Mineralogical and Geochemical Characterization of the Sta. Cruz Nickel Laterite Deposit, Zambales, Philippines

Abstract

In this study, we present mineralogical and geochemical characterization of samples systematically collected from a nickel laterite profile at the Sta. Cruz nickel laterite deposit, Zambales, Philippines. Wavelength-dispersive X-ray fluorescence spectroscopy (WDSXRF), mass-balance element mobility calculations, transmitted and reflected light microscopy, and previously reported results from coupled X-ray diffraction (XRD) and Rietveld refinement analyses reveal that the laterite profile investigated is composed of two main horizons—the limonite and saprolite zones—separated by a thin transitional zone. Based primarily on the mineral assemblage and major element chemistry, the main zones are further subdivided into subzones: upper limonite, lower limonite, transitional zone, upper saprolite, and lower saprolite. Garnierite veins were observed cutting the upper and lower saprolite subzones. Investigation of the structure of goethite within the limonite zone via Rietveld refinement shows that the crystallinity of goethite decreases with increasing Ni content and increasing crystallite size. This suggests that upwards through the limonite zone, as goethite ages, its crystallinity increases, which possibly results in the removal of Ni from its crystal structure and eventual remobilization to the lower laterite zones.

Ni(Co) Laterite Deposits of Southeast Asia: A Review and Perspective

“…Based on their lithostructural settings, these deposits are regrouped into two distinct metallogenic belts from north to south (Figure 3): the Philippine Mobile Belt (e.g., Sta. Cruz Ni and Intex Ni-Co deposits) and the Palawan-Mindoro Continental Block (e.g., Berong Ni-Co, Danao Ni, Dinagat Ni, Rio Tuba Ni, and Surigao Ni deposits) [23,28,[30][31][32][33]53,54]. The Philippine Mobile Belt was formed from the amalgamation of island arcs and north-south trending, east-dipping ophiolite suites, including a succession of ultramafic and mafic cumulates, residual harzburgites, lherzolites, dike-sill complexes, and volcanic rocks [55][56][57][58].…”

“…In the Philippines, the Ni(Co) laterite deposits are developed on the underlying mafic to ultramafic rocks comprising peridotites (harzburgite, dunite, and lherzolite), pyroxenites, and gabbros, which are found in ophiolite complexes of the Philippine Mobile Belt and the Palawan-Mindoro Continental Block (Figure 3) [30][31][32][33]47,72]. The Sta.…”

“…The Sta. Cruz Ni laterite deposit of the Philippine Mobile Belt is developed on harzburgite with minor chromitite and sporadic dunite lenses [31]. Harzburgite mainly consists of olivine and orthopyrox-ene, which are altered to serpentine and talc-chlorite, respectively [31].…”

“…Cruz Ni laterite deposit of the Philippine Mobile Belt is developed on harzburgite with minor chromitite and sporadic dunite lenses [31]. Harzburgite mainly consists of olivine and orthopyrox-ene, which are altered to serpentine and talc-chlorite, respectively [31]. At the Mindoro suture zone, the bedrock of Intex Ni-Co laterite deposits comprise lherzolite, harzburgite, and dunite, with serpentine veins cutting primary minerals in all types of bedrock [32].…”

“…In recent years, with the increase in nickel demand driven by the strong growth recorded by the Chinese economy, numerous studies have been conducted to investigate Ni(Co) laterite deposits in SE Asia. Previous studies have well documented these Ni(Co) laterite deposits in terms of geological, mineralogical, and geochemical characteristics, as well as the ore-forming process and exploration techniques [23][24][25][26][27][28][29][30][31][32][33][34]. Although these studies have provided a good foundation for further research and exploration work, few have proposed a brief summary of Ni(Co) laterite deposits in SE Asia, whereas most published literature is available in Chinese.…”