Paper Information

Journal:   IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY TRANSACTION A- SCIENCE   WINTER 2007 , Volume 31 , Number A1; Page(s) 73 To 87.
 
Paper: 

A FLUID INCLUSION STUDY OF A LARGE MVT BARITE-FLUORITE DEPOSIT: KOMSHECHEH, CENTRAL IRAN

 
 
Author(s):  RAJABZADEH M.A.*
 
* DEPARTMENT OF EARTH SCIENCES, FACULTY OF SCIENCES, SHIRAZ UNIVERSITY, SHIRAZ, I.R. OF IRAN
 
Abstract: 

The Komshecheh barite-fluorite deposit is the product of epigenetic hydrothermal mineralization in dolomitized limestone of Middle Triassic age. The deposit is structurally and lithologically controlled and occurs predominantly as bedded stratabound replacement sheets, although the veins and solution-collapse breccias constitute important modes of occurrence. Brecciation, dolomitization, silicification and mineralization are interrelated. Post-Eocene intrusions and NW-SE and NE-SW trending faults are important ore controls. The ore mineralogy is simple and consists of barite and fluorite with very minor galena, pyrite, chalcopyrite, malachite and azurite. Sulfides are extremely rare in the deposit. At least two episodes of deposition have been identified: an early stage of fluorite precipitation and a later barite-fluorite mineralization event with spatial and temporal variations in salinity and temperature. Thermometric investigations indicate that homogenization temperatures (TH) for primary and pseudosecondary fluid inclusions in the fluorite range from 89 to 244oC with a mode at 150oC, whereas those for primary fluid inclusions in barite range from 119 to 323oC with two modes at 150 and 250oC. Evidence for boiling is seen during barite deposition. The mean salinities measured are 12 and 10 equivalent weight percent NaCl for fluids in fluorite and barite, respectively. Hydrocarbons in the inclusions hosted by fluorite samples were also detected. Chemical analyses of fluids extracted from inclusions in fluorite and barite show compositions dominated by Na, Ca and Mg ionic species. Barite shows d34S values between 22.6 and 26.7 per mil. The comparatively narrow spread in d34S values suggests very uniform environmental conditions throughout the mineralization field. Consideration of these data in their geologic context favors a basinal source for the oreforming fluids which have been significantly affected by heating during intrusive emplacement. The deposition of barite and fluorite resulted from physicochemical changes in Ba-F-rich hydrothermal brines during mixing with sulfate-rich formational water and wall rock interaction.

 
Keyword(s): FLUORITE, BARITE, FLUID INCLUSION, MINERALIZATION, KOMSHECHEH, IRAN
 
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