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Geochemistry and geothermometry of volcanic rocks from Serra Branca, Iberian Pyrite Belt, Portugal

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Rosa, DRN and Inverno, CMC and Oliveira, VMJ and Rosa, CJP (2006) Geochemistry and geothermometry of volcanic rocks from Serra Branca, Iberian Pyrite Belt, Portugal. Gondwana Research, 10 (3-4). pp. 328-339.

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Abstract

Volcanic rocks from Serra Branca, Iberian Pyrite Belt, Portugal, consist of calc-alkaline felsic and intermediate rocks. The latter are massive andesites, whereas the former include four dacitic to rhyolitic lithologies, distinguishable on spiderdiagrams and binary plots of immobile elements. Zircon thermometry indicates that two felsic suites may have formed from different magmas produced at distinct temperatures, with only limited fractionation within each suite. Alternatively, all the felsic rocks can be related through fractionation of a single magma if the lower zircon saturation temperature obtained for one suite merely results from Zr dilution, mostly reflecting silicification. The relatively high magma temperatures at Serra Branca ease the classification of felsic rocks based on their HFSE contents and also indicate volcanogenic massive sulfide deposit favorability. This contrasts with other areas of the Belt that register lower magma temperatures and are subsequently barren. However, magma temperatures may have not been high enough to cause complete melting of refractory phases in which HFSE reside during crustal fusion of an amphibolite protolith, implying difficult discrimination of tectonic environments for the felsic rocks. The intermediate rocks were possibly formed by mixing between basaltic magmas and crustal material, compatible with volcanism in an attenuated continental lithosphere setting.

Item Type: Article
Keywords: Zr thermometry; calc-alkaline rocks; attenuated continental lithosphere, Iberian Pyrite Belt; Volcanogenic massive sulfide deposit; Zircon saturation temperatures; Porphyry; Volcanic
Journal or Publication Title: Gondwana Research
Page Range: pp. 328-339
Identification Number - DOI: 10.1016/j.gr.2006.03.008
Date Deposited: 09 Jul 2007
Last Modified: 18 Nov 2014 03:19
URI: http://eprints.utas.edu.au/id/eprint/1346
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