Structure and Evolution
One of the few potentially active volcanoes wholly within Bolivia, Tata Sabaya, is located on the northern shores of the Salar de Coipasa, on the Bolivian Altiplano (Figure 13.1;13.2). It is a symmetrical composite cone which is part of the E-W trending chain of edifices stretching from Cerro Pariani (Sacasani) in the east to Volcan Isluga (q.v.) to the west in Chile.
The edifice appears to have been built in four stages: (1) pyroclastic shield, (2) andesitic composite cone, (3) sector collapse that formed the large Holocene débris avalanche (DF) which appears to have crossed glacial lake terraces and spilled out across the Salar de Coipasa covering more than 300 square kilometers (Francis & Ramirez, 1985; Francis & Wells, 1988), and (4) lava flows and domes that filled in the amphitheater left by the collapse. A 200 m high remnant of the avalanche detachment scarp (ADS) is present on the SE flank. A small levée ridge left by the avalanche runs south eastwards across the lower flanks of the adjacent volcano, Cerro Pariani (Sacasani). The distal margin of the avalanche deposit is not preserved. Young lava flows (LF) are found on the western half of the edifice.
No information is available about the historic activity of the volcano. Although lava flow morphologies are well preserved on the volcano, they are not pristine, and it appears that there has been no activity within the last several hundred years at least.
There is no evidence of activity from the volcano (R. Carrasco, personal communication, 1989).
de Silva et al. (1993) reported that most Tata Sabaya whole-rock compositions fall in the range 60–62.5% SiO2 and evolve to be more silicic with time. The typical phenocryst assemblage is plagioclase > hornblende > hypersthene > augite > oxide. Many indicators of magma mixing (mixed phenocryst and matrix populations, resorption features, mixed glass compositions, contraindicative temperature indicators etc.,) are found at Tata Sabaya. Tata Sabaya is located 35 km east of the main Andean arc, but its rocks are compositionally similar to those from the northern (17–19°S) segment of the CVZ. The rocks are cal-calkaline, high in K2O, and enriched in LREE and extreme LILE enrichments (up to 1800 ppm Ba and Sr). 87Sr/86Sr (0.7056–0.7068) and 143Nd/144Nd (0.51217–0.51227) indicate crustal contamination, like other CVZ volcanoes.
Deruelle, B., & Brousse, R., 1984. "NuŽe ardente" deposits at Tata Sabaya volcano (Bolivian-Chilean Andes): pumices and lava blocks crystallized from a single magma at different depths. Rev. Geol. Chile. 22:3-15
de Silva, S.L., Davidson, J P., Croudacec, I.W., & Escobar. A., 1993. Volcanological and petrological evolution of Volcan Tata Sabaya, SW Bolivia. Journal of Volcanology and Geothermal Research, 55:305-335.
Francis, P.W., & Ramirez, C.F., 1985 "NuŽe ardente" deposits at Tata Sabaya volcano: a re-interpretation. Rev. Geol. Chile 24:107-110
Francis, P.W., & Wells G.L., 1988 Landsat Thematic Mapper Observations of dŽbris avalanche deposits in the Central Andes. Bull Volcanol. 50:258-278.