Re-Os Geochemistry to Test Recurrent Fluid Flow in the Crust

印度是全球资源发现和管理伙伴关系的下一个前沿。 印度中部的矿产资源勘探迫切需要广泛应用现代地质知识。 具体而言，矿石矿物所在岩石的年龄以及引入经济上重要的矿物的时间受到的限制非常少。 年龄关系是解释地质记录的基础。 例如，该团队的初步工作表明，金矿的引入比以前假设的晚了近20亿年。 这一认识需要新的印度中部成矿模型--这些模型表明Au是在最后一个主要超大陆盘古大陆分裂期间形成的。 调查人员将集中在印度中部的一个研究区域，大约在孟买和加尔各答之间的中间，该区域横跨横跨印度次大陆的一条主要地质线。 这一线性构造，即中印度构造带（CITZ），已经活跃了20多亿年，今天仍在继续产生地震。 由于矿石沉积与地壳中热流体的运动有关，因此确定矿石矿物的年代也可以确定流体运动的年代。 这种年龄控制将有助于我们了解CITZ的完整地质历史，并对其正在进行的地震活动产生影响。 该项目汇集了一个独特的多学科团队，具有互补的技能。 两名美国地球科学家和一名对构造和成矿过程有深入了解的博士生将与两名印度地球科学家和一名对区域地质有丰富了解的印度学生合作。 支持这一项目的独特工具是铼-锇（Re-Os）地球化学，由科罗拉多州立大学的AIRIE计划开发，用于矿物勘探和构造重建。 这两种稀有元素组成了一对放射性元素，Re的同位素衰变为Os的特定同位素，其半衰期几乎是地球年龄的十倍。 这两种元素在成矿环境中都有富集，从而为贵金属硫化物矿床的定年提供了机制。 此外，Os的同位素组成可作为示踪剂，揭示地球中金属的原始来源。地壳或上地幔。 Re-Os系统提供了一个新的窗口，在地球的构造原因和流体运动的时间？的外壳。 从历史上看，那些从事矿石地质学工作的人一直在寻找构造来理解成矿过程。 在提议的反向方法中，研究小组将利用矿石中的证据来了解构造过程。 因此，该项目开辟了一个新的途径，以广泛的领域的构造，同时提供地质年代学框架，为下一个世纪的可持续矿产开发？全球经济蓬勃发展的关键基地

India is the next frontier for partnerships in global resource discovery and management. Exploration for mineral resources in central India urgently needs broad application of modern geologic understanding. Specifically, the age of the rocks that host ore minerals, and the timing of introduction of economically important minerals are very poorly constrained. Age relationships are the foundation for interpretation of the geologic record. The team builds on preliminary work that has shown, for example, that the introduction of gold ore was nearly two billion years later than previously assumed. This realization demands new models for ore formation in central India - models that suggest Au formed during breakup of the last major supercontinent, Pangea. The investigators will concentrate on a study area in central India, roughly mid-way between Mumbai and Kolkata, which straddles a major geologic lineament that cuts across the Indian subcontinent. This lineament, the Central Indian Tectonic Zone (CITZ), has been active for more than two billion years, and continues to generate earthquakes today. Because ore deposition is tied to movement of hot fluids in the Earth's crust, dating the ore minerals also dates fluid movement. This age control will help our understanding of the full geologic history of the CITZ with implications for its on-going seismic activity. The project brings together a unique multi-disciplinary team with complementary skills. Two US geoscientists and a PhD student with advanced understanding of tectonics and ore-forming processes will team with two Indian geoscientists and an Indian student with solid knowledge of the regional geology. The unique tool underpinning this project is rhenium-osmium (Re-Os) geochemistry, as developed for application to mineral exploration and tectonic reconstructions by the AIRIE Program at Colorado State University. These two rare elements comprise a radioactive pair, as an isotope of Re decays to a specific isotope of Os with a half-life nearly ten times the age of the earth. Both elements are concentrated in the ore-forming environment, and thus provide a mechanism for dating precious metal-sulfide ore deposits. In addition, the isotopic composition of Os serves as a tracer, revealing the primary source of the metals in the earth?s crust or upper mantle. The Re-Os system offers a new window into the tectonic causes and timing of fluid movement in the earth?s crust. Historically, those working in ore geology have looked to tectonics for understanding of ore-forming processes. In the proposed reverse approach, the team will use the evidence from the ores to understand the tectonic processes. The project thus opens a new approach to the broad field of tectonics, while simultaneously providing the geochronologic framework for the next century of sustainable mineral development ? a critical base for the burgeoning global economy.