Collaborative Research: Lithospheric Structure and Evolution of the Rocky Mountain Transect of the Western U.S.: An Integrated Geological and Geophysical Investigation

这项合作研究旨在了解北美西南部落基山脉样带的岩石圈演化。该样带位于两个全球独一无二的构造体制的交界处，每个构造体制对了解大陆构造都具有至关重要的意义，共同代表着大陆岩石圈研究的杰出野外实验室。首先，一条1000公里宽的新元古代造山带记录了大陆物质从地幔源沿1.8Ga到1.6Ga之间的NE向边界快速增生并聚集到劳伦蒂亚南部。其次，目前西南部特别是落基山脉的高海拔是拉莱姆、第三纪和仍在进行的元古界岩石圈改造的表现，这导致了大陆内陆古老、寒冷、高速地幔和美国西部较热、低速地幔之间宽阔的NW向地幔边界带。通过研究跨越古代边界的现代岩石圈结构，P.I.希望更好地理解岩石圈演化过程中“主动”和“被动”过程之间的相互作用。他们的主要假设是，在美国西南部组装过程中产生的岩石圈结构深刻地影响了随后所有岩浆和构造事件中大陆岩石圈的物理和化学变化，包括与正在进行的小规模软流圈对流重组和软流圈置换岩石圈有关的事件。为了验证这一假设，他们提出了一套综合的多尺度实验，使用最先进的地球物理、地质和地球化学技术，旨在共同破译岩石圈的结构和演化，以及岩石圈形成和变形的过程。

9614638WillettThis collaborative study is aimed at understanding the evolution of the lithosphere of the Rocky Mountain transect in the North American southwest. This transect is located at the juncture of two globally-unique tectonic regimes, each of fundamental importance for understanding continental tectonics and together representing an outstanding field laboratory for studies of continental lithosphere. First, a 1000 km wide juvenile Proterozoic orogenic belt records rapid accretion of continental materials from mantle sources and their assembly to southern Laurentia along NE-trending boundaries between 1.8 and 1.6 Ga. Second, the present high elevation of the SW in general and the Rocky Mountains in particular, is the manifestation of Laramide, Tertiary, and still ongoing modification of Proterozoic Lithosphere that has resulted in a wide NW-trending mantle boundaray zone between old, cold, high velocity mantle in the continental interior and hotter, lower velocity mantle in the western U.S. By examining the present-day lithospheric structure across ancient boundaries, the P.I.s hope to better understand the interplay between "active" and "passive" processes during lithospheric evolution.Their principal hypothesis is that lithospheric structures produced during assembly of the southwestern U.S. have profoundly influenced physical and chemical modification of the continental lithosphere during all subsequent magmatic and tectonic events, including those related to the ongoing reorganization of small-scale asthenospheric convection and replacement of lithosphere by asthenosphere. To test this hypothesis, they propose an integrated set of multi-scale experiments using state-of-the-art geophysical, geological and geochemical techniques that, together, are designed to decipher lithosphere structure and evolution, and processes of lithosphere formation and deformation.***