Geology and Ore Deposits of the Bagacay Copper Mine, Samar, Philippines

Abstract

Ore deposits of the Bagacay mine are the first"Kuroko"type deposit discovered in the Philippine Islands. The mining area is composed of Tertiary pyroclastic sediments and volcanic rocks, underlying carbonaceous shale and coral limestone. The main working deposits, Guila-guila ore bodies, is considered sa a"Kuroko"type deposit which is blanket-like in shape directly underlying dolerite flow. "Black ore" consisting mainly of sphalerite, chalcopyrite, and pyrite, "yellow ore" chalcopyrite pyrite ore and"pyrite ore"are main component of the deposits. Marcasite, tetrahedrite, enargite and galena are not rare. Gypsum and barite are also common in argillized host rock, but smaller in amount. A part of carbonaceous shale has been mineralizod and formed high grade copper ore. It is presumable that carbonaceous shale and part of pyroclastics, capped by volcanic flow, have been secondarily replaced under submarine volcanic environment.