Economic Geology
Fattaneh Pourmohammad; Hossein Kouhestani; Amir Morteza Azimzadeh; Ghasem Nabatian; Mir Ali Asghar Mokhtari
Abstract
Mianaj Fe ore occurrence is located in the Takab-Angouran-Takht-e-Soleyman metallogenic zone, 100 km southwest of Zanjan. In this area, Fe mineralization occurs as lens-shaped bodies parallel to the foliation of schist and rhyolitic meta-tuff units (equal to Kahar Formation). Based on mineralography, ...
Read More
Mianaj Fe ore occurrence is located in the Takab-Angouran-Takht-e-Soleyman metallogenic zone, 100 km southwest of Zanjan. In this area, Fe mineralization occurs as lens-shaped bodies parallel to the foliation of schist and rhyolitic meta-tuff units (equal to Kahar Formation). Based on mineralography, ore mineral is magnetite, and quartz present as gangue mineral at Mianaj. The ore minerals show disseminated, laminated, banded, massive, vein-veinlet and replacement textures. Three stages of mineralization can be distinguished at Mianaj. The first stage is recognized as stratiform and stratabound lenses, laminated and disseminated crystals of magnetite parallet to the foliation of host rocks. Stage-2 mineralization is recognized by folding of ore bands, σ microfabric and boudinage of magnetite crystals, quartz pressure shadows and surrounding of foliation around magnetite crystals, and recrystallization of quartz and magnetite crystals. Stage-3 is recognized by quartz vein-veinlets that cut previous mineralization stages. Chondrite-nonmineralized REE pattern of host rocks and the mineralized samples indicate that mineralized samples are depleted in REE. This signature indicates mobility of REE by Cl and F-rich oxidized fluids during mineralization processes. Characteristics of Mianaj occurrence are comparable with metamorphosed and deformed volcano-sedimentary type of iron deposits.
Economic Geology
Rasoul Sepehrirad; Saeed Alirezaei; Amir Morteza Azimzadeh
Abstract
The Gazestan magnetite-apatite deposit is hosted within an upper Proterozoic-lower Cambrian volcanic-sedimentary sequence, known as Rizu series, in the Bafq district, Central Iran. The Gazestan deposit occurred in intensely altered felsic-intermediate subvolcanic and volcanic host rocks. Field observations, ...
Read More
The Gazestan magnetite-apatite deposit is hosted within an upper Proterozoic-lower Cambrian volcanic-sedimentary sequence, known as Rizu series, in the Bafq district, Central Iran. The Gazestan deposit occurred in intensely altered felsic-intermediate subvolcanic and volcanic host rocks. Field observations, drill core logging, petrographic studies, as well as geochemical and XRD data are indicative of differences in alterations assemblages and temporal/spatial distribution of the alteration products, compared to other iron oxide-apatite deposits in the Bafq district. Unlike many other Bafq district iron deposits, sodic alteration is only locally developed. Similarly, Ca+Fe or actinolitic alteration is poorly developed in Gazestan. Chloritic and sericitic alterations are most closely associated with ore formation in Gazestan. Chlorite commonly associated with magnetite, quartz and calcite in the altered host rocks. The chemical composition of chlorite falls in pycnochlorite and clinochlore fields. Calculated temperature for chlorite formation varies between 324-236 ºC. Sericite occurred both as a proximal alteration in ore zones, and as a distal alteration product in the volcanic and subvolcanic host rocks. Calcic-iron alteration is poorly developed in Gazestan. Potassic alteration marked by development of K- as well as biotite is only locally developed in Gazestan. Boron metasomatism occurs as quartz-tourmaline bands and disseminated grains in altered rocks. The scarcity and local nature of sodic (albitic) and calcic-iron (actinolitic) alterations, and the widespread and proximal chlorite alteration suggest that, compared to most other iron deposits of the Bafq district, Gazestan formed at relatively lower temperatures and possibly shallower depths.
Economic Geology
S. Maghfouri; M. R. Hosseinzadeh; A. Rajabi; A. M. Azimzadeh
Abstract
Darreh-Zanjir Zn-Pb deposit is located at the south of Taft city. Sulfide minerals in this deposit include sphalerite, galena and pyrite. Replacement, open space filling, vein-veinlet, breccia and massive are the typical textures in the Darreh-Zanjir deposit. Mineralization is associated with normal ...
Read More
Darreh-Zanjir Zn-Pb deposit is located at the south of Taft city. Sulfide minerals in this deposit include sphalerite, galena and pyrite. Replacement, open space filling, vein-veinlet, breccia and massive are the typical textures in the Darreh-Zanjir deposit. Mineralization is associated with normal fault. Gange mineral is dolomite and dolomitization is related to mineralization. Three types of dolomite have been recognized in the Darreh-Zanjir region: 1- Regional dolomite, formed during diagenesis of micritic limestone of the Taft formations and is exposed in whole region. It has dark gray color and fine crystals. 2- Thrusting dolomite, formed during compression and thrusting of the Taft formation on the Darreh-Zanjir formation, this dolomites are located at the vicinity of thrust fault.3- Mineralization and dolomitization occur adjacent to normal fault. This dolomite is known as hydrothermal dolomite (DH) and it decreases away from of sulfide mineralization. Geochemical studies suggest that high content of cadmium in sphalerites represents low temperature for ore forming fluid. Supergene and oxidation process caused change of sulfide minerals to non-sulfide minerals. Non-sulfide minerals of the Darreh-Zanjir deposit are smithsonite, hemimorphite, hydrozincite, cerrusite and Fe-oxides and hydroxides. The most important characteristics of mineralization at the Darrh-Zanjir deposit such as tectonic setting, post compression of normal fault controlling mineralization, host rocks, mineralogy, metal content as well as wall textures, show similarities with Mississippi Valley-type (MVT) Zn-Pb deposits.
