The Anagase "Kuroko-Type" Deposits: A Case Of A Volcanogenic Massive Sulfide Discovery On Samar Island, Philippines

JOSE. S. PORTACIO, JR. P. Geo.

Explorationist/Orefinder
100 Rome-Stockholm Sts., Greenpark Village, Manggahan, Pasig City, Philippines

Abstract

In 1978, a reconnaissance stream-sediment geochemical survey was carried-out by Boliden AB Philippine Branch over about 500 square kilometers of unexplored jungle territory in the Cretaceous volcanic-sedimentary package in North-Central Samar region. This survey resulted in the discovery of several volcanogenic massive sulfide occurrences in the dacitic-andesitic volcanic units.

The Anagase deposits which ranked as high priority targets for follow-up surveys, were explored in detail by geologic mapping on outcrops, trenches, test pits, shallow exploratory adits and crosscuts, plus soil and bedrock geochemical sampling. Subsequent geophysical surveys were carried out using Spontaneous Potential (SP), ground magnetics, IP-resistivity, and Very Low Frequency (VLF) methods.

Based on the encouraging surface geological criteria, supplemented by the results of an integrated approach of geochemical and geophysical techniques, the primary targets were drill-tested with 50 core holes aggregating a total depth of 3,444.95 meters. The drilling results yielded a resource of 1.3 million tons averaging 0.4% Cu, 3.7% Zn, 1.3 g/t Au, and 81 g/t Ag.

This paper presents the various parameters employed leading to the successful discovery and delineation of the Anagase "Kuroko-type" deposits during the early stage exploration.