Igneous-related Metallogenesis of the Great Basin

大盆地的火成岩成矿作用

• 批准号: 8903773
• 负责人: Mark Barton
• 金额: $ 4.54万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-07-01 至 1990-11-01
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8903773&HistoricalAwards=false
• 关键词: Igneous; related; Metallogenesis; Great; Basin

A two-fold study of igneous-related metallogenesis of Phanerozoic plutons in the Cordilleran miogeocline of the Great Basin is proposed: (1) district-scale studies of late-stage magmatic and mineralizing processes related to Cretaceous granitoids, concentrating lithophile-element mineralization (LEM) associated with two-mica granites; (2) a comparative investigation of the magmatism and metallogeny of Jurassic, Cretaceous, and Tertiary intrusions in the miogeocline. This proposal builds on the results of ongoing NSF supported studies of LEM and its regional context. Justifications for this approach include: (1) the LEM is of a type that has been little studied in the western United States, yet it shares many characteristics with important deposits elsewhere in the world; (2) examination of igneous-related metallogeny in a single, geologically uniform (at a large scale) area nominally eliminates lateral crustal heterogeneities as a cause for variation, enabling comparison of multiple examples of the same type of system and investigation of other factors such as long-term temporal changes in crustal thermal structure. Evaluation of LEM systems involves completing studies of local areas, and intensively studying one area (Birch Creek, CA), which contains a well exposed two-mica granite with related deformation, metamorphism and hydrothermal alteration. The approach combines detailed field work with geochemical and petrological studies. These will be complemented by collaborative geochronological and geophysical measurements. The main goals are to refine the descriptive and genetic understanding of Great Basin-type LEM and to compare it with other areas. Available data demonstrate the Great Basin Phanerozoic petrogeny and metallogeny correlate, and that they change systematically with time; they appear to reflect changes in crustal thermal structure (Barton, in press). Quantitative interpretation is hindered by insufficient data on the igneous rocks and ore deposits. Geochemical reconnaissance (whole rock and mineralogical, isotopic and elemental analyses ) of Jurassic and Tertiary intusions is proposed to complement ongoing studies of systematic variations in Cretaceous granitoids. This survey, along with continuing compilation of published data, will form the basis for better indentifying and interpreting regional temporal trends.

对大盆地科迪勒拉期古地斜显生宙深成岩成矿作用进行了两方面的研究：(1)区域规模的与白垩纪花岗岩有关的晚期岩浆和成矿作用研究，集中了与二云母花岗岩有关的亲岩元素成矿作用；(2)侏罗纪、白垩纪、第三纪侵入岩浆作用与成矿作用的对比研究。这项建议建立在国家科学基金会正在支持的关于LEM及其区域背景的研究结果的基础上。这种方法的理由包括：(1)LEM是一种在美国西部很少被研究的类型，但它与世界其他地方的重要矿床有许多共同特征；(2)在单一的、地质上统一的(大范围)区域内检查与火成矿有关的成矿作用，名义上消除了作为变化原因的地壳横向不均质性，从而能够比较同一类型系统的多个实例，并调查其他因素，如地壳热结构的长期时间变化。对LEM系统的评估包括完成局部地区的研究，并深入研究一个地区(加利福尼亚州白桦溪)，该地区包含一块暴露良好的两云母花岗岩，具有相关的变形、变质和热液蚀变作用。这种方法将详细的野外工作与地球化学和岩石学研究结合起来。这些措施将得到合作的地球年代学和地球物理测量的补充。主要目标是完善对大盆型LEM的描述和成因理解，并将其与其他地区进行比较。现有数据表明，大盆地显生宙成岩作用和成矿作用相互关联，并随时间系统地变化；它们似乎反映了地壳热结构的变化(Barton，正在出版中)。火成岩和矿床资料不足，阻碍了定量解释。建议对侏罗纪和第三纪直觉进行地球化学调查(全岩和矿物学、同位素和元素分析)，以补充目前正在进行的白垩纪花岗岩类系统变化的研究。这项调查连同继续汇编已公布的数据，将成为更好地查明和解释区域时间趋势的基础。