Reevaluation of metamorphic garnet-based P-T paths and their tectonic implications

变质石榴石 P-T 路径的重新评估及其构造意义

基本信息

批准号：
1918488
负责人：
Matthew Kohn
金额：
$ 25.78万
依托单位：
Boise State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1918488&HistoricalAwards=false
关键词：
Reevaluation metamorphic garnet based paths

项目摘要

This project investigates the degree to which natural crystals grow in chemical equilibrium. This information is central to the study of metamorphic rocks, especially the pressures and temperatures at which they form. The research examines rocks from several different mountain belts that have been subjected to different pressures and temperatures through geologic time. The project supports the education and training of graduate and undergraduate students, including students from underserved groups. In addition, samples collected during the research are the focus of undergraduate in-class mineralogy and petrology exercises at Boise State University, which serves an unique student demographic (significant percentages of Hispanic, returning, and veteran students). The central focus of this project is to critically evaluate the hypothesis that metamorphic crystals grow substantially out of chemical equilibrium in a rock. A novel approach using inclusion elastic thermobarometry is applied to recover temperature and pressure independent of mineral chemistry. Three main research questions include: (1) Does inclusion elastic barometry and thermometry yield significantly different P-T paths compared to thermodynamically-based methods? (2) Does inclusion elastic barometry and thermometry imply static growth of garnet cores, perhaps even encompassing entire crystals in low-grade rocks? (3) Do differences either in matrix strain or in bulk compositions that shift equilibrium garnet growth to higher temperatures reduce the amount of overstepping, the size of garnet cores, and the bias to calculated P-T paths? Analyses include measurements of pressure and temperature for four different orogenic belts: the northern Appalachians, central Alps, southernmost Chile, and central/eastern Himalaya. Results broadly evaluate the frequency and magnitude of disequilibrium garnet growth, as well as the effects of temperature and strain on garnet nucleation. This research includes a PhD student and undergraduate students to make measurements, interpret data, present results at international meetings, and write up results for publication.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目研究了自然晶体在化学平衡中生长的程度。这些信息是对变质岩石的研究，尤其是它们形成的压力和温度的核心。该研究检查了几个不同的山带的岩石，这些山带经过地质时期遭受了不同的压力和温度。该项目支持研究生和本科生的教育和培训，包括来自服务不足的小组的学生。此外，在研究期间收集的样本是博伊西州立大学本科矿物学和岩石学练习的重点，该大学服务于独特的学生人群（西班牙裔，返回和资深学生的很大一部分）。该项目的主要重点是批判性地评估变质晶体在岩石中的化学平衡中大大生长的假设。采用包含弹性热压测量法的一种新型方法用于恢复与矿物化学无关的温度和压力。三个主要的研究问题包括：（1）与基于热力学的方法相比，纳入弹性气压法和温度计是否会产生明显不同的P-T路径？（2）包含弹性气压和温度法是否暗示着石榴石岩心的静态生长，甚至可能包含低级岩石中的整个晶体？（3）在基质菌株中或散装组合物中的差异会降低平衡石榴石生长到更高的温度，从而减少了过度施加的量，石榴石核的大小以及对计算的P-T路径的偏见？分析包括四个不同造山带的压力和温度的测量：北阿巴拉契亚人，中央阿尔卑斯山，最南端的智利和中部/东部喜马拉雅山。结果广泛地评估了石榴石生长不平衡的频率和幅度，以及温度和应变对石榴石成核的影响。这项研究包括一名博士生和本科生，以进行衡量，解释数据，在国际会议上介绍结果以及为出版的成果写成结果。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和评估值得的支持。更广泛的影响审查标准。