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

以前nsf支持的研究已经获得了超过25个U-Pb锆石年龄，为阿迪朗达克的地质演化提供了一个重要的时间框架。在这些新结果中，至少有两个需要进一步的实地和化学研究。第1 ~1300 Ma变质岩出露于阿迪朗达克山脉南部和东部，呈现钙碱性倾向。这些岩石和相关的花岗质片麻岩表明存在早期的碰撞岩浆弧。在阿迪朗达克低地，~1300 Ma的海德派片麻岩也表现出钙碱性的趋势，可能还有第二次早期碰撞岩浆弧。这两个假定的与弧相关的地层在横跨两个地区的1160-1130 Ma岩质-炭质岩套就位之前相互对接。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，还利用野外和化学方法研究了海德组片麻岩的侵入史和变质火山史。此外，还建议将涉及分异趋势模拟的化学研究应用于戴安娜杂岩和马西地块的詹金斯山的超镁质岩脉和片岩。前者的横切正长岩年代为1154+3 Ma，后者携带来自1147=6 Ma Stark套的锰矿捕虏体，这将有助于限制目前不确定的斜长岩位的上年龄。

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.