Geology and tectonics of a middle Oligocene rhyolitic-dome suite in the south of the State of San Luis Potosí

Abstract

Topaz- and/or tin-bearing rhyolite is common in Mexico. It lies within an extensive belt that extends from the western United States to central Mexico. These rocks are of special interest because they are interpreted as products of partial melting of Precambrian continental crust, extruded during periods of extensional tectonism. Furthermore, there are some economic ore deposits associated with topaz rhyolite. Topaz rhyolite occurs in the middle Oligocene (32-26 Ma) San Luis Potosí volcanic field (SLPVF). Topaz is found near the vents or in the lava flows of the San Miguelito Rhyolite (K-Ar: 29.2 ± 0.8 Ma). This rhyolite is characterized by the phenocryst assemblage quartz + sanidine + Na plagioclase + biotite + opaque minerals. These rocks crystallized from fluorine-rich magmas. Topaz and tin were formed as vapor-phase minerals... In order to continue, download full text in PDF.