فهرست مطالب abbas moradian

The NNW-SSE trending Âj fault parallel to the Naein-Baft fault zone in the west of micro-continent of Central Iran, starts from the south of Mehriz and passes through the Urumieh-Dokhtar magmatic arc, to the southern margin of the Sanandaj- Sirjan metamorphic zone in south of Iran with N350 trend. The structural analysis of this fault in Urumieh- Dokhtar magmatic arc (Dehaj-Sarduiyeh magmatic belt) indicates a dextral oblique-slip mechanism. The paleo-stress analysis based on the data taken from the fault surfaces indicates the direction of the maximum stress in N040 parallel with the contractional movements of the Arabian plate towards the Central Iran. The Âj fault has caused many changes in the morphology of this area, one of the most important of which is the penetration of sub-volcanic dacite-rhyodacite plugs along its length. In the south of the studied area, this fault has caused the cut and dextral displacement of the ophiolites and Shahr-e-Babak fault zone. The Âj fault zone is active, because some rivers in its length are dextral displacement.

Andesites are located in the north of shahr-e-babak , central Iran, Urumieh- Dokhtar belt. The main texture in these rocks is porphyry and their phenocrysts are plagioclase (Andesine to Labradorite), pyroxene (Augite), amphibol (Tschermakite and Magnesiohornblende). These properties are signatures of calc- alkaline series formed in a volcanic arc setting. Based on geochemical studies, the rocks show enrichment in LREE rather than HREE. The lack of significant Eu anomalies in REE pattern indicates  oxidation state of magma during crystallization. Based on geochemical studies, the clinopyroxenes are Augite and have been crystallized from magma with almost 10% H2O. Fe3+ values of the clinopyroxenes reveal high oxygen fugacity in the magma. Based on the mineral chemistry data, pressure estimates from the clinopyroxenes in the range of 6-10 Kbr and composition yield the crystalization temperatures that range from 900-1100 OC.  Typically, clinopyroxenes occure at calc-alkaline orogenic igneous rocks. The plagioclase composition yield the crystalization temperatures that range from 650-750 OC. According to the present study, the rocks are probably the result of the subduction of the Neo-Tethys oceanic lithosphere below the Sanandaj-Sirjan zone, during the Eocene and in a volcanic arc environment.

The mantle peridotites of the Hadji-Abad ultramafic complex in Hormozgan province, show some petrological evolutions of the upper mantle of southern Iran. The complex includes harzburgite, lherzolite, dunite and chromitite. Evidences such as different generations of minerals, lobate boundaries between grains, elongation of cr-spinels and pyroxenes, incongruent melting related textures and exsolution lamellae of clinopyroxene in orthopyroxene show that the rocks in this peridotites have past a complex petrological history. The chemical composition of chromites in the Hadji Abad dunites and chromitites is similar to that of boninite melts, while, the mineral chemistry of the harzburgitic and lherzolitic show that the host peridotites belong to the upper mantle and have been depleted from incompatible elements due to 15 to 20 percent partial melting. Geo-thermometric calculations reveal that the studied peridotites equilibriated in upper mantle and spinel-peridotite stability field. Using tectonomagmatic discrimination diagrams shows that the Hadji-Abad ultramafic complex is part of an oceanic lithosphere above suprasubduction zone which has undegone partial melting, high temperature deformations and mantle metasomatism processes associated with this environment. These evidences along with the geological and tectonic setting of the Hadji Abad complex adjacent to the Zagros thrust indicate that the complex probably was created in a suprasubduction zone oceanic mantle section and then tectonically emplaced as part of Esfandagheh-Hadji-Abad mélange in the current situation during the upper Cretaceous. This information confirm the dependence of the Esfandagheh-Hadji-Abad ophiolite mélange on the Neotethyan oceanic lithosphere in southern Iran.

The studied area is located in the SE of Bam and Urumieh-Dokhtar Magmatic Arc. Based on petrographical and geochemical characteristics, studied rocks contain tonalite, granodiorite, granite and alkali granite. These rocks are metaluminous, weakly peraluminous, high-K, and calc-alkaline. The behavior of Y, Ba, Ce and Zr vs. SiO2 display the properties of the high temperature I-type granites. These granitoids plot in the field of VOG. Enriched LREE and LILE with depleted HFSE show characteristics of subduction related active continental margins. The ratios of Nb/U and Nb/La and Sm/Yb indicate the crustal contamination. Isotopic data and La vs. La/Sm diagram show the role of the lower crust and the old continental crust in magma evolution. According to the phenocrysts assemblage, REE pattern with negative Eu anomaly and La/Yb ratio to crustal thickness, studied rocks are fractionated from relatively dry magma which has undergone from shallow depths. Sm/Yb and La/Yb ratio display the mantle source is garnet-free source. The low to moderate degree of partial melting of garnet-free amphibolite is the source of the studied granitoids. Volatiles that is driven from subduction slab and melt of the subducted sediments play a significant role in the generation and evolution of their magma source.

Shan Abad–Raviz basic intrusions from the West of Rafsanjan (Kerman province), represent a part of Dehaj-Sarduyieh belt and intruded into the Eocene volcano-sedimentary rocks as dykes and apophyses. Thicknesses of the dikes and the diameters of the patches reach up to 4 and 10 meters respectively. In the field, they appear as dark intrusions contain sporadic euhedral pyroxene crystals with up to 5 mm in size. They are gabbro and diorite and their main minerals are plagioclase and pyroxenes set in a fine-grained matrix and show intergranular and porphyroid textures. These rocks have low-K calc-alkaline affinities and their geochemical characteristics tend to the subduction zone settings. In these rocks, 87Sr/86Sr and 143Nd/144Nd ratios vary between 0.70403 to 0.70409 and 0.5128 to 0.5129 respectively and εNd(i) values change between 3.52 to 6.6. These evidences along with the special textures show that their parent magmas affected by fractionation, assimilation and magma mixing processes. Considering that these rocks have intruded into the Eocene volcanics, we suggest that they represent the last stages of Eocene magmatism in the Cenozoic Kerman magmatic belt and intruded into the crust after the intiation of Neo-Tethys subduction beneath to Central Iranian block, probably in a continental margin tectonic setting.

In The northern part of Kerman Volcanic Belt, southwest of Rafsanjan (Deh-Zahir area), a series of diabasic intrusives have intruded into the Eocene andesitic lava flows and pyroclastic rocks. These plutons occur as irregular shaped bodies (up to 8 m in diameter) and dikes (up to 4 m in thicknesses). They show ophitic, sub-ophitic, and porphyritic textures and their major minerals include plagioclase (bytownite), and clinopyroxene (diopside), with titanomagnetite as secondary mineral. Based on The petrographic characteristics, presence of the enclaves and chemical variations from core to rims of the pyroxenes and plagioclases suggest that the parent magmas probably tolerated magma mixing processes. Geothermobarometric studies on the clinopyroxenes indicate a temperature range of 1050-1200oC and pressures of more than 2 kbar. Accordingly, beginning of the clinopyroxenes crystallization  can be considered approximately at the depth of 20 Km, i.e. in the middle crust. Furthermore, these evidences show that the oxygen fugacity was low and water vapor pressure was less than 10 kb during the crystallization of clinopyroxenes in the diabase rocks. Based on the chemical compositions of the clinopyroxenes, the primary magmas for these rocks had been calc-alkaline in nature and formed in a volcanic arc setting.

In the western part of the Joupar Mountains, a set of Neogene basic rocks cover the felsic rocks. Volcanic rocks suite consisting of basalt- andesite- dacite and rhyolite. Main minerals in basaltic ricks consist of olivine, plagioclase, pyroxen and have microphyric, glomeroprophyric, hyaloprophyric, intergranular textures. The volcanic rocks are enriched in LILE and LREE, and depleted HREE, and display highly fractionated REE patterns. Based on the tectonomagmatic environment diagrams, all alkalibasalt samples from the Joupar plot in the island arc setting of a subduction zone and show active continental setting characteristics. The primary magma of the studied rocks is the melting of 1-5% of a lherzolite garnet mantle source with phlogopite. The post collision convergence between Arabia and Eurasia continental plates, starting in Miocene, resulted in thermal perturbation processes in the underlying lithospheric mantle led to partial melting at a low degree, producing alkali- basalt magmas, with garnet remaining stable in the source region. The ascent of the basaltic magma and its emplacement in the lower crust resulted in the partial melting of the crustal materials and development of acidic magma. These processes led to the ascent and eruption of the felsic magmas prior to the mafic magmas. There are mineralogical as well as geochemical evidences that AFC-type processes were involved in the evolution of the Joupar volcanic rocks in Kerman

IntroductionBorate deposits are often important constituents of economic non - marine evaporates. They produce under arid climatic conditions in playa lakes (Floyd et al., 1998). In the south – western parts of the Kerman province, such as the Khatoonabad area (east of the city of Shahr –e –Babak) and Robat – Marvast basin (west of Shahr – e – Babak), there are several borate deposits. They can be seen mainly in Sanandaj – Sirjan depressions and they occur as borate bearing nodules beneath a thin layer of soil. In general, boron considerably reduces the thermal expansion of glass, provides good resistance to vibration, high temperatures and thermal shock, and improves its toughness, strength, chemical resistance and durability. It also greatly reduces the viscosity of the glass melt. These features, and others, allow it to form superior glass for many industrial and specialty applications (Garrett, 1998). In the past, the ancient residents used them as co-melting matters. Ulexite which is frequently found in the Khatoonabad playa (at 30 km South East of Shahr Babak) have Jewel properties (Ghaedi et al., 2014).
Materials and methodsAfter reviewing and Library Studies, geological field studies on the borate deposits were carried out from Shahr – e – Babak Playa. In order to take better samples, several pits were excavated with a depth of 30 cm to 1 meter so that borate minerals became apparent. X-ray diffraction analysis (IMIDRO, Karaj), and ICP AES (ALS CHEMEX, Canada) methods were carried out on representative samples taken from the studied area.
DiscussionField observations show that in the studied areas, borate bearing basins are fed by rivers which have originated from Sanandaj – Sirjan metamorphic rocks, Nain – Baft colored mélanges and igneous rocks of Urumieh – Dokhtar magmatic belt. Borate minerals also occur in fibrous aggregates and massive forms.
MineralogyXRD results show that the studied borate minerals mainly belong to the hydrated borates and contain ulexite, borax, gowerite, sassolite and inyoite. Geochemichal data indicate that the boron is the dominant constituent in the studied playa. Borate minerals are divided into two groups of hydrated and non-hydrated borate category (Palache et al., 1952.; Garrett, 1998). Both hydrated and non-hydrated borate minerals have been formed in the Shahr-e-Babak playa.
Hydrated borate in the study areas:Hydrated borates are those borates in which water molecules are involved (Garrett, 1998). In the studied area, the hydrated borate minerals include: Borax, Ulexite, Inyoite, Gowerite.
Non-hydrated borate in the study areas:In the Shahr-e-Babak playa, Sassolite non-hydrated borate minerals are abundant.
According to the XRD analyses performed on samples from the study areas, the hydrated borate minerals are more important minerals. The main economic valuable minerals include:1- Ulexite (NaCaB5O9.8H2O): Crystal Data: Triclinic. Point Group: 1 (Ghose et al., 1978). In the Shar – e - Babak playa, ulexite occurs as deposits with massive, cauliflower-like nodules and fibrous textures.
2- Borax (Na2B4O5(OH)4 •8H2O): Crystal Data: Monoclinic. Point Group: 2/m. Crystals are commonly short to long prismatic [001] (Levy and Lisensky, 1978). In the studied borate samples, it can be found in association with the other borate minerals, and often occurs in the form of salt marsh.
3- Gowerite (CaB6O8(OH)4 •3H2O): Crystal Data: Monoclinic. Point Group: 2/m (Erd et al., 1959). In the Khatoonabad samples, it was found as prismatic and spherical crystals along with ulexite.
4- Inyoite (CaB3O3 (OH)5 •4H2O): Crystal Data: Monoclinic. Point Group: 2/m (Christ, 1953). This mineral has been detected in the studied area by XRD.
Sassolite (H3BO3): Crystal Data: Triclinic. Point Group: 1 and as scaly pseudohexagonal crystals (Allen and Kramer, 1957). This mineral is found frequently in the Marvast Playa.
GeochemistryGeochemical data indicate that in the studied playa, boron is very abundant. Good correlation between the elements, such as B and Ca confirms the formation of Calcium bearing borate mineral in the studied areas.
OriginField observations show that in the studied areas, borate bearing basins are fed by rivers which have originated from the Sanandaj – Sirjan metamorphic rocks, Nain – Baft colored mélanges and igneous rocks of the Urumieh – Dokhtar magmatic belt.
ResultThe XRD results show that the studied borate minerals mainly are hydrated ones and contain ulexite, borax, gowerite, sassolite and inyoite. Geochemichal data confirm the frequency of boron in the playa. Good correlation between the elements such as B and Ca verifies the formation of Calcium bearing borate mineral in the studied areas.
AcknowledgementsThe authors wish to thank IMIDRO for performing XRD analyses.

Subvolcanic masses of Shah khairollah and Madvar located in the southeast of Urumieh-Dokhtar magmatic belt and northwest of Dehaj-Sardoieh belt, north and southeast of Shahr-e Babak city. Generally, these subvolcanic masses contain dacite, rhyodacite and rhyolite lavas. Mineralogically, they consist of plagioclase, amphibole, alkali feldspar, biotite and quartz and the dominant texture of the studied rocks are porphyritic. Based on Microscopic studies plagioclases show resorption and zoning and opaticitization is observed in the mafic minerals. Geochemical investigations show that the Madvar and the Shah khairollah masses are acidic in composition and all the rock samples fall in the field of calc-alkaline magmatic series, originated in an active continental margin arc setting. Chemical compositions of the studied rocks in spider diagrams show the significant enrichment in LREE rather than HREE, as well as Sr, K. The depletion of Pb, P, Pr, Zr, Y, Nb and Ti in those rocks are observed. The negative anomalies of Ta, Nb and Ti in the rocks studied is similar to those of the subducted rocks series. The values of MgO, Na2O , Ni, Cr and Mg#, depletion of Y and high ratios of LREE/HREE, Sr/Y (Ave. 137.26), La/Yb (Ave. 50) in the studied rocks are similar to those of adakites which have derived from partial melting of young oceanic crust. Geochemical characteristics of these two masses indicate the partial melting of oceanic crust prior to hydration and the low concentrations of Yb, Y, HREE, TiO2, is consistent with the partial melting of subducted oceanic crust slab under amphibolite facies conditions in the depth of 35 km.