فهرس المقالات volcanism

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  1 - Pliocene volcanic activity of the Harrat Ash-Sham, South of Syria: geochemistry and petrogenesis
  Safwan Dawod Ali Al-Mishwat Abdulkarim Al Abdalla
  The Cenozoic volcanic activity of the Harrat Ash Sham volcanic field in south of Syria is a part of the extensive magmatism that took place in the auxiliary extension faults along the Dead Sea Fault Zone from upper Eocene to Holocene. Pliocene volcanic rocks form an imp أکثر

  The Cenozoic volcanic activity of the Harrat Ash Sham volcanic field in south of Syria is a part of the extensive magmatism that took place in the auxiliary extension faults along the Dead Sea Fault Zone from upper Eocene to Holocene. Pliocene volcanic rocks form an important part of igneous succession in Syrian Part of Harrat as Sham. These rocks vary from basalts flows to scoria. Pliocene basalts are divided into three primary petrographic groups: olivine basalt, olivine-pyroxene basalt and basanite. The three petro-types are alkaline and have similar compositional ranges of major and trace elements. Variations in the contents of major and minor elements in the Pliocene basaltic rocks are very slight. Such homogeneity in the chemical composition indicates to the operation of petrological processes that reinforced each other during the genesis of these rocks. The geochemical characteristics of the Pliocene basalt rocks reflect crystallization from primitive basic magmas that have experienced limited crystal fractionation process subsequent to their derivation by partial melting of the upper mantle. تفاصيل المقالة
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  2 - Distribution and geochemical variations among paleogene volcanic rocks from the north-central Lut block, eastern Iran
  Saeed Saadat Charles Stern
  The Lut block in eastern Iran is a micro-continental block within the convergent orogen between the Arabian, Eurasian and Indian plates. Large areas of the north-central, eastern, and western Lut block are covered by volcanic rocks of Paleogene, Neogene and Quaternary a أکثر

  The Lut block in eastern Iran is a micro-continental block within the convergent orogen between the Arabian, Eurasian and Indian plates. Large areas of the north-central, eastern, and western Lut block are covered by volcanic rocks of Paleogene, Neogene and Quaternary age.  Peak volcanic activity took place in the north-central part of the Lut block during the Eocene, and then dramatically decreased, becoming more restricted to the eastern and western margins of the block during the late Miocene and Quaternary. There is also significant variation in chemistry between the Paleogene igneous rocks from the north-central part compared to the Neogene and Quaternary volcanic rocks from the western and eastern margins of the Lut block. The Neogene and Quaternary olivine basalts, which were erupted along both margins of the Lut block, are similar in trace element chemistry to the average composition of oceanic island basalt. In contrast, the Paleogene volcanic units of the north-central Lut block, which include basalts through rhyolites, follow both calc-alkaline and alkaline trends. Low TiO2 and high Ba/Nb and La/Nb ratios for both Paleogene basalts and andesitic samples from the north-central Lut block suggest affinities, at least for some of these samples, with convergent plate boundary arc magmas. LILE/HFSE ratios, interpreted as an indication of subduction signature, increase to the south-southwest of the central Lut block, where Neotethys oceanic crust was subducted beneath Iran in a northeastern direction from approximately Late Triassic to Late Oligocene time. We suggest that components derived from low angle subduction of this crust during the Mesozoic and early Tertiary were stored in the mantle lithosphere below the north-central Lut block until the Paleogene, when changing subduction geometry, associated with the collision of Arabia with Iran and the closing of Neotethys, caused hot asthenosphere to well up under the Lut block. This created the Eocene peak in volcanic activity, generating basalts from asthenospheric mixed with lithospheric melts, with both alkaline and calc-alkaline affinities. After this volcanism waned, becoming restricted during the Neogene to OIB-type alkaline basalts erupted through deep lithospheric structures along both the western and eastern margins of the Lut block. تفاصيل المقالة
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  3 - Petrological and geodynamical constraints of Chaldoran basaltic rocks, NW of Iran: evidence from geochemical characteristics
  Farhad Moharami Issa Azadi Mirsaleh Mirmohamadi Javad Mehdipour Ghazi Mohammad Rahgoshay
  Chaldoran area in NW of Iran has Mesozoic oceanic crust basement. The studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and Eocene lava flows. Ophiolitic mafic rocks show continental volcanic a أکثر

  Chaldoran area in NW of Iran has Mesozoic oceanic crust basement. The studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and Eocene lava flows. Ophiolitic mafic rocks show continental volcanic arc natures and Eocene lava flow shows OIB-like nature. During the Mesozoic,the Chaldoran region was situated in the active continental margin of the Iranian plate due to Neotetyhan subduction beneath the SSZ (Sanandaj-Sirjan Zone). As the Neo-Tethyan subduction regime changed, a rift in the Chaldoranareagenerated, which caused a continental back arc basin during the Upper Cretaceous. Along with spreading basin in the oceanic ridge, in the surface of new formed oceanic crust, some oceanic island were active and formed volcanoclastic rocks in the Chaldoran Oceanic crust. They were result of ascending continental arc nature plumes that formed in the sub-oceanic crust and up on Neo-Tethys subducted slab in the mantle wedge. After of finishing of spreading this basin in early time of Paleocene, sedimentation followed up to the Middle Eocene. In the Upper Eocene, alkaline and OIB-like volcanism was active in the Chaldoranareadue to breaking off the Neo-Tethyan subducted slab in the sub-oceanic crust of Chaldoran area and developed an asthenosphric window. تفاصيل المقالة
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  4 - Petrogenetic Evolution of Plio-Quaternary Mafic Lavas in Nehbandan (East Iran)
  Mohammad Reza Ghasempour Javad Mehdipour Ghazi Habib Biabangard Rahim Dabiri
  Both the Sistan Suture Zone of eastern Iran and the Nehbandan Fault contain Plio-Quaternary Nehbandan mafic lavas. Positive anomalies in the large ion lithophile elements (LILE) and negative anomalies in Nb (niobium) exist in these mafic lavas. This indicates the occurr أکثر

  Both the Sistan Suture Zone of eastern Iran and the Nehbandan Fault contain Plio-Quaternary Nehbandan mafic lavas. Positive anomalies in the large ion lithophile elements (LILE) and negative anomalies in Nb (niobium) exist in these mafic lavas. This indicates the occurrence of subduction magmatism and post-collision volcanism. Petrologic and geochemical analyses distinguished two groups of lava. Group I contains alkaline basalts with a slight depletion in Nb while Group II contains sub-alkaline basaltic andesite to andesite with a sharp depletion in Nb. Geochemical studies show that fractional crystallization and crustal contamination played an important part in the evolution of the Nehbandan lavas. Group II, however, was more greatly affected than Group I. Geochemical studies also indicate that these lavas may have been generated due to a low degree of partial melting (<5%) of garnet and the spinel-bearing lithospheric mantle; Group I shows more garnet than spinel while Group II shows the opposite. The research carried out for this paper suggests that the Plio-Quaternary Nehbandan mafic lavas were formed as a result of slab detachment or delamination and domination, an extensional condition correlated to the thinning of the crust and lithosphere in the Sistan Collision Zone. These conditions are concomitant with localized stretching along the Nehbandan Fault and the upwelling of magma forming mafic lavas. تفاصيل المقالة