Geochemistry in the Exploration of Nickeliferous Laterite

PABLITO M. ONG and ARTURO C. SEVILLANO

A. Soriano Corporation, Makati, Rizal (Philippines)

Abstract

Applied geochemistry was used in prospecting and in the preliminary exploration of four nickeliferous laterite deposits in Palawan, Philippines.

Near-surface soils were collected from a grid with a 300-m square sampling pattern. Based on the evaluation of geochemical results from the soil samples, each laterite prospect was subdivided into "geochemical areas", namely: (a) highly anomalous, (b) anomalous, (c) slightly anomalous, and (d) background areas.

At Long Point, Palawan, the first laterite prospect, the geochemical areas were probed by test pitting. The majority of test pits in the slightly anomalous to highly anomalous areas, particularly in the latter, penetrated possible nickel ore (>0.9% Ni) in laterite and/or in the subjacent decomposed ultramafic rocks. By contrast, most of the test pits sunk to check the background areas encountered nickel deposits which are below the cut-off grade.

Using the resulting geochemical anomaly maps as guides in the exploration of other laterite prospects, test pitting was largely confined to the slightly to highly anomalous portions of the nickeliferous laterite prospects. Sinking of unnecessary test pits in areas containing low-grade nickel was thus avoided resulting in substantial savings in exploration costs.