Abstract

GOZALVEZ, Martín Ricardo. Characterizationof San Martín pluton and associated tungsten deposits, Valcheta Department, Río Negro Province. Rev. Asoc. Geol. Argent. [online]. 2009, vol.64, n.3, pp.409-425. ISSN 0004-4822.

The San Martín pluton is formed by abiotitic granite border facies, a leucogranite central facies and cogeneticgranitic dykes and aplites. This pluton is a I-type metaluminous granite. Itwas seated in high crust levels in the middle Upper Permian (262 ± 5.2 Ma). Thepluton rocks show a textural evolution from medium grained hypidiomorphicbiotitic granites to fine grained allotriomorphic leucogranites, porphyriticdykes and miarolitic aplites, which suggest magma undercooling, watersaturation and exsolution of magmatic volatiles to favor tungsten removal andtransportation. There are two vein types in the San Martín pluton: 1) pre-tungstenmineralization veins, and 2) tungsten-bearing veins. The paragenetic sequencebegan with the first hydrothermal sterile stage (stage I), which formedpre-tungsten mineralization veins and generated potassium alteration in thewall rock. The second hydrothermal stage (stage II) formed the tungsten-bearingveins and deposited quartz, alkali feldspar and wolframite followed by quartzand wolframite. At the end of the stage II, quartz, sulphides, base andprecious metal sulphosalts and fluorite were deposited. A magmatic-hydrothermalsystem model is proposed where the San Martin pluton is the wall rock of thehydrothermal veins whose source is a highly differentiated granite intrusionlocated below. The granite intrusion would be a late stage of the graniticsystem of San Martín pluton.

Keywords : Tungsten-bearingveins; Granite; Petrography; Magmatic volatile phase.

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