فصلنامه زمین شناسی ایران
پیاپی 42 (تابستان 1396)

The polymetallic epithermal Glojeh ore deposit is located in the middle of the Tarom-Hashtjin metallogenic province in Alborz-Azarbayejan (western Alborz). It consists of four major epithermal veins, in the South Glojeh and the North Glojeh areas. Andesitic basalt and dacite are hosting the mineralization in the South Glojeh and the North Glojeh veins, respectively. The in Glojeh area rocks include intrusive rocks (granodiorite, granite and quartzmonzonite), diabasitic dikes, and volcanic rocks (dacite, rhyolite, andesitic basalt and tuff). Based on genetic and crossed relations of vein and vienlets, mineralization in the Glojeh occurs in three stages: (1) early stage of Cu-Au-As-Sb-Fe-bearing minerals; (2) mid stage of Pb-Zn-Cu-Cd-Ag-bearing minerals and (3) late stage of hematite-goethite-Ag-Bi-Au-Pb minerals. Mineralogy and minerals chemistry studies show that galena in stage 2 (substage 2B) have inclusions of silver bearing minerals. Important silver bearing minerals in Glojeh veins are argentite, native silver, Ag-tetrahedrite, polybasite, matildite and marrite. Gold mineralization occured in substage 1B (stage 1), and is associated with specular hematite (specularite) as native gold and in substage 3A (stage 3) as inclusions of native gold and eletrum in hematite and quartz. Alteration in Glojeh district consists of propylilitization, argillization, sericitization and silicification, that have well-developed and zoned in the around Glojeh veins and extends ≈ 30 meters into the host rocks. Chlorite geothermometry in argillic zone (stage 2) and propylitic zone (stage 3) are 275°C and 200°C, respectively. Mass balance calculations indicate that Al, Zr, Ti, Y, Nb, and HREE were immobile elements during alteration.

In order to determine biostratigraphy, facies and sequence stratigraphy of the Kalat Formation in the West of Kopet Dagh Basin, two Jozak and Chakhmaghlu stratigraphic sections were selected and sampled. The thickness of the Kalat Formation in the Jozak and Chakhmaghlu stratigraphic sections are 158 and 139m respectively, and its lithology consists mainly of gray to brown limestones and few marl. Biostratigraphic studies led to recognition of 32 genera and 15 species of benthic foraminifera and 11 genera and 6 species of planktonic foraminifera and then, Siderolites calcitrapoides-Sirtina orbitoidiformis Assemblage Zone was identified. Based on the indicated biozone and fossil contents, the age of the Kalat Formation is Maestrichtian. Petrographic analysis led to recognition of one silliciclastic and ten carbonate facies belonging to four depositional environments including tidal flat, restricted and semi-restricted lagoon, shoal and open marine. The identified facies were deposited on a homoclinal ramp setting. On the basis of facies distribution and depositional environments, two depositional sequences were proposed for the Kalat Formation. Depositional sequence 1 consists mainly of proximal open marine and shoal facies. Maximum flooding surface of this sequence is characterized by open marine facies containing echinoid and planktonic foraminifera. Depositional sequence 2 consists mainly of shoal facies rich in bioclast, intraclast, benthic foraminifera and rudist. MFS of depositional sequence 2 is represented by bioclast echinoid packstone facies. Comparison between sea level changes in the study area with eustatic sea level and Arabian Plate sea level curves show that sedimentation of the Kalat Formation was influenced by eustatic sea level change.

The Samen granitoid is located along the northwestern part of the Sanandaj- Sirjan Zone in the Southwestern of Malayer. Based on mineralogical and geochemical characteristics, five main facies have been recognized in the Samen granitoid which included granodiorite, monzogranite, syenogranite, alkali-feldspar granite and quartz-monzonite. Granodiorite is the main facies of the pluton and is more wide spread than other facies. Geochemistry of major elements indicates that the Samen granitoid is metalomious (ACNK=0.75) to peralomious (ACNK=1.21) and is classified as volcanic arc granites (VAG) related to active continental margins and petrochemically belongs to calc alkaline with high K rock series. Depletion in Nb, Zr, Hf, Y, Ti and HREE and enrichment in K, Rb, Cs, Th and LREE is consistent with an arc setting related to the subduction of Neo-Tethyan oceanic crust beneath the Sanandaj-Sirjan zone. The pluton has been contaminated by interaction with upper crust. In the Samen district both calcic exoskarn (grossular-andradite/augite-diopside) and endoskarn (tremolite-actinolite/epidote) occur along the contacts between granitoid and marble. The present study indicates that geochemical characteristics of the granodiorite and quartz-monzonite Samen rocks are similar to the averages for Au-Cu- and Fe- skarns granitoids, whereas the geochemical characteristics of the monzogranite, syenogranite and alkali-feldspar granite are similar to averages for Sn- and Mo-skarn granitoids. Based on oxidizing conditions and magma evolution, the Samen granitoid is characterized by relatively unevolved to moderately evolved and oxidized suites, as in most Au-Cu core metal associations globally.

Field relations and petrographical features show that formation of the metapelitic rocks in Western Iran were influenced by different metamorphic conditions in south and north of Alvand Batholite (Jurassic age). The intrusion of the Batholith into pelitic host rocks in the northern area (Cheshin Village) produced hornfelsic metamorphic rocks which contain staurolite, kyanite, garnet and sillimanite, whereas in the southern area (Tuyserkan city) these rocks contain, cordirite, andalusite, garnet and sillimanite. Mineral assemblages in the metapelitic rocks in two areas (in the north and south) are different. Using multiple equilibria temperature, pressure and fluid composition have been calculated for the formation of both northern and southern rocks respectively, as temperature (~600-630 ºC), pressure (~2-4 kbar), and fluid composition (XCO2 as low as 0.17) for northern rocks and temperature (~600-750 ºC), pressure (~4 kbar) and low (άH2O) for southern rocks.
P-T results indicate that geothermal gradients in two areas (North and South) are respectively 42.5 and 58 ºC/km which conform Barrow and Buchan metamorphic series.
Pseudosections were constructed using the Theriak/Domino program. Results of this method are in good agreement with other methods. Therefore, the Hamadan metamorphic rocks have experienced multiple episodes of metamorphism driven by burial and heating during arc construction and collision during subduction of a Neo Tethyan seaway in the Jurassic-Cretaceous, and these events are associated with different metamorphic series in parts of metamorphic aureole of the Alvand complex.

The Zargoli granodiorite is located in the northwest of Zahedan in Sistan suture zone. This granodiorite intruded a flysch-like unit at Oligocene and its SiO2 contents range from 62.4 to 66 wt. %. This gronodiorite is calc-alkaline, metaluminous and I-type. The Zargoli granodiorite shows negative anomaly of Ta, Ti, Nb, Eu and positive anomaly of Rb, Ce, La, Ba, Sr in spider diagrams suggesting that these rocks have been derived from the partial melting of lower crust. This magma was contaminated with flysh- type sediments during emplacement in Sistan suture zone. Discriminative diagrams indicate a volcanic arc (VAG) and active continental margin (ACM) tectono-magmatic setting for this pluton.

Independent estimates of deterministic and probabilistic methods of hazard analysis in the region of Tabas City were conducted in this study . Gutenberg - Richter relation for Tabas was obtained by analyses of seismic data based on LogN= 2.3 - 0.50 Ms. The greatest horizontal acceleration on Tabas city is 0.7g rsulted from Shotori thrust with a shaking power of 7.4 Richters. The obtained results show that, Kalmard fault with length of 170 km and distance of 50 kilometers from Tabas, has the highest impact after Shotori thrust. So that, the most expected seismic (8.93 Richter), the maximum relative intensity at the center (8.32), the maximum horizontal displacement at the center (29.82cm) and the maximum vertical displacement (66.70cm) are the result of this fault on Tabas. Using geostatistical analysis tool in ArcGIS (ordinary kriging), a suitable model was introduced for mapping the maximum gravitational acceleration. Using this map, zones with high and very high seismic risks and two liner earthquake sources with NE- SW trend (west of Tabas) as a result of Kalmard and Ladar faults and NW-SE (east of Tabas) as a result of Shotori, Esfandiar and Nayband faults were identified.

The North Tabriz Fault (NTF) is the most prominent tectonic structure in the Northwest of Iran. The results of this study show that this fault has a major impact on hydrogeological conditions of the local aquifer. Plio-Quaternary volcanic ash and tuff layers constitute the only unconfined aquifer of this area which directly lies on Miocene red marl as aquifer bed rock. Northern part aquifer bed rock is placed in the higher level than the southern part. This could be the reason for the existence of the reverse dip-slip movement of fault in this area, which causes the northern part (hanging wall) trust over the southern part (footwall). Sharp differences in aquifer bed rock level at relatively low distances (less than 200 m), can be a sign of near-vertical slope of fault in this area. An obvious groundwater level differences which reaches to more than 8 meters, along with the apparent differences between groundwater qualities across the fault at a low distance (about 200 meters) show a barrier behavior of fault. Total depth of the southern part wells is four times compared to the northern parts. Total annual discharge of southern part wells is about eight times of northern parts. Total hardness and ions concentrations of groundwater samples shows that most of the northern part samples are not suitable for drinking purposes, but the southern part samples are suitable. Also, all of the northern part samples have the negative Langelier index (corrosive). All of the southern part samples have the positive (very close to zero) Langelier index and suitable for industrial usages. Therefore this is a reason why most of industries in this area were located in the southern part of the fault.