The Paleoproterozoic Aripuana Zn-Pb-Ag (Au, Cu) Volcanogenic Massive Sulfide Deposit, Mato Grosso, Brazil: Geology, Geochemistry of Alteration, Carbon and Oxygen Isotope Modeling, and Implications for Genesis

• DOI: 10.2113/econgeo.108.4.781
• Publication Date: 2013-05-03T06:41:17Z
• Authors: J. C. Biondi; R. V. Santos; L. F. Cury
• Keywords: Isotope Geochemistry

Aripuana is a Paleoproterozoic (1.76-1.75 Ga), stratiform, volcanogenic Zn-Pb-Ag-(Au-Cu) massive sulfide deposit, has an estimated resource of 11.6 million metric tons (Mt) ore, and located on the south-southwest border Amazon craton (Brazil). resides in caldera composed strongly fractionated, felsic metavolcanic rocks, transitional between calc-alkaline tholeiitic compositions. The entire region was metamorphosed into lower greenschist facies (1.68-1.63 Ga) deposit subsequently thermally metasomatized (1.56-1.53 Ga).

The mineralized bodies are lenticular elongated. They at base sequence turbidites, which overlie dacitic rhyolitic ignimbrites. rocks footwall silicified, sericitized, chloritized, hanging-wall carbonate rhythmites hydrothermal marbles, breccias, breccia-like + talc tremolite chlorite rock, talc-, tremolite-, biotite-rich carbonate- fluorite-bearing cherts.

The formed during least four submarine-exhalative cycles siliceous marbles marls represent initial phase each cycle, followed by coprecipitation pyrite pyrrhotite sphalerite argentiferous galenas ± chalcopyrite, were disseminated clay-carbonate breccias or lenses. This fluoritic cherts argillites, (fluorite?) rhythmites, turbidites to close cycle.

The variation total rare earth element (REE) contents Eu Ce anomalies indicates that original sediments mixtures smectitic clay deposited below redoxcline. Isotopic analysis identified δ 18OSMOW values 8 13‰ 13CPDB −7 −1‰. Modeling isotopic data showed mineralizing fluids distinct based proportion magmatic fluid mixed with seawater. Carbonate minerals precipitated while activity volcanism evolved from exhalative exhalative-explosive character temperatures increasing 100° 200°C.

The regional metamorphism biotite-, talc-rich rocks; it recrystallized minerals, foliated folded all caused limited decarbonation sites where contained silica smectite. However, signatures maintained. thermal erased metamorphic foliation, metasomatism generated veinlets sulfides.