Z. Nasr Esfahani; M. H. Emami; S. J. Sheikhzakariaee; S. H. Tabatabaei
Abstract
The study area is located in the Isfahan province and at the north of East Alloun Abad village. This area is a part of Urmia - Dokhtar belt in Central Iran. A large part of the area is formed from Eocene igneous rocks. These rocks include basaltic andesite and pyroclastic rocks of ignimbrite and ...
Read More
The study area is located in the Isfahan province and at the north of East Alloun Abad village. This area is a part of Urmia - Dokhtar belt in Central Iran. A large part of the area is formed from Eocene igneous rocks. These rocks include basaltic andesite and pyroclastic rocks of ignimbrite and tuff. These rocks show porphyritic and microlithic texture with plagioclase, amphibole and clinopyroxene as the main mineral constituents. The secondary minerals such as chlorite, calcite, epidote and iron oxide are formed due to alterations. Electron microprobe analyses reveals that clinopyroxenes are diopside - augite. The study of clinopyroxene chemistry showed that the water was between 2 to 10% during clinopyroxene crystallization. The parental magma was calc-alkaline and tectonic setting is a subduction-related environment, based on clinopyroxene composition. Geothermobarometry of clinopyroxene gives temperature range of 925-1091°C and pressures range of 2-10 kbars for the formation of clinopyroxene in these rocks.
A Nakini; M Mohajjel; A Yarmohammadi
Abstract
Anjireh-Vejin Mines of Tiran are located 60 km west of Isfahan. Exposed rocks in these mines are Early Cretaceous (Early Baremian-Albian) in age. These rock units are exposed in NW-SE trending anticlines plunging shallowly to SE in three Vejin Paein, Vejin Bala and Anjireh-Chekab Mines. Folding in all ...
Read More
Anjireh-Vejin Mines of Tiran are located 60 km west of Isfahan. Exposed rocks in these mines are Early Cretaceous (Early Baremian-Albian) in age. These rock units are exposed in NW-SE trending anticlines plunging shallowly to SE in three Vejin Paein, Vejin Bala and Anjireh-Chekab Mines. Folding in all three mines exhibits same style, indicating that the mines are closely structurally related. At the SW side of all the mines, anticlines formed above the hangingwall of a major reverse fault are breached and expose older Cretaceous units. In the trenches of Anjireh-Chekab mines, which cut the steeply-dipping and overturned limb of the anticlines, older rock units are observed. In the trench cutting the Vejin Bala mine, layers in the SW limb are of steeply-dipping to locally overturned attitudes. Structural evidence from these mines clearly indicated that all the three mines are situated in a unique anticline with overturned SW limb and a folding style that consistently characterize “break-thrust fold” model. This anticline plunges gently by 15º to N150º. In btreak-thrust model, as folding progressively advances, a major reverse fault is being generated along the overturned limb of the anticline, which is well observed along the SW part of the mines in the study area. The mines are separated by E-W trending faults producing the present geometry. In addition to presenting a fold style model, we explored the relation between faults and fractures in all the mines using field observations and satellite images. Fractures are dominantly oriented along NW-SE direction sub-parallel with the strike of the axial plane of the anticlines. Structural analysis revealed three types of ore concentrations: 1) parallel to the original stratigraphic layering, 2) along the reverse fault in the overturned limb of the anticline, and 3) in the fracture systems.
S.T Delavar; I Rasa; M Lotfi; G Borg; N Rashidnejad Omran; P Afzal
Abstract
Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized ...
Read More
Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized in the deposit: 1-layers and lenses, concordant with layering; and 2-discordant secondary forms along the fractures. In Tangedezan deposit two mineralized carbonate facies have been distinguished: 1- dolomitic limestone facies (Microsparite) containing three major mineralization horizons with simple ore mineral paragenesis such as galena, sphalerite and pyrite replacing the host rock and filling the porosities and fractures; and 2- crystallized argillaceous limestone facies with very weak Zn-Pb mineralization in disseminated form. The deposit includes two parts of supergene in surface and sulfides in depth. The simple ore paragenesis comprises of hemimorphite, smithsonite, cerussite, galena, sphalerite and pyrite. Ag and Cd elements have noticeable grade and could be contemplated as by product. All accomplished investigations and evidences such as geological characteristics, mineralized facies, supergene and sulfide development, ore body geometry, ore minerals paragenesis, texture and structures in different scale, existing alterations specially dolomitization and lithogeochemical studies all reveal that Tangedezan deposit is a Zn-Pb Mississippi Valley Type (MVT) deposit.
M. Sakhdari; M. Yazdi; M. Behzadi
Abstract
The Shanegh area is located in central part of Sanandag-Sirjan zone, 28km southeast of Delijan. Rock units exposing in the area consists of sedimentary (carbonate, sandstone, siltstone) volcano- sedimentary (andesite to andesitic tuff, tuff) and intrusive host rocks. The volcano- sedimentary units thought ...
Read More
The Shanegh area is located in central part of Sanandag-Sirjan zone, 28km southeast of Delijan. Rock units exposing in the area consists of sedimentary (carbonate, sandstone, siltstone) volcano- sedimentary (andesite to andesitic tuff, tuff) and intrusive host rocks. The volcano- sedimentary units thought to be of Eocene to Quaternary ages which have been intruded by plutonic units. The main host rocks are monzonite, quartz monzonite, andesite and diorite. The host rocks have been altered by pervasive hydrothermal fluids. The alterations are sericitization, kaolinitization, carbonatization and silicification. The host rocks are characterized by fault or shear zones, vein systems, stockwork and dyke mineralization. Ore mineral assemblages are pyrite, chalcopyrite, Fe-oxide and Fe-hydroxides. We did not find gold minerals in our microscopic studies but the gold has been found in the lithogeochemical exploration. The results show that maximum grade of gold in some veins is about 2760 ppb and the mean grade of gold about 80 ppb. Comparing shanegh area main characteristics with epithermal gold deposits, shanegh area has the most similarities with epithermal gold mineralization; therefore, it is considered to be of this type.
