Collaborative Research: Miocene Volcanism in the Sierra Nevada, California: Stratigraphy, Volcanology, Geochronology and Structural Geology

加州大学圣巴巴拉分校和南密西西比大学的这项合作研究计划将建立内华达山脉北部至中部中新世火山岩的区域地层结构和年代学框架，同时重建构造环境和火山过程。主要目的是评价这些中中新世火山岩的构造意义及其与现代和古代俯冲、盆地和山脉伸展以及热点背景的关系。将制作详细的火山和沉积岩相图，并用来确定同火山断裂的性质和时间。西尔兰角砾岩的岩石学、图像分析和扫描电子显微镜(SEM)成像将被用来研究和量化碎屑和基质的类型、形态、尺寸和破碎类型(脆性、韧性、过渡性)，并将结果与所有可信成因的已公布的火山角砾岩实例进行比较。将完成代表性岩套(包括所有待测年样品)的初步XRF地球化学分析，并与角砾岩中具有基质的碎屑的成分进行比较。为了测试我们时代数据的地质一致性，40Ar/39Ar年代学的采样将集中在包含至少三到四个不同年代单位的地层序列上。将完成单矿物颗粒(总熔融)的Ar年代学以及增量阶梯加热实验。

AbstractEAR-0125050SkillingUniversity of Southern MississippiThis Collaborative Research proposal between the UC Santa Barbara and the University of Southern Mississippi will establish a regional stratigraphic structural and geochronological framework for Miocene volcanic rocks of the northern to central Sierra Nevada, and at the same time reconstruct structural settings and volcanological processes. The main motivation is to evaluate the tectonic significance and relationship of these mid-Miocene volcanic rocks to modern and ancient subduction, Basin and Range extension, and hotspot settings. Detailed volcanic and sedimentary lithofacies maps will be produced and used to determine the nature and timing of synvolcanic faulting. Petrography, image analysis and Scanning Electron Microscope (SEM) imaging of the Sierran breccias will be employed to study and quantify clast and matrix types, morphologies, dimensions and fragmentation styles (brittle, ductile, transitional), and results will be compared with published examples of volcanic breccias of all plausible origins. Preliminary XRF geochemical analysis of representative suites (including all samples to be dated) will be completed and compared with compositions of clasts with matrices in the breccias. To test for geological consistency in our age data, sampling for 40Ar/39Ar geochronology will concentrate on stratigraphic successions containing at least three or four different datable units. Ar geochronology of single mineral grains (total fusions) as well as incremental step heating experiments will be completed.