GEOLOGICAL SOCIETY OF THE PHILIPPINES

 

Geological Characterization of the Infanta Nickel Laterite Deposit, Brooke’s Point, Palawan

Rufo S. Cabanlig, Jr. 1, Omar Teogenes A. Alfonso2, Rikki Pamela L. Pineda1, Marvin M. Ubaldo1, Brenda C. Jumangit1, Godfrey E. Atienza1 and Jane Kristine A. Teves1

1MacroAsia Corporation, 12/F, Allied Bank Center, 6754 Ayala Avenue, Makati City
2 MacroAsia Corporation, Infanta Nickel Project, Bgy. Ipilan, Brooke’s Point, Palawan

Abstract

The Infanta Nickel Laterite Deposit in Ipilan, Brooke’s Point, Palawan was discovered in the early 1970’s and later mined by Infanta Mineral and Industrial Corporation (IMIC) in 1977 to 1978. The IMIC’s name was later changed to MacroAsia Corporation (MAC) in 1995. MAC entered into a Mineral Production and Sharing Agreement (MPSA No. 220-2005-IVB) with the Republic of the Philippines in December 2005. The UP Geoscience Foundation, Inc. (GSF) was commissioned to do a preliminary assessment of the area in August of 2006 and the first phase of Geological and Resource Evaluation of the prospect was completed in March 2007. Subsequently, four additional core drilling and two test pitting campaigns were undertaken.

Similar to other nickel laterite deposits in South Palawan, the area is underlain by the Palawan Ophiolite which is comprised of an ultramafic complex, gabbro, pillow basalts and its sedimentary carapace. The ultramafic complex consists of lherzolites, harzburgites, dunites, pyroxenites and peridotites. These ultramafics, with lherzolites being dominant in the area, serve as parent materials of the laterite deposit. Serpentinization plays a major role as evidenced by the presence of serpentine, talc and chlorite in core samples and under the microscope. Silicification is also apparent as boxworks formed along fractures. Also associated with the presence of silica are garnierite which appear as its coating material. Minor occurrences of metamorphics, dunite and basalt have also been observed. Weathered schists present in the western portion of the tenement are the favored upland farmlots of the kaingineros.

Core samples were obtained and assayed to determine its mineral composition. Chemical analyses identified a 14-mineral suite. Among the metals and minerals identified are Ni, Co, Fe and MgO. Limonite yielded Ni values of < 1% to about 1.64%. In most of the samples, Ni content increased in the saprolite layer with values in the range of < 0.5% to as high as 2.72%. Average for both limonite and saprolite layers combined is about <0.5% to 1.72%. Cobalt, on the other hand, displayed decreasing values from limonite (0.04 - 0.25%) to saprolite (<0.05 to 0.27%). The average values for the limonite-saprolite layers are from <0.05 to 0.27%. Iron also exhibited decreasing values of >20 - 48.18% in the limonite layer to <10 - 48.95% in the saprolite layer. Average values for both limonite-saprolite range from 15.20 - 41.11%. MgO concentrations show an increasing trend from limonite (>0.80 – 17.60%) to saprolite (>3.0 – 36.52%) while average values range from 1.39 Laterite thickness range from about 2 meters to 37.4 meters with an average of about 15.18 meters. Thickness of limonite ranges from 0.6 to 24 meters. Limonite is generally thicker than saprolite which is 0.4 to 20 meters in thickness.

Relationship between Ni-enrichment and rock type is inferred. Another factor is the degree of serpentinization which may influence the leaching process and subsequent metal accumulation. On the other hand, factors which may have dictated laterite formation and thickness are topography, climate, rock mineralogy, geologic structures and time. These are discussed in relation to the extent at which the deposit in the area has developed.

 

 
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