RUI: U-Pb Zircon Geochronology of Adirondack Metamorphosed Igneous Rocks

之前由美国国家科学基金会支持的研究已经提供了超过25个U-Pb锆石年龄，为阿迪朗达克山脉的地质演化提供了一个重要的时间框架。在这些新的结果中，至少有两个需要进一步的实地和化学研究。第一批~1300 Ma的变质玄武岩出露于阿迪朗达克南部和东部，呈钙质趋势。这些岩石和与之伴生的花岗片麻岩暗示了早期碰撞岩浆弧的存在。在阿迪朗达克低地海德学派的片麻岩中，年龄约1300 Ma的片麻岩也表现出钙碱性趋势，可能还有第二次早期的碰撞岩浆弧。这两个假定与弧形有关的地体在1160-1130 Ma横跨这两个地区的锰质-碳质花岗岩套侵位之前相互对接。认为化学研究对格伦维尔省板块构造演化具有重要意义。此外，海德学派片麻岩的侵入历史和变质火山岩历史将通过野外和化学手段进行研究。还建议对Diana杂岩和Jenkins山中的超镁铁质岩脉和岩席进行化学研究，包括对分异趋势的模拟。在马西地块。前者横切正长岩的年龄为1154±3 Ma，后者携带来自1147 Ma=6 Ma斯塔克岩套的红柱石包体，这将有助于约束目前尚不确定的斜长岩侵位的上位年龄。

Previous NSF-supported research has made available over 25 U-Pb zircon ages that have provided an important temporal frame- work for the geological evolution of the Adirondacks. Among these new results are at least two that require further field and chemical investigation. The first ~1300 Ma mettonalitic rocks exposed in the southern and eastern Adirondakcs and exhibiting calcalkaline trends. These rocks, and associated granitic gneiss, suggest the presence of an early collisional magmatic arc. Within the Adirondack Lowlands Hyde School Gneiss of ~1300 Ma age also exhibits calcalkaline trends and perhaps a second early collisional magmatic arc. These two postulated arc-related terranes docked against one another prior to the emplacement of the 1160-1130 Ma mangeritic-charnockitic suite which traverses both regions. It is proposed that chemical studies be critical to the plate tectonic evolution of the Grenville Province. In addition, the intrusive vs. metavolcanic history of the Hyde School Gneiss is to be investigated by field and chemical means. It is also proposed that chemical studies involving the modelling of differentiation trends be applied to ultramafic dikes and sheets in the Diana Complex and on Jenkins Mt. in the Marcy massif. The former crosscuts syenite dated at 1154+3 Ma and the latter carries xenoliths of mangerite from the 1147=6 Ma Stark suite will help constrain the currently uncertain upper age of anorthosite emplacement.