Structure and Evolution
Cerro Tuzgle (Figure 31.1) occupies an important position as it is the most easterly of the Holocene polygenetic volcanoes in the Central Andes. It is located on the eastern margin of the Argentinian puna, about 120 km east of the main arc and 500 km from the trench. Volcanic activity here is thought to be related to Quarternary extensional faulting along the El Toro lineament (Coira & Kay, 1993). The simple edifice is ~0.5 Ma to Recent in age and is built on a platform of older ignimbrites (Coira & Kay, 1989). Satellite cones (i.e. C) and flank lava flows in various states of preservation are present. Early lava flows extend to distances of 9 km to the north of the present volcano. Remnants of possible débris avalanches (DF) from the NE and southern flanks of the volcano can also be discerned on the satellite image. Many youthful looking flank lava flows were erupted from the well preserved summit crater (SC). These have morphologies consistent with dacitic and andesitic compositions. While their morphology and preservation suggest recent activity, all except one show some degradation and are mantled with aeolian material. The exception is the large, low-albedo lava flow on the southern flank (L), which overlies hydrothermally altered material in the summit region. It is the most recent event from Tuzgle, and may represent renewed activity after a period of quiesence at the volcano. A sulphur mine (La Betty) has been worked near the summit.
Coira and Kay (1989, 1993) make no mention of any current activity at this volcano. A hot spring (Agua Caliente del Tuzgle) is present in the Quebrada Agua Caliente, 6 km northwest of the volcano.
Coira and Kay (1989) have made the only study of this volcano and their findings are summarized below. The rocks of Tuzgle range from andesite to dacite (57 - 70% SiO2) and contain physical and chemical evidence for magma mixing and interaction with the crust. For instance, non-equilibrium mineral assemblages indicate magma mixing, while plagioclase bearing xenoliths and quartz rimmed with pyroxene are taken to indicate crustal involvement. The lavas have relatively high trace element abundances (e.g. Ba 420-690) and are characterised by within plate characteristics (e.g. La/Ta 12-18; Ba/La 10-12). Th, U and K contents are relatively high to Ba (e.g. K/Ba 38-61; Ba/Th 25-42). Decrease in 87Sr/86Sr from 0.70762 to 0.79762 in the early ignimbrites, dacites and andesites to 0.70660 in the youngest andesite suggests decreasing involvement of crust with SiO2 through time. Coira and Kay published more detailed geochemical evidenceor maga origins in 1993.
Coira, B, & Kay, S.M., 1989. Cerro Tuzgle - Quaternary Andean volcanism in the eastern Puna-Altiplano plateau, Argentina. IAVCEI, New Mexico Bureau of Mining and Mineral Resources, Bulletin 131, p55.
Coira, B., and Kay, S.M., 1993. Implications of Quaternary volcanism at Cerro Tuzgle for crustal and mantle evolution of the Puna Plateau, Central Andes, Argentina. Contributions to Mineralogy and Petrology, 113(1): 40-58.