Collaborative Research: Equilibrium and Kinetic Studies of New Trace Element Thermobarometers

合作研究：新型微量元素温压计的平衡和动力学研究

• 批准号: 1551343
• 负责人: Jay Thomas
• 金额: $ 37.62万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551343&HistoricalAwards=false
• 关键词: Collaborative; Research; Equilibrium; Kinetic; Studies

This project is a collaborative effort between Rensselaer Polytechnic Institute (RPI) and Syracuse University (SU) to develop tools and strategies to "reverse engineer" key minerals of Earth's continental crust - that is, to learn how and when these materials formed and the conditions experienced since their origin. Consider, for example, the benefits of being able to "read" the history of a single grain of sand simply by measuring its content of key chemical elements: Was it formed during an episode of mountain building or during a volcanic eruption? How far did it travel from its source? Was it associated with a potentially valuable ore deposit at the time of formation? This project will involve laboratory synthesis of selected minerals over a range of temperature and pressure conditions, followed by measurement of the amounts of elemental impurities incorporated during growth (the concentrations of aluminum and titanium in quartz, for example, depend strongly on the temperature and pressure of quartz formation). The broader purpose of the project is to develop "chemical tools" for all researchers to use in deciphering events and processes of our planet's past - from mountain building to formation of ore deposits.A decade of experimental research at RPI has focused on evaluating the effects of pressure (P) and temperature (T) on the solubilities of low-abundance elements in key minerals of the continental crust. This enterprise has been called "trace-element thermobarometry" because each application is based on the concentration of a single, marginally compatible element in a common or otherwise strategic mineral phase (e.g., Ti in zircon). These thermobarometers differ in fundamental ways from "conventional" thermobarometers based on major-element phase equilibria, and they have a key advantage: if the system is properly constrained, the concentration of a single impurity in a single mineral can be used as an indicator of its crystallization T and/or P. To date, this effort has produced thermo(baro)meters based on the Ti content of zircon, the Ti content of quartz ("TitaniQ"), the Zr content of rutile, and the Zr content of titanite. The value of these thermobarometers has been enhanced significantly through experimental calibration of the diffusion laws for all relevant impurities in the phases of interest, so users can assess the robustness of the thermobarometers for specific real-world applications. Efforts to date have had significant impact in the geoscience community (as judged by literature citations), but the development of trace-element thermobarometers and the improvement of "old" ones is far from complete. The proposed work is aimed at providing a full toolbox of thermobarometers for crustal systems that includes cross-checks of the various P-T indicators. Specifically, the TitaniQ calibration will be extended to lower P for application to volcanic rocks, and Ti-in-zircon will be more thoroughly assessed for P effects. Entirely new systems and applications will also be pursued, including the development of P-T indicators based on Ti in coesite for ultra high-pressure (UHP) rocks, Al in quartz to complement TitaniQ, Si and Al in rutile, and Ti in both K-spar and in kyanite. Equilibrium studies of all new systems will be complemented by diffusion measurements of the relevant elements. Further, the pressure-volume-temperature properties of fluid inclusions in crystals from experimental run products will be used in conjunction with trace-element thermobarometers to confirm accuracy of our calibrations at relatively low P-T applications. The proposed study involves implementation of techniques specifically in experimental geochemistry, but the applications of our results extend across a substantial expanse of geoscience, including not only igneous and metamorphic petrology but also ore-deposits research, structural geology, tectonics, and sedimentology.

该项目是伦斯勒理工学院（RPI）和锡拉丘兹大学（SU）之间的合作努力，旨在开发工具和策略，以“逆向工程”地球大陆地壳的关键矿物-也就是说，了解这些材料如何以及何时形成以及自其起源以来所经历的条件。 例如，考虑一下能够通过测量其关键化学元素的含量来“阅读”一粒沙子的历史的好处：它是在造山运动期间形成的还是在火山爆发期间形成的？它从源头传播了多远？它在形成时是否与潜在的有价值的矿石存款有关？该项目将涉及在一定温度和压力条件下对选定矿物进行实验室合成，然后测量生长过程中掺入的元素杂质量（例如，石英中铝和钛的浓度在很大程度上取决于石英形成的温度和压力）。 该项目的更广泛的目的是为所有研究人员开发“化学工具”，用于破译我们星球过去的事件和过程-从造山到矿床的形成。RPI十年的实验研究集中在评估压力（P）和温度（T）对大陆地壳关键矿物中低丰度元素溶解度的影响。 这项事业被称为“痕量元素温压法”，因为每种应用都是基于单一的、勉强相容的元素在共同的或其他战略性矿物相中的浓度（例如，锆石中的Ti）。 这些温压计与基于主元素相平衡的“传统”温压计有根本的不同，它们具有一个关键优势：如果系统被适当地约束，则单一矿物中单一杂质的浓度可用作其结晶T和/或P的指示。迄今为止，这种努力已经产生了基于锆石的Ti含量的热（气压）计，石英（“TitaniQ”）的Ti含量、金红石的Zr含量和钛铁矿的Zr含量。 通过对感兴趣相中所有相关杂质的扩散定律进行实验校准，这些温压计的价值得到了显著提高，因此用户可以评估温压计在特定实际应用中的稳健性。 迄今为止的努力在地球科学界产生了重大影响（根据文献引用判断），但微量元素温压计的开发和“旧”温压计的改进远未完成。拟议的工作旨在为地壳系统提供一个完整的温压计工具箱，其中包括对各种P-T指标进行交叉检查。 具体而言，TitaniQ校准将扩展到较低的P，以应用于火山岩，并将更彻底地评估锆石中的钛对P的影响。 还将寻求新的系统和应用，包括开发基于柯石英中的Ti的超高压（UHP）岩石的P-T指标，石英中的Al以补充TitaniQ，金红石中的Si和Al，以及钾晶石和蓝晶石中的Ti。对所有新系统的平衡研究将辅之以有关元素的扩散测量。此外，压力-体积-温度特性的流体包裹体在晶体中的实验运行产品将被用于与微量元素温压计，以确认我们的校准在相对较低的P-T应用的准确性。拟议中的研究涉及实施技术，特别是在实验地球化学，但我们的研究结果的应用范围广泛的地球科学，不仅包括火成岩和变质岩石学，而且矿床研究，构造地质学，构造学和沉积学。