Petrology
Ali Lotfi Bakhsh
Abstract
In the north of Ardabil (from Namin to Lahroud) there are widespread sequences of Eocene and Quaternary mafic to intermediate and felsic magmatic activities with different compositions. The composition of these rocks varies from basaltic lavas as well as dacitic and rhyolitic domes in Namin to basalt ...
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In the north of Ardabil (from Namin to Lahroud) there are widespread sequences of Eocene and Quaternary mafic to intermediate and felsic magmatic activities with different compositions. The composition of these rocks varies from basaltic lavas as well as dacitic and rhyolitic domes in Namin to basalt and basaltic andesite in Lahroud area. The chemical composition of olivine from olivine basaltic lavas indicates a forsterite composition changing from 67.8 to 92.7. Clinopyroxenes show diopside composition whereas plagioclase has labradorite to bytownite composition. Garnet xenocrysts in the rhyolitic domes have an almandine composition. These rocks are characterized by the enrichment in LREEs compared to the HREEs. Mafic-intermediate rocks show shoshonitic to high-K calc-alkaline composition whereas dacitic and rhyolitic domes show adakitic signature. Geochemical and isotopic characteristics of basaltic-andesitic rocks indicate their genesis are related to the partial melting of a metasomatized mantle wedge, re-fertilized by sediments and fluids from the subducting slab in the Eocene subduction zone of Iran. The geochemical and isotopic signatures of dacitic-rhyolitic domes indicate their origin from partial melting of the lower parts of the thickened continental crust of Iran.
Petrology
Jalil Ghalamghash; Meysam Akbari; Reza Jamal
Abstract
The Taftan volcano hosts an extensive volcanic activity during Late Miocene to Quaternary where took place over Makran-Chagai subduction zone. Taftan rocks are mainly basaltic andesite, andesite, trachyandesite, and dacite that occur as lavas and pyroclastic rocks. They are characterized by basic-intermediate ...
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The Taftan volcano hosts an extensive volcanic activity during Late Miocene to Quaternary where took place over Makran-Chagai subduction zone. Taftan rocks are mainly basaltic andesite, andesite, trachyandesite, and dacite that occur as lavas and pyroclastic rocks. They are characterized by basic-intermediate inclusions enclosed by acidic groundmass, and disequilibrium textures in plagioclase phenocrysts including sieve texture, zoning, and dissolution margin, which may reflect magma mixing. These rocks record high-K calc-alkaline to calc-alkaline affinity with enrichment in LREE and LILE relative to HREE and HFSE, respectively. These features, coupled with the clear depletion in HFSE (such as Nb, Ta, and Ti) are consistent with typical subduction-related volcanic arcs. Taftan primary melts might have been produced by ~15% partial melting of spinel lherzolite mantle. The normalized multi-element patterns which mimic the upper continental crust values, and enrichment in Pb, Th, U, and Rb agree well with magma evolution by assimilation and fractional crystallization (AFC). The available isotopic geochronology dataset reveal that the youngest volcanoes of the Makran-Chagai magmatic arc are Bazman and Kuh-e-Sultan volcanoes. A geochemical comparison of these volcanoes highlights that magmatism in the Taftan where the crust is thick, underwent a higher degree of crustal assimilation en route to the surface.
Petrology
hojjat hajhassani; Jalil Ghalamghash; Mansour Vousoughi Abedini; Rahim Dabiri; Hamideh Rashid
Abstract
The leucocratic granite emplaced as small masses and dykes in the Alvand batholith. The leucocratic granite consists of tourmaline alkali granite, biotite alkali granite, arfvedsonite alkali granite, rutil alkali granite, and biotite- muscovite granites with alkaline and peraluminous affinities. They ...
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The leucocratic granite emplaced as small masses and dykes in the Alvand batholith. The leucocratic granite consists of tourmaline alkali granite, biotite alkali granite, arfvedsonite alkali granite, rutil alkali granite, and biotite- muscovite granites with alkaline and peraluminous affinities. They show enrichments of LREEs relative to HREEs and LILE relative to HFSE with negative anomalies in Nb, Ta and Ti, in normalized trace element diagrams. The leucocratic granite of the Alvand batholith resemble A-type and can be further classified in two of A and A' types granite. The trace elements content of A-type is much higher than A'-type granite. Based on geochemical data, it seems that A- and A'-type granites were generated from partial melting of mantle source. As mantle magma ascends, fractionate and empalce into the crust, A-type leucocratic are formed with minimal contamination and A'-type leucocratic with significant contaminant with continent crust are formed. Field and geochronology data suggest that the leucocratic granite were generated in the late Jurassic, which is contemporaneous with the subduction of the Neo-Tethys oceanic crust beneath the central Iran. It seems that the leucocratic granites were emplaced during a local extensional phase as dykes and small bodies in the Alvand batholith.
Petrology
Mahnoush Bahjati; A. Ahmadi; Habib Biabangard
Abstract
The volcanic rocks of Kuleh sangi-Malek siah kuh igneous complex consist of alkalibasalt, basalt, basaltic andesite, andesite, dacite and trachyte. In the SiO2 versus K2O diagram, the basaltic samples are plotted in the shoshonitic field and the subalkaline samples are plotted in the medium K calc alkaline ...
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The volcanic rocks of Kuleh sangi-Malek siah kuh igneous complex consist of alkalibasalt, basalt, basaltic andesite, andesite, dacite and trachyte. In the SiO2 versus K2O diagram, the basaltic samples are plotted in the shoshonitic field and the subalkaline samples are plotted in the medium K calc alkaline series field. The average La/Yb, Rb/Zr and Cs/Hf ratios in basalts are 7, 47 and 63 times those of N-MORB, respectively. Considerable enrichment of LILEs, LREEs and relative depletion of HREEs indicate that the magmas originated from a mantle source more enriched than that of OIB, where phlogopite and garnet are stable. Using non-modal batch melting model, the compositions of the mafic samples are mainly consistent with about 5% melting of a phlogopite-bearing and garnet-bearing lherzolite with a mixture of about 80% and 20%, respectively. AFC models using Pb versus Ce/Pb and Rb versus K/Rb, show that the fractionated samples have undergone simultaneous crustal assimilation and fractional crystallization. It seems that the assimilation and the fractionation had been taken place with the same rate. Depletion in Y and elevated ratio of Sr/Y of fractionated rocks in addition to Rb/Nb ratio more than 8, could be considered as evidence for crustal assimilation.
Economic Geology
yegane khoramtash; farajolah fardoost
Abstract
The Saghari copper deposit is located 120 Km at Southwest of shahrood, within in the eastern part of Toroud-Chahshirin magmatic arc. Mineralization in the Saghari area occured within volcanic and pyroclastic units of Eocene. Based on the field, laboratory investigations and geochemical analysis, the ...
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The Saghari copper deposit is located 120 Km at Southwest of shahrood, within in the eastern part of Toroud-Chahshirin magmatic arc. Mineralization in the Saghari area occured within volcanic and pyroclastic units of Eocene. Based on the field, laboratory investigations and geochemical analysis, the outcropped rocks in the Saghari deposit are andesite, andesite-basalt, basalt, dacite and several exposures of pyroclastic rocks such as tuff and agglomerate. The rocks are high-k, calc-alkaline to a small amount of shoshonitic in nature, and are formed at a magmatic arc setting in a subduction zone. Basic to intermediate dyke bodies intruded Eocene volcanic-pyroclastic sequences. The host rocks have been affected by argillitic, sericitization, chloritzation, carbonatization and oxide-Fe (limonite, hematite and goethite). The textures and structures of mineralization are vein-veinlet, replacement, open space filling and disminated. According to the mineralography studies, main minerals of copper are malachite, chalcocite, covellite, chalcopyrite, chrysocolla and rare native copper. Malachite and chalcosite are the most abundant minerals. Geochemical studies indicate that copper has a relative correlation with silver.also based on studies of fluid inclusion, the depth of the ore, formation temperature and salinity are 100-200 meter, 100-140 °c and 5-15 WtNaCl%. Copper mineralization in the Saghari deposite has similarities in mineralogy, host rock, texture, structure and geometry with manto-type and volcanic red bed copper deposits.
Petrology
Siavash Omidianfar; mohammad rahgoshay; Iman Monsef
Abstract
Koudakan Granitoid located in 100 km South of Birjand and 18 km North of Ghaleh-Zari mine in eastern Iran. It belong to the Lut Block volcanic–plutonic belt. These intrusive rocks (Eocene-Oligocene) petrogaphicaly composed of Diorite, Monzodiorite, Quartzmonzodiorite, Tonalite, Porphyritic Tonalite, ...
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Koudakan Granitoid located in 100 km South of Birjand and 18 km North of Ghaleh-Zari mine in eastern Iran. It belong to the Lut Block volcanic–plutonic belt. These intrusive rocks (Eocene-Oligocene) petrogaphicaly composed of Diorite, Monzodiorite, Quartzmonzodiorite, Tonalite, Porphyritic Tonalite, Granodiorite, Granite and Porphyritic Granite. Plutonic rocks in this area have features typical of high-K calc-alkaline to shoshonite series, metaluminous and belong to I-type Granitoides. Enrichment in LILE rather than HFSE (RbN/YN: 38.12-124.93), negative anomalies of Nb and Ti and enrichment in LREE rather than HREE (LaN/YbN: 6.74-12.03) in all of samples are important evidences for the formation of this rocks in a subduction related magmatic belt. Positive anomalies of Pb and K indicate the involvement of continental crust in evolution of parental magma. Parallel trend of the samples in spider diagrams show that they are co-genetic. Elements ratios and Different discrimination diagrams show the formation of this rocks in an active continental margin with about less than 45 Km crustal thickness in per-collision steps. Parental magma has been generated by low degree partial melting (less than 5%) of an enriched peridotite in mantle wedge (Spinel lherzolite.).
Petrology
zahra badrzadeh
Abstract
Abstract The studied Chaltian granitoid is located in the endpoint of the southern Sanandaj–Sirjan Zone. This pluton has Low-Al trondhjemitic composition with tholeiitic to transitional nature. The intrusion has been intruded in the early Mesozoic volcanic and sedimentary rocks. According to U-Pb ...
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Abstract The studied Chaltian granitoid is located in the endpoint of the southern Sanandaj–Sirjan Zone. This pluton has Low-Al trondhjemitic composition with tholeiitic to transitional nature. The intrusion has been intruded in the early Mesozoic volcanic and sedimentary rocks. According to U-Pb SHRIMP age dating of zircon grains, this pluton was intruded at the 187.5 ±3.2Ma ago. Studied pluton has low Al2O3, Sr/Y, (La/Yb)N ratio and less fractionated REE pattern. In the primitive mantle normalized spider diagrams, studied samples show enrichment of LIL elements such as K, Rb, Ba and Th relative to HFS elements and has negative anomaly in Ta, Nb and Ti elements, which are considered characteristic of magmas generated in subduction related settings. In terms of their origin, based on geological and geochemical characteristics, trondhjemitic melt has been generated by low pressure dehydration melting of amphibolitic source in an continental extensional tectonic setting related to subduction environment.
Pooneh Eshbak; Azadeh Malekzadeh Shafaroudi; Mohammad Hassan Karimpour
Abstract
Jalambadan area is located northwestern Sabzevar, Khorasan Razavi province, and southwestern Quchan-Sabzevar magmatic belt. Geology of the area includes of andesitic-trachyanesitic volcanic rocks, which is intruded by monzodioritic to dioritic subvolcanic intrusive rocks. The texture of igneous rocks ...
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Jalambadan area is located northwestern Sabzevar, Khorasan Razavi province, and southwestern Quchan-Sabzevar magmatic belt. Geology of the area includes of andesitic-trachyanesitic volcanic rocks, which is intruded by monzodioritic to dioritic subvolcanic intrusive rocks. The texture of igneous rocks is porphyry and the main minerals are plagioclase, alkali fldespar, pyroxene, hornblende, and magnetite. Age of intrusive rocks determined 44.7 to 45.2 Ma (Middle Eocene-Lutetian), using zircon U-Pb method. Geochemically, igneous rocks of the area are calc-alkaline and were formed at subduction zone. Relativelly, enrichment in LREE relative to HREE and enrichment of K, Rb, Cs, and Sr relative to Ti and Nb elements are observed in all of samples. Eu anomaly and Sr/Y ratios can be attributed to the presence of residual plagioclase and a few garnet in a source. (87Sr/86Sr)i (0.703708 to 0.704444), (143Nd/144Nd)i (0.512858 to 0..512933), and εNd I (5.42 to 6.88) values of intrusions and geochemical signatures of volcanic rocks indicate magma is drived from partial melting (7-5% for intrusions and 15-25% for volcanic rocks) of spinel lherzolite mantle wedge above subducted slab, which is assimilated slightly with upper continental crust very little.
E. Alizadeh; Gh. R. Ghadami; D. Esmaeily; J. Omrani; A. Golmohammadi
Abstract
The Roshtkhar intrusive rocks are located in the northeastern part of the Roshtkhar prospecting area (KhorassanRazavi province), along the eastern edge of the Khaf-Kashmar-Bardaskan volcano-plutonic belt, north of the Dorouneh Fault and on the southern part of the Sabzevar structural zone. The intusive ...
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The Roshtkhar intrusive rocks are located in the northeastern part of the Roshtkhar prospecting area (KhorassanRazavi province), along the eastern edge of the Khaf-Kashmar-Bardaskan volcano-plutonic belt, north of the Dorouneh Fault and on the southern part of the Sabzevar structural zone. The intusive rocks consist mainly ofsyenite to monzonite with minor amount of syenite porphyry, monzonite porphyry, and diorite porphyry with granular and porphyry texture, respectively. According to the geochemical data, the Roshtkhar intrusive rocks are calc-alkaline granitoid series with high-K to shoshonitic affinity, magnesian, metaluminous, and belong to I-type granites.Chondrite-normalized Rare Earth Element and mantle-normalized trace-element spider diagrams display enriched in LILE and LREE and also Th, depleted in HFSE and weak depletion in HREE and Y, along with negative anomalies of Nb,Ta, and Ti, that are characteristic of the post-collisional calc-alkaline rocks along with a continental active margin tectonic setting. In spite of the low ratios of Nb/U, Nb/La and Ce/Pb, the Sm/Yb (2.8-3.9) ratios reveals low contamination of magmas with upper continental crust. According to geochemistry of trace elements and REE, the main cause of magmatism in Roshtkhar area was melting of a metasomatized lithospheric mantle (E-MORB) with spinel lherzolite composition accompanied by in the presence of phlogopite. Multiple element and REE pattern, abundance of K2O/Na2O in Roshtkhar intrusive rocks show contamination and mixing with acidic magma ofamphibolitic lower crust due to temperature of mantle magma and AFC process played important roles in magma evolution. La vs. La/sm diagram illustrate partial melting and also according to K, positive anomalies of Rb, Ba, K, Th, U, and Pb, and the negative anomalies of Nb, Ti, Ta, and Ba associated with high La (La > 29), it seems partial melting of lower continental crust has played an important role in the genesis of the Roshtkhargranitoids rocks. Based on field investigation, petrographic studies, and lithogeochemistry using the granitoids discrimination tectonic setting diagrams, it seems that the Roshtkhar intrusive rocks were generated in a post-collisional extensional environment in a continental margin arc setting with partial melting of the mantle-lower crust within the Khaf-Kashmar-Bardaskan belt.
J. Rasouli; M. Gorbani
Abstract
Delfard area is located in the northwestern of Jiroft, formed the northwestern part of the Jabālbārez granitoid complex, in Uromiyeh- Dokhtar magmatic belt. The Jabālbārez granitoid complex has a wide range of rocks inclusive from diorite to alkali granite, which were formed by magmatic differentiation ...
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Delfard area is located in the northwestern of Jiroft, formed the northwestern part of the Jabālbārez granitoid complex, in Uromiyeh- Dokhtar magmatic belt. The Jabālbārez granitoid complex has a wide range of rocks inclusive from diorite to alkali granite, which were formed by magmatic differentiation process over the several course of consecutive pulses. Last pulses are masses of porphyry that showed evidence of copper mineralization. One of these intrusive bodies is Delfard. Copper mineralization in Delfard area is more important than other parts of Jabālbārez. Consequently, in the area, three porphyry masses showing the evidence of porphyry copper mineralization. Chalcopyrite, Pyrite, Malachite, Azurite and Magnetite are indicative minerals. Alteration zones in Delfard area are silicic, potassic, arjelic, phyllic, and propylitic that can be correlated with Lovell and Gilbert model. According to studies, Delfard has high potential for exploration and drilling. The average copper content in the ore is about 1800 ppm. Petrogenesis review of the mafic rocks in Delfard area shows that these rocks originated from a richer source than NMORB. In addition, the rocks of Delfard area are Flux melting pointer that happened in the subduction of oceanic crust under the adjacent crust. In other words, the sequence of calc-alkaline rocks of Delfard area attributed to compressional tectonic regime that intrusived and erupted along the Uromiyeh- Dokhtar zone with development and high volume in the form of magmatic horizons. Finally, petrogenesis of studied granite series is similar to the calc-alkaline granitoids, which was originated from basaltic magma mantle metasomatised by fluids from the subducted slab. Based on zircon U-Pb geochronology,the age of Delfard granitoid is 15/83±1/3 Ma. One can imagine that, magmatic differentiation process was completed in a short time and intrusive body was sequentially penetrated and placed in the earth's crust in a short time.
M. Amiri; A. Ahmadi Khalaji; Z. Tahmasbi; R. Zarei Sahamieh; H. Zamanian
Abstract
The intrusive bodies of Almogholagh Batholith, in western Iran are emplaced into the Sanandaj–Sirjan magmatic-metamorphic zone and comprise three main groups: (1) gabbro-diorite, (2) quartz syenite, and (3) quartz monzonite, which crop out in most of the area. The quartz syenite and quartz monzonite ...
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The intrusive bodies of Almogholagh Batholith, in western Iran are emplaced into the Sanandaj–Sirjan magmatic-metamorphic zone and comprise three main groups: (1) gabbro-diorite, (2) quartz syenite, and (3) quartz monzonite, which crop out in most of the area. The quartz syenite and quartz monzonite rocks, having characteristics such as metaluminous, generally ferroan, alkalic to alkali-calcic types, high content of Na2O+K2O, Zr, Ce, Ga, Y, Nb, Ta, REE, and depletion in Eu, Sr and Ti, show the features of borderline between A1 and A2-type granitoids with more A1-type affinity. On the basis of the results of the various diagrams, the gabbroic-dioritic rocks show between A1 and I-type granitoids nature with more I-type affinity. Distinctive peak patterns in spider diagrams accompanied by (La/Yb)CN values of 2.4 to 6.1 and Ba/La ratio >3 indicate magmatic activity in a volcanic arc environment, and the characteristics (Ba/Rb)CN<1, (Ba/Th)CN 143Nd/144Nd > 0.512638, εtNd >0, εtSr >0, high content of Nb, Ta and very high content of Zr (589 ppm) indicate that there was a subsidiary subduction after the initial collision for a long time and the magmas of Amogholagh batholiths were originated from mantle wedge, overlying the subduction zone or from mantle components around fragments resulting from delamination between continental crust and mantle lithosphere, demonstrating the involvement of subduction zone fluids, high flux of mantle-derived halogen-rich volatiles, and contamination within the crust during the petrogenesis of intrusions.
N. Sarhaddi; A. Ahmadi; Z. Firoozkoohi; M. Jami
Abstract
The Lakhshak granodiorite body with Oligo-Miocene age crops out in flysch sediments of northwest of Zahedan. This body has been intruded by dykes with variable color indices ranging from mesocratic to melanocratic, and NE-SW trend. Based on field observations, , melanocratic dykes have cut mesocratic ...
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The Lakhshak granodiorite body with Oligo-Miocene age crops out in flysch sediments of northwest of Zahedan. This body has been intruded by dykes with variable color indices ranging from mesocratic to melanocratic, and NE-SW trend. Based on field observations, , melanocratic dykes have cut mesocratic dykes in some parts.This indicates that mesocratic dykes are younger than the melanocratic types. Different thickness (2 to 12m) of dykes shows the effect of tectonic activities and magama injection into structural joints, and the formation of dykes during tectonic activity. In terms of lithology, the Lakhshak body is composed of granodiorite, dacitic mesocratic dykes and melanocratic dykes of microdioritic and andesitic types. The granodiorite body and the two types of dykes are of I type nature, and are calc-alkaline, high-K calc-alkaline and metaluminous. Based on the geochemical characteristics, dykes and granodiorite show enrichment in LILE, LREE such as Ba, Cs, Rb, Eu and Pb, and depletion in HFSE, HREE such as Nb, Ti and Ta, which are related to index characteristics of the volcanic arc setting of an active continental margin. Pb positive anomaly may demonstrate continental crust assimilation by magma associated with mantle metasomatism. Based on field observation and petrogenesis, the Lakhshak granodiorite and mesocratic-melanocratic dykes originated from magmatic activity of subducted oceanic crust (Sistan plate) beneath the continental plate (Afghan block). The parental magma of the Lakhshak granitoid was originated from melts resulted from amphibolite melting, and dykes are the late derivative of magma recrystallization granodiorite.
M Aghazadeh
Abstract
The Sar Cheshmeh mine, a world-class porphyry copper deposit, is located in the Kerman metallogenic zone. The rock outcrops in the deposit are Eocene basalt, basaltic andesite and andesite, Oligocene granular and porphyry granodioritic intrusions and Miocene Sar Cheshmeh granodioritic porphyry stock, ...
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The Sar Cheshmeh mine, a world-class porphyry copper deposit, is located in the Kerman metallogenic zone. The rock outcrops in the deposit are Eocene basalt, basaltic andesite and andesite, Oligocene granular and porphyry granodioritic intrusions and Miocene Sar Cheshmeh granodioritic porphyry stock, granitic late fine-grained porphyry and andesitic to dacitic hornblende, plagioclase, and biotite porphyry dykes. In the spider diagrams, studied rocks show LILE enrichment and HFSE depletion pattern similar to volcanic arc rocks. Eocene volcanic rocks and Oligocene granular and porphyry granodioritic intrusions represent typical magmas characteristics of volcanic arcs whereas Miocene intrusions and dykes have adakitic nature. The (La/Yb)N ratio in the volcanic rocks and Oligocene intrusions varies between 1-5 and 7-11 respectively, while Miocene intrusions and dykes show highest amount of this ratio(20-40). Low aboundancy of HREE in the Miocene intrusions and dykes implies that garnet have been in the source, which has been formed due to increasing crustal thickness during Oligocene and Miocene. According to U-Pb dating, the Sar Cheshmeh porphyry stock and granitic late fine grained have been emplaced in 12.97 ± 0.23 Ma and 12.37 ± 0.1 Ma respectively, while hornblende porphyry dykes has been intruded in 12.16 ± 0.8 Ma. According to trace element characteristics in zircon crystals, Miocene intrusions and dykes originated from same source. Middle Miocene intrusions and dykes have been generated in a post collisional tectonic setting from various degree partial melting of amphibolitic mafic lower crust with variable garnet.
M Aghazadeh; Z Badrzadeh; A Castro
Abstract
The studied Roudbar and Abhar plutons are located in the western Alborz zone and Taroum subzone. These intrusive bodies show metaluminous and shoshonitic nature and they cut the Eocene volcanic and sedimentary rocks. In the studied plutons, monzonite and quartz monzonite terms are dominant. According ...
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The studied Roudbar and Abhar plutons are located in the western Alborz zone and Taroum subzone. These intrusive bodies show metaluminous and shoshonitic nature and they cut the Eocene volcanic and sedimentary rocks. In the studied plutons, monzonite and quartz monzonite terms are dominant. According to geochemistry, these plutons were crystallized from non-primary magma, and have been experienced fractional crystallization. In the primary mantle normalized spider diagrams and chondrite normalized REE diagrams, studied samples show clear enrichment in the LREE and LILE and depletion in the HFSE. The primary magma originated from 1-5% partial melting of phlogopite bearing lithospheric mantle with spinel lherzolite composition that metasomatized by subduction agents. According to U-Pb SHRIMP dating, these plutons were intruded during 37.8 to 38.9 Ma in the late Eocene and in a post-collision tectonic setting.
K Shiaian; J Ghalamghash; M Vosoughi Abediny; F Masoudi
Abstract
The Bazman volcano is located in the Makran Magmatic Arc. The pyroclastic rocks and lava with rhyodacitic to basaltic composition and calc-alkaline affinities erupted from the central and lateral craters of this volcano during the Quaternary period. The primitive mantle normalized Multi-elements diagrams ...
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The Bazman volcano is located in the Makran Magmatic Arc. The pyroclastic rocks and lava with rhyodacitic to basaltic composition and calc-alkaline affinities erupted from the central and lateral craters of this volcano during the Quaternary period. The primitive mantle normalized Multi-elements diagrams show a relatively high abundance of LIL relative to HFS incompatible elements with negative anomalies of Nb and Ti. Their chondrite–normalized REE patterns are slightly enriched in LREE relative to HREE with negative Eu anomalies. These geochemical features suggest that the volcanic rocks of bazman formed in a subduction setting by partial melting of metasomatized mantle. On the base of La/Yb vs Dy/Yb and La/Sm vs Sm/Yb diagrams the sources of the magmas is phlogopite-spinel-lherzolite or/and phlogopite-garnet- lherzolite.
M Aghazadeh; Z Badrzadeh
Abstract
In the northwestern Iran mica-and amphibole-rich lamprophyres crop out mainly as dyke and they cut Pre-Pliocene strata. They exposed in the Arasbaran, EslamyPeninsula, and Mishu range. According to the mineralogy and mineral chemistry, amphibole-rich lamprophyres have kaersutite type amphiboles and diopside ...
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In the northwestern Iran mica-and amphibole-rich lamprophyres crop out mainly as dyke and they cut Pre-Pliocene strata. They exposed in the Arasbaran, EslamyPeninsula, and Mishu range. According to the mineralogy and mineral chemistry, amphibole-rich lamprophyres have kaersutite type amphiboles and diopside phenocrysts in the matrix of same mafic minerals, feldspars, and altered glass. These lamprophyres in some thin sections have olivine and phlogopite. Mica-rich lamprophyres include phlogopite and diopside phenocrysts in the matrix of same mafic minerals, abundant glass and secondary minerals. According to the mineralogy, mineral chemistry, and geochemistry, amphibole-rich lamprophyres are alkaline and show camptonite-sannaite composition but mica-rich lamrophyres are calc-alkaline and represent minette composition. Alkaline lamprophyres represent characteristics of OIB type magma while calc-alkaline lamprophyres show characteristics of magmas originated in the subduction dominant tectonic setting. Sorkheh amphibole-bearing lamprophyres show both alkaline and calc-alkaline type lamprophyres. Regarding to geochemical features both calc-alkaline and alkaline lamprophyres originated from heterogeneous mantle with different proportions of spinel, garnet and hydrous minerals (e.g. phlogopite and amphibole). Calc-alkaline lamprophyres originated from a mantle enriched in phlogopite and alkaline lamprophyres originated from lithospheric mantle that metasomatised by deep mantle and enriched in amphibole. Both mentioned mantles associated in the petrogenesis of the Sorkheh amphibole- bearing lamprophyres. The lamprophyres were emplaced in the post collisional tectonic setting.
S Afzali; N Nezafati; M Ghaderi; J Ghalamghash; M.R Ghassemi; A Karimi Bavandpur
Abstract
The Gazestan magnetite–apatite deposit is situated 78 km east of Bafq. The Gazestan deposit is located in Bafq-Poshtebadam subzone of Central Iran structural zone. The rock units in the area belong to the Rizu series and consist of carbonate rocks, shale, tuff, sandstone and volcanics. In addition ...
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The Gazestan magnetite–apatite deposit is situated 78 km east of Bafq. The Gazestan deposit is located in Bafq-Poshtebadam subzone of Central Iran structural zone. The rock units in the area belong to the Rizu series and consist of carbonate rocks, shale, tuff, sandstone and volcanics. In addition to sedimentary and volcanic rocks, intrusive rocks in the form of stock and dyke outcrop as diorite gabbro, gabbro, diabase, quartz-monzonite and granite in various places. The green rocks with acidic to intermediate composition (trachyte and dacite demonstrate green color due to alteration) host iron and phosphate mineralization which in some localities, show subvolcanic facies. The alteration is more obvious in the volcanic rocks and includes chloritization, argillic, silicification, and also formation of mafic minerals such as epidote, tremolite and actinolite. The host rocks are strongly altered. Mineralization at the Gazestan deposit comprises a combination of iron oxides and apatite with various ratios accompanied by quartz and calcite, observed in different forms mainly within the trachytic-dacitic rocks and a small proportion in the rhyolites. Five forms of mineralization are distinguished in the area including massive iron ore with minor apatite, apatite-magnetite ore, irregular vein-veinlets (stockwork) in the brecciated green rocks, disseminated, and pure massive apatite veins. The host rocks in the Gazestan area plot on calc-alkaline field. Comparison of the most important characteristics of the Gazestan deposit (including tectonic setting, host rock, mineralogy, alteration, structure and texture) with those of various types of mineralization in the world suggest that the deposit is quite similar to the iron oxide - apatite deposits.
H. A. Tajeddin; E. Rastad; A. Yagoubpour; M. Mohajjel
Abstract
Barika deposit is the first and only recognized gold (and silver) rich – massive sulfide deposit in Iran which is located at 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are volcano sedimentary metamorphosed rocks in green ...
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Barika deposit is the first and only recognized gold (and silver) rich – massive sulfide deposit in Iran which is located at 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are volcano sedimentary metamorphosed rocks in green schist facies, and include association of metaandesite, metatuffite, phyllite and slate rocks, among which the metaandesitic unit (KMv1) is host rock of the deposit. Ore mineral assemblages in stratiform part of the deposit, which contain massive and banded pyrite and barite associated with subordinary silica bands, are very variable in composition and consist of pyrite, sphalerite, galena, stibnite and a variety of sulfosalt minerals and electrum. Ore mineral assemblage in silicic veins in stringer zone, are simpler and consist of pyrite, galena, sphalerite, tetrahedrite and rare chalcopyrite. Average gold and silver grades in stratiform ore are 4.2 and 260 g/t respectively and in silica stringer veins are 0.7 and 30 g/t. Base metal content in both part of the deposit is less than 1%. Lithotectonic study and trace and rare earth elements diagrams associated with Ce/Pb and Nb/U ratios of the metavolcanic rocks in the deposit area indicate that the rocks were generated from a lithospheric mantle source in the active continental margin of the SSZ. A geochemical study of Barika deposit reveals that distribution patterns and correlation coefficient of ore elements in parts of the Barika stratiform ore and stringer zone are completely in correlation with an undeformed massive sulfide deposit. The geochemical documents indicate that despite the metamorphism and highly deformation on the deposit, the primary distribution patterns and proportion of the ore elements are well conserved, as geochemical characteristics of the Barika deformed deposit is as well as correlated with an undeformed gold- rich volcanogenic massive sulfide deposit. However there is clear textural evidence for remobilization of As, Sb, Ag and Pb minerals together with Au in Barika deposit, but, remobilized constituents of the ores do not appear to have moved beyond the margins of the ore bodies and primary metal zonation.
M. Sadeghian; H. Ghasemi; Z. Farsi
Abstract
Chah Salar granitoidic pluton is located in the N of Chah-Salar village, SW of Neishabour, in the northern margin of structural Central Iran zone. This pluton intruded in Sabzevar ophiolitic Zone and based on the field observations, petrographical and geochemical classification diagrams, its lithological ...
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Chah Salar granitoidic pluton is located in the N of Chah-Salar village, SW of Neishabour, in the northern margin of structural Central Iran zone. This pluton intruded in Sabzevar ophiolitic Zone and based on the field observations, petrographical and geochemical classification diagrams, its lithological composition composed of diorite, quartzdiorite, granodiorite and alkali feldspar granite. Alkali feldspar granites as a much fractionated end-members of this rock association are intruded in this pluton in the form of dikes or apophyse shapes. Granitic pegmatites and their associated quartzolites are the most differentiated end-member of this rock association. Their subvolcanic equivalents such as pyroxene-bearing andesite, andesite, trachyandesite and dacite cut this pluton in the forms of dikes or domes. The studied rocks show variety of textures including granular, myrmekitic, graphic, porphyritic, microlitic porphyry and pilotaxitic. Except alkali feldspar granites which are highly fractionated, the other lithological compositions, on the variations diagrams of major, trace and rare earth elements versus SiO2 or differentiation index show continuous compositional variations. This pluton has calc-alkaline and metaluminous nature and belongs to I-type granitoids. Also tectonic setting discrimination diagrams indicate that the Chah Salar granitoidic pluton belongs to volcanic arc granitoids (VAG) and continental arc granitoids (CAG). Detailed investigations of field geology, petrography and geochemical characteristics indicate that magma-forming of this pluton is resulted from partial melting of subducted oceanic slab (metabasite) or metasomatized mantle wedge and then evolved by fractional crystallization, magma contamination or magma mixing.
Z. Sadeghi; H. Mehdizadeh; M. Sadeghian
Abstract
Kuh- Shah granitoidic pluton is located in the NE part of 1:100000 geological map of Baft. Lithological composition of this pluton includes Alkali- feldspar granite, granite, granodiorite, quartzdiorite, diorite and gabbro. This pluton has been intruded in volcaniclastics ...
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Kuh- Shah granitoidic pluton is located in the NE part of 1:100000 geological map of Baft. Lithological composition of this pluton includes Alkali- feldspar granite, granite, granodiorite, quartzdiorite, diorite and gabbro. This pluton has been intruded in volcaniclastics of Eocene age. On the variation diagrams the trends of major and trace elements of studied samples indicate the continuity of lithological compositional range of this pluton and they have been from differentiation of a basic (basaltic) magma. From the genetic classification point of view the studied granitoidic pluton is from I type granite and it belongs to magnetite series. Based on the geochemical features Kuh-Shah granitoidic pluton is metaluminous with high and medium potassic calc-alkaline nature. High amounts of LILE and low amount of HFSE on the spider diagrams show that the parental magma of these rocks have been enriched from trace elements and incompatible elements. Based on the tectonic setting discrimination diagrams, this pluton is belong to VAG type and therefore it has been resulted from subduction of neotethys oceanic crust beneath the central Iran continental crust.
