The porphyry Cu-(Mo-Au) deposit at Altar (Argentina)

Tracing gold distribution by vein mapping and LA-ICP-MS mineral analysis

Carmen Zwahlen, Stefania Cioldi, Thomas Wagner, Roger Rey, Christoph Heinrich

Forskningsoutput: TidskriftsbidragArtikelVetenskapligPeer review

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The Altar porphyry Cu-(Mo-Au) deposit occurs in the Miocene to early Pliocene copper belt of the high Andes of western Argentina, close to the Chilean border. A cluster of late Miocene porphyries intruded a more extensive complex of early Miocene rhyolitic to andesitic volcanic and subvolcanic rocks. Potassic alteration in the Central Porphyry was partially overprinted by feldspar-destructive alteration and finally by argillic to advanced argillic alteration. Early stockwork veins have been cut successively by quartz-pyrite veins, tourmaline veins, and enargite veins. Based on correlation analysis of assay results and mapped abundances of these four vein types, we estimate that approximately 11 to 26% of the copper in the Altar orebody is associated with enargite veins, whereas the remainder is associated with the early stockwork veining and potassic alteration. Gold concentration is low compared with typical Cu-Au porphyries of the Andean back-arc region, but higher than in the giant Miocene deposits of Chile, at an average Au/Cu ratio of 0.14 × 10−4 by weight across the Central Porphyry orebody at Altar. Gold is dominantly associated with chalcopyrite in the domain of stockwork veining and potassic alteration. Small-scale assays in combination with petrographic observations and laser ablation-inductively coupled plasma-mass spectrometry microanalyses show that a significant fraction of the gold in the stockwork veins is enclosed in pyrite as submicroscopic particles attached to inclusions of a Bi-Te-Pb-Ag–enriched Cu-Fe sulfide phase. Microscopic grains of native gold also occur along grain boundaries between pyrite and chalcopyrite, and rarely as larger particles in enargite veins.
Originalspråkengelska
TidskriftEconomic Geology and the Bulletin of the Society of Economic Geologists
Volym109
Utgåva5
Sidor (från-till)1341-1358
Antal sidor18
ISSN0361-0128
DOI
StatusPublicerad - 2014
MoE-publikationstypA1 Tidskriftsartikel-refererad

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title = "The porphyry Cu-(Mo-Au) deposit at Altar (Argentina): Tracing gold distribution by vein mapping and LA-ICP-MS mineral analysis",
abstract = "The Altar porphyry Cu-(Mo-Au) deposit occurs in the Miocene to early Pliocene copper belt of the high Andes of western Argentina, close to the Chilean border. A cluster of late Miocene porphyries intruded a more extensive complex of early Miocene rhyolitic to andesitic volcanic and subvolcanic rocks. Potassic alteration in the Central Porphyry was partially overprinted by feldspar-destructive alteration and finally by argillic to advanced argillic alteration. Early stockwork veins have been cut successively by quartz-pyrite veins, tourmaline veins, and enargite veins. Based on correlation analysis of assay results and mapped abundances of these four vein types, we estimate that approximately 11 to 26{\%} of the copper in the Altar orebody is associated with enargite veins, whereas the remainder is associated with the early stockwork veining and potassic alteration. Gold concentration is low compared with typical Cu-Au porphyries of the Andean back-arc region, but higher than in the giant Miocene deposits of Chile, at an average Au/Cu ratio of 0.14 × 10−4 by weight across the Central Porphyry orebody at Altar. Gold is dominantly associated with chalcopyrite in the domain of stockwork veining and potassic alteration. Small-scale assays in combination with petrographic observations and laser ablation-inductively coupled plasma-mass spectrometry microanalyses show that a significant fraction of the gold in the stockwork veins is enclosed in pyrite as submicroscopic particles attached to inclusions of a Bi-Te-Pb-Ag–enriched Cu-Fe sulfide phase. Microscopic grains of native gold also occur along grain boundaries between pyrite and chalcopyrite, and rarely as larger particles in enargite veins.",
keywords = "1171 Geosciences",
author = "Carmen Zwahlen and Stefania Cioldi and Thomas Wagner and Roger Rey and Christoph Heinrich",
year = "2014",
doi = "10.2113/econgeo.109.5.1341",
language = "English",
volume = "109",
pages = "1341--1358",
journal = "Economic Geology and the Bulletin of the Society of Economic Geologists",
issn = "0361-0128",
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The porphyry Cu-(Mo-Au) deposit at Altar (Argentina) : Tracing gold distribution by vein mapping and LA-ICP-MS mineral analysis. / Zwahlen, Carmen; Cioldi, Stefania; Wagner, Thomas; Rey, Roger; Heinrich, Christoph.

I: Economic Geology and the Bulletin of the Society of Economic Geologists, Vol. 109, Nr. 5, 2014, s. 1341-1358.

Forskningsoutput: TidskriftsbidragArtikelVetenskapligPeer review

TY - JOUR

T1 - The porphyry Cu-(Mo-Au) deposit at Altar (Argentina)

T2 - Tracing gold distribution by vein mapping and LA-ICP-MS mineral analysis

AU - Zwahlen, Carmen

AU - Cioldi, Stefania

AU - Wagner, Thomas

AU - Rey, Roger

AU - Heinrich, Christoph

PY - 2014

Y1 - 2014

N2 - The Altar porphyry Cu-(Mo-Au) deposit occurs in the Miocene to early Pliocene copper belt of the high Andes of western Argentina, close to the Chilean border. A cluster of late Miocene porphyries intruded a more extensive complex of early Miocene rhyolitic to andesitic volcanic and subvolcanic rocks. Potassic alteration in the Central Porphyry was partially overprinted by feldspar-destructive alteration and finally by argillic to advanced argillic alteration. Early stockwork veins have been cut successively by quartz-pyrite veins, tourmaline veins, and enargite veins. Based on correlation analysis of assay results and mapped abundances of these four vein types, we estimate that approximately 11 to 26% of the copper in the Altar orebody is associated with enargite veins, whereas the remainder is associated with the early stockwork veining and potassic alteration. Gold concentration is low compared with typical Cu-Au porphyries of the Andean back-arc region, but higher than in the giant Miocene deposits of Chile, at an average Au/Cu ratio of 0.14 × 10−4 by weight across the Central Porphyry orebody at Altar. Gold is dominantly associated with chalcopyrite in the domain of stockwork veining and potassic alteration. Small-scale assays in combination with petrographic observations and laser ablation-inductively coupled plasma-mass spectrometry microanalyses show that a significant fraction of the gold in the stockwork veins is enclosed in pyrite as submicroscopic particles attached to inclusions of a Bi-Te-Pb-Ag–enriched Cu-Fe sulfide phase. Microscopic grains of native gold also occur along grain boundaries between pyrite and chalcopyrite, and rarely as larger particles in enargite veins.

AB - The Altar porphyry Cu-(Mo-Au) deposit occurs in the Miocene to early Pliocene copper belt of the high Andes of western Argentina, close to the Chilean border. A cluster of late Miocene porphyries intruded a more extensive complex of early Miocene rhyolitic to andesitic volcanic and subvolcanic rocks. Potassic alteration in the Central Porphyry was partially overprinted by feldspar-destructive alteration and finally by argillic to advanced argillic alteration. Early stockwork veins have been cut successively by quartz-pyrite veins, tourmaline veins, and enargite veins. Based on correlation analysis of assay results and mapped abundances of these four vein types, we estimate that approximately 11 to 26% of the copper in the Altar orebody is associated with enargite veins, whereas the remainder is associated with the early stockwork veining and potassic alteration. Gold concentration is low compared with typical Cu-Au porphyries of the Andean back-arc region, but higher than in the giant Miocene deposits of Chile, at an average Au/Cu ratio of 0.14 × 10−4 by weight across the Central Porphyry orebody at Altar. Gold is dominantly associated with chalcopyrite in the domain of stockwork veining and potassic alteration. Small-scale assays in combination with petrographic observations and laser ablation-inductively coupled plasma-mass spectrometry microanalyses show that a significant fraction of the gold in the stockwork veins is enclosed in pyrite as submicroscopic particles attached to inclusions of a Bi-Te-Pb-Ag–enriched Cu-Fe sulfide phase. Microscopic grains of native gold also occur along grain boundaries between pyrite and chalcopyrite, and rarely as larger particles in enargite veins.

KW - 1171 Geosciences

U2 - 10.2113/econgeo.109.5.1341

DO - 10.2113/econgeo.109.5.1341

M3 - Article

VL - 109

SP - 1341

EP - 1358

JO - Economic Geology and the Bulletin of the Society of Economic Geologists

JF - Economic Geology and the Bulletin of the Society of Economic Geologists

SN - 0361-0128

IS - 5

ER -