F Sarjoughian; A Kananian; A Esna-Ashari; J Ahmadian
Abstract
The Kuh-e Dom intrusion with calc-alkaline nature, in the northeast of Ardestan is located in the central part of the Urumieh-Dokhtar Magmatic Arc and includes the felsic and intermediate-mafic units. The felsic unit consists of monzogranite, granodiorite, quartz monzonite and quartz monzodiorite, whereas ...
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The Kuh-e Dom intrusion with calc-alkaline nature, in the northeast of Ardestan is located in the central part of the Urumieh-Dokhtar Magmatic Arc and includes the felsic and intermediate-mafic units. The felsic unit consists of monzogranite, granodiorite, quartz monzonite and quartz monzodiorite, whereas the intermediate-basic rocks comprise gabbro, diorite, quartz diorite, monzodiorite and monzonite. The acidic dykes intruded this intrusion and its surrounding rocks. The various mafic microgranular enclaves of dioritic, quartz dioritic, monzodioritic and quartz monzodioritic composition exposed in the acidic rocks. The zircon U-Pb dating by the LA-ICP-MS method indicates that the ages of the felsic rocks, intermediate-mafic rocks, acidic dikes and enclaves are 51.1±0.4 Ma, 53.9±0.4 Ma, 49.95±0.64 Ma and 50.3±0.8 Ma respectively. These ages are in good agreement with the lower-middle Eocene age of the intrusive body, which is simultaneous with subduction of the Neotethys oceanic crust underneath the Central Iran. This result is in agreement with the previous geochemical result.
F Sarjoughian; A Kananian; J Ahmadian
Abstract
The alkali feldspars and plagioclases in the Kuh-e Dom intrusive rocks show compositionally and microtexturally zoning structure. The feldspar crystals in the various lithologies such as granite- granodiorite samples, diorite- gabbro samples and relatively high frequency microgranular mafic enclaves ...
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The alkali feldspars and plagioclases in the Kuh-e Dom intrusive rocks show compositionally and microtexturally zoning structure. The feldspar crystals in the various lithologies such as granite- granodiorite samples, diorite- gabbro samples and relatively high frequency microgranular mafic enclaves existing in the acidic intrusion were analyzed using electron microprobe. The results of the microprobe analysis in the acidic, basic- intermediate rocks and enclaves indicated the normal and reverse zoning in the samples. The chemical compositions of plagioclases ranges from albite (An 9.4) in the rim to labradorite (An: 50.6) in the core for acidic rocks, and from andesine (An: 30.5) in the rim to labradorite (An: 56.4) in the core for the basic- intermediate rocks, and from oligoclase (An: 19.8) to labradorite (An: 66.5) in the enclaves. The frequently of rare elements such as Ba, Sr, Fe and Mg in the feldspars show various and oscillatory patterns. The oscillatory pattern of the major and minor elements from core to rim in the feldspar crystals suggests an effective role of magma mixing phenomena in forming of the Kuh-e Dom intrusion.
K. Kalantari; A. Kananian; A. Asiabanha; M. Eliassi
Abstract
Paleogene basic to intermediate lava flows of Central Alborz, in the northeast of Qazvin city (Zarjebostan), include trachy-andesite, basaltic trachy-andesite and basaltic andesite. These volcanic rocks are high-K calc-alkaline rocks. Based on the high LILE/HFSE and LREE/HREE ratios ...
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Paleogene basic to intermediate lava flows of Central Alborz, in the northeast of Qazvin city (Zarjebostan), include trachy-andesite, basaltic trachy-andesite and basaltic andesite. These volcanic rocks are high-K calc-alkaline rocks. Based on the high LILE/HFSE and LREE/HREE ratios and their similar composition to subduction volcanic rock suites; it seems that they have formed in a subduction zone. The subduction process has little effect on the concentration of Zr, Ta, Hf, Sm, Tb, Nd, Eu and Y elements, while it has strong influence on concentration of Th, U and La elements. Due to high Ba/La, Ba/Ta and La/Ta ratios and low TiO2 content of lavas, they could be attributed to magmatic arc setting. Th/Yb vs. Ta/Yb diagrams and association of study suite with extensive volume of acidic tuffs, indicate that these rocks have been formed in an active continental margin.
M. Mirmohammadi; A. Kananian
Abstract
Qareaghaj mafic-ultramafic intrusion (QMUI) is located in northwest Iran, 36 km NW from Urmia city. The QUMI is composed mainly of non-mineralized mafic and Fe-Ti-P-rich ultramafic rocks (FTP). The mafic rocks, mainly coarse-grained gabbro, microgabbro, metagabbro and ortho-amphibolite, ...
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Qareaghaj mafic-ultramafic intrusion (QMUI) is located in northwest Iran, 36 km NW from Urmia city. The QUMI is composed mainly of non-mineralized mafic and Fe-Ti-P-rich ultramafic rocks (FTP). The mafic rocks, mainly coarse-grained gabbro, microgabbro, metagabbro and ortho-amphibolite, have simple mineral assemblage (plg + cpx + ilm). Based on field observations, petrography and geochemistry, they are directly related to each other (comagmatic). The FTP forms numerous layers and sill-like bodies, ranging in thickness from ~5cm to several meters. These rocks with high proportions of olivine, apatite, ilmenite and magnetite, show unusual bulk composition (e.g., SiO2~21-30 wt%, Fe2O3t ~ 26-42 wt%, TiO2~5-11 wt%, MgO~9-20 wt%, P2O5 up to 5.1 wt%, Cr~40-160 ppm, Ni~7-73ppm, ∑REE~10-340ppm). The FTP totally included by mafic rocks with sharp and concordant contact shows magmatic lamination and follows general NW-SE trend of the QMUI. Field relationship, petrography and geochemical data suggest that the FTP is not related to mafic host rocks and indeed intruded later into gabbros during plastic, high temperature deformation in local shear zone.
A. Kananian; M. Rezaei-Kahkhaei; D. Esmaeili
Abstract
The Lakhshak granitoid pluton which is located at 10 km northwest of Zahedan, has intruded into the Eocene flysch sediments with an elliptical shape and NW-SE direction. This pluton after emplacement has been cut by numerous dykes with NE-SW trend. These dykes comprised about ...
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The Lakhshak granitoid pluton which is located at 10 km northwest of Zahedan, has intruded into the Eocene flysch sediments with an elliptical shape and NW-SE direction. This pluton after emplacement has been cut by numerous dykes with NE-SW trend. These dykes comprised about 20-30% of the Pluton with various compositions, ranging from granodiorite to monzodiorite in composition.
The Lakhshak plutonic rocks are mainly metaluminous, calc-alkaline and belong to I type granites based on the P2O5 and Th content versus SiO2. Regarding TiO2 content these rocks resemble the continental margin granites. The MgO, Na2O, Ni, Cr content as well as Mg# and depletion in Y, these plutonic rocks are similar to the adakite, a rock type produced by partial melting of young oceanic crust. The low Ba/La content of the studied samples may suggest that subducted slab suffered dehydration prior to partial melting.
These rocks are enriched in LIL, LREE, however, they are depleted in HREE and Y. In addition, they show negative anomalies of Nb, Ta, P and Ti, and positive anomaly of Pb. The negative anomalies of Nb and Ta may indicate the effect of mantle wedge metasomatism by oceanic crust. The positive anomaly of Pb may demonstrate continental crust assimilation by magma associated with mantle metasomatism.
It seems that Lakshak pluton has been formed by subduction of Sistan young oceanic crust under the Afghan Block. Moreover, the low content of HREE and Y besides a decreased ratio of Yb versus SiO2, Y<15.13, Yb<1.2 and existence of amphibolite enxenoliths in these rocks may suggest partial melting of amphibolites. The latter is formed during the oceanic crust subduction in depth more than 35 km.
