Precious-metal-bearing Volcanogenic Massive Sulfide Deposits, Campo Morado, Guerrero, Mexico

The Campo Morado precious-metal-bearing, volcanogenic massive sulfide
deposits occur in a lower Cretaceous, bimodal, calc-alkaline volcanic sequence
in a major northerly trending belt in the Guerrero Terrane in northeastern
Guerrero, Mexico. During upper Cretaceous to Early Tertiary greenschist-facies
regional metamorphism, the rocks were deformed strongly into a northeast verging
fold-and-thrust belt. Three later stages of weak deformation were dominated,
respectively, by kink folds, broad warps, and extensional faults. Most deposits
occur in the upper part of a sequence of felsic flows and heterolithic
volcanoclastic rocks or at its contact with overlying chert and
argillite-sandstone. The Reforma and El Rey massive sulfide deposits are on the
overturned limb of a major, thrusted anticline, and the Naranjo and El Largo
massive sulfide deposits are to the south on the upright limb of the same major
fold. The La Lucha and San Rafael massive sulfide occurrences are in an upper
plate to the southwest which was thrusted over the plate containing the Naranjo
and El Largo deposits. In several of the deposits, Au, Ag, Zn, and Pb are
concentrated near the stratigraphic top, and Cu is concentrated near the
stratigraphic base. Major minerals are pyrite, quartz, ankerite, sphalerite,
chalcopyrite, and galena. Minor minerals are tennantite-freibergite,
arsenopyrite, and pyrrhotite. Gold and Ag occur in argentian gold, and Ag also
occurs in tennantite freibergite. The cumulative inferred resource of massive
sulfide for the Reforma, Naranjo, El Rey, and El Largo deposits exceeds 30 Mt,
with the latter two deposits incompletely delineated. Underlying pyrite-quartz
stockwork zones contain chalcopyrite, chlorite, and sphalerite. Hydrothermal
alteration minerals in the stratigraphic footwall are pyrite, quartz, chlorite,
ferroan dolomite, and ankerite. In the stratigraphic hangingwall, hydrothermal
alteration minerals are sericite, calcite-dolomite, and lesser clay minerals and
quartz. The deposits belong to a low-sulfidation, volcanogenic massive sulfide
system formed in a subaqueous environment, and are of the bimodal, siliciclastic
Keywords: Precious metals, Sulfide deposits, Volcanic, Mexico, Minerals
Full Access to Technical Paper
PDF version for $20.00
Sort By:  Relevance
Showing results 1 - 6
Summary: The Geological Society has its own quarterly journal called Exploration
and Mining Geology, for the publication of Canadian and international papers on
applied aspects of mineral exploration and exploitation, including mineral
deposit geology, geochemistry, and geophysics, mining geology, mineral resource
appraisal and estimation methods, environmental geology, and case histories. The
editor of the journal is Jeremy P. Richards
Publication: Exploration & Mining Geology
Issue: 2
Volume: 6
Year: 1997
Web Page
Summary: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<META content="text/html; charset=unicode" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 9.00.8112.16440"></HEAD>
<BODY>The mechanism by which stratiform ore deposits of PGE (platinum-group
elements) are laid down in ultramafic igneous complexes is not completely clear.
Early studies by the author and coworkers on numerical analyses of the
convective cooling of low-Rayleigh-number magma chambers...
Publication: Exploration & Mining Geology
Author(s): ALAN RICE: Departments of Geology and Physics, Rhodes University, Grahamstown 6140, South Africa
Keywords: PGE, Ultramafic igneous complexes, Magma chambers, Suspended
Issue: 2
Volume: 6
Year: 1997
Summary: Economic Mn-oxide ore deposits of commercial grade occur in the Rhodope massif near Kato Nevrokopi in the Drama region, Northern Greece. The Mn-oxide mineralization has developed by weathering of continental hypogene rhodochrosite-sulphide veins. The vein mineralization is confined by tectonic shear zones between marble and metapelites, extending laterally into the marble as tabular, pod or lenticular oreshoots (up to 50 m ?? 20 m ?? 5-10 m). Supergene oxidation of the hypogene mineralization...
Publication: Exploration & Mining Geology
Author(s): M.K. NIMFOPOULOS: Institute of Geology and Mineral Exploration (IGME), 546-26 Thessaloniki, Macedonia, Greece; R.A.D. PATTRICK: Department of Earth Sciences, The University of Manchester, Manchester M13 9PL, England, U.K.; K.M. MICHAILIDIS: Department of Mineralogy-Petrology-Economic Geology Aristotle University, 540-06 Thessaloniki, Macedonia, Greece; D.A. POLYA and J. ESSON: Department of Earth Sciences, The University of Manchester, Manchester M13 9PL, England, U.K.
Keywords: Ore deposits, Geology, Geochemistry, Vein mineralization, Supergene oxidation
Issue: 2
Volume: 6
Year: 1997
Summary: The Croft diorite in central England belongs to a suite of Caledonian igneous rocks collectively known as the South Leicestershire diorite complex. Although the intrusions occupy separate outcrops, they are linked at depth to form a single pluton, buried beneath a cover of Triassic sediments (Le Bas, 1972; 1982, Allsop and Arthur, 1983). Both the Caledonian diorites and the overlying sub-Triassic unconformity have been affected by a complex history of alteration and mineralization which can...
Publication: Exploration & Mining Geology
Author(s): K. PEARSON and C.A. JEFFREY: Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH, U.K.
Keywords: Caledonian igneous rocks, Intrusions, Deuteric effect, Sodic enrichment, Laumontite veins, Analcime veins, Calcite veins, Mineralization
Issue: 2
Volume: 6
Year: 1997
Summary: Detailed petrographical and geochemical studies have been carried out on the igneous and sedimentary rocks in the Omai area, part of the Paleoproterozoic Barama-Mazaruni greenstone belt, Guyana. The stratigraphic succession at Omai begins with basalts, associated with mafic ultramafic intrusives and poorly-sorted conglomerates; these are overlain by andesites and quartzfeldspar porphyries, with pelites and tuffaceous sediments at the top. The volcanic-sedimentary succession was intruded by a...
Publication: Exploration & Mining Geology
Author(s): GABRIEL VOICU, MARC BARDOUX, LUC HARNOIS: Département des Sciences de la Terre, Université du Québec à Montréal, Montréal, QC, Canada H3C 3P8 and ROBERT CRÉPEAU:
Omai Gold Mines, Georgetown, Guyana, South America
Keywords: Petrographical studies, Geochemical studies, Guyana, Basalts, Mafic-ultramafic
intrusives, Conglomerates
Issue: 2
Volume: 6
Year: 1997
Summary: Most large skarn deposits are zoned in both space and time relative to
associated intrusions. Zonation occurs on scales from kilometers to micrometers,
and reflects infiltrative fluid flow, wallrock reaction, temperature variations,
and fluid mixing. The most spectacular examples of skarn zonation usually occur
at the skarn-marble contact, where transitions between monomineralic bands can
be knife sharp. Other small-scale examples occur in zoned veins and individual
mineral crystals....
Publication: Exploration & Mining Geology
Author(s): LAWRENCE D. MEINERT: Department of Geology, Washington State University, Pullman, Washington 99164-2812, U.S.A.
Keywords: Skarn deposits, Skarn zonation, Mineral exploration
Issue: 2
Volume: 6
Year: 1997
Powered by Coveo Enterprise Search