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ALTERATION AND MINERALIZATION IN THE RAIGAN PORPHYRY SYSTEM, IRAN: EVIDENCE FROM FLUID INCLUSIONS

AUTHOR/S: HEZARKHANI, A.
Sunday 1 August 2010 by Libadmin2003

3rd International Scientific Conference - SGEM2003, www.sgem.org, SGEM2003 Conference Proceedings/ ISBN: 954-918181-2, June 9-13, 2003, 17- 26pp

ABSTRACT

The Raigan porphyry copper system is located in southeastern Iran (Kerman
province), and is associated with diorite/granodiorite to quartz-monzonite of Miocene
age that intruded Eocene volcano-sedimentary rocks. Copper mineralization was
accompanied by mainly phyllic and lass potassic alteration. Field observations and
petrographic studies demonstrate that emplacement of the Raigan stock took place in
several intrusive pulses, each with associated hydrothermal activity. Molybdenum is
not reported in any stage of hydrothermal evolution through the system. Due to lack
of information, the petrogenesis interpretation is mainly based on the field
observation. It seems that early hydrothermal alteration produced a potassic
assemblage (orthoclase-biotite) in the central part of the stock, propylitic alteration
occurred contemporaneously with potassic alteration, but in the peripheral parts of the
stock, and phyllic alteration occurred later, overprinting all the earlier alteration (the
most majority alteration in the Raigan system). The early hydrothermal fluids are
represented by high temperature (487 oC to 598 oC), high salinity (up to 61.1 wt %
NaCl equiv.) liquid-rich fluid inclusions, and high temperature (397 oC to 401 oC),
low-salinity, vapor-rich inclusions. These fluids are interpreted to represent an
orthomagmatic fluid which boiled episodically; the brines are interpreted to have
caused potassic alteration, containing first generation of chalcopyrite. Propylitic
alteration is attributed to a liquid-rich, lower temperature (523 oC to 298 oC), Ca-rich,
evolved meteoric fluid. Influx of meteoric water into the system, and mixing with
magmatic fluid produced deep albitization, and shallow phyllic alteration. This influx
also caused dissolution of early formed copper sulfides and remobilization of Cu into
the sericitic zone where it was resystemed in response to a boiling-induced decrease
in temperature. Supergene alteration was minor and restricted to a thin blanket of Cusulfides.

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