Adirondack Thermal History

纽约的阿迪朗达克山脉是从德克萨斯州延伸到拉布拉多的格伦维尔省的一个离群点。这个地形代表了12亿到10亿年前存在的一个巨大山脉带的深深侵蚀的根源。就像今天的喜马拉雅山一样，这些山脉经历了强烈的加热和压力，然后是侵蚀，使岩石在地球深处形成？的地壳冷却和上升到表面，占地形，矿床，和该地区的娱乐潜力。这项研究将应用新开发的地球化学技术来确定形成这些岩石的热历史和流体历史。这项研究将测试在阿迪朗达克山脉的一系列岩石类型和地点的试点研究的结果。第一项研究提出，令人惊讶的快速冷却和隆升发生在西北部阿迪朗达克山脉沿着一个主要的糜棱岩带，延伸超过300公里（迦太基-科尔顿，Bonamici等人，2011年）。新的结果将测试这个模型，约束峰值变质温度，并评估同心？正中靶心等温线的模式，传统上被解释为是由于圆顶隆起。 冷却和隆升速率将与正在进行的U-Pb地质年代学研究相结合，以测试在奥塔万造山运动（~1050 Ma）结束时阿迪朗达克高地隆升的竞争理论。本项目将为高级变质岩的氧同位素测温和测速研究开辟一条新的途径。从小型1-10样品中精确原位分析氧同位素比的新能力μ m点将用于分析被耐火主体矿物铠装的矿物夹杂物，并量化在冷却期间形成的晶内扩散梯度。这些配置文件将模拟更新的代码快速晶界扩散模型。样品将主要从麻粒岩相岩石中选择。将在阿迪朗达克山脉对石榴石石英测温法进行详细测试，并进行一系列露头自洽测试，其他矿物系统将在当地进行测试。石榴石+石英在一系列正片麻岩和变质沉积物中很常见，因此可以在整个正片麻岩中应用相同的压力独立温度计。温度将计算石榴石中的石英包裹体，并在石英包围石榴石冠，这些T？将与石英岩中石榴石的温度和其他地质测温方法进行比较。氧同位素剖面将在钛铁矿、石榴石以及选定的锆石和辉石的单晶中测量。

The Adirondack Mountains, New York are an outlier of the Grenville Province that stretches from Texas to Labrador. This terrain represents the deeply eroded roots of a vast mountain belt that existed 1200 to 1000 million years ago. Like the Himalaya today, these mountains were subjected to intense heating and pressure, followed by erosion, allowing rocks formed deep in the Earth?s crust to cool and rise to the surface, accounting for the topography, ore deposits, and recreational potential of the region. This study will apply newly developed techniques of geochemistry to determine the thermal and fluid history that formed these rocks. This study will test the results of a pilot study in a range of rock types and localities in the Adirondacks. That first study proposed that surprisingly rapid cooling and uplift occurred in the NW Adirondacks along a major mylonite zone that extends over 300 km (Carthage-Colton, Bonamici et al. 2011). The new results will test this model, constrain the peak metamorphic temperatures, and assess the significance of the concentric ?bulls-eye? pattern of isotherms that has classically been interpreted to result from domical uplift. Cooling and uplift rates will be combined with on-going studies of U-Pb geochronology to test competing theories for uplift of the Adirondack Highlands at the end of the Ottawan Orogeny (~1050 Ma). This project will develop and apply a new approach to studies of oxygen isotope thermometry and speedometry in high-grade metamorphic rocks. Novel capabilities for accurate and precise in situ analysis of oxygen isotope ratios from small 1-10 μm spots will be employed to analyze mineral inclusions that are armored by refractory host minerals and to quantify intracrystalline diffusion gradients that formed during cooling. These profiles will be modeled with updated code for the Fast Grain Boundary diffusion model. Samples will be selected primarily from granulite facies rocks. Garnet-quartz thermometry will be tested in detail across the Adirondacks with a series of outcrop tests for self-consistency, and other mineral systems will be tested locally. Garnet + quartz are common in a range of orthogneisses and metasediments, allowing the same pressure independent thermometer to be applied across the terrane. Temperatures will be calculated for both quartz inclusions in garnet, and in quartz surrounded by garnet coronas, and these T?s will be compared to those from garnets in quartzite, and to other geothermometry. Oxygen isotope profiles will be measured in single crystals of titanite as well as garnet, and selected zircons and pyroxenes.