Formation Mountain

As much the gold, how much the Uranian one, keeps certain relation with the presence of pyrite and carbonosa substance. The pyrite is the most abundant cloudy mineral occurring under the form to nodular and idiomrfica. 2.2.2. Important JACOBINA auriferous deposits are associates to the conglomerates of the Formation Mountain range of the Stream, that had been deposited in a system of fluvial draining, anastomosada*, that flua of east for west. Under the structural point of view the Jacobina Group is described as a homoclinal, diving strong for east. It is divided block-type, separate for originated imperfections, mainly, for proceeding compressivos efforts southeastern. Basic levees occupy generally, the imperfection plans and in its outcrops they are characterized by a negative relief, enters the Christians of quartzitos and conglomerates. 2.2.3.

SALIENT CHARACTERISTICS OF DEPOSITS PLACERS the mineralgica composition of the deposits includes pyrite as diverse types of grains in matrices of the conglomerates, together with quartz, feldspato and Moscovite. Other minerals heavy are uraninita, garnet, cromita, titanita, rutilo, monazita, xenotima, apatite, tourmaline, ilmenita, columbita, crindum, cassiterita, osmiridium and diamond. Gold is concentrate together with uraninita detrtica, but the lesser U/Au reasons occur in the thicker pebble bands, suggesting that the gold originally deposited together with the sediments thickest and that uraninita was loaded river below (they downstream) * for bigger distances, fruit of the difference of density of these two minerals. Some authors suggest that the Au has been introduced in the Basin of Witwatesrand for hidrotermais fluids soon after its burial. They would be fluid of the metamrfico type, with alteration associated with a reducing fluid, of low salinity, similars to the ones of greenstone belts. The fluids would have been canalized throughout structures, surfaces of discord and acamamento, having the precipitation of the been gold dominated for reactions with carbonosas or rich rocks in iron. These rocks are found intent immediately above of the discord surfaces.

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