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MASS CHANGES ASSOCIATED WITH HYDROTHERMAL ALTERATION ZONES IN THE SAR-CHESHMEH PORPHYRY COPPER DEPOSIT, IRAN

AUTHOR/S: HEZARKHANI, A.
Sunday 1 August 2010 by Libadmin2002

2nd International Scientific Conference - SGEM2002, www.sgem.org, SGEM2002 Conference Proceedings/ ISBN: 954-918181-2, June 9-15, 2002, 49- 50pp

ABSTRACT/Full article not available/

The Sar-Cheshmeh porphyry copper deposit is located in
southeastern Iran and is associated with diorite/granodiorite to quartzmonzonite
of Miocene age. Copper mineralization was accompanied with
both phyllic and potassic alteration. Three main mineralization related
alteration episodes (potassic, transition, and phyllic alterations) have been
studied in terms of mass transfer and element mobility during the
hydrothermal evolution of the Sar-Cheshmeh deposit. In order to illustrate
these changes quantitatively, isocon plots (Grant, 1986) have been applied.
Isocon plots illustrate that Al, Ti were relatively immobile during
alteration, and that mass was essentially conserved alteration (pervasive
alteration form). At all stages in the evolution of the hydrothermal system,
the volume changes is close to zero. In the potassic alteration zone, there is
an obvious enrichment of K, and depletions of Na, Ca, and Fe. These
changes were due to replacement of plagioclase and amphibole by Kfeldspar
and biotite, respectively. Potassic alteration was associated with
large addition of Cu as might be expected from the occurrence of
disseminated chalcopyrite in this zone. In the transition alteration zone, Ca,
Cu and Fe were added, Na and Mg were relatively unchanged, and K and
Ba were depleted. The loss of K and Ba relatively to Na reflects
replacement of K-feldspar by albite. Phyllic alteration was accompanied by
the depletion of Na, K, Fe and Ba and strong enrichment of Si and Cu. The
losses of Na, K and Fe reflect the sericitization of alkali feldspar and
destruction of ferromagnesian minerals. The addition of Si is consistent
with the widspread silicification, which is a major feature of phyllic
alteration and the addition of Cu with mobilization from the both potassic
and transition zone which is depleted in this element.


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