ON THE FORM AND THE MINERALIZATIONS OF COPPER ORES IN THE ORO DENORO MINE, BRITISH COLUMBIA, CANADA

Abstract

The Oro Denoro Copper mine is one of the contact ore deposits scattered in Boundary District, British Columbia, Canada. Many investigations such as geological surveys, geophysical prospectings, prospectings by drilling and underground prospectings were carried out at this mine and other mines around it from 1956 to 1968. The geology of the Oro Denoro mine consists of sedimentary rock and various kinds of intrusive igneous rocks. The sedimentary rock belongs to the Brooklyn Formation of the Palaeozoic era which consists principally of limestone and calcareous rock containing small amounts of tuff, pyroclastics, argillite and sharpstone. These sedimentary rocks have been widely given the folding and faulting. They were given the contact metasomatism by the intrusion of the granodiorite batholith of the Mesozoic era called Lion Creek Intrusive and Emma Intrusive. The ore deposits are mainly grown around the skarn zone and granitic rocks. The characteristics of the ore deposits are as follows: (1) The metallic mineral in the copper ore consists largely of chalcopyrite containing a very small amounts of bornite and ores of gold and silver. The metallic gangue minerals are pyrite, magnetite, hematite, pyrrhotite and other iron ores. (2) The zone rich in copper is divided into two types. (a) The zone rich in copper is made up by various types of veins or banded ore bodies, the mineral deposition of which is controlled by many fissures in the sakrn zone. As a result the continuity of the zone rich in copper is poor and the copper ore is produced as wedge or rib. (b) The zone rich in copper shows bedded ore bodies, the mineral deposition of which is controlled by fissures in layered limestone, fracture zones or permeable skarn. As a result the copper content in the ore bodies is low, although they are big. (3) In general the mineralization is active in z ones where the skarnization has been advanced. The skarn accompanied by chalocopyrite is discontinuous, of irregular shape and distributed mainly in the central zone of the zone of high grade skarn. The grade of the skarnization is decreased concentrically on the horizontal cross section from its center to the outside. (4) The kinds of the skam minerals are nearly the same every place, which consist largely of garnet such as andradite and grossularite rich in calcium found in contact metasomatic deposits in Japan.