The formation of Ab Torsh barite deposit, Kerman province, with a view on the geochemistry of rare earth elements and stable isotopes of oxygen and sulfur
Subject Areas : The Application of Chemistry in Environment
hossein kalantar hormozi
1
,
Farhad Ehya
2
,
ghodratollah rostami paydar
3
,
sara maliki kheyme sari
4
1 - Islamic Azad University,Behbahan Branch
2 - Department of Geology, Behbahan Branch, Islamic Azad University, Behbahan, Iran
3 - geology department,islamic azad university,ahwaz branch
4 - geology department,,islamic azad university,behbahan branch
Keywords: barite, geochemistry, rare earth elements, isotop,
Abstract :
Barite can form in various geological environments, as it is found in a wide range of mineral deposit types. To determine the origin and physicochemical conditions under which the Ab Torsh barite deposit was formed, a comprehensive study was carried out using petrographical, REE geochemical, O and S isotopic. Barite mineralization occurs at Ab Torsh as a stratabound vein in the Senonian sedimentary rock units. Barite is accompanied by quartz and subordinate malachite, chrysocolla, Fe and Mn oxides and hydroxides, galena, azurite, fluorite, pyrite, and bornite. The brecciated host rocks cemented by barite imply an epigenetic origin for the barite mineralization. The ∑REE values are very low in barites (5.32-14.56 ppm), with chondrite-normalized patterns displaying LREE enrichment relative to HREE. The REE elemental ratios show that seawater with a highly modified geochemical signature (connate waters) acted as the barite depositing fluid. The δ18O and δ34S values in barites (+10.4‒+11.1‰ and +27.3‒+27.8‰, respectively) and δ34S values in galena (+6.3 and +7.9‰) indicate that sulfate (and thus sulfur) originated from sulfate carrying connate waters and/or evaporites. The Ab Torsh deposit is classified here as a structure (unconformity)-related barite deposit. It is concluded that intense faulting and the resulting brecciation of the host rocks probably provided the conduits needed for upward migration of the deep mineralizing fluids from a basinal brine source. Barite was formed where these ascending Ba-bearing hydrothermal fluids encountered sulfate-containing connate waters trapped within the overlying Senonian strata and or the descending meteoric waters that gained sulfate from evaporite-bearing rock units.
