The Mantos Blancos copper deposit: an upper Jurassic breccia-style hydrothermal system in the Coastal Range of Northern Chile
Author
dc.contributor.author
Ramírez, Luis E.
Author
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Palcios, Carlos
es_CL
Author
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Townley Callejas, Brian
es_CL
Author
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Parada Reyes, Miguel
es_CL
Author
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Sial, A. N.
es_CL
Author
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Fernández Turiel, J. L.
es_CL
Author
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Gimeno, D.
es_CL
Author
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García Valles, M.
es_CL
Author
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Lehmann, B.
es_CL
Admission date
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2014-01-07T13:30:42Z
Available date
dc.date.available
2014-01-07T13:30:42Z
Publication date
dc.date.issued
2006
Cita de ítem
dc.identifier.citation
Miner Deposita (2006) 41: 246–258
en_US
Identifier
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DOI 10.1007/s00126-006-0055-9
Identifier
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https://repositorio.uchile.cl/handle/2250/125991
General note
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Artículo de publicación ISI
en_US
Abstract
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The Upper Jurassic Mantos Blancos copper
deposit (500 Mt at 1.0% Cu), located in the Coastal Range
of northern Chile, displays two superimposed hydrothermal
events. An older phyllic alteration probably related to
felsic magmatic–hydrothermal brecciation at ∼155 Ma, and
younger (141–142 Ma) potassic, propylitic, and sodic
alterations, coeval with dioritic and granodioritic stocks
and sills, and dioritic dikes. Main ore formation is
genetically related to the second hydrothermal event, and
consists of hydrothermal breccias, disseminations and
stockwork-style mineralization, associated with sodic
alteration. Hypogene sulfide assemblages show distinctive
vertical and lateral zoning, centered on magmatic and
hydrothermal breccia bodies, which constitute the feeders
to mineralization. A barren pyrite root zone is overlain by
pyrite-chalcopyrite, and followed upwards and laterally by
chalcopyrite-digenite or chalcopyrite-bornite. The assemblage
digenite–supergene chalcocite characterizes the central
portions of high-grade mineralization in the breccia
bodies. Fluid inclusions show evidence of boiling during
the potassic and sodic alteration events, which occurred at
temperatures around 450–460°C and 350–410°C, and
salinities between 3–53 and 13–45 wt% NaCl eq.,
respectively. The hydrothermal events occurred during
episodic decompression due to fluid overpressuring,
hydrofracturing, and sharp changes from lithostatic to
hydrostatic conditions. Sulfur isotope results of hypogene
sulfide minerals fall in a narrow range around 0 per mil,
suggesting a dominance of magmatic sulfur. Carbon and
oxygen isotopic data of calcites from propylitic alteration
suggest a mantle-derived carbon and oxygen isotope
fractionation due to low-temperature alteration.