Petrology and geochemistry of the Tacana Volcanic Complex, Mexico-Guatemala: evidence for the last 40,000 yr of activity

The Tacaná Volcanic Complex (TVC) on the border of Mexico and Guatemala rises above Mesozoic metamorphic and Tertiary plutonic and volcanic rocks. The TVC consists of three volcanic edifices which, from NE-to SW, are named Chichuj, Tacaná, and San Antonio. Chichuj volcano is constituted mainly of andesitic lava flows (59-63 wt.% SiO2). Tacaná volcano is composed of basaltic-andesite lava flows (56-61 wt.% SiO2), and andesitic and dacitic domes (61-64 wt.% SiO2), surrounded by fans of block-and-ash flow deposits of 38 000, 28 000, and 16 000 yr BP with andesitic juvenile clasts (60-63 wt.% SiO2). San Antonio volcano is built of lava flows, andesitic and dacitic domes (58-64 wt.% SiO2), and one block-and-ash flow deposit dated 1,950 yr BP. The isotope ratios of the TVC andesites varies from 0.70455 to 0.70459 87Sr/86Sr and 0.51275 to 0.51280 143Nd/144Nd. A mafic enclave has ratios of 0.70441 for 87Sr/86Sr and 0.51282 for 143Nd/144Nd. The rocks belong to the sub-alkaline suite and follow the characteristic trend of calc-alkaline rocks, with medium-K content and negative anomalies of Nb, Ti, and P, and enrichment in LREE as is typical of orogenic zones.