Alkaline Rocks and Carbonatites of the World

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Los Cobres

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Occurrence number: 
008-00-004
Country: 
Argentina
Region: 
Salta
Location: 
Longitude: -66.25, Latitude: -23.8

A peralkaline granite pluton covering 7x3 km cuts and hornfelses Ordovician sediments of the Chiquero Formation northeast of Cobres on the Sierra de Los Cobres. The granite consists of microcline, albite, riebeckite, aegirine and accessories, including pyrochlore. Biotite and amphibole syenites crop out amongst modern sediments east of the granite, but the amphibole is ferrohastingsite and the pyroxene augite. However, tinguaite has been found in the Los Cobres area (Quartino & Llambias, 1964, p. 7).

Age: 
Rb-Sr whole rock determinations on riebeckite granite from near El Rangel at the northern end of the intrusion gave 123±6 and 129±8 Ma (Halpern & Latorre, 1973, Table 1).
References: 
HALPERN, M. & LATORRE, C. O. 1973. Estudio geocronologico inicial de rocas del noroeste de la Republica Argentina. Revista de la Asociacion Geologica Argentina, 28, 195-205. QUARTINO, B. J. & LLAMBIAS, E. 1964. Synopsis on rocks with alkaline affinities in the Argentine Republic. International Geological Congress, Report of the 22nd Session, India, 16 1-12. TOSELLI, A. J. & TOSELLI, J. N. R. 1977. El pluton granitico alcalino de la Sierra de Los Cobres, Prov. de Salta, Argentina. Acta Geologica Lilloana, 13‚ 169-85.
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