LITHOLOGY OF KIMBERLITE PIPE ORFICE OF CAMACHIA

Abstract

First diamonds were discovered in Angola in 1912. In the next 40 years, diamond mining was conducted from alluvial deposits. To date, the country are found about 700 kimberlite deposits. Camachia kimberlite pipe was put into operation in 2005. It is among the ten largest mines of the world and is located in the north-eastern part of Angola. Camachia tube is oval in shape with a diameter of about 650 m and an area of about 30 acres. The host rocks of kimberlite pipes are typically Archean gneisses, migmatites, which are covered volcanic-sedimentary rocks whose power in the crater of the tube is about 100 m. The total area of host rocks is about 1,2 millions m3 and weighs is about 600 000 tons. Morphologically tube is complicated, double and consists of two tubes and craters, and east crater tube partially destroyed west crater tube. Lithological composition of the western crater is differed from the east crater. Diamondiferous pipes are different. The reason for this is probably under different conditions of their formation. The upper part of the deposit is represented mainly by river - alluvial deposits. Besides river alluvium are presented in varying amounts talus, proluvial and colluvial deposits, which are difficult to separate because of their multiple mixing. Currently, the diamonds are extracted from alluvial deposits, since the depth of pit is small, from 5 to 20 m. The rocks tube Camacho East are presented volcanic rocks hypabyssal magmatic phase (kimberlites) and post-magmatic rocks phases (autolytic kimberlite breccia xenoliths). The rocks of crater are presented by various volcanic-sedimentary rocks: tuff-siltstone, tuff-sedimentary breccia, tuff-sedimentary xenoliths. Conducted research allowed identifying and describing medium link of kimberlite rock transformation from their crystalline rocks to the sediments and showing the possibility of determining of sludge capacity formation in the southern and northern latitudes. Also, this study allows determining the gradient of the primary alluvium rate of transfer to the secondary alluvial deposits and after that to offshore field. As a result, medium link, between kimberlite and offshore field can be divided to the smaller links in order to develop general method of searching alluvial deposits of diamonds.