フィリピン, シパライ銅山の開発

抄録

Copper was discovered at the present Sipalay Mine in midthirties, and was explored by San Remigio Mining Co. for years before the World War II, but did not produce much except some high grade oxide ore.
After the war, several mining companies made inspection of the property but no attempt was made to develope it until 1953. Mitsui Mining & Smelting Co., at the invitation of Elizalde & Co., made an inspection and found it to be huge “Porphyry Copper” type deposit. To undertake more through exploration, an exploration company, Sipalay Copper Mining Co., was organized under Elizalde & Co. and started exploration in full blast. After two years of extensive and intensive trenching, diamond drilling and tunnelling, 12 million tons of are assaying 0.9% copper were blocked out in Binuling orebody.
In the fall of 1955, it was decided to develop and exploit it under the management of the Present Marinduque Mining & Industrial Corp., Considering the shallow occurrence of the orebody and large lateral extent, open pit mining was adopted. Accordingly, by January 1956 the construction of 4, 000 tons/day mill and stripping of Binulig orebody were started and by May of the following year production commenced, followed by first shipment of concentrate in August.
While concentrating the mining operation in Binulig, exploration of other areas of the property was continued which resulted in blocking out of 8 million tons in Baclao area by 1959 and delivery of are therefrom started in 1960. On the other hand, the results of diamond drilling in Binulig and the geological observations made as it was being mined, all pointed toward the possiblity of existence of another orebody in the adjoining area across the river. This area was a rice field owned by a private party, so the diamond drilling was started soon after its purchase in 1961. Beyond expectation, this developed into huge orebody now known as Cansibit deposit.
With the discovery of Cansibit, mill was expanded to 5, 000 tons per day in 1963 and at the same time its development was undertaken. By January 1965 three pits, namely, Binulig, Baclao, and Cansibit were producing and in November of the same year, copper production per month exceeded 2 million-pound mark for the first time, of which record was broken repeatedly during the subsequent months in 1966.
The are reserve as of January 1, 1966 reached 75 million tons which justified the further expansion of the mill and preparation is well under way to mill 6, 500 tons/day by January 1967. By then, Binulig pit will be mined out after producing 11 million tons of are and will give way to Cansibit which will be the major producer for years to come. It is noteworthy that Sipalay is the only producer of molybdenite concentrate in the Philippines since 1959. The copper production up to the end of 1965 amounted to 72, 000 million tons all of which were exported to Japan.
The present paper is to introduce this remarkable mine to Japanese mining circle, principally on the mining aspect of the operation which will include pit design, equipment used and their performance, problems encountered, specially on the drainage problem of Cansibit pit. Special mention is made on the use of Sauerman excavator for the stripping of Cansibit orebody.