Characterizing Eastern North American Mantle Using Re-Os

本文对北美东部的地幔捕虏体和蛇绿岩（保存完好的海洋岩石圈）进行了研究，目的是约束从太古代到中生代大西洋裂陷的地幔岩石圈的演化。这两套不同的岩石圈样本不同的地幔区域，将提供关于次大陆岩石圈地幔演化和对流软流圈地幔形成海洋岩石圈的补充信息。这项工作的第一个目标是表征在纽约州北部、佛蒙特州和魁北克省的煌斑岩岩脉和金伯利岩中发现的一组地幔捕虏体。这些捕虏体包含了北美东部从太古宙到白垩纪地幔演化的信息。第二个目标是确定横跨阿巴拉契亚山脉的构造侵位蛇绿岩中铬铁矿的Re-Os系统。这些蛇绿岩均在奥陶纪短时间内结晶就位。这组样品将有助于评估对流地幔在锇同位素方面的非均质性，以及俯冲板源锇在超俯冲带海洋岩石圈形成过程中的可能作用。本科生研究人员将执行本提案中概述的大部分工作，作为独立研究或高级论文项目的一部分。本研究的主要贡献将是更好地理解造山活动中岩石圈的形成过程。

MinarikEAR-0229995Mantle xenoliths and ophiolites (preserved oceanic lithosphere) from eastern North America will be studied with the purpose of constraining the evolution of mantle lithosphere from the Archean through the Mesozoic Atlantic rifting. These two different suites sample different mantle regions and will return complementary information on the evolution of the subcontinental lithospheric mantle, and the convecting athenospheric mantle which gives rise to oceanic lithosphere. The first goal of this work is to characterize a set of mantle xenoliths found in lamprophyre dikes and kimberlites in upstate New York, Vermont, and Quebec. These xenoliths hold information about the evolution of the mantle under eastern North America from the Archean to the Cretaceous. The second goal will be to determine the Re-Os systematics of chromites from tectonically emplaced ophiolites spanning the length of the Appalachians. These ophiolites all crystallized and were emplaced within a short period of time during the Ordovician. This sample set will allow an evaluation of the heterogeneity of the convecting mantle with respect to osmium isotopes, and of the possible role of subducting slab-derived osmium during the formation of supra-subduction zone ocean lithosphere.Undergraduate student researchers will perform much of the work outlined in this proposal as part of independent research or senior thesis projects. The major contributions of this study will be a better understanding of the processes of creation of lithosphere during mountain-building events.