Mineral chemistry of the ophiolitic peridotites and gabbros from the Serow area: Implications for tectonic setting and locating the Neotethys suture in NW Iran

AbstractThe late Cretaceous Kızıldağ ophiolite forms one of the best exposures of oceanic lithospheric remnants of southern Neotethys to the north of the Arabian promontory in Turkey. The ultramafic to mafic cumulate rocks, displaying variable thickness (ranging from 165 to 700 m), are ductiley deformed, possibly in response to syn-magmatic extension during sea-floor spreading and characterized by wehrlite, olivine gabbro, olivine gabbronorite and gabbro. The gabbroic cumulates have an intrusive contact with the wehrlitic cumulates in some places. The crystallization order of the cumulus and intercumulus phases is olivine (Fo86–77)± chromian spinel, clinopyroxene (Mg#92–76), plagio-clase(An95–83), orthopyroxene(Mg#87–79). The olivine, clinopyroxene, orthopyroxene and plagioclase in ultramafic and mafic cumulate rocks seem to have similar compositional range. This suggests that these rocks cannot represent a simple crystal line of descent. Instead the overlapping ranges in mineral compositions in different rock types suggest multiple magma generation during crustal accretion for the Kızıldağ ophiolite. The presence of high Mg# of olivine, clinopyroxene, orthopyroxene, and the absence of Ca-rich plagioclase as an early fractionating phase co-precipitating with forsteritic olivine, suggest that the Kızıldağ plutonic suite is not likely to have originated in a mid-ocean ridge environment. Instead the whole-rock and mineral chemistry of the cumulates indicates their derivation from an island arc tholeiitic (IAT) magma. All the evidence indicates that the Kızıldağ ophiolite formed along a slow-spreading centre in a fore-arc region of a suprasubduction zone tectonic setting.

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Mineral chemistry and formation conditions of calc-silicate minerals of Qozlou Fe skarn deposit, Zanjan Province, NW Iran

Arabian Journal of Geosciences ◽

10.1007/s12517-019-4814-1 ◽

2019 ◽

Vol 12 (21) ◽

Author(s):

Mir Ali Asghar Mokhtari ◽

Hossein Kouhestani ◽

Kazem Gholizadeh

Keyword(s):

Mineral Chemistry ◽

Skarn Deposit ◽

Silicate Minerals ◽

Porphyritic Granite ◽

Nw Iran ◽

High K ◽

Ore Minerals ◽

Mineralized Zone ◽

Supergene Processes ◽

Carbonaceous Rocks

Abstract The Qozlou Fe skarn deposit is located at the Abhar–Mahneshan belt of the Central Iranian Zone. It is associated with Upper Eocene porphyritic granite that intruded into the Upper Cretaceous impure carbonaceous rocks. The Qozlou granite has high-K calc-alkaline affinity and is classified as subduction-related metaluminous I-type granitoids. Skarn aureole in the Qozlou is composed of endoskarn and exoskarn zones, with the exoskarn zone being the main skarn and mineralized zone. It includes garnet skarn, garnet-pyroxene skarn, pyroxene skarn, epidote skarn, and pyroxene-bearing marble sub-zones. The Qozlou Fe deposit is 300 m long and 5–30 m wide. Magnetite is the main ore mineral associated to pyrite, chalcopyrite, and pyrrhotite. Garnet, clinopyroxene, actinolite, epidote, calcite, and quartz occur as gangue minerals. Covellite, hematite, and goethite were formed during the supergene processes. The ore and gangue minerals have massive, banded, disseminated, brecciated, vein–veinlets, replacement, and relict textures. EPMA data indicate that garnets have andradite–grossularite compositions (Ad39.97–100–Gr0–49.62) and clinopyroxenes have diopsidic composition (En29.43–42.5–Fs14.31–20.99–Wo43.08–50.17). Based on mineralogical and textural criteria, skarnification processes in the Qozlou skarn can be categorized into three discrete stages: (1) isochemical (metamorphic–bimetasomatic), (2) metasomatic prograde, and (3) metasomatic retrograde. Anhydrous calc-silicate minerals (garnet and clinopyroxene) were formed during the prograde metasomatic stage, while ore minerals and hydrous calc-silicate minerals were formed during the retrograde ore-forming sub-stage. Temperature and ƒO2 conditions range between 430 and 550 °C and 10−26 and 10−23, respectively, for the metasomatic prograde stage. The retrograde metasomatizing fluids had likely ƒS2 = 10−6.5 and temperatures < 430 °C at the beginning of the ore-forming sub-stage.

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Polyphase tectonothermal events recorded in metamorphic basement rocks from the northern Altyn Tagh, southeastern Tarim Craton

10.5194/egusphere-egu2020-3195 ◽

2020 ◽

Author(s):

Zhongmei Wang ◽

Chunming Han ◽

Wenjiao Xiao ◽

Patrick Asamoah Sakyi

Keyword(s):

Tectonic Setting ◽

Volcanic Rocks ◽

Mineral Chemistry ◽

Metasedimentary Rocks ◽

Exposed Rock ◽

Altyn Tagh ◽

Argillaceous Rocks ◽

Southeastern Margin ◽

Minimum Age ◽

Tarim Craton

&#160; Paleoproterozoic is a pivotal time for understanding the geochronological framework of the Tarim Craton. Located on the southeastern margin of the Tarim Craton, the northern Altyn Tagh is the main exposed region for Paleoproterozoic magmatic-metamorphic rocks. These rocks are diverse, diachronous and modified by multiple magmatic and/or metamorphic events. In this study, we performed systematic analyses on the amphibolite, felsic gneisses, and metasedimentary rocks in the Aketashitage area, southeastern Tarim Craton, including petrography, mineral chemistry, and whole-rock geochemistry, as well as in-situ zircon U-Pb ages and Hf isotopes, to examine the Paleoproterozoic magmatic-metamorphic events in the northern Altyn Tagh. Geochemically, the amphibolite and felsic gneisses in the Aketashitage area seemingly represent the typical bimodal associations of mafic and acidic volcanic rocks. In addition, the felsic gneisses are characterized by high Sr and low Y contents, with high Sr/Y and LaN/YbN ratios, and indistinctive Eu anomalies, closely resembling high-SiO2 adakites derived from subducted basaltic slab-melt. The palimpsest textures and geochemical features of the Aketashitage metasedimentary rocks suggest that their protoliths are argillaceous rocks. The amphibolite has a metamorphic age of 1.96 Ga, and the felsic gneisses yield crystallization ages of 2.54-2.52 Ga. For the metasedimentary rocks, the major age peaks of 2.72 Ga, 2.05 Ga and 1.97 Ga are consistent with the magmatic and/or metamorphic events in the study area. The minimum age peak suggests that the depositional age is no earlier than 1.97 Ga. The geochemical and geochronological evidences documented by the exposed rock associations in the Aketashitage area suggest a subduction-related tectonic setting in the Paleoproterozoic. Our new data combined with the previous studies indicate that the Paleoproterozoic magmatism and metamorphism in the northern Altyn Tagh area are nearly synchronous, and both are likely related to oceanic subduction.

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Petrography, mineral chemistry and geochemistry of hornblenditic autholiths and hornblenditic xenoliths from volcanic alkaline rocks from North West of Marand (NW Iran)

Iranian Journal of Crystallography and Mineralogy ◽

10.29252/ijcm.25.4.681 ◽

2018 ◽

Vol 25 (4) ◽

pp. 681-696 ◽

Cited By ~ 1

Author(s):

AliAkbar Khezerlou ◽

◽

Nasir Amel ◽

Mohsen Moayed ◽

Ahmad Jahangiri ◽

...

Keyword(s):

Mineral Chemistry ◽

Alkaline Rocks ◽

North West ◽

Nw Iran

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Mineral chemistry and Tectonic setting of diabasic dykes of Kamyaran ophiolite complex, Western Iran

Iranian Journal of Crystallography and Mineralogy ◽

10.18869/acadpub.ijcm.25.3.609 ◽

2017 ◽

Vol 25 (3) ◽

pp. 609-618 ◽

Cited By ~ 1

Author(s):

Majid Sudi Ajirlu ◽

robab Hajialioghli ◽

mohsen Moazzen ◽

◽

...

Keyword(s):

Tectonic Setting ◽

Mineral Chemistry ◽

Ophiolite Complex ◽

Western Iran

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Geochemistry of Cretaceous subduction initiation related cumulate gabbros in a forearc setting from Chaldoran ophiolite, NW Iran

10.5194/egusphere-egu2020-21232 ◽

2020 ◽

Author(s):

Mahleqa Rezaei ◽

Mohssen Moazzen ◽

Tian-Nan Yang

Keyword(s):

Source Region ◽

Mineral Chemistry ◽

Ultramafic Rocks ◽

Nw Iran ◽

Subduction Initiation ◽

Rock Types ◽

Original Magma ◽

Ree Patterns ◽

Ree Pattern ◽

Cretaceous Subduction

The Neo-Tethys-related Chaldoran ophiolite in NW Iran and at the Turkish border is a part of the larger Khoy ophiolite. Cumulate and isotropic gabbro along with serpentinized peridotite, pillow basalt, pelagic limestone, rare radiolarites, and volcano-sedimentary units are the main rock types in the area. The gabbros occur as lenses with ultramafic rocks, or as relatively large exposures with fault contact with ultramafic rocks. In this study, we provide new whole-rock geochemistry, mineral chemistry and zircon U/Pb age for the cumulate gabbros from the Chaldoran area. Gabbros have tholeiitic composition and are highly depleted. Chondrite normalized rare earth elements (REE) pattern for gabbros are comparative with REE patterns for N-MORB, but overall with more depleted features. The N-MORB normalized multi-elements pattern shows high depletion in HREE and HFSE and enrichment in some LREE and LILEs. Negative anomaly for some HFSE relative to N-MORB, along with enrichment in LILE for the samples indicates the source region as subduction influenced mantle. The cumulated gabbro whole rock and Clinopyroxenes geochemistry indicate an intra-oceanic forearc setting for the studied samples. They also have many similarities to boninite in mineral and whole rock geochemistry. U-Pb zircon dating of the gabbro samples indicates 95.3-114.1 Ma ages for the generation of the gabbros parent magma. The original magma was related to the later stages of the forearc setting in the subduction initiation (SI) stage. This &#8216;SI&#8217; related Albian-Cenomanian the Chaldoran depleted gabbro likely are the continuation of Taurus SI related late Cretaceous ophiolite complexes in Turkey.

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Petrology and mineral chemistry of peraluminous Marziyan granites, Sanandaj-Sirjan metamorphic belt (NW Iran)

Geologica Carpathica ◽

10.1515/geoca-2015-0031 ◽

2015 ◽

Vol 66 (5) ◽

pp. 361-374 ◽

Cited By ~ 4

Author(s):

Esmaiel Darvishi ◽

Mahmoud Khalili ◽

Roy Beavers ◽

Mohammad Sayari

Keyword(s):

Mineral Chemistry ◽

White Mica ◽

Granitic Rocks ◽

Calc Alkaline ◽

Metamorphic Belt ◽

Nw Iran ◽

The North ◽

Continental Plate ◽

High K ◽

Type Granite

AbstractThe Marziyan granites are located in the north of Azna and crop out in the Sanandaj-Sirjan metamorphic belt. These rocks contain minerals such as quartz, K-feldspars, plagioclase, biotite, muscovite, garnet, tourmaline and minor sillimanite. The mineral chemistry of biotite indicates Fe-rich (siderophyllite), low TiO2, high Al2O3, and low MgO nature, suggesting considerable Al concentration in the source magma. These biotites crystallized from peraluminous S-type granite magma belonging to the ilmenite series. The white mica is rich in alumina and has muscovite composition. The peraluminous nature of these rocks is manifested by their remarkably high SiO2, Al2O3and high molar A/CNK (> 1.1) ratio. The latter feature is reflected by the presence of garnet and muscovite. All field observations, petrography, mineral chemistry and petrology evidence indicate a peraluminous, S-type nature of the Marziyan granitic rocks that formed by partial melting of metapelite rocks in the mid to upper crust possibly under vapour-absent conditions. These rocks display geochemical characteristics that span the medium to high-K and calc-alkaline nature and profound chemical features typical of syn-collisional magmatism during collision of the Afro-Arabian continental plate and the Central Iranian microplate.

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