Jurassic(?) Emplacement of the Golconda Allochthon, West-Central Nevada: Implications for the Late Paleozoic - Mesozoic Tectonic Development of Western North America

内华达州中西部戈尔康达阿洛奇顿的侏罗纪（？）侵位：对北美西部晚古生代-中生代构造发展的影响

• 批准号: 0074117
• 负责人: Clyde Northrup
• 金额: --
• 依托单位: Boise State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-15 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0074117&HistoricalAwards=false
• 关键词: Jurassic; Emplacement; Golconda; Allochthon; West

Jurassic(?) emplacement of the Golconda Allochthon, west-central Nevada: Implications for the Late Paleozoic - Mesozoic tectonic development of western North AmericaWalter S. SnyderClyde J. NorthrupEAR-0074117ABSTRACT:From a north-south line that bifrucates Nevada to the present-day coast, the continental crust of western North America has been constructed by the repeated accretion of tectonic terrains. One of those events was the emplacement of the Golconda Allochthon (GA) which is widely regarded as the principal structural expression of the Late Permian to earliest Triassic (approx. 240 million years ago) Sonoma Orogeny. A critical evaluation of available timing constraints, however, indicates that east-directed emplacement of the GA may have occurred as late as the Middle Jurassic - perhaps 75 My after the Sonoma event. Confident interpretation of the role of the GA in the late Paleozoic to Mesozoic history of western North America awaits clarification of key field relationships and more precise age control of igneous plutons and volcano-sedimentary rocks that constrain the age of the Golconda Thrust. Proposed research will evaluate this hypothesis through a combination of: 1) targeted field mapping to clarify critical field relations; 2) structural/kinematic analysis to establish the transport direction of the Golconda Thrust; 3) U-Pb geochronology to precisely date Mesozoic plutons that either cut, or are cut by the Golconda Thrust; and 4) whole-rock isotope geochemistry to compare initial isotopic ratios of Mesozoic plutons within the GA to those of plutons in the adjacent structural basement. If valid, a Jurassic age of Golconda thrusting would significantly impact current interpretations of the late Paleozoic and Mesozoic tectonic evolution of western North America.

Jurassic（？）内华达州中西部戈尔康达外来岩的侵位：对北美西部晚古生代-中生代构造发展的意义摘要：从南北走向的内华达州到现在的海岸线，北美西部的大陆地壳是由构造地形的反复增生而形成的。其中一个事件是Golconda Allochthon（GA）的就位，它被广泛认为是晚二叠世至早三叠世的主要构造表现（约1000年）。2.4亿年前）索诺马造山运动。然而，对现有时间限制的关键评估表明，GA向东侵位可能发生在中侏罗世--可能是索诺马事件后75百万年。对GA在晚古生代至中生代北美西部历史中的作用的可靠解释，有待于澄清关键领域的关系和更精确的年龄控制的火成岩岩体和火山-沉积岩，限制戈尔孔达逆冲断层的年龄。拟议的研究将通过以下方式对这一假设进行评估：1）有针对性的实地测绘，以澄清关键的实地关系; 2）结构/运动学分析，以确定戈尔孔达逆冲断层的运输方向; 3）U-Pb地质年代学，以精确确定中生代侵入岩的年代，这些侵入岩要么被戈尔孔达逆冲断层切割，要么被切割;（4）全岩同位素地球化学研究，比较GA内中生代岩体与邻近构造基底岩体的初始同位素比值。如果有效的话，侏罗纪时期的戈尔康达逆冲推覆作用将显著影响目前对北美西部晚古生代和中生代构造演化的解释。