Petrology
Mohammad Saadat; Robab Hajialioghli; Mohssen Moazzen
Abstract
The Qotur metamorphic complex in west of Khoy is consist of various metamorphic rocks including of metabasites, metapelitic and meta-calcareous rocks and serpentinites. The metagabbros form main outcropping rocks in the area. Plagioclase and pyroxene are the main porphyroclasts of metagabbros. Epidote, ...
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The Qotur metamorphic complex in west of Khoy is consist of various metamorphic rocks including of metabasites, metapelitic and meta-calcareous rocks and serpentinites. The metagabbros form main outcropping rocks in the area. Plagioclase and pyroxene are the main porphyroclasts of metagabbros. Epidote, tremolite/actinolite, calcite and chlorite are formed during low grade metamorphism of these rocks. Based on geochemistry results, protolite compositions of the investigated rocks are plotted on the gabbroic field of the classification diagram. They have calc-alkaline magmatic series. Considering the discrimination tectonic diagrams the Qotur metagabbroic rocks have been formed at the island arc tectonic setting. On the basis of U-Pb zircon geochronological data, the rocks are formed at 162.6±7.6 Ma corresponds to the late Jurassic (Oxfordian). On the basis of results obtained from isotopic dating and geochemical data of the Qotur metagabbros, we suppose that they formed related to the sialic back arc basin of Neotethys, Jurrasic Island arc rocks of Sevan-Akera zone corresponds to the North branch of Neotethys oceanic suture and/or in continuation of the Piranshahr and Serow ophiolites as a Zagros-Bitlis Zone. However perecise results will be need to tectonic works and more geochemical and isotopic data from variety of metamorphic and igneous rocks.
Economic Geology
shahriar keshtgar; Sasan Bagheri; shahriar keshtgar
Abstract
Abstract The Mahirud volcano-plutonic Complex (MVPC), known as Cheshmeh Ostad Group, an rock assemblage including several plutons and volcano-sedimentary successions, crops out at the northeastern part of the Sistan Suture Zone. Igneous rocks of the MVPC, consist of volcanic lavas and pyrclastic rocks, ...
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Abstract The Mahirud volcano-plutonic Complex (MVPC), known as Cheshmeh Ostad Group, an rock assemblage including several plutons and volcano-sedimentary successions, crops out at the northeastern part of the Sistan Suture Zone. Igneous rocks of the MVPC, consist of volcanic lavas and pyrclastic rocks, are andesitic basalt, diabase, microgabbro and dacite that were intruded by the late cretaceous granitoids. The volcanic rocks have characteristics of the calc-alkaline to tholeiitic magmatic series. The spider patterns normalized to N-MORB and Chondrite is similar to the ones belong to the supra-subduction zone (SSZ) and Islanc arcs ( IAT). The EPMA studies on the key minerals in volcanic rocks such as clinopyroxene , brought the same results. The pribable presence of an island-arc chain in the Sistan Suture Zone, which some of its parts are considered here as the MVPC, is comparable to continuation of the pakistanian Chagai-Raskoh and Kuhistan Cretaceous-Eocene island-arc/s in east. Considering this reality, we must expect to have a larger ocean much wider than what was already proposed for the Sistan Ocean as a narrow oceanic seaway in Continental rifting setting.
S Hassanpour; S. Alirezaei
Abstract
The Masjeddgaghi Cu-Au deposit is located to the southeast of the Arasbaran zone, NW Iran, to the south of the Lesser Caucasus. Mineralization in Masjeddaghi is associated with an Eocene dioritic subvolcanic pluton intruded into older volcanic and sedimentary rocks. The Masjeddaghi intrusive body is ...
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The Masjeddgaghi Cu-Au deposit is located to the southeast of the Arasbaran zone, NW Iran, to the south of the Lesser Caucasus. Mineralization in Masjeddaghi is associated with an Eocene dioritic subvolcanic pluton intruded into older volcanic and sedimentary rocks. The Masjeddaghi intrusive body is high-K, calc alkaline, and meta-aluminous, and formed in an island arc subduction/collision setting. Hydrothermal alteration is distinguished by a potassic core marked by secondary biotite and K-spar that grades outward into a chlorite-rich propylitic halo. The ore minerals include chalcopyrite, associated with minor chalcocite, bornite, tetrahedrite, and trace molybdenite. Pyrite and magnetite are common associates. The Masjeddaghi deposit is elliptical in plan view, 500 x 400 m in diameters, and mineralization has been traced for several hundred meters from surface exposures. 40Ar/39Ar geochronology on secondary biotite from potassic alteration zone indicates that mineralization, and by corollary, the emplacement and crystallization of the Masjeddaghi porphyritic intrusion, occurred in 54.07 ± 0.53 Ma. The Masjeddaghi ore deposit shows geology, mineralization and alteration characteristics comparable to those typical of island arc type porphyry Cu-Au systems. Masjeddaghi ore deposit shows geology, mineralization and alteration characteristics similar to island arc porphyry type systems.
R Hajialioghli; H Fakharinezhad; M Moazzen
Abstract
The study area (Siyah-Cheshmeh), is located to the south Maku in the Khoy-Maku ophiolite zone. The various outcropped metamorphic rocks include serpentinites, metabasites (green schist, amphibolite) and meta-pelitic rocks (slate, mica-schist) with interlayers of marble and quartzite. The amphibolites ...
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The study area (Siyah-Cheshmeh), is located to the south Maku in the Khoy-Maku ophiolite zone. The various outcropped metamorphic rocks include serpentinites, metabasites (green schist, amphibolite) and meta-pelitic rocks (slate, mica-schist) with interlayers of marble and quartzite. The amphibolites can be classified as actinolite-amphibolite, epidote-actinolite- amphibolite, biotite-amphibolite, amphibolite and garnet-amphibolite. They have fine- to coarse-grained granoblastic texture. On the basis of whole rock chemistry, the protolith composition of the amphibolites has been determined as basalts with tholeiitic and less commonly, calc-alkaline affinities, developed in an island arc setting. The negative anomaly of Nb as well as small enrichments in LILE and LREE support arc related and tholeiitic signatures for the protolith. Considering the unknown age of the studied amphibolites, it is difficult to propose an appropriate tectonic model for formation of the investigated rocks. If the amphibolites are related to the Khoy-Maku ophiolitic complex, then they would be the result of subduction of the northern branch of the Neotethys ocean basin, development of an island arc and eventually metamorphism of the rocks due to closure and collision. Since the age is not clear, it is not possible to conclude unequivocally if the rocks are results of the Neotethys subduction system or they are related to an older, possibly a Precambrian subduction system. Dating the rocks will help to propose a suitable model for their formation.
M Alimohammadi; S Alirezaei; M Ghaderi; D.J Kontak
Abstract
The Daraloo and Sarmeshk copper deposits lie in a northwest-trending fault zone, 10 km long and 0.5-1 km wide in the southern section of the Kerman copper belt, south Iran. The area is marked by a series of Late Eocene-Oligocene granodiorite and Miocene porphyritic tonalite-granodiorite intrusions that ...
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The Daraloo and Sarmeshk copper deposits lie in a northwest-trending fault zone, 10 km long and 0.5-1 km wide in the southern section of the Kerman copper belt, south Iran. The area is marked by a series of Late Eocene-Oligocene granodiorite and Miocene porphyritic tonalite-granodiorite intrusions that cut Eocene andesitic and basaltic lava flows and pyroclastic rocks. Mineralization in both deposits is associated with the Miocene porphyritic intrusions. Both volcanic and plutonic rocks are intruded by post-mineralization diabasic, andesitic and rhyolitic dykes. Representative samples from various rocks were analyzed for major oxides and a wide range of elements. The samples display calc-alkaline affinities; the volcanic rocks are metaluminous, and the intrusive rocks are peraluminous. On primitive mantle- and chondrite-normalized plots, all rocks are characterized by enrichment in large ion lithophile elements and light rare earth elements, relative to high field strength elements and heavy rare earth elements. The features, combined with the negative anomalies for Nb, Ta, and Ti, are characteristic of the subduction- related magmas.The Miocene tonalites are most fractionated, with LaN/YbN ratios ranging between 7.81 and 18.21. This ratio in granitoid rocks is between 6.61 and 7.56. The volcanic rocks are least fractionated, with LaN/YbN ratios from 1.52 to 5.16 .The geochemical attributes of the intrusive bodies from both Daraloo and Sarmeshk are consistent with significant contribution from sediments and crustal materials in the source area, compared to that introduced by fluids released from a subducting slab. The volcanic rocks are, however, appear to have been least affected by crustal materials, but slightly influenced by slab-derived fluids. Plots of samples from all plutonic and volcanic rocks on various discrimination diagrams indicate a transition from an island-arc setting in Paleocene-Eocene to a continental margin volcanic arc setting in Neogene. This is in agreement with earlier works on the evolution of the Kerman belt.
