Collaborative Research: Geochronology of Carbonate Mineralization in the Lithosphere

合作研究：岩石圈碳酸盐矿化的地质年代学

• 批准号: 1019845
• 负责人: Ethan Baxter
• 金额: $ 17.71万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1019845&HistoricalAwards=false
• 关键词: Collaborative; Research; Geochronology; Carbonate; Mineralization

The solid earth plays a major role in the long-term geologic carbon cycle. Atmospheric, oceanic, and mantle derived CO2 or CO2-rich fluids reacts with silicate minerals and/or dissolved cations in the lithosphere to form secondary carbonate minerals in a variety of geological environments (regional metamorphism, contact metamorphism, subduction zone metamorphism, hydrothermal and ore-forming systems in the continental and oceanic crust, sedimentary basins, and weathering). The net rate, timescales, and fluxes of CO2 into secondary carbonates via these carbonation reactions thus exerts a first order control on the global carbon cycle balance, and serves as a monitor of broader chemical transport via fluid flow and related tectonic processes within these diverse lithospheric contexts. In order to interrogate and quantify these matters of rate, timing, and flux of CO2 (and hydrothermal fluid flow in general) within the lithosphere over geologic (i.e. 1 Myrs) timescales, an accurate and precise carbonate geochronometer is required. Carbonate geochronology has proven to be a significant challenge due to natural complexities and analytical limitations. This study is focused on improving our ability to directly measure the timing of carbonate mineralization by refining and validating both the U/Pb and Sm/Nd carbonate geochronometers. Its developmental emphasis will be on the less-frequently tested Sm/Nd system for carbonates, and on the subsequent integration and cross-checking of Sm/Nd and U/Pb data. This development will take advantage of new analytical and sample preparation techniques that have already been developed at BU and elsewhere. Preliminary data suggest that carbonate minerals datable by Sm/Nd do exist, though the exact context and identity of the datable mineral?s occurrence is not clear. The team will seek to refine carbonate geochronology by, 1) careful sample characterization to identify the exact minerals that are ultimately being dated as well as their geological occurrence, 2) refining sample preparation methods to separate and extract datable co-genetic phases for precise Sm/Nd and U/Pb geochronological analysis, 3) establish protocols for testing the accuracy of carbonate geochronology. Three field contexts of carbonate mineralization will be explored including 1) regional metamorphic carbonate, 2) hydrothermal carbonate associated with sulfide/sulfate or ore forming systems, and 3) modern carbonates forming at hot springs and on the sea floor.This project will provide new tools that solid-earth geoscientists can use to 1) explore, quantify, and illuminate the role of the solid-earth in the global geological carbon cycle, and 2) explore the rate, timing, and flux of fluid flow and associated chemical transport and tectonic processes in the lithosphere in general. Through undergraduate coursework and high school outreach programs in place at BU and Stanford, students will be educated as to the relevance of the solid earth in broader geoscience issues including carbon management, climate, and earth evolution. The project will bring together two geochemists with complementary tools and interests and will contribute to the establishment of new lab infrastructure at Stanford for an early career PI. The BU graduate student who will drive this research will contribute to work in both the BU and Stanford labs.

固体地球在长期的地质碳循环中起着重要作用。 大气，海洋和地幔衍生的二氧化碳或富含二氧化碳的液体与岩石层中的硅酸盐矿物质和/或溶解的阳离子反应，在多种地质变质，地质变质，接触变质，接触变质，俯冲区变质和矿化系统中，在各种地质变质环境中形成次级碳酸盐矿物质，在风化）。 因此，通过这些碳酸反应将二氧化碳的净速率，时间尺度和通量进入二级碳酸盐，因此对全球碳循环平衡进行了一阶控制，并用作这些多样的岩石圈环境中流体流和相关构造过程的更广泛的化学转运的监控。 为了审问和量化岩石圈中二氧化碳的速率，时机和通量的问题（以及一般的水热流动流），而不是地质（即1 MyRS）的时间表，这是一个准确而精确的碳酸盐地球量。 由于自然复杂性和分析局限性，碳酸盐地质学已被证明是一个重大挑战。 这项研究的重点是提高我们通过精炼和验证U/PB和SM/ND碳酸盐地球工程学的直接测量碳酸盐矿化时间的能力。 它的发展重点将放在碳酸盐较少测试的SM/ND系统上，以及随后的SM/ND和U/PB数据的集成和交叉检查。 这种开发将利用BU和其他地方已经开发的新分析和样品制备技术。 初步数据表明，碳酸盐矿物质的数据确实存在，尽管尚不清楚数据矿物的确切上下文和身份。 该团队将寻求通过1）仔细的样本表征来完善碳酸盐的年代学，以确定最终正在陈述的确切矿物质以及其地质出现，2）精炼样品制备方法，以分离和提取数据可数据的共同基因阶段，以精确的SM/ND和U/PB地球货量分析，3）确定carbyate ochbonate Geoch的协议。 将探索碳酸盐矿化的三个田间环境，包括1）区域变质碳酸盐，2）与硫酸/硫酸盐或矿石形成系统相关的水热碳酸盐，以及3）3）在温泉和沿海地板上形成的现代碳酸盐，将在固体地球地球地球地球上使用固体，并提供固定的地球地球地球地球层，并提供固定的工具。碳循环和2）探索岩石圈中流体流和相关化学转运和构造过程的速率，时机和通量。 通过BU和Stanford的本科课程和高中课程计划，将对学生在更广泛的地球科学问题中的相关性进行教育，包括碳管理，气候和地球演化。 该项目将通过互补的工具和兴趣汇集两名地球化学主义者，并将为在斯坦福大学建立新的实验室基础设施做出贡献。 将推动这项研究的BU研究生将有助于在BU和Stanford Labs的工作。