The granite-hosted Variscan gold deposit from Santo Antonio mine in the Iberian Massif (Penedono, NW Portugal): constraints from mineral chemistry, fluid inclusions, sulfur and noble gases isotopes

• Type: Article in International Scientific Journal
• Date: 2019

Authors

Neiva, AMR (Author) Other; Moura, A (Author) FCUP; Leal Gomes, CAL (Author) Other; Pereira, MF (Author) Other; Corfu, F (Author) Other

Journal

Title: Journal Of Iberian Geology

Vol. 45

Pages: 443-469

ISSN: 1698-6180

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 4 Citations

Scopus - 5 Citations

Other information

Authenticus ID: P-00Q-K7T

DOI: 10.1007/s41513-019-00103-1

Abstract (EN): The study area is located in the Central Iberian Zone, a major tectonic unit of the Iberian Massif (Variscan belt). In this region the basement is composed of Cambrian-Ordovician sedimentary and minor volcanic rocks that underwent deformation and metamorphism during the Carboniferous. These metamorphic rocks host ca. 331-308 Ma granitic plutons emplaced during the D-2 extensional and D-3-D-4 contractional deformation phases. The gold-bearing quartz veins from the Santo Antonio mine (Penedono region) occur in granite formed at 310.1 +/- 1.1 Ma and post-dated the peak of metamorphism. Gold-silver alloy is included in quartz, but mainly occurs in spaces between grains or micro-fractures within arsenopyrite of all three generations and less in pyrite. Late sulphides and sulphosalts were deposited along fractures mainly in arsenopyrite, and locally surrounding the gold-silver alloy grains. Ferberite, scheelite and stolzite replace arsenopyrite. The abundant aqueous carbonic fluids and the occurrence of a low-salinity fluid and their minimum possible entrapment temperature of 360-380 degrees C suggest that this gold-forming event began during the waning stages of the Variscan orogeny. The mean delta S-34 values of arsenopyrite and pyrite are - 4.7 parts per thousand and - 3.8 parts per thousand, respectively. He-Ar-Ne isotopic data suggest a crustal origin. The ascent of the granite magma has provided the heat for remobilization of gold, other metals and metalloids from the metamorphic rocks. This gold-arsenopyrite deposit has thus similar characteristics as other selected gold-arsenopyrite deposits from the Iberian Massif, but it contains tungstates.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 27