| dc.description.abstract | The Uberaba Formation, of Campanian age, outcrops mainly within and near the Uberaba city. It consists of volcaniclastic rocks of alkaline character and lithic sandstones and greenish colored conglomerates showing fluted cross-stratification. Heavy minerals present are ilmenite, garnet, perovskite and magnetite, with minor clinopyroxenes, plagioclase, quartz, calcite, and apatite. The volcanic contribution to the Uberaba Fm. probably represents a mixture of alkaline volcanics from sources within the Upper Paranaíba region, aged between 87 and 83 Ma. This observation is supported by the whole rock analysis of the Uberaba Fm. showing an alkaline signature with high levels of barium, tantalum, lanthanum and niobium, and high thorium due to perovskite, a common mineral in alkaline districts. The detrital contribution within the Uberaba Fm. is derived from erosion of the Serra Geral Fm., as well as from the Canastra and Araxá groups. The source of alluvial diamonds within the Triangulo Mineiro is not well understood and may have a relationship with the known alkaline intrusions. Kimberlite and lamproite as the main source contributions to the Uberaba Fm. were discounted because they do not have sufficient number or size nearby that they could have provided the millions of carats of alluvionar diamond already recovered in the region. A correlation between the Uberaba Fm. and the diamond-bearing conglomerates of the Romaria region (MG) is not sustained. | |
