GENESIS OF FERRUGINOUS BAUXITE DEPOSITS IN BUCAS GRANDE ISLAND, SURIGAO MINERAL RESERVATION, MlNDANAO

Fernando B. Esguerra
Philippine Bureau of Mines

 

 

 

 

ABSTRACT



Deposit of ferruginous bauxites, closely associated with aluminous lateritic soils, occur at several places on Bucas Grande Island, situated within the Surigao Mineral Reservation, Mindanao.

Based on chemical composition, the investigation conducted by the Philippine Bureau of Mines indicates three principal types of alumina-bearing residual materials. They are as follows: (1) Type A - averaging 52.69% AI2O3, 18.32% Fe and 11.16% SiO2, approximately 1.2 million dry metric tons; (2) Type B - averaging 42.88% AI2O3, 25.29% Fe and 8.70 SiO2, roughly 8 million dry metric tons, and (3) Type C containing 12.77-32.77% AI2O3, 35.31-47.48% Fe and 1.75 - 4.31% SiO2, about 200 million dry metric tons.

The essential aluminum minerals of the ferruginous bauxite are gibbsite and kaolinite. Iron is present chiefly as hematite and/or goethite. The accessory minerals are chromite, magnetite, quartz and feldspar. The mineral forms of nickel, cobalt, manganese and titanium in the finely divided soil materials have not been positively determined.

The ferruginous bauxite and laterite deposits, believed to have been developed contemporaneously, are residual products of weathering in situ of various mafic and ultramafic rocks, together with their clastic derivatives. An attempt is made in the present study to analyze the chemical, mineralogical and lithological variations of these parent rocks in relation to the contrasting compositions of the weathering products.

 

 

 

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