Geochemistry and Occurrence of Chromite in the Ophiolite Complex, Samar Island and Homonhon Island, in Philippines

The chrome ore deposits in the Samar and the Homonhon islands of Philippines are worldly competitive and significant, since chromites in the laterites in weathered zone were partly enriched in the alluvial sediments and the cost for their production is cheaper than other primary chrome ore deposits. It is well understood that the occurrence of chromite ores is confined to layered mafic intrusions represented by the Bushveld Complex in South Africa and to ophiolite assemblages distributed in Turkey, India, Philippines, Cuba, Oman, Cyprus, and Russia, etc. Cr ores concentrated in laterite at the Samar Island and the Homonhon Island are the secondary product by enrichment of chromite originated from a primary orebody into sediments of alluvial deposit and big Cr -ore deposits competitive to other dealers due to the low cost of production. Chromites occur in the dunite as a massive orebody or vein and in the pyroxenite as one of major component minerals. The chromites from the former and the latter are completely different in the ratio of Cr/Fe in their chemical composition. The dunite and the pyroxenite located on the surface are strongly serpentinized and changed into laterite under favorable weathering condition. Strong resistant minerals such as a chromite and a magnetite which are separated from the original source rocks remained as residual minerals within the laterite and the enriched secondary Cr ore deposit has formed by gravitic separation during remobilization and transportation of the lateritic sediments.