Formation and Deformation of Pyrite and Implications for Gold Mineralization in the El Callao District, Venezuela

• DOI: 10.2113/econgeo.109.2.457
• Publication Date: 2013-12-21T00:12:47Z
• Authors: G. Velasquez; D. Beziat; S. Salvi; L. Siebenaller; A. Y. Borisova; G. S. Pokrovski; P. De Parseval

Research Article| March 01, 2014 Formation and Deformation of Pyrite Implications for Gold Mineralization in the El Callao District, Venezuela German Velásquez; Velásquez 1Universidad Central de Venezuela, Instituto Ciencias la Tierra, Avenida Los Ilustres, Chaguaramos, Caracas 3895, Venezuela2Université Toulouse, CNRS, Géosciences Environnement Institut Recherche pour le Développement, Observatoire Midi-Pyrénées, 14 Av. Edouard Belin, F-31400 France Search other works by this author on: GSW Google Scholar Didier Béziat; Béziat 2Université Stefano Salvi; Salvi † †Corresponding author: e-mail, [e-mail] Luc Siebenaller; Siebenaller Anastassia Y. Borisova; Borisova France3Geological Department, Moscow State University, Vorobevu Gory, 119899, Moscow, Russia Gleb S. Pokrovski; Pokrovski Philippe De Parseval Economic Geology (2014) 109 (2): 457–486. https://doi.org/10.2113/econgeo.109.2.457 Article history received: 23 Feb 2013 accepted: 17 May first online: 09 Mar 2017 Cite View This Citation Add to Manager Share Icon Facebook Twitter LinkedIn MailTo Tools Get Permissions Site Velásquez, Béziat, Salvi, Siebenaller, Borisova, Pokrovski, Parseval; Venezuela. 2014;; doi: Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Dropdown Menu input auto suggest filter your All ContentBy SocietyEconomic Advanced Abstract The mining district is most important gold-producing region It hosted Paleoproterozoic Guasipati-El greenstone belt, which forms part Guayana craton, Venezuelan extension Guiana Shield South America. consists volcanic volcanosedimentary sequences that were affected several deformation events, particularly localized shear zones. Colombia mine, largest active mine district, produces 4 tonnes (t) (128,600 oz) gold annually with reserves estimated at 740 t (24 Moz) grades up 60 g/t. mineralization concentrated within a vein network corridor, fracture-hosted mesh interconnected quartz-ankerite-albite veins enclosing fragments altered metabasaltic host rocks. occurs mostly spatially associated pyrite, it as invisible gold, micron-sized native inclusions, filling fractures.Based on optical scanning electron microscopy-backscattered observations, two types pyrite are recognized: simple-zoned less common oscillatory-zoned pyrite. Both consist mineral inclusion-rich core clearer rim; however, latter composed complex rhythmic overgrowths alternating As-rich As-poor bands. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis elemental mapping reveal presence all generations highest concentrations (5–23 ppm Au) found rims, correlate As (16,000–23,000 ppm). In bands, Au (up 1.5 ppm) (300–6,000 decrease about an order magnitude. Copper, Bi, Te, Sb, Pb, Ag always occur cores, suggesting least sulfosalt nanoparticles these metals metalloids. Visible grains small inclusions throughout rim both types, well fractures it. occurrences, chalcopyrite, sphalerite, tellurobismuthite, ankerite, albite, chlorite accompany fineness ranges between 900 930.At early stage formation, formed expense which, turn, resulted from alteration Fe-Ti oxides. Gold, together chalcophile elements, was incorporated structure likely destabilization metal sulfide complexes during ankerite replacement. Subsequent cyclic reactivations zone caused development pressure shadows around generating local repeated decreases pressure, triggered boiling hydrothermal fluid, evidenced primary fluid containing immiscible liquid-rich vapor-rich aqueous-carbonic fluids. process responsible number physical-chemical changes liquid, contributed formation As- Au-rich pyrite: (1) removal H2O into vapor phase, inducing saturation dissolved remaining liquid; (2) increase pH due partition H2S CO2 vapor, thus decreasing solubility minerals; (3) adiabatic temperature, lowering liquid. Waning restored precipitation until onset new cycle. Because drops more significant adjacent open spaces, probably crystallized near newly whereas away them. Previously underwent fracturing reactivation deformation, especially through brittle events postdated shearing, resulting pulverization created porosity facilitated circulation remobilization structurally bound elements (Ag, Cu, Sb), reprecipitated form sulfides, tellurides, either or larger fractures. facilitates exceptionally high tenor deposit, where corridor intersected Santa Maria fault. You do not have access content, please speak institutional administrator if you feel should access.