EL YACIMIENTO DE HIERRO DEL ARROYO VALENTINES. (FLORIDA, URUGUAY) Parte I - LA MENA FERRÍFERA

Very important reserves of iron ore with 35-40% Fe, are surrounding Valentines in Treinta y Tres and Florida departaments (Uruguay). This ore appears in limbs of folds in a high-grade metamorphic area with great tectonics. In this paper is studied the ore petrography. This is formed principally by quartz, magnetite and augitaegirine, but in surface, it passes, by weathering, into a rock formed by quartz and hematite. We have observed every stage of partial alteration and from there, it is deduced supergenic phenomena of uralitization and martitization. The resultant amphibol passes in surface to serpentine, which is partially eliminated by lixiviation. These weathering phenomena cause in increase in the iron content in weight in the superficial rock, from a value of 38% at dephts greater than 30 m, to 39.5-40% in surface. Texture nearly responds to that of an itabirite, but with a high-grade metamorphism and therefore, bigger grain size end different mineralogy.