Geology and Hydrothermal Alteration of the Low Sulfidation

Abstract

Abstract:The Pantingan Gold System (PGS) is a vein-type epithermal prospect exposed within the summit caldera of Mount Mariveles, Bagac, Bataan (Luzon), Philippines. It consists of nine major veins, eight of which trend NW-WNW and distributed in an en echelon array. The eastern tips of these veins appear to terminate near the NE-NNE trending Vein 1, which is located in the easternmost portion of the prospect. Metal assay results on vein and wall rock samples indicate concentrations of 0.01 to 1.1 g/ton Au, trace to 34 g/ton Ag and 0.003 to 0.02 % Cu. Andesite lava flow deposits host the PGS. Potassium-Argon isotopic dating of these andesites yields a narrow age range of 0.88 ± 0.13 to 1.13 ± 0.17 Ma. The surface exposures of the veins (up to 5 m wide) are encountered at different levels between 590-740 masl. These commonly display a massive texture although banding prominently occurs in Vein 1. The veins consist of gray to cream-colored crystalline and chalcedonic quartz and amorphous silica. Pyrite is the most ubiquitous sulfide mineral. It occurs either as fine-grained disseminations and aggregates in quartz or as infillings in vugs. Calcite, marcasite and bornite are also occasionally noted in the deposit. The prospect shows silicic, argillic, propylitic and advanced argillic alteration zones. Silicic and argillic alterations are confined in the immediate wall rocks of the quartz veins. Argillic alteration grades to a propylitic zone farther away from the veins. The advanced argillic alteration zone, indicated by a suite of acidic clay minerals that include kaolinite, dickite, pyrophyllite and alunite, might have been imprinted during the late stages of gold deposition. As a whole, the PGS displays geological and mineralogical features typical of gold mineralization in a low sulfidation, epithermal environment. It is also representative of a young, tectonically undisturbed gold deposit.

Geological hazards of SW Natib Volcano, site of the Bataan Nuclear Power Plant, the Philippines

“…Prior to the present report, the best available geological assessments of Natib Volcano were those of Almero (1989), Ruaya & Panem (1991) and Payot et al (2008). However, Ruaya & Panem's work, which delineates the summit caldera deposits, springs and faults, was narrowly focused on the geothermal prospects of the Bataan volcanic arc.…”

Behavior of Major and Trace Elements during Ore Deposition: Example from the Low‐Sulfidation Pantingan Gold System, Mount Mariveles, Bataan, Philippines

“…Whole-rock K-Ar dating of a basaltic andesite and an andesite sample located near the center of the caldera fl oor at elevation 700 m a.s.l. yielded a narrow isotopic age range of 0.88 ± 0.13 to 1.13 ± 0.17 Ma ( Payot et al , 2005 ). The prospect consists of nine principal vein structures, the majority of which strike WNW -NW and dip steeply to the SW.…”

“…The low-sulfi dation Pantingan Gold System is situated within the central portion of the Plio-Pleistocene Mount Mariveles volcano in the Bataan Peninsula, southern Luzon, Philippines ( Payot et al , 2005 ). It is hosted by a sequence of andesitic lava and pyroclastic …”

“…In general, the unaltered andesitic host rocks display a porphyritic texture characterized by a phenocryst assemblage consisting of plagioclase, amphibole, pyroxene and quartz set in a groundmass composed of fi ne-grained plagioclase laths, volcanic glass (±clay), and iron oxides ( Payot et al , 2005 ). Results of X-ray diffraction (XRD) analysis on air-dried and ethylene glycolated samples constrained the existence of the advanced argillic alteration halo ( Payot et al , 2005 ). This includes clay minerals such as illite, kaolinite, dickite, smectite, pyrophyllite, alunite, natroalunite and montmorillonite.…”

About the Special Issue: Collection of Achievements on Earth Resources from AUN/SEED-Net

“…Maglambayan et al (2005) report the mode of occurrence of Carlin-type like gold prospects hosted in silicified carbonate rocks in Surigao del Norte, northeastern Mindanao, Philippines. Payot et al (2005), on the other hand, describe the geology and hydrothermal alteration of the Pantingan lowsulfidation gold system, exposed in the caldera of Mt. Mariveles volcano, Bataan peninsula, central Luzon, Philippines.…”