From Jurassic shores to Cretaceous plutons: Geochemical evidence for paleoalteration environments of metavolcanic rocks, eastern California
Volcanic and plutonic rocks exposed in east-central California record a long history of metasomatism and/or metamorphism within the Mesozoic Cordilleran continental arc. We use whole-rock and mineral elemental compositions, along with standard and cathodoluminescence petrography to characterize alteration histories of Late Triassic to Middle Jurassic metavolcanic rocks in the Ritter Range, White-Inyo Mountains, and Alabama Hills. Although alkali-metasomatism is widespread and pervasive, ratios and abundances of Ce, Th, Tb, and Ta suggest that mafic protoliths from the White-Inyo Mountains were shoshonitic, whereas those from the Ritter Range were calc-alkaline. Alkali exchange apparently modified the compositions of many metavolcanic rocks. Much of this metasomatism may have occurred at low-temperature (T) conditions, and attended or shortly postdated deposition of the volcanic protoliths. High δ 18 O values for K-rich metatuffs from