Late-Variscan multistage hydrothermal processes unveiled by chemical ages coupled with compositional and textural uraninite variations in W-Au deposits in the western Spanish Central System Batholith

Geologica Acta

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Title Late-Variscan multistage hydrothermal processes unveiled by chemical ages coupled with compositional and textural uraninite variations in W-Au deposits in the western Spanish Central System Batholith
 
Creator Timón-Sánchez, S.M.
López-Moro, F.J.
Romer, R.L.
Rhede, D.
Fernández-Fernández, A.
Moro-Benito, C.
 
Subject Uraninite; U-Pb dating; W-Au deposits; Spanish Central System Batholith; Variscan belt.
 
Description The scheelite skarn from Los Santos and the W-Au veins from El Cabaco district, located in the Spanish Central System Batholith (SCSB), are some of the best-known tungsten ore deposits in Spain. Uraninite is an accessory mineral in both deposits, which underwent several hydrothermal flow events. Chemical and textural characteristics, as well as electron microprobe U-Th-Pb uraninite chemical data from the different stages of the skarn and the vein-type mineralizations, are presented here. Based on these data the uraninite was able to be classified into two groups. Group I uraninite has an octahedral habit and occurs as inclusions in K-feldspar relicts of the leucogranite related to Los Santos skarn formation. It shows high Th (6.95 to 8.51wt.% ThO2) and high Rare Earth Elements (REEs) contents (0.55 to 1.38wt.% ∑REE2O3). Group II uraninite occurs i) associated to El Cabaco granite, in a greenish selvage-style greisen and its reddish envelope and in the mineralized rimming quartz veins and ii) in Los Santos high-temperature endoskarn and anorthite skarn, where it is associated with U-rich mica. This uraninite type has lower Th and ∑REE2O3contents than Group-I uraninite. The mineral chemistry and the assemblage and textural relationships suggest that Group-I uraninite is magmatic and the attained U-Th-Pb chemical age of 300±4Ma is interpreted as the magmatic age of the skarn-forming aplite granites in the western part of the SCSB. Group-II uraninite includes two events: i) hydrothermal uraninite, which yields an age of 295±2Ma, dates a strong alkali mobilization and early tungsten deposition and ii) a later hydrothermal process, around 287±4Ma, that resulted in sulfides and late scheelite precipitation and widespread silicification. Finally, the gold deposition is younger than this silicification according to textural criteria. Therefore, W-Au deposits in the western part of the SCSB were formed by superposition of several processes that took place some 15Ma after the skarn-forming granite crystallized. Comparable W, W-Au and U deposits in the Variscan orogenic belt show a similar timing of hydrothermal events, suggesting that the hydrothermal history was controlled by large-scale Late-Variscan tectonic processes.
 
Publisher Geologica Acta
Geologica Acta
Geologica Acta
 
Contributor
 
Date 2019-01-31
 
Type info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion

 
Format application/pdf
 
Identifier http://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2019.17.1
10.1344/GeologicaActa2019.17.1
 
Source Geologica Acta; Vol 17; 1-19
Geologica Acta; Vol 17; 1-19
Geologica Acta; Vol 17; 1-19
1696-5728
1695-6133
 
Language eng
 
Relation http://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2019.17.1/28456
 
Coverage Spanish Central System Batholith; Variscan belt
Paleozoic
skarn; quartz veins; granitoids
 
Rights Copyright (c) 2019 Geologica Acta
 

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