Collaborative Research: Age and Correlation of the Protolith of the Pelona-Orocopia-Rand Schist: Implications for Cordilleran Late Mesozoic-Early Tertiary Tectonics

9902960巴特中生代晚期至古近纪方济各会杂岩、大峡谷群/海岸山脉蛇绿岩和加州的Sierra内华达州岩基构成了古代安第斯式会聚板块边缘的经典例子。 在加州中部，这些单位定义了一个简单的模式，但在加州南部被打乱。 此外，在南加州，弧杂岩坐落在一个神秘的片岩上，根据一个明显横切的火成岩体的年龄，它太老了，不可能是方济会或大峡谷序列的变质等价物，但合乎逻辑的是，片岩应该与这些岩石中的一组相关。 最近从片岩碎屑锆石测年产生的年龄与白垩纪岩石的相关性兼容，导致老火成岩体是一个包体或构造卵石在片岩，而不是横切片岩的可能性。 该项目将对该系统的片岩碎片进行更多的碎屑锆石研究，以确定其年龄并将其归入正确的原岩序列。 这个长期存在的谜团的解决将大大澄清和简化这个经典地区的聚合历史。

9902960BarthThe late Mesozoic to Paleogene Franciscan Complex, Great Valley Group/Coast Ranges ophiolite, and the Sierra Nevada batholith of California comprise on of the classic examples of an ancient, Andean-style convergent plate margin. In central California these units define a simple pattern, but are disrupted in southern California. Additionally, in southern California, the arc complex sits on an enigmatic schist that, based on the age of an apparently cross-cutting igneous body, is too old to be the metamorphosed equivalent of either the Franciscan or the Great Valley sequence, yet it is logical that the schist should correlate with one of these sets of rocks. Recent dating of detrital zircons from the schist has produced ages compatible with correlation to the Cretaceous rocks, leading to the possibility that the old igneous body is an inclusion or tectonic pebble in the schist rather than crosscutting the schist. This project will persue additional detrital zircon studies of the schist fragments of this system in order to confirm its age and to assign it to the correct protolith sequence. Resolution of this long-standing enigma will greatly clarify and simplify the convergent history of this classic area.