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Relationships between mineralization and silicic volcanism in the central AndesExisting models for the genesis of porphyry copper deposits indicate that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. It is noted that sites of porphyry-type subvolcanic tin mineralization in the Eastern Cordillera of Bolivia are distinguished by the absence of such andesitic structures. The surface expression of a typical subvolcanic porphyry tin deposit is thought to be an extrusive dome of quartz latite porphyry, sometimes related to a larger caldera structure. Evidence from the El Salvador porphyry copper deposit in the Eocene magmatic belt in Chile indicates that it too may be more closely related to a silicic volcanic structure than to an andesitic stratovolcano. The dome of La Soufriere, Guadeloupe is offered as a modern analog for the surface expression of subvolcanic mineralization processes, with the phreatic eruptions there indicating the formation of hydrothermal breccia bodies in depths. It is pointed out that the occurrence of mineralized porphyries, millions of years after caldera formation, does not necessarily indicate that tin intrusions and mineralization are not genetically related to the subcaldera pluton, but may be a consequence of the long thermal histories (1-10 million years) of the lowermost parts of large plutons.
Document ID
19840041940
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Francis, P. W.
(Lunar and Planetary Institute Houston, TX, United States)
Halls, C.
(Imperial College of Science and Technology London, United Kingdom)
Baker, M. C. W.
(Hunting Geology and Geophysics Fyshwick, Australia)
Date Acquired
August 12, 2013
Publication Date
January 1, 1983
Publication Information
Publication: Journal of Volcanology and Geothermal Research
Volume: 18
ISSN: 0377-0273
Subject Category
Geophysics
Accession Number
84A24727
Distribution Limits
Public
Copyright
Other

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