Mineralized and unmineralized calderas in Spain; Part I, evolution of the Los Frailes Caldera |
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| Authors: | C G Cunningham A Arribas Jr J J Rytuba and A Arribas |
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| Institution: | (1) U.S. Geological Survey, 959 National Center, 22092 Reston, Virginia, USA;(2) Department of Geological Sciences, University of Michigan, 1006 C.C. Little Building, 48109 Ann Arbor, Michigan, USA;(3) U.S. Geological Survey, 345 Middlefield Road, 94025 Menlo Park, California, USA;(4) XII, Commission of the European Communities, Rue de la Loi 200, B-1049 Brussels, Belgium |
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| Abstract: | The Cabo de Gata volcanic field of southeastern Spain contains several recently-recognized calderas. Some of the calderas are mineralized with epithermal gold, alunite, and base metal deposits, and others are barren, and yet they formed under generally similar conditions. Comparison of the magmatic, geochemical, and physical evolution of the Los Frailes, Rodalquilar, and Lomilla calderas provides insight into the processes of caldera evolution that led to precious-metal mineralization. The Los Frailes caldera formed at 14.4 Ma and is the oldest caldera. It formed in response to multiple eruptions of hornblende dacite magma. Following each eruption, the area collapsed and the caldera was invaded by the sea. Dacite domes fill the lower part of the caldera. Pyroxene andesites were erupted through the solidified core of the caldera and were probably initially responsible for magma generation. The Los Frailes caldera did not evolve to rhyolites nor was it subjected to the amount of structural development that the younger, mineralized Rodalquilar and Lomilla calderas were. |
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