RUI: Sm-Nd Investigations within the Adirondack Mts., New York

申请资金支持对用U-Pb锆石方法定年的阿迪朗达克变质岩进行Sm-Nd研究。主要关注约1300 Ma的调性岩（高地）和阿拉斯加-调性片麻岩（低地）。初步结果表明，高原片麻岩具有相对年轻的nd模式年龄（~1300 ~ 1450 Ma），表明它们代表了此时阿迪朗达克地区注入了新的地壳物质。同样的资料表明，在安大略省中央变质沉积带的~1250 Ma的重质岩（Elzevir岩体）也是如此。这些岩石的化学性质表明它们是弧源性的，它们的存在表明阿迪朗达克-中央变质沉积带地区在~1300 Ma时以弧岩浆活动为主。本研究旨在对已知年龄的阿迪朗达克高原调性岩和相关片麻岩进行全面的Sm-Nd分析。此外，将对~1250 Ma的低地花岗岩进行研究，以确定它们是否表现出与高地相似或不同的nd模式年龄。这些结果应该有助于澄清阿迪朗达克高地和低地是否代表着沿着迦太基-科尔顿糜棱岩带缝合在一起的不同地形。此外，nd模式年龄将有助于确定低地花岗岩类是否代表幼年地壳添加。还将收集与斜长岩有关的变质沉积物和片麻岩的资料，以确定它们的来源和演化。所有这些结果对格伦维尔省的进化史具有重要意义。

Funds are requested to support Sm-Nd investigations of Adirondack metamorphic rocks that have been dated by U-Pb zircon methods. Attention is focused primarily on ~1300 Ma tonalites (Highlands) and alaskitic-tonalitic gneiss (Lowlands). Preliminary results suggest that the Highland gneisses have relatively young Nd-model ages (~1300-1450 Ma) indicating that they represent infusions of new crustal material into the Adirondack region at this time. The same data indicate that this is also true of ~1250 Ma tonaltiic rocks (Elzevir plutons) in the Central Metasedimentary Belt of Ontario. The chemistry of all these rocks suggests that they are arc-derived, and their presence suggests that the Adirondack-Central Metasedimentary Belt region was dominated by arc magmatism at ~1300 Ma. The present study is designed to provide a thorough Sm-Nd analysis of the Adirondack Highland tonalites and related gneisses whose age is known. In addition, ~1250 Ma Lowland granitoids will be investigated to determine whether they exhibit Nd-model ages similar to, or differing from, those of the Highlands. These results should help to clarify whether, or not, the Adirondack Highlands and Lowlands represent distinct terranes sutured together along the Carthage-Colton Mylonite Zone. In addition, the Nd-Model ages will help to ascertain whether the Lowland granitoids represent juvenile crustal additions. Data will also be collected for metasediments and gneisses related to the anorthosites in order to constrain their sources and evolution. All of these results have significant implications for the evolutionary history of the Grenville Province.