Petrology
Reza Jamal Omidi; Saeid Hakimi Asiabar; Shahrooz Haghnazar; Mansour Vosoghi Abedini
Abstract
Tarom mountains are located at the southwestern end of the Alborz mountain range with an approximate northwest-southeast direction. Tashvir region is a part of the northern margin of the Tarom mountains. Most igneous rocks in this area include basalt, andesitic basalt, and interlayers of tuff. Enrichment ...
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Tarom mountains are located at the southwestern end of the Alborz mountain range with an approximate northwest-southeast direction. Tashvir region is a part of the northern margin of the Tarom mountains. Most igneous rocks in this area include basalt, andesitic basalt, and interlayers of tuff. Enrichment of LIL elements with positive anomalies of Ce, P, Sm, and depletion of Nb, Ta, Zr, Hf, and Th, elements and also K2O/Na2O and Ba/Rb ratios in the rock samples of Tashvir area, indicate magma contamination with the lower crust. The evidence of crustal contamination and the ratio of Nb/Y and Zr/Y in the samples indicate that the basalts of the Tashvir region belong to the source of the plume. Alkaline, shoshonitic, and peraluminous nature, REE enrichment (i. e. Ba, Rb, and Sr), low titanium content, origin, and depth of magma indicate they're belonging to the rift environment. In this study, in addition to determining the characteristics of igneous rocks in the Tashvir area, the results of several previous studies are plotted on the map of the Tarom mountains. Accordingly, the tectonic setting of the Tarom range is divided into two parallel sub-regions with magmatic arc and rift-type eruptions, which expansion of this rift zone has stopped before it evolve as a back-arc basin.
Petrology
Mohsen Moayyed; Farzaneh ValinasabZarnagh; Ahmad Jahangiri; Hosein Azizi
Abstract
there are Discontinuous outcrops of volcanic rocks in the northern regions of Maku. The volcanic rocks were metamorphosed in the green schist facies. These volcanic complex were bimodal and compose of acidic and basic lava and pyroclastic rocks. The lava of this unit covers the Cambrian and equivalent ...
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there are Discontinuous outcrops of volcanic rocks in the northern regions of Maku. The volcanic rocks were metamorphosed in the green schist facies. These volcanic complex were bimodal and compose of acidic and basic lava and pyroclastic rocks. The lava of this unit covers the Cambrian and equivalent of Lashkarak rock units and is progressively covered by Devonian dolomitic units. The geochemical data of metabasic and metarhyolite rocks signify transitional to alkaline nature of the primary magma and they have a negative gradient of REE and LREE / HREE ratio of those rocks are high and enriched inHFS elements. Metarhyolite rocks are similar to the rift setting rhyolites (A1-Type). Geochemical data indicate that the studied rocks are due to fractional crystallization of basic magma with crustal contamination, and in particular, the studied rocks have a genetic relationship and originate from a commen magma. The magma of the studied rocks generated by 3-10 percent partial melting of an enriched garnet peridotitic mantle source in an intra-continental extensional rift setting. This tectonic setting is concordant with the known extensional rift setting governed on other parts of Iran during the early Paleozoic, primary stages of generation and development of the Paleotethys.
M Derakhshi; H Ghasemi; T Sahami
Abstract
The Soltan Maydan Basaltic Complex indicates the most important, thickest, and most voluminous early Paleozoic magmatic activity in Iran outcropping in the eastern Alborz structural zone, in the north-northeast of Shahrud. This complex overlies the late Ordovician Ghelli Formation and is overlain by ...
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The Soltan Maydan Basaltic Complex indicates the most important, thickest, and most voluminous early Paleozoic magmatic activity in Iran outcropping in the eastern Alborz structural zone, in the north-northeast of Shahrud. This complex overlies the late Ordovician Ghelli Formation and is overlain by the early Devonian Padeha Formation. The field evidences show more than 50 lava flows erupting frequently in the sub-aerial and submarine environments. This complex comprises of a continuous fractional spectrum including basalt, basaltic andesite, trachybasalt and basaltic trachyandesite that has undergone medium to high degrees of alteration. The geochemical data and diagrams signify transitional to alkaline nature of the primary magma, genetic relationship among all rocks of this complex due to fractional crystallization, none or weak role of magmatic contamination in magma evolution, and generation of primary magma by 15-17 percent partial melting of an enriched garnet peridotitic mantle source in an intra-continental extensional rift setting. This tectonic setting is concordant with the known extensional rift setting governed on the Alborz and Central Iran zones during the early Paleozoic, especially late Ordovician-Silurian, primary stages of generation and development of the Paleotethys.
F. Gharib; Y. Lasemi; M. H. Emami
Abstract
The clastic facies of Kahar Formation were identified in the studied sections of coastal, deltaic and fluvial and also carbonate facies in shallow marine environments. The vertical displacements of Kahar Formation in these study sections show an overall major transgressive upward cycle. The petrography ...
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The clastic facies of Kahar Formation were identified in the studied sections of coastal, deltaic and fluvial and also carbonate facies in shallow marine environments. The vertical displacements of Kahar Formation in these study sections show an overall major transgressive upward cycle. The petrography of plutonic and semi- plutonic igneous rocks indicate that they consist mainly of monzogabbro- diorite and in some cases, alkaline syenite. According to the results of Kahar Formation's plutonic rocks petrography and studies of related facies, the basin of this formation was a continental rift.
