Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications

Carbonate minerals are common gangue minerals in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile. They can be subdivided into two principal groups on the basis of the paragenetic relationships. Paragenetically early carbonates occur together with quartz and sulfide minera...

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Autores principales:	Bissig,Thomas, Donoso,Daisy, Guerra,Nelson C, Dipple,Gregory M
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2007
Materias:	Epithermal Low sulfidation Carbonates Ultraviolet fluorescence Stable isotopes
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200007
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spelling	oai:scielo:S0716-020820070002000072007-09-07Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implicationsBissig,ThomasDonoso,DaisyGuerra,Nelson CDipple,Gregory M Epithermal Low sulfidation Carbonates Ultraviolet fluorescence Stable isotopes Carbonate minerals are common gangue minerals in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile. They can be subdivided into two principal groups on the basis of the paragenetic relationships. Paragenetically early carbonates occur together with quartz and sulfide minerals in banded veins and are closely associated with precious metal mineralization. These carbonates are compositionally complex, consisting of calcite, finely intermixed with ankerite, kutnohorite, rhodochrosite and dolomite, but also contain up to 0.8 wt% PbC0(3) and up to 4.1 wt% ZnC0(3). In contrast, the paragenetically late carbonates are relatively pure calcite, although dolomite has been recognized locally. Late calcites contain less than 3.5 wt% MnC0(3), less than 0.5 wt% ZnC0(3) and less than 2.7 wt% FeC0(3) and are also distinct from the early carbonates in that they exhibit moderate to intense red fluorescence under short-wave ultraviolet light. The red fluorescence color is likely related to moderate Mn contents in calcite, combined with trace amounts of Pb, but low Fe and Mg concentrations. Late carbonates are interpreted to have precipitated from C0(2)-rich steam-heated fluids and are not directly associated with ore. 8(18)0 compositions of both, early and late carbonates generally range between 21.1 and 14.1 %o relative to the Standard Mean Ocean Water (VSMOW). However, two samples of late calcite yielded 8(18)0 values of 3 and 5%o, respectively. The calculated composition of water in equilibrium with calcite at the estimated temperature of deposition of 230°Cyielded 8(18)0 values between 6 and 13%o, but negative values of -3.1 and -5.1%o for two samples of late calcite. Although the low 8(18)0 values for two of the late calcitesand oxygen isotopic data of vein quartz from earlier studies suggest precipitation from a meteoric fluid, the heavy isotopic signature of most carbonates indicates that the mineralizing fluid was overall heterogeneous. 8(13)C values range between -8.9%o and +1.5%o relative to the Pee Dee Belemnite (VPDB) standard and are consistent with a meteoric or magmatic origin, in some samples probably with a minor contribution of organic carbon. Periodic involvement of a fluid with a strong magmatic component or, alternatively, meteoric water which has undergone extensive evaporation probably played an important role in the hydrothermal system. The complex stable isotope signature of El Peñón is interpreted as indicative for arid climatic conditions as a meteoric origin of the fluid is not as evident as in similar deposits emplaced in more pluvial regionsinfo:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Revista geológica de Chile v.34 n.2 20072007-07-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200007en10.4067/S0716-02082007000200007
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Epithermal Low sulfidation Carbonates Ultraviolet fluorescence Stable isotopes
spellingShingle	Epithermal Low sulfidation Carbonates Ultraviolet fluorescence Stable isotopes Bissig,Thomas Donoso,Daisy Guerra,Nelson C Dipple,Gregory M Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications
description	Carbonate minerals are common gangue minerals in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile. They can be subdivided into two principal groups on the basis of the paragenetic relationships. Paragenetically early carbonates occur together with quartz and sulfide minerals in banded veins and are closely associated with precious metal mineralization. These carbonates are compositionally complex, consisting of calcite, finely intermixed with ankerite, kutnohorite, rhodochrosite and dolomite, but also contain up to 0.8 wt% PbC0(3) and up to 4.1 wt% ZnC0(3). In contrast, the paragenetically late carbonates are relatively pure calcite, although dolomite has been recognized locally. Late calcites contain less than 3.5 wt% MnC0(3), less than 0.5 wt% ZnC0(3) and less than 2.7 wt% FeC0(3) and are also distinct from the early carbonates in that they exhibit moderate to intense red fluorescence under short-wave ultraviolet light. The red fluorescence color is likely related to moderate Mn contents in calcite, combined with trace amounts of Pb, but low Fe and Mg concentrations. Late carbonates are interpreted to have precipitated from C0(2)-rich steam-heated fluids and are not directly associated with ore. 8(18)0 compositions of both, early and late carbonates generally range between 21.1 and 14.1 %o relative to the Standard Mean Ocean Water (VSMOW). However, two samples of late calcite yielded 8(18)0 values of 3 and 5%o, respectively. The calculated composition of water in equilibrium with calcite at the estimated temperature of deposition of 230°Cyielded 8(18)0 values between 6 and 13%o, but negative values of -3.1 and -5.1%o for two samples of late calcite. Although the low 8(18)0 values for two of the late calcitesand oxygen isotopic data of vein quartz from earlier studies suggest precipitation from a meteoric fluid, the heavy isotopic signature of most carbonates indicates that the mineralizing fluid was overall heterogeneous. 8(13)C values range between -8.9%o and +1.5%o relative to the Pee Dee Belemnite (VPDB) standard and are consistent with a meteoric or magmatic origin, in some samples probably with a minor contribution of organic carbon. Periodic involvement of a fluid with a strong magmatic component or, alternatively, meteoric water which has undergone extensive evaporation probably played an important role in the hydrothermal system. The complex stable isotope signature of El Peñón is interpreted as indicative for arid climatic conditions as a meteoric origin of the fluid is not as evident as in similar deposits emplaced in more pluvial regions
author	Bissig,Thomas Donoso,Daisy Guerra,Nelson C Dipple,Gregory M
author_facet	Bissig,Thomas Donoso,Daisy Guerra,Nelson C Dipple,Gregory M
author_sort	Bissig,Thomas
title	Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications
title_short	Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications
title_full	Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications
title_fullStr	Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications
title_full_unstemmed	Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications
title_sort	vein carbonates in the low sulfidation epithermal au-ag district of el peñón, ii región, chile: environment of formation and exploration implications
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2007
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200007
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Vein carbonates in the low sulfidation epithermal Au-Ag District of El Peñón, II Región, Chile: environment of formation and exploration implications

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