Minerals chemistry and geothermobarometry of Dourbeh and Nari intusive bodies of W Urumieyeh, NW Iran (original) (raw)
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Revista Geoaraguaia, 2020
Dehaj-Sarduieh volcano-plutonic belt in Kerman province of Iran represents a part of Urumieh-Dokhtar Magmatic assemblage which is mainly composed of granodiorite, quartz diorite, tonalite granite and granophyre. These rocks emplaced in Eocene volcanic and pyroclastic deposits rocks and are considered to be Oligo-Miocene in age. Geochemical studies showed that the amphibole minerals in diorite and granodiorites are calcic in composition and range from actinolite to magnesio-hornblende. Geochemical and mineralogical results revealed that these bodies have been generated in the lower part of the lower crust at a temperature of 700 to 750 °C, with an oxygen fugacity of-13.57 to-15.76 and a low pressure of 1 to 3 kb through mixing of mantle-derived mafic magma with crustalderived felsic melts. These amphiboles are subduction-related and in accordance with the tectono-magmatic features suggested for these massifs, they show the characteristics of subduction and active continental margin environments. Field observations and mineralogical-geochemical evidence revealed that the original magma has been calc-alkaline in composition and metaluminous I-type. It is also showed that the process of fractional
TURKISH JOURNAL OF EARTH SCIENCES, 2015
The South Dehgolan intrusion in the Sanandaj-Sirjan Zone ranges in composition from calc-alkalic monzogabbro to syenite to alkalic granite. This suite is composed mainly of variable proportions of quartz, K-feldspar, plagioclase, biotite, hornblende, and pyroxene. The plagioclase composition varies between albite to labradorite. The biotites are Mg-to Fe-rich in the monzogabbro to granite, respectively. The amphiboles are calcic and the composition varies from magnesiohornblende to actinolite. Clinopyroxene compositions fall in the diopside-augite field. The average calculated near-solidus crystallization temperatures are 774 °C, 655 °C, and 775 °C for the monzogabbro-monzodiorite, syenite, and granite, respectively. Calculated average pressures of emplacement are 1.7, 1.3, and 1.9 kbar for the monzogabbro-monzodiorite, syenite, and granite rocks, respectively, crystallizing at different respective depths of about 6.7, 5.0, and 7.3 km. The interpreted oxygen fugacities in the monzogabbro-monzodiorite and syenite rocks are typical of arc magmas, with oxygen fugacities above the Ni-NiO buffer. Water contents in the monzogabbro-monzodiorite and syenite were calculated to range from 4.7 to 4.4 wt.% and in the granite is 3.8 wt.%. High water and volatile contents in the monzogabbro to syenite may have allowed the magma to reach shallower crustal levels. During the evolution of this magmatic system to higher silica contents, there was an increase in the activity of oxygen and decrease in the temperature and the emplacement depth from the monzogabbro-monzodiorite to syenite rocks; this is consistent with the typical evolution of the granitoid rocks. However, the calculated higher temperature and pressure and low ƒO 2 and H 2 O content in the later granite reflects notable differences in its origin and crystallization conditions. The range in mineral compositions is this intrusive suite is consistent with a relationship to subduction of the Neotethys oceanic crust beneath the Central Iranian microcontinent, although there was a change from calc-alkaline to alkaline magmatism.
2020
The gabbroic rocks in the Gysel area of the Central Alborz Mountains in north Iran are intruded into the Eocene Volcano-sedimentary units. The main gabbroic rocks varieties include gabbro porphyry, olivine gabbro, olivine dolerite and olivine monzo-gabbro. The main minerals phases in the rocks are plagioclase and pyroxene and the chief textures are sub-hedral granular, trachytoidic, porphyritic, intergranular and poikilitic. Electron microprobe analyses on minerals in the rock samples shows that plagioclase composition ranges from labradorite to bytonite, with oscillatory and normal chemical zonings. Clinopyroxene is augite and orthopyroxene is hypersthene to ferro-hypersthene. Thermometry calculations indicate temperatures of 650˚C to 750˚C for plagioclase crystallization and 950˚C to 1130˚C for pyroxene crystallization. Clinopyroxene chemistry reveals sub-alkaline and calc-alkaline nature for the parental magma emplaced in a volcanic arc setting.
Arabian Journal of Geosciences, 2018
The Haji Abad intrusion is a well-exposed Middle Eocene I-type granodioritc pluton in the Urumieh-Dokhtar magmatic assemblage (UDMA). The major constituents of the investigated rocks are K-feldspar, quartz, plagioclase, pyroxene, and minor Fe-Ti oxide and hornblende. The plagioclase compositions fall in the labradorite, andesine, and oligoclase fields. The amphiboles range in composition from magnesio-hornblende to tremolite-hornblende of the calcic-amphibole group. Most pyroxenes principally plot in the field of diopside. The calculated average pressure of emplacement is 1.9 kbar for the granodioritic rocks, crystallizing at depths of about 6.7 km. The highest pressure estimated from clinopyroxene geobarometry (5 kbar) reflects initial pyroxene crystallization pressure, indicating initial crystallization depth (17.5 km) in the Haji Abad granodiorite. The estimated temperatures using two-feldspar thermometry give an average 724°C. The calculated average temperature for clinopyroxene crystallization is 1090°C. The pyroxene temperatures are higher than the estimated temperature by feldspar thermometry, indicating that the pyroxene and feldspar temperatures represent the first and late stages of magmatic crystallization of Haji Abad granodiorite, respectively. Most pyroxenes plot above the line of Fe 3+ = 0, indicating they crystallized under relatively high oxygen fugacity or oxidized conditions. Furthermore, the results show that the Middle Eocene granitoids crystallized from magmas with H 2 O content about 3.2 wt%. The relatively high water content is consistent with the generation environment of HAG rocks in an active continental margin and has allowed the magma to reach shallower crustal levels. The MMEs with ellipsoidal and spherical shapes show igneous microgranular textures and chilled margins, probably indicating the presence of magma mixing. Besides, core to rim compositional oscillations (An and FeO) for the plagioclase crystals serve as robust evidence to support magma mixing. The studied amphiboles and pyroxenes are grouped in the subalkaline fields that are consistent with crystallization from I-type calc-alkaine magma in the subduction environment related to active continental margin. Mineral chemistry data indicate that Haji Abad granodiorites were generated in an orogenic belt related to the volcanic arc setting consistent with the subduction of Neo-Tethyan oceanic crust beneath the central Iranian microcontinent.
Mineralogical and Geochemistry of intrusive rocks south of Moein Abad (East Iran, Zirkouh Qaen)
Iranian Journal of Crystallography and Mineralogy
The study area is located in Tertiary plutonic belt of Lut Block. Tertiary intrusive injection in Cretaceous limestone caused the formation of skarn in this region. Injection intrusive changes the texture and mineralogy of limestone and skarn or marble formed. A lensshaped iron mineralization mainly occurred in the border of intrusions and calcareous unit. Petrological studies show that the whole combination intrusive quartz-monzonite, quartz monzonite to granodiorite variables. These granitoids are sub-alkaline series and they are metaaluminous. Geochemical features show that they belong to I-type granitoids. Enrichment in Light rare earth elements (LREE) rather than HREE and a slight negative anomaly of Eu are important evidence that show the intrusions were formed in a magmatic belt on subductions zone and belong to calc-alkaline volcanic arc setting in active continental margins. Different geochemical graphs show consistency granitoid intrusions in south of Moein Abad with iron skarn-related intrusions.
Geological Quarterly, 2013
The study area is a part of the NW to SE strik ing Sanandaj-Sirjan meta mor phic belt in west ern Iran. The Alvand Pluton, consist ing of rocks that range in com po si tion from gab bro to gran ite, is the ma jor mag matic rock com plex of this area. Gabbroic rocks in clude ol iv ine gab bro, gab bro norite, norite and gab bro. Rocks around the Alvand Pluton were sub jected to dif fer ent P-T con di tions due to polymetamorphism. Com mon meta mor phic rocks are meta-pelites, but some meta-psammites, meta-basites and meta-car bon ates also oc cur. Slates, phyllites, schists, migmatites and hornfelses are ma jor rock units of meta-pelites in the meta mor phic se quence. Based on min eral chem is try, the high est tem per a ture of crystallisation (1300°C) was de ter mined for the ol iv ine gab bros, and the low est tem per a ture (950°C) was cal cu lated for the hornblende-bear ing gabbros. Clinopyroxene-plagioclase ba rom e try sug gests that pres sures near 5 to 6 kbars pre vailed dur ing the crystallisation of the var i ous mafic rocks. P-T es ti mates yield max i mum tem per a tures of 700-750°C at 5-6 kbars for the high-grade meta morphic rocks from the meta mor phic au re ole around the pluton. These re sults in di cate that the heat re leased from the Alvand Pluton (T = 950-1300°C), which in truded the meta mor phic rocks at mid dle and up per crustal lev els, was suf fi cient to cause par tial melt ing lead ing to for ma tion of the metatexites, diatexites and restite-rich S-type gran ites. Dur ing this pro cess, part of the deep-seated gab bro-dioritic rocks were trans ported to higher crustal lev els by vis cous, en clave-and crys tal-rich gra nitic mag mas of the par tial melt ing zone.
Journal of Asian Earth Sciences, 2015
The Mahoor Cu-Zn-bearing porphyritic granitoid rocks belong to the Lut Block volcanic-plutonic belt (central Eastern Iran). These granitoid rocks occur mainly as dykes and stocks that intrude into Eocene volcanics and pyroclastic rocks. Petrographically, all the studied intrusives display porphyritic textures with mm-sized phenocrysts, most commonly of plagioclase and hornblende, embedded in a fine-grained groundmass with variable amounts of plagioclase, hornblende, clinopyroxene, quartz and opaque minerals. Hydrothermal alteration affected these granitoid rocks, as revealed by the common occurrence of sericite, chlorite, titanite, epidote and calcite. Chemical classification criteria show that the intrusives may be named as gabbrodiorites, diorites, monzodiorites and tonalites. Major elements geochemistry reveals that all the studied lithologies are typically metaluminous (A/CNK 6 0.9). Magnetic susceptibility (1485 Â 10 À5 SI) together with mineralogical and geochemical features shows that they belong to magnetite granitoid series (I-type). Trace element patterns normalized to chondrite and primitive mantle are very similar to each other and show enrichments in LREE relative to HREE and in LILE relative to HFSE, as well as negative anomalies of Ta, Nb and Ti. Eu/Eu ⁄ ratios vary from 0.88 (in the most mafic composition) to 0.65, showing that plagioclase played a role in magma differentiation. LA-MC-ICP-MS U-Pb zircon data from a diorite, yielded similar concordia ages of ca. 31.88 ± 0.2 Ma (Error: 2r), which corresponds to the Oligocene period. These granitoid rocks have (87 Sr/ 86 Sr)i values vary between 0.7055 and 0.7063. In terms of isotopic compositions, while eNdi is between À0.6 and À2.5, suggesting that magmas underwent contamination through being exposed to the continental crust. The whole set of geochemical data agree with the emplacement of the studied intrusions in a magmatic belt above a subduction zone. Primitive magmas should have formed by melting of mantle wedge peridotite, and during magma ascent to crustal levels, both magma differentiations took place by crystal fractionation and crustal contamination. Sulfide mineralizations (pyrite, chalcopyrite and sphalerite) related to these granitoid rocks is common and occurs as both disseminated and hydrothermal veins, indicating a high mineralization potential for this area.
Petrology and Geochemical Properties of the Granitoid Complex of Chahar-Gonbad, Southeast Iran
Open Journal of Geology, 2017
The Chargonbad batholite is located in Sirjan and southeast of magmatic zone of Urumieh-Dokhtar. The main volume of this rocks consisted of Granodiorite and Monzogranite, but it's also consists of Quartzdiorite, Tonalite and Syenogranite. They have allotrimorphic granular texture with subordinate porphyritic texture. Their enclaves consist of: xenoliths enclaves, microgranular mafic enclaves (Diorite to Quartzdiorite in composition) and autolite enclaves (Tonalite, granodiorite and monzogranite in composition). The Chargonbad batholite rocks are also cut by different types of dykes which are mainly consisted of dykes and veins of pegmatic stage, microgranular dykes (andesit and andesit basaltic in composition) and microgranular dykes that are similar to mafic enclaves. Evidence shows that regional examples represent properties of granitoids type I. As well as, Granite of Granitoid body of this area has magnesium nature and shows the cordellarian granites features. Based on the tectonomagmatic environment determination diagrams, all samples from the Chahargonbad study area located in the arc island setting due to subduction and show the characteristic of active continental margin setting.
Revista Geoaraguaia, 2020
Batholith of Shirkuh, Yazd, is part of the central Iranian structural zone, located southwest of the province. The lithology of this complex comprises mostly monzogranite and granodiorite and some quartz monzonite, quartz monzodiorite and syenogranite.Plagioclase, quartz, orthoclase, biotite and amphibole are the dominant minerals in these rocks. The composition of plagioclases varies from labradorite to oligoclase, and alkali feldspars belong to the orthoclase category. Amphiboles are calcic, rich in iron and Fe-Mg-Mn amphiboles, and range from ferro-hornblende to tschermakite, and tschermakite hornblende. According to various geobarometry methods using the amphibole composition, it is estimated that the calc-alkaline batholith has been formed in a supra-subduction tectonomagmatic environment at 700-900 °C and 0.8-1.5 kbar pressure under high oxygen fugacity. Moreover, based on the thermometry results of feldspars, the emplacement temperature was obtained in the 770-920 °C range by the Anderson method for the Shirkuh granitoid batholith.