Sedimentologic control of the uranium ore from Žirovski Vrh

Abstract

Lithologic features of the uranium bearing Val Gardena formation from Žirovski Vrh have been reexamined. Striking differences in the colour of adjacent sandstones and mudstones as well as pebble associations occurring in different conglomerate beds and primary sedimentary structures have been studied thoroughly. The whole formation is subdivided into ten lithostratigraphic horizons. In the mid of the sequence five of them make a 125 meter thick ore-bearing zone. The fifth and the sixth horizon appear to be rich in ore. The main ore-bearing rock of the former is a conglomerate composed of the oblate mudstone pebbles, but the ore occurs also in a common gray conglomerate The most important ore type of the sixth horizon is bound to the oblate pebble conglomerate filling up paleochannels. Somewhat higher ore contents are associated with silicified and anthracitized woods as well as with lenses and beds of dark gray and black mudstone. They are common also along the contact of green and gray sandstone. An interesting feature was obtained from drilling net carried out in a part of the ore deposit and transferred to the horizontal plane. In this way the paleochannels were revealed in form of a band system indicating the proper distribution of the ore bodies. The bands tend to split and to unit again. They are some ten meters in width and ten times as much in length.