The volcanic and magmatic evolution of Volcán Ollagüe, a high-K, late Quaternary stratovolcano in the Andean Central Volcanic Zone

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doi: 10.1016/0377-0273(93)90065-Y
Authors:Feeley, Todd C.; Davidson, Jon P.; Armendia, Adolfo
Author Affiliations:Primary:
University of California, Department of Earth and Space Sciences, Los Angeles, CA 90024, United States
Other:
Servicio Geologico de Bolivia, La Paz, Bolivia
Volume Title:Journal of Volcanology and Geothermal Research
Source:Journal of Volcanology and Geothermal Research, 54(3-4), p.221-245. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-0273
Publication Date:1993
Note:In English. 58 refs.; illus. incl. 1 table, geol. sketch maps
Summary:Volcán Ollagüe is a high-K, calc-alkaline composite volcano constructed upon extremely thick crust in the Andean Central Volcanic Zone. Volcanic activity commenced with the construction of an andesitic to dacitic composite cone composed of numerous lava flows and pyroclastic deposits of the Vinta Loma series and an overlying coalescing dome and coulée sequence of the Chasca Orkho series. Following cone construction, the upper western flank of Ollagüe collapsed toward the west leaving a collapse-amphitheater about 3.5 km in diameter and a debris avalanche deposit on the lower western flank of the volcano. The deposit is similar to the debris avalanche deposit produced during the May 18, 1980 eruption of Mount St. Helens, U.S.A., and was probably formed in a similar manner. It presently covers an area of 100 km2 and extends 16 km from the summit. Subsequent to the collapse event, the upper western flank was reformed via eruption of several small andesitic lava flows from vents located near the western summit and growth of an andesitic dome within the collapse-amphitheater. Additional post-collapse activity included construction of a dacitic dome and coulée of the La Celosa series on the northwest flank. Field relations indicate that vents for the Vinta Loma and post-collapse series were located at or near the summit of the cone. The Vinta Loma series is characterized by an anhydrous, two-pyroxene assemblage. Vents for the La Celosa and Chasca Orkho series are located on the flanks and strike N55°W, radial to the volcano. The pattern of flank eruptions coincides with the distribution in the abundance of amphibole and biotite as the main mafic phenocryst phases in the rocks. A possible explanation for this coincidence is that an unexposed fracture or fault beneath the volcano served as a conduit for both magma ascent and groundwater circulation. In addition to the lava flows at Ollagüe, magmas are also present as blobs of vesiculated basaltic andesite and mafic andesite that occur as inclusions in nearly all of the lavas. All eruptive activity at Ollagüe predates the last glacial episode (∼11,000 a B.P.), because post-collapse lava flows are overlain by moraine and are incised by glacial valleys. Present activity is restricted to emission of a persistent, 100-m-high fumarolic steam plume from a vent located within the summit andesite dome. Sr and Nd isotope ratios for the basaltic andesite and mafic andesite inclusions and lavas suggest that they have assimilated large amounts of crust during crystal fractionation. In contrast, narrow ranges in 143Nd/144Nd and 87Sr/86Sr in the andesitic and dacitic lavas are enigmatic with respect to crustal contamination.
Subjects:Alkali metals; Alkaline earth metals; Amphibole group; Andesites; Andesitic composition; Biotite; Calc-alkalic composition; Cenozoic; Chain silicates; Chemical composition; Eruptions; Genesis; Igneous rocks; Inclusions; Isotopes; Lava flows; Mafic composition; Magmas; Major elements; Metals; Mica group; Mineral inclusions; Nd-144/Nd-143; Neodymium; Petrography; Petrology; Phenocrysts; Pleistocene; Potassium; Quaternary; Radioactive isotopes; Rare earths; Rb-87/Sr-86; Rubidium; Sheet silicates; Silicates; Sr-87/Sr-86; Stable isotopes; Stratovolcanoes; Strontium; Trace elements; Upper Pleistocene; Volcanic features; Volcanic rocks; Volcanoes; Xenoliths; Andes; Antofagasta Chile; Bolivia; Central Andes; Chile; Potosi Bolivia; South America; Chasca Orkho Series; La Celosa Series; Northeastern Chile; Ollague; Southwestern Bolivia; Vinta Loma Series
Coordinates:S212500 S210500 W0680700 W0682000
Abstract Numbers:93M/4893
Record ID:1993000244
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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