ALUMINOUS LATERITIC SOIL OF THE LUTAWON BASIN AREA, NONOC ISLAND SURIGAO PROVINCE, PHILIPPINES'

FERNANDO B. ESGUERRA

 

 

 

 

ABSTRACT



Aluminous lateritic soil containing as much as 40 per cent alumina (Al2O3) is found on the Lutawon Basin area, Nonoc Island, Surigao Mineral Reservation, Philippines. The area is underlain by clastic sedimentary rocks, probably of upper Miocene age. During the Pliocene or early Pleistocene, the land surface was subjected to extensive laterization.

Hand auger drilling and sampling conducted on a 100-meter grid pattern indicated 3,428,945 dry metric tons of aluminous laterite containing 22.81% Al2O3R, 3.03% SiO2 , and 38.37% Fe. The laterite, covering an area of 74 hectares, is 1.6 to 17.5 meters thick. Al2O3: SiO2, increases towards the upper portion of the mantle.

The U.S. Bureau of Mines Laboratory in Albany, Oregon, upon request of the Philippine Bureau of Mines, made differential thermal analyses and microscopic studies on three samples, supplemented by chemical and spectrographic work. The principal minerals are gibbsite and goethite with subordinate quantity of kaolinite depending on the silica content, Chromite, talc (P), and chlorite comprise the accessory minerals.

It is believed that the aluminous lateritic soil of the Lutawon Basin area had been developed by tropical chemical weathering in situ of conglomerate derived mostly from ultramafic and metamorphic rocks.

 

 

 

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