Ignimbrites of the Cerro Galan Caldera, NW Argentina

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doi: 10.1016/0377-0273(85)90071-X
Authors:Sparks, R. Stephen J.; Francis, Peter W.; Hamer, R. D.; Pankhurst, R. J.; O'Callaghan, L. O.; Thorpe, R. S.; Page, R.
Author Affiliations:Primary:
Univ. Camb., Dep. Earth Sci., Cambridge, United Kingdom
Open Univ., United Kingdom
Br. Antarct. Surv., United Kingdom
Br. Antarct. Surv. at Inst. Geol. Sci., United Kingdom
Serv. Geol. Nac., Argentina
Volume Title:Journal of Volcanology and Geothermal Research
Source:Journal of Volcanology and Geothermal Research, 24(3-4), p.205-248. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-0273
Publication Date:1985
Note:In English. 34 refs.; illus. incl. 5 tables, strat. cols., geol. sketch map
Summary:This 35 X 20 km resurgent caldera is the largest post-Miocene caldera so far identified in the Andes. The complex developed along two prominent N-S reverse faults on a late Precambrian to late Palaeozoic basement which was uplifted in the early Miocene. Volcanism began prior to 15 m.y. Dacite to rhyodacite magma ascended along the faults erupting at least nine times between 7 and 4 m.y. (K/Ar); these are the Toconquis ignimbrite formation of which the total D.R.E. volume is > 500 km3. Two m.y. later a single major eruption formed the 1000 km3 Cerro Galan ignimbrite and the caldera and is thought to have been caused by the foundering of a cauldron block into the magma chamber. The later ignimbrite differs from the earlier in being a pumice-poor, crystal-rich deposit with few lithic clasts, no basal plinian deposit and no proximal lag breccias. The composition of the pumice clasts is a very uniform rhyodacite with higher SiO2 and lower K2O content than the Toconquis ignimbrites. Compositional zonation in the magma chamber is not indicated. Post-caldera extrusions occurred soon after eruption and resurgent doming, causing radial tilting of the ignimbrites and overlying lake sediments, and forming the central mountain range. [R.E.S.]
Subjects:Absolute age; Basement; Calderas; Cenozoic; Dacites; Dates; Igneous rocks; Ignimbrite; K/Ar; Magmas; Petrology; Pumice; Pyroclastics; Quaternary; Rb/Sr; Rhyodacites; Tectonics; Volcanic features; Volcanic rocks; Volcanism; Volcanology; Andes; Argentina; Catamarca Argentina; South America; Blanco Ignimbrite Member; Cerro Galan Caldera; Cerro Galan Ignimbrite Member; Cueva Negra Ignimbrite Member; Evolution; Lower Leon Muerto Ignimbrite Member; Middle Merihuaca Ignimbrite Member; Northwestern Argentina; Real Grande Ignimbrite; Toconquis Ignimbrite Formation; Upper Leon Muerto Ignimbrite Member; Upper Merihuaca Ignimbrite Member
Coordinates:S300000 S250000 W0650000 W0690000
Abstract Numbers:86M/1053
Record ID:1985062834
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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