PETROLOGY
Year:2019 | Volume:9 | Issue:36|Papers Count:10

The plutonic bodies in the Soursat complex are parts of the widespread plutonic bodies in the Sanandaj-Sirjan zone. Based on field observations and microscopic studies, the study area is dominated by hornblende gabbro, quartz diorite, monzodiorite, granodiorite, monzogranite and tonalite. According to geochemical studies, the granitoids of Turke Dare and Khangholi are characterized by I-type nature, high K calc-alkaline, metaluminous composition and plotted on Volcanic Arc granite area (VAG) with 87Sr/86Sr(i) and ε Nd(t) values equal to 0. 70448,-0. 12. The overall geochemical signatures represent that monzodiorites generated from magma that derived from mantle which subjected to assimilation and contamination processes. The Pichaghci, Hamzeh Ghasem and the Northeast Khangholi bodies are I-type, metaluminous to peraluminous and calc-alkaline which are plotted in the volcanic arc granite area (VAG) with 87-86-2. 82. These geochemical study granodiorites generated from mixing of mantle-derived magma with crustal melts. The Ghare zagh and Ouch dare monzogranite bodies are S-type, peraluminous and calc-alkaline which are plotted in continental-continental collision area with high values of 87Sr/86Sr (i) and ε Nd(t) equal to 0. 94476, 0. 879276 and-6. 71,-6. 61 representing that monzogranites originated from crustal melts. The Tonalite group is I-type, calc-alkaline, peraluminous, with low values of La/Yb, Sr/Y and Nb/Ta ratios and low fractionated patterns of rare earth elements (REE), negative anomaly of Eu. On the base of these data, it can be concluded that the group resulted from amphibolitic crust that generated from thickened mafic crust or under plate basalts under low pressures and low deep with the presence of plagioclase in the source area.

The Chekneh subvolcanic domes with dacite and trachydacite compositions from the Miocene is located 110 km NE of Sabzevar, and are parts of the North Sabzevar-South Ghochan magmatic belt. The dome rocks have porphyry, sieve, trachytic and glomeroporphyritic textures, consisting of plagioclase and amphibole. Primitive mantle normalized spider diagram and chondrite-normalized REE patterns of the study domes suggest that they are enriched in LREE and LILE and are depleted in HREE and HFSE. They are calc-alkaline with significant negative HFSE (e. g., P, Nb and Ti) anomalies and (La/Yb)N>12 which are characteristics of magmas formed in active continental margin. Based on SiO2, high Sr/Y, low K2O/Na2O and low Y, Yb, Cr and Mg# contents, the study rocks are similar to high-silica adakites (HSA). Thus, it seems that the parent magma of the study domes was originated from amphibole eclogite or garnet amphibolite rocks of metamorphosed Neotethys oceanic lithosphere during its subduction beneath the southern part of eastern Alborz in the Miocene. The initial 87Sr/86Sr (0. 7039-0. 7043) and ɛ Nd10Ma (2. 9-4. 98) of the Chekaneh domes is similar to MORB composition, which are coincided with those adakites originated from the partial melting of the Cenozoic oceanic lithosphere.

The study area is located northwest of Gol-e Gohar mine (Bahram Gur Protected Zone) in Sirjan, the Kerman Province, a part of the Sanandaj-Sirjan zone. The area is mainly dominated by metamorphic rocks with their basic igneous origin and sedimentary including slate, phyllite, schist (garnet schist, amphibole schist, mica schist, kyanite schist), epidote amphibolite, amphibolite, gneiss, quartzite and marble. Among the study rocks, amphibolites with different minerals paragenesis, have been experienced the highest metamorphic grade to amphibolite facies. The basic igneous rocks ranging in composition from tholeiitic to calc-alkaline are the source rocks of the studied amphibolites and the oceanic crust is their protolith. As the discrimination geochemical diagrams display the amphibolites of the study area probably belong to back arc tectonic environments, which are very similar to mid-ocean ridges (MORB). The primary magma of the igneous rocks and the protolith of amphibolites were derived from spinel-peridotite. Furthermore, on the geochemical diagrams which were used for the purpose of this study, the positive Ba and negative Nb anomalies along with low Nb/U ratio show that the magma of the protolith has been subjected to crustal contamination during rising to the surface. All the geochemical data indicate that the magma has emplaced in a supra-subduction environment related to Neotethys Ocean.

Tourmaline occurs in the biotite-muscovite granite of Mashhad as nodule, euhedral tourmalines in pegmatite and aplite, quartz-tourmaline veins, tourmaline-rich veins and radial tourmalines. Compositionally, they all are between schorl and dravite end-members and alkali group tourmalines. The euhedral tourmalines in pegmatite and aplite are Fe-enriched schorl whereas the nodule, quartz-tourmalines, the radial and the vein tourmalines are Mg-rich schorl. The higher Mg concentration in these tourmalines relative to those of the pegmatite and aplite are probably related to the crystallization of Fe-rich minerals including biotite, garnet, and the pegmatite and aplite tourmalines during the evolution of granitic magma. The LA ICP (MS) results indicate that all types of studied tourmalines are characterized by low trace element abundances and have more concentration of Sr, Ga, Li, Be, Sn, Pb as well as some transitional elements. The tourmalines studied show similar REE patterns, LREE enrichment and positive Eu anomalies. The low Ba, Rb, W, Sn، Y, Nb and HREE concentrations can be due to crystallization of some minerals such as garnet, biotite, muscovite and feldspar prior to the tourmalines. The correlation between major and trace elements of the tourmalines is the effects of atomic sites and thermodynamic in the crystal chemistry and the behavior of trace elements in the tourmalines.

The Heydarabad ophiolitic mé lange is hosted in the Sistan suture zone, which marks the boundary between the Lut and the Afghan continental blocks and comprises of mantle peridotites and crustal sequence. The studied mantle peridotites are dominated by harzburgite and clinopyroxene-rich harzburgite that formed in mid-ocean ridge (MOR) setting. These mantle peridotites, due to the effect of hydrothermal solutions, have been altered. Moreover, iron-copper mineralization developed by the influence of hydrothermal fluids moving through the fractures and the faults. The textures and structures of mineralization formed as open space filling, disseminated, vein-veinlet and replacement. Two important stages could be recognized for the mineralization in this area. The first stage includes processes, which caused the development of sulphide mineralization in the mantle peridotites. The second stage is related to oxide fluids, which led to magnetite mineralization. Based on detailed electron microprobe study, olivine, orthopyroxene, clinopyroxene and spinel are the essential rock forming-minerals of the rocks under study. Most of the olivines from the mantle peridotites are serpentinized but some, with forsterite composition, are fresh. The composition of the ortho-and clinopyroxenes is enstatite and diopside respectively and the spinels are classified as Al-rich Cr-spinel type.

The East Sanadaj magmatic rocks of the northern Sanandaj-Sirjan Zone, part of Zagros Orogen, comprise several intrusive bodies that were generated during northeastward subduction of Neo-tethys beneath the Iranian sector of the Eurasian plate. From the east Sanadaj to Galali, mafic-intermediate intrusions of Late Jurassic age, have significant out crops in Kangareh, Saranjianeh, Ghorveh, Shanevareh and Galali. These rocks are calc-alkaline, metaluminous (ASI=0. 51-0. 95) and mostly magnesisan. As SiO2 increases, the chemistry of rocks changes to ferroan and high-K. These rocks present enrichment of LILE relative to HFSE, the low LREE/HREE fractionation ((La/Lu)N=1. 5-14. 6) considerably fl atter chondrite-normalized REE profiles, Eu positive anomaly (Eu/Eu*= +0. 63-+3. 75). Primitive features of Sr-Nd isotopes Combined with HFSE and REE ratios, as source indicators, prove the mantle derived magma as a source of these rocks. Geochemical modelings indicate mafic-intermediate rocks of east Sanadaj, originated from spinel lherzolithic magma with hydrous components such as amphibole. Fractionation of these hydrous minerals have important role in evolution of magma. The combined monitoring of geochemical data and REE patterns, isotopic data were performed in order to unravel the compositional changes from calc-alkaline-magnesisn rocks to high alkaline-ferroan rocks of this area. The results denied bimodality of source magma and confirmed the important role of differentiation in magma evolution.

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

Lower Jurassic volcanic-sedimentary sequence in the southern end of the Sanandaj-Sirjan zone, north of Mata village (southwest Jiroft), composed of tuffaceous limestone, calcareous tuff, limestone, including felsic volcaniclastic and basaltic volcanic rocks with northwest-southeast trend; which here geochemical characteristics and petrogenesis of the basaltic rocks of this sequence have been studied. Basalts texture is dominantly microporphyritic with clinopyroxene and plagioclase as the main minerals set in an intergranular to intersertal of plagioclase, clinopyroxene, apatite, opaque minerals and chlorite originally glassy matrix. On the basis of petrographic and geochemical data, basaltic rocks have tholeiitic affinity. These basalts are Light REE-depleted tholeiites similar to REE pattern of the N-MORB, However they are characterized by the enrichment of LILE over HFSE and negative Nb– Ta anomalies which are subduction zone trace element signatures. Based on trace element ratios, Mata basaltic rocks were derived from partial melting of a depleted lithospheric mantle source which enriched by subduction zone components. Meanwhile they fractionated on upwelling. Based on field and geochemical data, Mata basalts are interpreted to have formed in an initial back-arc basin behind the Sanandaj-Sirjan magmatic arc at Lower Jurassic time.

The magmatic activities in north Qazvin, as a part of the Western Alborz zone, contain a sequences of volcanic lavas associated with pyroclastic rocks with Eocene age. According to petrographical investigations, volcanic lavas are basalt, basaltic andesite, pyroxene andesite, trachy-andesite, dacite and rhyolite. The texture of these rocks is more porphyritic with fine-grained groundmass including plagioclase, clinopyroxene, quartz, alkali feldspar, amphibole and biotite minerals. On the basis of geochemical features, all samples show high-K calc-alkaline to shoshonitic affinities. Also, these rocks are enriched in LREE and LILE, and depleted in HFSE characteristic of calc-alkaline series in subduction-related environment. Petrogenesis indicate that the mafic lavas have been derived from 5 to 10 % partial melting of enriched garnet lherzolite mantle source. Qazvin volcanic lavas have moderate Nb/Yb and Ta/Yb ratios indicative of an enriched mantle source compositions (e. g., E-MORB). Furthermore, these lavas have high values of Th, U and Pb consistent with slab-related sediments and/or crustal contamination in their mantle source.

The fourteen numbers of ultrabasic volcanoes eruption in the west of Nowbaran are located in the west margin of Iranian central zone near to the Sanandaj-Sirjan zone. The combination of volcanic material consists mainly of low viscosity lava and in some cases pyroclastic material. According to the petrography and geochemical data, these rocks are nephelinite and melilite-nephelinite. Several chemical characterizations such as low content of SiO2, high rate of CaO and MgO, depleted from HFSE and enrichment of LILE, shown the magma originated from depleted mantle source. Ti and Nb negative anomalies presented the subduction component for this magma source. The Nawbaran magma with sodic-alkaline nature, formed within plate geodynamic environment. The geochemical evidences have shown the magma originated from enrichment garnet-lherzolite mantle with low partial melting (1-3%) in the 90 to 110 km depth of earth surface. Existence of mantle calcite, calcium rich apatite and perovskite whit the high rate of CaO and MgO in the rocks composition signed the carbonated component and carbonate metasomatism is candidate for the evolution of west Nawbaran young magmatism.