Geology, Mining, and Mineral Potential of Southern Venezuela

SEG Discovery ◽  
2005 ◽  
pp. 5-22
Author(s):  
Dominic Channer ◽  
Elsa Graffe ◽  
Pedro Vielma
Keyword(s):  
Gold Mineralization ◽  
Mining Industry ◽  
Development Planning ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Private Companies ◽  
Diamond Mining ◽  
Wide Range ◽  
Felsic Volcanic ◽  
Artisanal Miners

ABSTRACT The highly prospective Precambrian Guyana shield south of the Orinoco River in Venezuela can be divided into five main provinces: Imataca, Pastora-Botanamo, Cuchivero, Amazonas, and Roraima. The combination of gold-rich granite-greenstone belts, felsic volcanic and granitic terrains, highly diamondiferous kimberlites, widespread gold and diamond placers, and large unexplored areas makes this region an exciting exploration province. Important mineralization events occurred at different times over a wide range of geologic time, from 3.2 Ga for banded iron formation in Imataca, 2.0 to 1.9 Ga for gold mineralization in Pastora-Botanamo, 0.71 Ga for diamondiferous kimberlite emplacement in Cuchivero, and the Tertiary for formation of enriched iron ores and bauxite ores in Imataca and Amazonas. Iron and aluminum mining is controlled by state mining corporations, with current annual ore production of 23 and 5.2 Mt, respectively. Gold mining is divided between state and private companies and artisanal operations. Total gold production is probably about 750,000 oz per year, including artisanal production. All diamond production is currently artisanal, with total estimated annual production of 500,000 ct. When current project go into production, Venezuela’s gold and diamond production will pass 1.3 Moz/yr and 1 Mct/yr, respectively. Artisanal mining is a key part of the gold and diamond-mining industry in Venezuela, and prospective exploration and mining companies must be aware of this; they should include projects with artisanal miners and local communities in their exploration and development planning.

scholarly journals Gold Mineralization in Banded Iron Formation in the Amalia Greenstone Belt, South Africa: A Mineralogical and Sulfur Isotope Study

2013 ◽  
Vol 63 (2) ◽  
pp. 119-140 ◽  
Author(s):  
Kofi Adomako-Ansah ◽  
Toshio Mizuta ◽  
Napoleon Q. Hammond ◽  
Daizo Ishiyama ◽  
Takeyuki Ogata ◽  
...  
Keyword(s):  
South Africa ◽  
Greenstone Belt ◽  
Sulfur Isotope ◽  
Gold Mineralization ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Isotope Study

scholarly journals A Fonte dos Metais da Mina de Ouro do Schramm, Santa Catarina: Evidências de Dados de Isótopos de Pb e Elementos Terras Raras

2005 ◽  
Vol 32 (1) ◽  
pp. 51
Author(s):  
FLÁVIO FRANÇA NUNES DA ROCHA ◽  
ARTUR CEZAR BASTOS NETO ◽  
MARCUS VINÍCIUS DORNELLES REMUS ◽  
VITOR PAULO PEREIRA
Keyword(s):  
Gold Mineralization ◽  
Isotope Composition ◽  
Shear Zones ◽  
Iron Formation ◽  
Gold Mine ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Santa Catarina ◽  
Lead Isotope Composition ◽  
Ree Patterns

The source of the ore elements in the Schramm gold mine, localized in central part of Santa Catarina shield, has been constrained based on lead isotope composition of galena and sulfosalts, and the rare earth element (REE) patterns of the ore. The Pb207/ Pb206 model age obtained in galena and lillianite-gustavite series from the mineralization yields an age of 1.88 Ga. It is higher than the estimated age of the deposit (» 534 Ma). The Pb isotopic composition obtained in these minerals indicates that the age of Schramm mine source is similar to that of the galena of the Ribeirão da Prata mine (Pb-Zn-Cu-Ag). This mine is located 25 Km southwest of the Schramm gold mine witch is hosted in the tension fracture zone conjugated with the first order shear zone that contains the Ribeirão da Prata deposit. The similarities between Pb-isotope compositions of both deposits could indicate that they were contemporaneous and derived from the same regional lead source. The REE patterns of the ore samples of Schramm mine are similar to that of the pyroxenites and banded iron formations from the Archean Santa Catarina Granulitic Complex that host the Schramm gold mine. They present low REE contents with flat patterns and lack Eu anomalies. The comparison among the isotopic data from this mine with those from other places indicates that the banded iron formation and mafic-ultramafic granulitic gneisses are the source of the gold mineralization. This evidence agreed with the hypothesis that the ore fluids were derived from retrogressive metamorphism reactions of Santa Catarina Granulitic Complex in the shear zones during the final stage of Brasiliano orogenic cycle.

Structure of veins in a gold–pyrite deposit in banded iron formation, Amalia greenstone belt, South Africa

1986 ◽  
Vol 123 (6) ◽  
pp. 601-609 ◽  
Author(s):  
J. R. Vearncombe
Keyword(s):  
Greenstone Belt ◽  
Quartz Vein ◽  
Gold Mineralization ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Vein Wall ◽  
Quartz Veins ◽  
Anticlockwise Rotation ◽  
Fibre Growth ◽  
Mineralizing Fluids

AbstractFibrous quartz veins in deformed banded iron formation of the Amalia greenstone belt, southwestern Transvaal, are spatially related to gold–pyrite mineralization in both wallrock and vein inclusions. Poles to quartz vein orientations show a general parallelism with mineral elongation and fold plunges of the principal deformation in the wallrock. Quartz vein fibres show a consistent anticlockwise rotation, late components being subparallel to the elongation lineation, suggesting veining was probably synchronous with the principal deformation. Antitaxial fibrous veins, which dominate the mineralized banded iron formation, formed by the process of crack–seal which channelled mineralizing fluids along the vein walls, increasing the potential for fluid–wallrock interaction. Gold mineralization in quartz veins occurs in wall-parallel slivers of banded iron formation which have been plucked off the vein wall during antitaxial fibre growth. Mineralization can be explained by a process of fluid–wallrock interaction with sulphidation and gold precipitation.

scholarly journals Isolation and Genomic Characterization of Desulfuromonas soudanensis WTL, a Metal- and Electrode-Reducing Bacterium from Anoxic Deep Subsurface Brine

2016 ◽  
Author(s):  
Jonathan P. Badalamenti ◽  
Zarath M. Summers ◽  
Chi Ho Chan ◽  
Jeffrey A. Gralnick ◽  
Daniel R. Bond
Keyword(s):  
Single Molecule ◽  
Homoserine Lactone ◽  
Geobacter Sulfurreducens ◽  
Iron Formation ◽  
Carbon Limitation ◽  
Redox Potentials ◽  
Deep Biosphere ◽  
Banded Iron Formation ◽  
Hydrogen Electrode ◽  
Wide Range

ABSTRACTReaching a depth of 713 m below the surface, the Soudan Underground Iron Mine (Soudan, Minnesota, USA) transects a massive Archaean (2.7 Ga) banded iron formation, providing a remarkably accessible window into the terrestrial deep biosphere. Despite carbon limitation, metal-reducing microbial communities are present in potentially ancient anoxic brines continuously emanating from exploratory boreholes on Level 27. Using graphite electrodes deposited in situ as bait, we enriched and isolated a novel halophilic iron-reducing Deltaproteobacterium, Desul-furomonas soudanensis strain WTL, from an acetate-fed three-electrode bioreactor poised at +0.24 V (vs. standard hydrogen electrode). Cyclic voltammetry revealed that D. soudanensis releases electrons at redox potentials approximately 100 mV more positive than the model freshwater surface isolate Geobacter sulfurreducens, suggesting that its extracellular respiration is tuned for higher potential electron acceptors. D. soudanensis contains a 3,958,620-bp circular genome, assembled to completion using single-molecule real-time (SMRT) sequencing reads, which encodes a complete TCA cycle, 38 putative multiheme c-type cytochromes, one of which contains 69 heme-binding motifs, and a LuxI/LuxR quorum sensing cassette that produces an unidentified N-acyl homoserine lactone. Another cytochrome is predicted to lie within a putative prophage, suggesting that horizontal transfer of respiratory proteins plays a role in respiratory flexibility among metal reducers. Isolation of D. soudanensis underscores the utility of electrode-based approaches for enriching rare metal reducers from a wide range of habitats.

sPhysicochemical conditions of fluid–wall rock interaction at amphibolite-facies conditions in two Archean hydrothermal gold deposits in the Mt. York District, Pilbara Craton, Western Australia

1995 ◽  
Vol 32 (7) ◽  
pp. 993-1016 ◽  
Author(s):  
P. Neumayr ◽  
J.R. Ridley ◽  
D.I. Groves
Keyword(s):  
Western Australia ◽  
Gold Mineralization ◽  
Wall Rock ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Rock Interaction ◽  
Wall Rock Alteration ◽  
Geochemical Analyses ◽  
Pilbara Craton

Synamphibolite facies Archean gold mineralization in the Mt. York District, Pilbara Craton, Western Australia, is hosted in metamorphosed banded iron formation (Main Hill–Breccia Hill prospect), amphibolites, and ultramafic schists (Zakanaka prospect). Mineralization at Main Hill occurs in quartz breccias with sulfide matrices and in altered wall rock adjacent to quartz–biotite–amphibole ± clinopyroxene veins. Alteration associated with quartz veins is zoned, with biotite—pyrrhotite vein selvedges and a distal calcic-amphibole, arsenopyrite–lôllingite zone. Hydrothermal biotite and actinolite have highest Mg/(Mg + Fe) ratios where associated with abundant sulfarsenides in the distal alteratin zone. Whole-rock geochemical analyses and calculated metasomatic reactions indicate the addition of K, Al, S, As, Au, Ag, and Ni during hydrothermal alteration. Mineralization at Zakanaka is characterized by a broad wall rock alteration halo of biotite–amphibole, and zoned quartz–calc silicate veins proximal to ore. Wall rock adjacent to the veins contains pyrrhotite, pyrite, and gold. The alteration is explained by K-metasomatism distal to mineralization and K and Ca metasomatism proximal to mineralization. Balanced metasomatic reactions and mass-balance calculations indicate addition of K and depletion of Na, Ca, Mg, and Fe in distal alteration zones and addition of K, Ca, Mg, Fe, and Ti in proximal zones. Gold precipitation at both prospects occurred through loss of S, and possibly As, from the ore fluid during sulfidation reactions with Fe-rich amphiboles and biotites to form Mg-enriched equivalents and sulfarsenides. Changes in the oxidation state of the ore fluid may have enhanced gold precipitation, though pH changes are unlikely to have been important. The controls on mineralization are thus similar to those at many lower temperature, mesothermal deposits. The lack of consistently increasing Mg ratios of calc-silicate phases with increasing intensity of alteration and sulfidation at Main Hill may be the result of coupled substitutions in amphiboles and biotites during infiltration of a fluid with high-S, but low-As, activities.

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