Writers : KarimI.A & Rastad.E
Refference : Geosciences Scientific Quarterly Journal,No.:33-34,P.:20
Publishing Year : 1380

Abstract :
Nakhjirkuh celestite deposit is located at 165 km SE of Tehran. The studied area is a part of Central Iran tectono-sedimentary zon including Mesozoic and Tertiary rock units as well as Quaternary sediments. The Qom Formation which hosts the ore deposit, consists 01 limestone, marl, mudstone and gypsum.ln a general stratigraphic section of Qom Formation, from bottom to top, there are three celestite bearing horizons(l,Il,III).
In the horizon(l) country rocks are bioclastic limestone, oolithic limestone and brecciated micrite. Geometry of celestite is lenticulai shape and ore textures are Open Space Filling(O.S.F.), disseminated and cross-cutting with a paragenesis of calcite, celestite, gypsum anc iron oxides. Facies analysis studies suggest a back-reef lagoon and supratidal to shallow subtidal environments for deposition fades of the horizon. In horizon(l) the celestite has formed in early diagenesis with disseminated texture and in burial diagenesis with O.S.F. anc cross-cutting textures.
In the horizons(Il) and (Ill) country rocks are marl and limestone. These horizons have a layered geometry which can be traced abou
2km along the strike. In the western part of the mining district, celestite facies laterally grades to gypsum. The ore textures in these horizon! (II, III) are Diagen!tic Crystallization Rhytmites (D.C.R.s),disseminated, banded, O.S.F. and massive with a paragenesis of celestite, barite calcite, gypsum, dolomite and iron oxides. The depositional environment of the horizons(lI), (Ill) is shore lagoon. Due to the increasing ir salinity, micrite, gypsum and probably celestite precipitated as synsedimentary. In these horizons, during the early diagenesis celestite ha! been formed from porewater, as primary and replacement mineral (celestite replaced gypsum). In the burial diagenesis a Sr-rich brin obscurred the main parts of synsedimentary and early diagenetic features and has been formed D.C.R.s in addition to replacement 0 celestite after gypsum. Crystallization of the celestite in pressure solution planes, geode formation and inter- layerd cross-cuffing features an some of the other burial dia!enetic textures.
Subject List : Celestite