Skip to Main Content
GEOREF RECORD

Fluid inclusion and stable isotope study of the Esfordi apatite-magnetite deposit, central Iran

Morteza Jami, Alistair C. Dunlop and David R. Cohen
Fluid inclusion and stable isotope study of the Esfordi apatite-magnetite deposit, central Iran
Economic Geology and the Bulletin of the Society of Economic Geologists (October 2007) 102 (6): 1111-1128

Abstract

The Esfordi apatite-magnetite deposit is situated in the Bafq district of central Iran. It is one of the most P rich deposits in that district and is hosted by a sequence of early Cambrian rhyolitic volcanic rocks and intercalated shallow-water sediments. The zoned and strata-bound ore has a prominent Fe-oxide-rich core and an overlying body of breccia that is rich in apatite and hematite. The P-rich ore is associated with a proximal body of amphibole alteration within a pervasively altered sequence of volcanic rocks dominated by secondary K-feldspar. There are three major paragenetic stages of mineralization, each with characteristic hydrothermal fluid compositions indicated by apatite textures, fluid inclusion, and isotopic data. Type 1 apatite is mainly associated with the Fe-oxide-rich (magnetite-apatite) core and displays dissolution textures. The overlying, brecciated P-rich ore is dominated by vein-style apatite-hematite mineralization, dominated by type 2 apatite. Type 1 apatite has homogenization temperatures of 375 degrees to 425 degrees C and indicated salinities of 14.0 to 18.0 wt percent NaCl equiv. The magnetite has delta (super 18) O values of -0.1 to 1.7 per mil, suggesting precipitation from fluids with a dominantly magmatic source with delta (super 18) O of 7.8 to 9.6 per mil at approximately 400 degrees C. Type 2 apatite contains fluid inclusions that homogenize between 195 degrees and 295 degrees C, with indicated salinities of 13.0 to 19.0 wt percent NaCl equiv. The hematite associated with this assemblage has delta (super 18) O values of -0.2 to 2.3 per mil, which would be in equilibrium with fluids having delta (super 18) O values of 10.7 to 13.2 per mil at approximately 250 degrees C. These isotopically heavy fluids could have evolved through interaction of magmatic fluids with cooler saline fluids in the underlying and adjacent carbonate-rich sequences. Late-stage quartz-carbonate assemblages contain type 3 apatite and quartz with fluid inclusions that homogenize at 145 degrees to 155 degrees C and delta (super 18) O values of 16.0 to 17.1 per mil, corresponding to fluids having delta (super 18) O values of -0.7 to -2.1 per mil. These late fluids may have been derived from the introduction of a cooler, less saline and isotopically depleted fluid such as seawater. The fluid inclusion and stable isotope data indicate an evolving hydrothermal system involving at least three different fluids, ranging from an early, moderately hot and saline fluid through progressively cooler and more dilute fluids similar to those reported from other Kiruna-type deposits in the Bafq district.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 102
Serial Issue: 6
Title: Fluid inclusion and stable isotope study of the Esfordi apatite-magnetite deposit, central Iran
Affiliation: University of New South Wales, School of Biological, Earth and Environmental Sciences, Sydney, N.S.W., Australia
Pages: 1111-1128
Published: 200710
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 49
Accession Number: 2008-063232
Categories: Economic geology, general, depositsIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., strat. col., 3 tables, geol. sketch maps
N31°30'00" - N33°15'00", E55°00'00" - E56°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200814
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal