Abstract

MONTENEGRO, Teresita; ETCHEVERRY, Ricardo O.; LEAL, Pablo R.  and  DE BRODTKORB, Milka K.. Scheelite oredeposit associated with lamprophyres and biotitite in San Martín District, SanLuis province. Rev. Asoc. Geol. Argent. [online]. 2009, vol.64, n.3, pp.447-457. ISSN 0004-4822.

Towards thenortheast of the Sierra de San Luis several wolfram ore deposits occur. In SanMartín district they are divided into three groups: Los Avestruces, LaEsperanza and Cerrito Blanco. The geology of this area is formed of the Conlarametamorphic complex composed of schists (with a strike of 300º north),granitoids and pegmatites. In the same area subsaturated chalco-alkalinelamprophyres also appear as subvertical bodies with NW-NE strikes. Toward theboundaries of these rocks, the amount of biotite rises gradually from 80 to 90%developing a biotitite rock due to metasomatic processes and the superimposeddeformation. This biotitite is rich in K, Rb and W among other elements. Thescheelite mineralization (with quartz, biotite and tourmaline as non oreminerals) occurs in veins that are usually hosted between the lamprophyres andthe wall rocks. Scheelite also appears between the schist planes of thebiotitite rocks as well as disseminated crystals in quartz aggregates. Thismineralization took place from fluids with XH₂O: 0.87/0.82 - XCO₂:0.11/0.16 - XNaCl: 0.015/0.013 - (CH₄) meanwhile the scheelite,according to the fluid inclusions studies, precipitated from unmixing processesbelow 320°C and 2.3 kb. Achaliana orogeny and the intrusion of LasChacras-Piedras Coloradas batholiths (Devonian-Carboniferous) were theresponsible for the slight rise of the fluids from the basement, the generationof fault structures through which they rose, the metasomatism and themineralization.

Keywords : Lamprophyres; Biotite-enriched rock; Scheelite; H₂O-CO₂-NaCl-(CH₄).

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