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Keywords = NW Iberian Variscides

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42 pages, 35266 KiB  
Article
Relative Abundance and Compositional Variation of Silicates, Oxides and Phosphates in the W-Sn-Rich Lodes of the Panasqueira Mine (Portugal): Implications for the Ore-Forming Process
by António Mateus, Jorge Figueiras, Ivo Martins, Pedro C. Rodrigues and Filipe Pinto
Minerals 2020, 10(6), 551; https://doi.org/10.3390/min10060551 - 19 Jun 2020
Cited by 10 | Viewed by 4989
Abstract
Panasqueira is a world-class W-Sn-Cu lode-type deposit located in Portugal. It consists of a dense swarm of subhorizontal quartz lodes criss-crossed by several ENE–WSW and N–S fault zones, bordering Late Variscan granite and hosted in Late Ediacaran—Early Cambrian metasediments. The relative abundance and [...] Read more.
Panasqueira is a world-class W-Sn-Cu lode-type deposit located in Portugal. It consists of a dense swarm of subhorizontal quartz lodes criss-crossed by several ENE–WSW and N–S fault zones, bordering Late Variscan granite and hosted in Late Ediacaran—Early Cambrian metasediments. The relative abundance and compositional variation (assessed with EPMA) of the main silicates, oxides and phosphates forming the quartz lodes and their margins were examined, aiming to explore: (i) mineral and geochemical zonation at the mine scale; and (ii) some conclusions on the chemical nature of prevalent fluid inflows and T-conditions of mineral deposition. Quartz lodes nearby or far from the known greisen-granite cupola display significant differences, reflecting multiple fluid influxes of somewhat distinct composition related to various opening and closing events extending for several My, ranging from an early “oxide–silicate stage” (OSS) to a “main sulfide stage” (MSS), and further on to a post-ore carbonate stage (POCS); however, a rejuvenation event occurred after MSS. The onset of OSS was placed at ca. 299 ± 5 Ma and the rejuvenation event at ca. 292 Ma. The OSS was confined to ?500 ? T ? 320 °C, following rutile and tourmaline growth under ?640 ? T ? 540 °C (depending on aSiO2). The rejuvenation event (?440–450 °C) preceded a late chlorite growth (?250–270 °C) and the progression towards POCS. Full article
(This article belongs to the Special Issue Granite-Related Mineralization Systems)
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