Advancements in U-Pb dating of deep crustal structures and magmatic/meteoritic events in relation to biotic evolution in earth history

地球历史上与生物进化相关的深部地壳结构和岩浆/陨石事件的 U-Pb 测年进展

• 批准号: 4261-2007
• 负责人: Krogh, Thomas
• 金额: $ 0.1万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=419867
• 关键词: Advancements; Pb; dating; deep; crustal

Precise uranium-lead analyses of minute (microgram) quantities of the mineral 'zircon' that crystallize during formation, reheating, or ductile flow events provide detailed scenarios of the evolution of the Earth's crust during periods of mountain building. When enormous continental plates collide, this produces over-thickened stacks of crustal rocks such that the lower part of the thrust stack is heated from below and softened and slides further inland. This must have happened under the Rocky Mountains as this thick pile of sedimentary material, once at the ocean bottom, now sits above an older continent. To understand processes that took place along the interface, 10 - 20 km below the Earth's surface where we cannot see, we must find a very old mountain root where the mountains have since been removed by erosion. The Grenville Province, well exposed along Georgian Bay, Ontario, is such a root. Here, geologists who study the rock record observe both the old, cold solid lower plate and the soft, hot overlying rocks that moved overtop during a great plate collision more than a billion years ago. In short, we discover the nature of the processes that put the Rockies in their place.

对在形成、再加热或韧性流动事件期间结晶的矿物“锆石”的微量（微克）的精确铀铅分析提供了造山期间地壳演化的详细情况。当巨大的大陆板块碰撞时，这会产生过度增厚的地壳岩石堆，使得逆冲断层的下部从下面被加热并软化，并进一步向内陆滑动。这一定发生在落基山脉下，因为这厚厚的沉积物，曾经在海底，现在坐落在一个古老的大陆之上。为了了解在地球表面以下10 - 20公里处我们看不见的界面沿着发生的过程，我们必须找到一个非常古老的山根，那里的山脉已经被侵蚀移走了。格伦维尔省，沿着乔治亚湾，安大略省，是这样一个根。在这里，研究岩石记录的地质学家观察到古老、寒冷的固体下部板块和柔软、炎热的覆盖岩石，这些岩石在十亿多年前的一次大板块碰撞中移动到顶部。简而言之，我们发现了将落基山脉置于其位置的过程的本质。