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A Preliminary Study on the Aghbolaq (Fe, Cu) Skarn Deposit, Oshnavieh, NW Iran: Constraints on Metasomatic Fluid Evolution
Author(s) -
SIAHCHESHM Kamal,
KHAJEMOHAMMADLO Nasrin,
CALAGARI Ali Asghar,
ABEDINI Ali
Publication year - 2021
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.14689
Subject(s) - skarn , metasomatism , geology , fluid inclusions , meteoric water , geochemistry , quartz , andradite , hydrothermal circulation , magmatic water , ore genesis , magnetite , mineralogy , paleontology , mantle (geology) , seismology
Abstract The Aghbolaq skarn deposit is located in the Urumieh‐Golpayegan plutonic belt, NW Iran. The garnetite skarn (stage I) has been intensely cross‐cut by the magnetite‐garnet skarn (stage II) which were, in turn, cut and offset by the ore‐hosting quartz veins/veinlets (stage III). The predominance of andradite (Adr 82.5–89.1 ) and its high Fe 3+ /Al ratio (up to 1685) apparently supports the high f O 2 , salinity and prevalence of magmatic/hydrothermal fluids involved, rather than meteoric waters, during the magnetite‐garnet skarn formation. Two major groups of fluid inclusions, namely aqueous (LV, LVS) and aqueous–carbonic (LV C , LL C V C ), were recognized in garnet and quartz veins that, especially in growth zones and along intra‐granular trails, better display fluid inclusion assemblages (FIAs) than those in clusters. The prograde magnetite‐garnet skarn was formed by the metasomatic fluid at relatively high T h (209–374°C), under a lithostatic pressure of ∼200 bars. The retrograde mineralized quartz veins were formed at temperatures ranging from 124°C to 256°C, by dilute and less saline (2.57–11.93 wt% NaCl eq.) hydrothermal fluids under a hydrostatic pressure of ∼80 bars. The fluid evolution of the Aghbolaq skarn began with an earlier simple cooling of metasomatic fluid during the prograde stage, followed by the later influx of low salinity meteoric fluids during the retrograde stage.