The Cerro Purico shield complex, North Chile

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Authors:Francis, P. W.; McDonough, W. F.; Hammill, M.; O'Callaghan, L. J.; Thorpe, R. S.
Author Affiliations:Primary:
Lunar and Planet. Inst., Houston, TX, United States
Other:
Dartmouth Coll., United States
Open Univ., Dep. Earth Sci., United Kingdom
Volume Title:Andean magmatism; chemical and isotopic constraints
Volume Authors:Harmon, R. S., editor; Barreiro, Barbara A.
Source:p.106-123; American Geophysical Union, special symposium ; Andean magmatism; chemical and isotopic constraints, Baltimore, MD, June 1983, edited by R. S. Harmon and Barbara A. Barreiro. Publisher: Shiva Publ., Nantwich, United Kingdom. ISBN: 0-906812-60-7
Publication Date:1984
Note:In English. 1.45-0.77 m.y.Shiva Geol. Series; illus. incl. 2 tables
Summary:Cerro Purico is a 1.3 m.y.-old ignimbrite shield volcano. The first erupted unit was the rhyolitic Toconao ignimbrite (87Sr/86Sr 0.7100), followed, after an erosional interval, by the dacitic Purico ignimbrite with the same radiometric age (87Sr/86Sr 0.7085). Andesitic to dacitic lavas and extrusive domes were later emplaced in the summit region. The upper part of the Purico ignimbrite contains banded and mafic (andesitic) pumices isotopically indistinguishable from the hosts. The younger dome (Chascon) contains basaltic xenoliths characterized by Sr isotope ratios (0.7059) lower than the host dacite (0.7073). The rocks of the Cerro Purico complex as a whole are characterized as low TiO2, high K, calc-alkaline types with major and trace-element contents closely similar to other Central Andean volcanoes. A complex magmatic history is required to explain the origin of mafic pumice clasts and isotopically contrasted mafic xenoliths. Simple crustal anatexis cannot account for the range of compositions observed. [J.M.H.]
Subjects:Absolute age; Alkaline earth metals; Anatexis; Andesites; Cenozoic; Dacites; Dates; Geochemistry; Igneous rocks; Inclusions; Isotopes; K/Ar; Magmas; Metals; Pleistocene; Polyphase processes; Processes; Quaternary; Rare earths; Rhyolites; Shield volcanoes; Sr-87/Sr-86; Stable isotopes; Strontium; Trace elements; Volcanic rocks; Volcanoes; Volcanology; Xenoliths; Andes; Antofagasta Chile; Central Andes; Chile; South America; Cerro Purico; Evolution; Northern Chile; Purico Ignimbrite; Toconao Ignimbrite
Abstract Numbers:85M/1691
Record ID:1985005784
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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