Scientists study aluminum-rich soil formation in Samar

Scientists from the University of the Philippines—Diliman have examined a karst bauxite deposit in Paranas, Samar, a site known to contain aluminum and rare earth elements.

The study is part of efforts to guide the sustainable management of the province’s mineral resources and identify other potential deposits in the country, the researchers said.

Karst bauxite deposits form when alumino-silicate rocks undergo extreme weathering inside cavities or sinkholes in limestone terrain, according to the study by researchers Lyle Andre Arenque, Jillian Aira Gabo-Ratio, and Betchaida Payot.

The team collected samples from two test pits, dug up to four meters deep, and from an existing drill core that extended 11.2 meters below the surface.

X-ray diffraction analysis revealed key mineral phases in the bauxite, including boehmite and gibbsite, which are rich in aluminum.

“XRD analysis of drill core samples identified the primary mineral phases as boehmite, gibbsite, goethite, hematite, anatase, and kaolinite," the study said.

The occurrence of aluminum-bearing minerals such as boehmite and gibbsite indicates silica depletion from clay minerals, a process often accompanied by continuous dehydration and compaction,” it added.

The study said boehmite and hematite—dehydrated or partially dehydrated minerals—may develop during prolonged dry periods in tropical regions, while humid climates favor the formation of gibbsite and goethite.

X-ray fluorescence results also showed high concentrations of alumina and iron oxide, along with silicon dioxide, calcium oxide, phosphorus pentoxide, and titanium dioxide.

The study noted that alumina, iron oxide, and titanium dioxide concentrations decrease from the surface toward the bedrock, while silicon dioxide, calcium oxide, and phosphorus pentoxide levels increase.

The Paranas bauxite deposit is managed by Alumina Mining Philippines Inc. and is in the advanced stages of exploration, with numerous drilling activities conducted from 2003 to 2017.—MCG, GMA Integrated News