Production of Jurassic rhyolite by anatexis of the lower crust of Patagonia

摘要: Abstract The mid-Jurassic Marifil and Chon-Aike volcanic rocks of eastern Patagonia are part one the largest silicic igneous provinces known. Rb Sr geochronology indicates eruptive ages 175–190 Ma for complex (mostly Toarcian-Aalenian). majority isotopically uniform, with initial 87Sr/86Sr= 0.7067 ± 0.0003 eNdt = −4 2. Primary magmas andesitic composition were generated by partial melting mafic “Grenvillian” lower crust, indentified depleted-mantle model 1150–1600 Ma. Lower crustal pyroxene-granulite xenoliths can be modelled as residual Jurassic source, although they may alternatively co-genetic cumulates. dacite-rhyolite suite formed crystal-liquid fractionation processes from primary andesites: involving multistage crystallization re-melting during magma ascent, later stages evolution being explicable fractional plagioclase, amphibole accessory minerals. province represents large-scale reworking associated unique tectonic environment Gondwana break-up.