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爆发和地震的位置和时间，并在更长的时间尺度上控制着山脉带的位置。一些最活跃的构造区域发生在板块聚合的地方，通常是一个板块在另一个板块下移动（“俯冲”），例如喜马拉雅山脉，印度-澳大利亚板块目前正在欧亚板块下俯冲。俯冲带是重要的混合区。例如，地表物质和流体通常被拉或拖到地球的深部地幔中，地幔物质可以被带到地表。为了更好地了解发生在俯冲带的关键过程的力学，重要的是要认识和调查古代俯冲带。特别是，必须认识到岩石和流体存在于地球表面，被带到数百公里的地幔中，然后返回到表面。这项研究的目标是开发工具来识别和表征曾经在俯冲带中被带到很深的岩石和流体（或熔体），并最终使用这些长途旅行的材料作为记录器或指示器，记录今天发生在主要俯冲带中的过程。该项目由岩石学地球化学和EPSCoR（刺激竞争性研究的实验计划）项目共同资助，代表了缅因州鲍登学院和马萨诸塞州大学之间的合作。该研究将为Bowdoin College的本科生提供一个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。 虽然人们普遍认为，在许多板块构造碰撞中，特别是在中生代（距今5亿年），地表物质被俯冲到高压和超高压下，但超高压变质作用（“UHP变质作用”）的实际证据通常被更年轻的事件所掩盖。拟议研究的主要目标是确定哪些因素有利于保存极端变质作用的证据。最终目标是解开超高压岩石上的叠印效应，深入了解超高压构造作用的机制，并可能开发新的方法来识别在超高压条件下变质的岩石，但现在几乎没有这种转变的证据。这一认识可能会提高我们的能力，以确定在较老的构造环境中的超高压变质作用的证据。在罗多彼变质杂岩、保加利亚和希腊，选择了五个相对容易到达的地点进行详细研究。这五个地区都经历过超高压变质作用，但地质证据被不同程度地叠印和模糊。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，来自鲍登学院和马萨诸塞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，显微结构和地质年代学证据，并突出强调叠印和掩盖这一记录的结构和岩石学过程。