Fluid Inclusion Investigations of the Raigan Porphyry Copper System, Kerman-Bam, Iran

摘要

The Raigan porphyry copper system is associated with diorite/granodiorite to quartz-monzonite plutons of Miocene age that intruded Eocene volcano-sedimentary rocks. Several stages of hydro-thermal alteration and associated mineralization occurred within the system. The main intense hydrothermal alterations are of potassic, phyllic, and propylitic types, especially within and adjacent to the diorite/granodiorite intrusive stock. Copper mineralization was accompanied by mainly phyllic and less potassic alteration. Early hydrothermal alteration produced a potassic assemblage (orthoclase-biolite) in the central part of the stock, propylitic alteration occurred contemporaneously with potassic alteration in peripheral parts, and phyllic alteration occurred later, overprinting all the earlier alterations. The early hydrothermal fluids are represented by high-temperalure (487 deg C to 598 deg C), high-salinity (up to 61.1 wt percent NaCl equiv.) liquid-rich fluid, inclusions, and high-temperature (397 deg C to 401 deg C), low-salinity, vapor-rich inclusions. These fluids are interpreted to represent a very hot orthomagmatic fluid that boiled episodically; the brines evidently caused potassic alteration, producing the first generation of chalcopyrite. Propylitic alteration is attributed to a liquid-rich, lower-temperature (523 deg C to 298 deg C), Ca-rich, evolved meteoric fluid. Based on this research, the temperature of mineralizing fluids was too high to produce an economic porphyry copper deposit at Raigan.