Adirondack Thermal History

阿迪朗达克热历史

• 批准号: 1144454
• 负责人: John Valley
• 金额: $ 27.23万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-01 至 2015-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144454&HistoricalAwards=false
• 关键词: Adirondack; Thermal; History

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.

纽约州的阿迪朗达克山脉是格伦维尔省的一个异类，从德克萨斯州延伸到拉布拉多。这一地形代表了1200至10亿年前存在的巨大山带被深深侵蚀的根部。就像今天的喜马拉雅一样，这些山脉经历了强烈的加热和压力，然后是侵蚀，使得岩石在地球深处形成？地壳冷却并上升到地表，这说明了该地区的地形、矿藏和娱乐潜力。这项研究将应用最新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。这项研究将在阿迪朗达克山脉的一系列岩石类型和地点测试一项试点研究的结果。第一项研究提出，惊人的快速冷却和隆起发生在西北阿迪朗达克山脉，沿着一条延伸超过300公里的主要mylonite带（Carthage-Colton, Bonamici et al. 2011）。新的结果将检验这一模型，限制峰值变质温度，并评估同心“靶心”的意义。等温线的模式被经典地解释为是由圆顶隆起造成的。降温和抬升速率将与正在进行的U-Pb年代学研究相结合，以检验渥太华造山运动（~1050 Ma）末期阿迪朗达克高地抬升的竞争理论。本项目将为高品位变质岩的氧同位素测温测速研究提供一种新的方法。新颖的功能，准确和精确的原位分析氧同位素比率从小1-10 &amp；#956；M点将用于分析被难熔寄主矿物包裹的矿物包裹体，并量化冷却过程中形成的晶内扩散梯度。这些剖面将用更新后的快速晶界扩散模型代码进行建模。样品将主要从麻粒岩相岩石中选择。石榴石-石英测温技术将在整个阿迪朗达克地区进行详细测试，并进行一系列的自一致性露头测试，其他矿物系统将在当地进行测试。石榴石+石英在一系列正长石和变质沉积层中很常见，允许在整个地层中应用相同的不依赖压力的温度计。将计算石榴石中的石英包裹体和被石榴石日冕包围的石英的温度，以及这些T？将S与石英岩中石榴石的S进行比较，并与其他地温测量进行比较。氧同位素剖面将在钛矿、石榴石、选定的锆石和辉石的单晶中进行测量。