和流体被带到地幔数百公里处，然后又返回地表。这项研究的目标是开发工具来识别和表征曾经深入俯冲带的岩石和流体（或熔体），并最终使用这些远行的材料作为俯冲带中发生的过程的记录器或指示器。今天的主要俯冲带。该项目由岩石学与地球化学和 EPSCoR（刺激竞争性研究的实验计划）项目共同资助，代表缅因州鲍登学院和马萨诸塞大学之间的合作。该研究将为鲍登学院的本科生提供与麻省大学研究生互动的机会，并为两个机构的学生提供使用现代分析仪器进行高水平研究的机会。 尽管人们普遍认为，在许多板块构造碰撞中，特别是在显生宙（距今5亿年前），地表物质都俯冲到高压和超高压下，但超高压变质作用（“UHP变质作用”）的实际证据是通常被较年轻的事件所掩盖。拟议研究的主要目的是确定哪些因素有利于保存极端变质作用的证据。最终目标是揭示叠印对超高压岩石的影响，深入了解超高压构造作用的机制，并有可能开发新方法来识别在超高压条件下变质的岩石，但现在几乎没有保留这种转变的证据。这一见解可能会提高我们识别较古老构造环境中超高压变质作用证据的能力。罗多彼变质杂岩内五个相对容易到达的地点（保加利亚和希腊）已被选择进行详细研究。这五个地点都经历过超高压变质作用，但地质证据都不同程度地被套印和模糊。通过实地考察、为期 10 周的夏季研究所以及未来两年的合作研究，鲍登学院和麻省大学的学生和教师研究人员将描述高压和超高压变质作用的岩石学、微观结构和地质年代学证据，并强调构造和岩石学过程掩盖并掩盖了这一记录。