GEOCHRONOLOGY OF THE GRANITOID HOSTED SALAMANGONE GOLD DEPOSIT, LOURENÇO DISTRICT, AMAPÁ, BRAZIL.

SONIA APARECIDA ABISSI NOGUEIRA, JORGE SILVA BETTENCOURT, COLOMBO CELSO GAETA TASSINARI

Resumo


The Salamangone deposit occurs in the Lourenço Gold District, Amapá. It is associated to Paleoproterozoic metamorphosed supracrustal rocks and a calc-alkaline complex. The deposit lies within a metaluminous to weakly peraluminous, calc-alkaline tonaliticgranodioritic pluton. The Au-mineralization consists of an epigenetic quartz-vein system, enriched in Au and As, and structurally controlled by a ductile-brittle shear zone. U-Pb zircon analyses of tonalite gave a crystallization age of 2.16 ± 0.13Ga, whereas Sm-Nd TDM model ages of tonalite and granodiorite range from 2.24 and 2.34Ga. eNd(T) vary from +2.88 to +3.02. Additional whole rock Rb-Sr isochron ages on granitoids yielded values in the range of 2.17 to 2.28Ga, with 87Sr/86Sr initial ratio of 0.702. The isotopic data and geochemical signature of granitoids suggest that the Lourenço region, as well as the neighboring areas in French Guyana, represents a vast area largely floored by accreted juvenile arc terranes without evidence of Archean crust contamination, being related to the development of a calc-alkaline magmatic arc, which was produced within the Maroni-Itacaíunas Province, during a major Paleoproterozoic orogenic event.

Palavras-chave


Amazonian Craton; Paleoproterozoic; Tonalite-trondhjemite-granodiorite(TTG); Gold mineralization.

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