The mafic intrusive Moskin and Parvaneh regions in the northwest and south of Urmia were investigated for their geochemistry and petro-physical properties such as size,shape,and spatial distribution of their crystals....The mafic intrusive Moskin and Parvaneh regions in the northwest and south of Urmia were investigated for their geochemistry and petro-physical properties such as size,shape,and spatial distribution of their crystals.This type of study can be a powerful tool for analyzing the history of magma crystallization,along with geochemistry examinations.The gabbroic calc-alkaline rocks,with the Early Cenozoic is the relative age,consist of coarse plagioclase and amphibole with rare clinopyroxene and olivine in the Sanandaj-Sirjan zone at sedimentary-structural subdivisions of Iran.The depletion of HFSEs and enrichment of LILEs as arc-related rocks,as well as lower crust contamination(Nb/Th and K/Ce)symptoms,show that these gabbros formed at the continental arc setting from an enriched source.Considering the geographical position and relative age of the gabbros,they possibly outcropped during the Neo-Tethys subduction processes after the enrichment by considerably lower crust effects.The amphibole and plagioclase crystals with considerable abundance show linear crystal size distribution(CSD)patterns with a slope of(-1/Gt)-3 to-4 for amphiboles and plagioclase except for Parvaneh plagioclase which shows-16.The annealing(Ostwald ripening)caused the convex CSD on the small grains part at Parvaneh gabbro.Therefore,the ratio of nucleation to growth rates(J/G)for these minerals is 5-6 times,only for Parvaneh plagioclase is ten times which numerous nuclei were made by a significant degree of overstepping in the rocks.There is no magma mixing evidence because of the linear(one population of crystals)CSD patterns.The shape of amphibole crystals in gabbros is bladed(with S/I=0.4-0.5 and I/L=0.1-0.3)and bladed to tabular for plagioclase(S/I=0.4 and I/L=0.6-0.7).The spatial distribution patterns(SDPs)are calculated from a big R-value based on the nearest neighbor’s theory for amphibole and plagioclase crystals,confirming clustered SDP for all of them.Also,the dihedral angle measurements(between amphibole and plagioclase grains)display that solid-state equilibrium is prevailing in the rocks.In this study,we tried to establish a relationship between geochemistry and petro-physical results and investigate the evolution of igneous rocks more accurately and all-inclusive.We should not neglect the importance of quantifying the texture of rocks.展开更多
The Gysian ophiolite of NW Iran is located at the intersection of the ophiolite belts of SE Turkey,NE Iraq,and Iran,and provides the opportunity to investigate the preserved subduction and obduction history of an impo...The Gysian ophiolite of NW Iran is located at the intersection of the ophiolite belts of SE Turkey,NE Iraq,and Iran,and provides the opportunity to investigate the preserved subduction and obduction history of an important tectonic site that has not previously been studied.The serpentinized peridotites of the Gysian ophiolite contain the assemblagelizardite+chrysotile+spinel/Mg-spinelwith relict clinopyroxene(diopside)and very rare relict orthopyroxene and olivine.The compositions of clinopyroxenes and spinels are more consistent with the formation of the inferred protolithharzburgitesinafore-arcorsupra-subduction zone instead of an abyssal environment.The Gysian ophiolite is a remnant of the Neo-Tethyan arc-ophiolitic system and records shallow subduction(<50 km,indicated by the absence of antigorite)in the Late Cretaceous to Paleocene beforeobductionalongthrustfaultsoverthecontinental margin.We review the spatial trends of the metamorphic grade of the Neo-Tethyan ophiolites in this region and provide detailed information about the petrology and mineral chemistry of the Gysian ophiolite.展开更多
基金financial support from the Natural Science Foundation of Urmia University。
文摘The mafic intrusive Moskin and Parvaneh regions in the northwest and south of Urmia were investigated for their geochemistry and petro-physical properties such as size,shape,and spatial distribution of their crystals.This type of study can be a powerful tool for analyzing the history of magma crystallization,along with geochemistry examinations.The gabbroic calc-alkaline rocks,with the Early Cenozoic is the relative age,consist of coarse plagioclase and amphibole with rare clinopyroxene and olivine in the Sanandaj-Sirjan zone at sedimentary-structural subdivisions of Iran.The depletion of HFSEs and enrichment of LILEs as arc-related rocks,as well as lower crust contamination(Nb/Th and K/Ce)symptoms,show that these gabbros formed at the continental arc setting from an enriched source.Considering the geographical position and relative age of the gabbros,they possibly outcropped during the Neo-Tethys subduction processes after the enrichment by considerably lower crust effects.The amphibole and plagioclase crystals with considerable abundance show linear crystal size distribution(CSD)patterns with a slope of(-1/Gt)-3 to-4 for amphiboles and plagioclase except for Parvaneh plagioclase which shows-16.The annealing(Ostwald ripening)caused the convex CSD on the small grains part at Parvaneh gabbro.Therefore,the ratio of nucleation to growth rates(J/G)for these minerals is 5-6 times,only for Parvaneh plagioclase is ten times which numerous nuclei were made by a significant degree of overstepping in the rocks.There is no magma mixing evidence because of the linear(one population of crystals)CSD patterns.The shape of amphibole crystals in gabbros is bladed(with S/I=0.4-0.5 and I/L=0.1-0.3)and bladed to tabular for plagioclase(S/I=0.4 and I/L=0.6-0.7).The spatial distribution patterns(SDPs)are calculated from a big R-value based on the nearest neighbor’s theory for amphibole and plagioclase crystals,confirming clustered SDP for all of them.Also,the dihedral angle measurements(between amphibole and plagioclase grains)display that solid-state equilibrium is prevailing in the rocks.In this study,we tried to establish a relationship between geochemistry and petro-physical results and investigate the evolution of igneous rocks more accurately and all-inclusive.We should not neglect the importance of quantifying the texture of rocks.
基金The current work is financially supported by Urmia University research branch。
文摘The Gysian ophiolite of NW Iran is located at the intersection of the ophiolite belts of SE Turkey,NE Iraq,and Iran,and provides the opportunity to investigate the preserved subduction and obduction history of an important tectonic site that has not previously been studied.The serpentinized peridotites of the Gysian ophiolite contain the assemblagelizardite+chrysotile+spinel/Mg-spinelwith relict clinopyroxene(diopside)and very rare relict orthopyroxene and olivine.The compositions of clinopyroxenes and spinels are more consistent with the formation of the inferred protolithharzburgitesinafore-arcorsupra-subduction zone instead of an abyssal environment.The Gysian ophiolite is a remnant of the Neo-Tethyan arc-ophiolitic system and records shallow subduction(<50 km,indicated by the absence of antigorite)in the Late Cretaceous to Paleocene beforeobductionalongthrustfaultsoverthecontinental margin.We review the spatial trends of the metamorphic grade of the Neo-Tethyan ophiolites in this region and provide detailed information about the petrology and mineral chemistry of the Gysian ophiolite.
