Sh Eghtesadi; M Shokati Amghani
Abstract
Modelingof bouguer gravity anomaly and tsunami warning due to Makran subduction zone (case study: Beris region)
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Modelingof bouguer gravity anomaly and tsunami warning due to Makran subduction zone (case study: Beris region)
Gh Ghadami; A Moradiane Shahre Babaki; S.M Mortazavi
Abstract
More than 20 tonalitic to granodioritic plutonic domes, Oligo-Miocene in age, have intruded into the older volcanic rocks, in southeast of Urumieh- Dokhtar Magmatic Belt, northwest of Shahr-e-Babak. These rocks have granoporphyritic texture and consist of Phenocrysts of plagioclase, amphiboles and biotites. ...
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More than 20 tonalitic to granodioritic plutonic domes, Oligo-Miocene in age, have intruded into the older volcanic rocks, in southeast of Urumieh- Dokhtar Magmatic Belt, northwest of Shahr-e-Babak. These rocks have granoporphyritic texture and consist of Phenocrysts of plagioclase, amphiboles and biotites. The geochemical data show calc-alkaline affinities of these rocks , which formed in volcanic arc (I type) of an active continental margin. These data also show LILE and LREE enriched normalized multi-element patterns, and depleted of HFSE (Nb, Ta and Ti). Primitive mantle-normalized REE patterns display a dramatic decrease from LREE to HREE without any Eu anomaly. They have higher SiO2, Al2O3 and Sr content and Sr/Y and La/Yb ratios and lower MgO, Y and Yb contents than the normal calc-alkaline rocks, which reveal their adakitic characteristics. The high content of Sr, LREE enrichments, absente of Eu anomaly, HREE depletion, Y and Yb depletion pattern suggest the existence of garnet, amphibole and absence of plagioclase in the source rocks. Our data suggest that the plutons produced by partial melting of amphibole-eclogite or garnet-amphibolite, due to the subduction of Neotethys oceanic slab under the Central Iran continent.
M. E. Moslempour; M. Khalatbari-Jafari; T. Morishita; M. Ghaderi
Abstract
Mantle sequences exposed in west of Fannuj-Maskutan area comprise of lherzolite and porphyroclastic cpx-bearing harzburgite in the lower part and recrystallized fine-grained lherzolite with chromitite lenses in the upper parts of the sequence. Petrography studies and microprobe data show evidence ...
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Mantle sequences exposed in west of Fannuj-Maskutan area comprise of lherzolite and porphyroclastic cpx-bearing harzburgite in the lower part and recrystallized fine-grained lherzolite with chromitite lenses in the upper parts of the sequence. Petrography studies and microprobe data show evidence of melt/peridotite interactions, post-melting processes and subsolidus interactions associated with the appearance of two generations of deformed primary pyroxene-olivine and fine-grained pyroxene-olivine-amphibole neoblasts. Second generation of minerals formed as inclusion, interstitial and fine-grained. These two groups of minerals have different geochemical characteristics, i.e., the first group are comparable with abyssal peridotites and the second group are comparable to suprasubduction peridotites. Therefore, the chemical compositions of different generations of minerals show different petrogenesis for ultramafic rocks of the Fannuj-Maskutan ophiolitie complex. Interpretation of whole rock chemical data indicate that these rocks have a depleted MORB mantle source which underwent 5-15% partial melting. Rare earth element patterns normalized with chondrite standard values and compared with patterns of depleted MORB mantle (DMM), indicate enrichment in LREE/MREE ration and show U-shape patterns. Thus, the peridotites of the Fannuj-Maskutan ophiolitie have experienced multistage evolution and show characteristics of abyssal environment to suprasubduction zone. It might be said that transition from abyssal environment to suprasubduction has been affected by fluids derived from the subducted slab.
I. Monsef; M. Rahgoshay; M. H. Emami
Abstract
The Late Jurassic to Early Cretaceous Orzuieh volcanic sequence is exposed in the southern part of the Sanandaj – Sirjan Zone. Major and trace element geochemistry shows magma evolution from the transitional to the calc-alkaline series. Clinopyroxene compositions are similar to their composition ...
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The Late Jurassic to Early Cretaceous Orzuieh volcanic sequence is exposed in the southern part of the Sanandaj – Sirjan Zone. Major and trace element geochemistry shows magma evolution from the transitional to the calc-alkaline series. Clinopyroxene compositions are similar to their composition in subduction setting and support a volcanic arc related environment. REE and trace element diagrams show enrichment patterns in LREE relative to HREE and depletion in Nb and Ta elements. This magmatic sequence has been originated from the mantle source with effect of liquids and sediment resulted from the subducting slab. The Orzuieh volcanic sequence is probably originated during the subduction of the Neo-Tethyan Oceanic lithosphere under the Sanandaj – Sirjan Zone, during the Late Jurassic to Early Cretaceous time, in the volcanic arc tectonic environment.
