In east-central California, Triassic to Jurassic metavolcanic rocks occur as roof pendants that were intruded by the northwest-trending, predominantly Cretaceous Sierra Nevada batholith. Throughout the Seirran arc, there are widespread metavolcanic rocks showing complicated alteration histories including feldspar replacement. For example, the metavolcanic quartz latite tuff of Skelton Lake displays effects of both contact metamorphism and low-T metasomatism. Understanding these alteration histories is important because they inform our ability to infer igneous origins, deformation history, paleogeography, and potential mineral deposits in similar settings.

This project aims to understand the reaction mechanisms that altered feldspars during low-T metasomatism and those related to contact metamorphism of the quartz latite tuff of Skelton Lake in east-central California. Building upon existing cathodoluminescence (CL) and back-scattered electron imaging (BSE), I will analyze the samples using electron back-scatter diffraction (EBSD), allowing us to determine the crystallographic orientation of replacement and original grains, and compare samples to existing CL images. Interface-coupled dissolution-precipitation (ICDP) is a reaction mechanism in which the dissolution of a mineral is coupled with the simultaneous precipitation of a replacement mineral on the dissolved surface. The preservation of crystallographic orientation during the replacement of parent grains is one criterion for identifying ICDP. Field emission scanning electron microscopy (FE-SEM) will be used for high-resolution imaging to detect the presence of microporosity, another criterion for ICDP.