U-Pb zircon age of metafelsite from the Pinney Hollow Formation; implications for the development of the Vermont Appalachians
U-Pb zircon age of metafelsite from the Pinney Hollow Formation; implications for the development of the Vermont Appalachians
复制标题
Pinney Hollow 地层中的变辉长岩的 U-Pb 锆石年龄；
DOI：
10.2475/ajs.299.2.157
复制
发表时间：
1999
影响因子：
2.9
通讯作者：
J. Aleinikoff
中科院分区：
文献类型：
--
作者：
G. Walsh;J. Aleinikoff
佛蒙特州中部的Pinney Hollow组是晚元古代至寒武纪Iapetan被动边缘发展期间沉积在劳伦阶边缘的裂谷碎屑岩至漂移阶段盖层序列的一部分。常规锆石U-Pb数据表明，来自Pinney Hollow地层的变长岩的年龄为571+或-5 Ma。地球化学数据表明，变霏细岩（现在是一种石英钠长片麻岩或花岗岩）的原岩是流纹岩，其来源是板内花岗岩和洋脊花岗岩环境之间的过渡性物质，并且可能穿过部分扩张的大陆地壳。过渡的设置是一致的，与以前的数据从变基性岩的平尼空心形成，并支持的想法，源岩浆通过大陆地壳的断裂边缘的劳伦克拉通。571+或-5 Ma的年龄提供了新英格兰裂谷碎屑盖层序列的第一个地质年代学年龄，并确立了Pinney Hollow地层的晚元古代年龄。平尼凹陷的晚元古代年龄证实了盖层序列的原地和准原地岩石之间存在一个重要的映射逆冲断层。这些研究结果支持的解释，Taconic根区位于佛蒙特州阿巴拉契亚山脉的腹地的东侧的绿色山阿巴拉契亚。
The Pinney Hollow Formation of central Vermont is part of a rift-clastic to drift-stage sequence of cover rocks deposited on the Laurentian margin during the development of the Iapetan passive margin in Late Proterozoic to Cambrian time. Conventional U-Pb zircon data indicate an age of 571+ or -5 Ma for a metafelsite from the Pinney Hollow Formation. Geochemical data indicate that the protolith for the metafelsite, now a quartz-albite gneiss or granofels, was rhyolite from a source that was transitional between a within-plate granite and ocean-ridge granite setting and probably came through partially distended continental crust. The transitional setting is consistent with previous data from metabasalts in the Pinney Hollow Formation and supports the idea that the source magma came through continental crust on the rifted margin of the Laurentian craton. The 571+ or -5 Ma age provides the first geochronologic age from the rift-clastic cover sequence in New England and establishes a Late Proterozoic age for the Pinney Hollow Formation. The Late Proterozoic age of the Pinney Hollow confirms the presence of a significant mapped thrust fault between the autochthonous and para-autochthonous rocks of the cover sequence. These findings support the interpretation that the Taconic root zone is located in the hinterland of the Vermont Appalachians on the eastern side of the Green Mountain massif.