The major and trace elements and Sr-Nd-Pb isotopes of Miocene host granitoid rocks and their mafic microgranular enclaves（MMEs） were studied to understand the petrogenesis of MMEs in the Kashan complex, which is par...The major and trace elements and Sr-Nd-Pb isotopes of Miocene host granitoid rocks and their mafic microgranular enclaves（MMEs） were studied to understand the petrogenesis of MMEs in the Kashan complex, which is part of the Urumieh-Dokhtar magmatic belt（Iran）. The host rocks consist of quartz-diorite and tonalite associated with a dioritic intrusion. The enclaves show microgranular texture and the same mineralogy as their respective host with plagioclase, quartz and biotite. MMEs have a diorite to quartz-diorite composition and show geochemical characteristics mostly between their granitoid host and the diorite intrusion. Chondrite-normalized REE patterns of all samples are moderately fractionated [（La/Yb）N=2.1 to 12.9]. The MMEs display in part small negative Eu anomalies（Eu/Eu＊=0.54 to 0.99）, with enrichment of LILE and depletion of HFSE. The enclaves show emplacement depth of -4 to 6 km which is comparable with the host rocks. Moreover, the Hornblende-plagioclase equilibrium temprature of MMEs yields average temperatures of 795℃ which is slightly higher than the host ones. Identical mineral compositions and Nd-Sr-Pb isotopic features of MME-host granitoid pairs indicate interactions and parallel evolution of MME and enclosing granitoid in the Kashan plutons. Additionally, the geochemical and isotopic investigations of host and dioritic intrusions suggest a common source for their genesis. A thermal anomaly induced by underplated basic magma into a hot crust would have caused partial melting in the lower crust to generate Kashan granitoid rocks.展开更多
The KoheSiah Volcanoes are located in the North of Qorveh city in the west of Iran. The KoheSiah volcanoes include several craters bearing domes located in the Kordestan Province, between latitudes 35°23'...The KoheSiah Volcanoes are located in the North of Qorveh city in the west of Iran. The KoheSiah volcanoes include several craters bearing domes located in the Kordestan Province, between latitudes 35°23'13.54” to 35°21'26.63”N and longitudes 47°54'38.26”E to 47°56'01.42”E. Based on the petrographic and geochemical analysis, the volcanic rocks in the KoheSiah area are classified as basalt, Alkali basalt, trachy-andesites and mugearite. The studied samples are alkaline with sodic to potasic feature based on Na2O/K2O ratios and belonging to Shoshonite series. Most of the alkaline volcanic rocks in the study area fall in the field of within in plate basalts (WPB) and represent of a mantle metasomatism trend associated with variable degrees in the partial melting of an enriched mantle source.展开更多
Given special tectonic and climatic conditions, Iran has the most diverse land-forms and beautiful geological phenomena, which could attract many scientific, adventurous tourists and geological researchers. The presen...Given special tectonic and climatic conditions, Iran has the most diverse land-forms and beautiful geological phenomena, which could attract many scientific, adventurous tourists and geological researchers. The present study aims at studying and introducing wonderful geomorphological attractions and numerous geotourism potentials of very hot paradise of the earth, e.g. Dasht-e Lut of Iran, a desert which contains a collection of exclusive desert relieves and geological and geomorphological records of the world. Such unique perspectives as the biggest Nebkhas of the world, the largest Yardangs or Kaluts of the world, the hottest point of the earth, as well as rare species of desert structures such as salt marshes and salt polygons, Gandom Beryan Hill, massive sand dunes, Barchans, clay zones in pretty shapes, saline river , etc., present a vast and diverse extension of geographical beauties and phenomena of the desert. Using library studies, interpretation of satellite images and field studies, this study has been conducted. The results of the studies show that Lut Desert has considerable capability for carrying out complementary studies as well as effect on economic development process in national and international levels. In addition, geotourism development obstacles in Lut Desert are identified, and such solutions as development of ways for access to attractions, erection of geotourism development centers, advertisement and introduction of the desert's attractions, dispatch of guides with tourists, promotion of the region security, extension of accommodations and… for better use of the potentials of the desert, are provided. Furthermore, towards developing the region geotourism, some other fun and exciting activities such as sand skiing, racings and desert rallies, endurance cycling, sun bath, star observation, camel riding and so on, are suggested. Obviously, having various desert attractions and multiple geotourism potentials, Dasht-e Lut has the capability of being considered among global geoparks of UNESCO.展开更多
In the west and south-west part of Salafchegan near Zavarian village in Iran (in central Iranian volcano plotonic belt), there are some volcanic rocks. Based on petrography and geochemistry findings, these volcanic ro...In the west and south-west part of Salafchegan near Zavarian village in Iran (in central Iranian volcano plotonic belt), there are some volcanic rocks. Based on petrography and geochemistry findings, these volcanic rocks are Basalt, Andesite, Tracky-Andesite, Trackyte, Latite, Dacite. Tectono-magmatic diagram Y versus Zr shows the magmatic arc setting and Zr/TiO2 versus Ce/P2O5 diagram contrasts post colligenal magmatic arcs. The HFSE depletion in the MORB spider diagram shows significant volcanic arc magmatism. The high enrichment of Eu, Sr, Th, Rb, Cs, K (LFS elements) and Y, Zr, Hf shows negative anomaly and subduction tectonic setting. Based on MORB, Chondrite and primitive mantle spider diagrams, LREE have enriched to HREE in this area. The results of petrography, geochemistry and tectonic setting studies in this area, indicate that neogene magmatism occurred in post colligenal tectonic setting—subduction of Neo-thetise ocean under central Iranian plate in neogen era.展开更多
Kerman region where Sarcheshmeh zone is located includes the end part of Uremia-Dokhtar Zone. Extrusive igneous group in Sarcheshmeh is as follows: 1) andesite and 2) rhyodacite. The group of intrusive igneous rocks i...Kerman region where Sarcheshmeh zone is located includes the end part of Uremia-Dokhtar Zone. Extrusive igneous group in Sarcheshmeh is as follows: 1) andesite and 2) rhyodacite. The group of intrusive igneous rocks includes 1) porphyry granite, 2) porphyry granodiorite, and 3) porphyry diorite. Nochoon mine is located at 4 km of southwest of Sarcheshmeh copper mine and it comprises of a group of extrusive igneous rocks as follows: 1) andesite, and 2) dacite. Based on results of microprobe analysis, pyroxene mineral’s composition in these rocks of diopside and augite indicates amphiboles of composite zone of magnesium hosting type and existing plagioclases in regional rock for labradorite and bitonit composition. The most common compounds are chlorite with formula among antigorite and amosite. Comparison of magnetite mineralization in Sarcheshmeh and Nochoon indicates vein mineralization in Nochoon and disseminated granulation in Sarcheshmeh and particularly concerning to chalcopyrite, Nochoon includes more veins than Sarcheshmeh.展开更多
Oblique continent—continent collision between Iranian microcontinent and Arabian plate is the main cause of transpression and transtension regimes in this area. Zagros orogeny in this area resulted in formation of va...Oblique continent—continent collision between Iranian microcontinent and Arabian plate is the main cause of transpression and transtension regimes in this area. Zagros orogeny in this area resulted in formation of various structures including thrust fault-related folds, dextral and sinistral, strike slip faults, normal fault related to dextral strike slip fault. Thrust faults within the area under study are duplex with general trend of NW-SE and dip toward the north-east with right slip component. Strike slip fault regime acts as tear fault and it is active yet. Therefore, simultaneous presence of thrusts and strike slip faults illustrates convergent dextral transpressional tectonic regime while this transpressional regime accompanied with transtension as well;since normal faults are also seen in alluvium around depression of Sirjan which can be as a result of extension stresses due to strike slip faults activity of the district. The results achieved from geometry and kinematic analysis of west of Sirjan structures indicate that structures of the area have characteristics of internal part of Zagros orogeny.展开更多
This paper elucidates the compositional studies on clinopyroxene, plagioclase of basalts to andesitic rocks of Torud area to understand the geotectonic and geothermobarometry conditions.?Early?Eocene-Oligocene calc-al...This paper elucidates the compositional studies on clinopyroxene, plagioclase of basalts to andesitic rocks of Torud area to understand the geotectonic and geothermobarometry conditions.?Early?Eocene-Oligocene calc-alkaline volcanic rocks are exposed around Torud in the Central Iranian zone. Volcanic rocks consist of basaltic, andesite basalt, Tracyandesite, and andesite. Minerals in the volcanic rocks exhibit degrees of disequilibrium features. Plagioclase as dominant mineral in these rocks generally displays oscillatory zoning. Mineral chemistry studies show that clinopyroxenes in the volcanic rocks are diopside, augite and plotted in medium pressure field. The clinopyroxene composition yields the crystallization temperatures 900°C?- 1000°C. The mineral composition indicates that these rocks are formed in a tensional environment.展开更多
This paper studies on clinopyroxene, plagioclase of andesitic to dacite rocks of Nochun area to understand the geotectonic and geothermobarometry conditions. Eocene calc-alkaline volcanic rocks are exposed in Nochun t...This paper studies on clinopyroxene, plagioclase of andesitic to dacite rocks of Nochun area to understand the geotectonic and geothermobarometry conditions. Eocene calc-alkaline volcanic rocks are exposed in Nochun that are near the Sarcheshmeh cooper mine. Volcanic rocks consist of andesitic to dacite rocks. Minerals in the volcanic rocks exhibit degrees of disequilibrium features. Plagioclase as dominant mineral in these rocks generally displays oscillatory zoning;sieves or dusty, cores are usually Ca-rich. Petrographic evidence and varying anorthite content (10% to 90%) of plagioclase and temperature estimates of clinopyroxene indicated fractional crystallization condition later than hydrothermal alteration and partial metasomatism occurred. The varying content indicates that the parent’s magma was generated from subalkaline composition and then hydrothermal alteration affected phenocryst minerals and matrix of andesitic to dacite rocks. The equilibration temperatures of clinopyroxene showed (800°C - 1200°C). Thus, in mafic minerals development of sieve textures in plagioclase, reaction rims, zoning and heterogeneity of plagioclase phenocrysts, the resorbed and embayed phenocrysts, unique composition of clinopyroxene phenocrysts;support fractional crystallization at deep reservoir and high pressure condition as an important process in the evolution of these rocks.展开更多
The area which is being studied is located in northwest of Isfahan, 30 kilometers south of Kashan, and southern section of Qmasar. The longitude of the area of study is 51°19'13"E to 51°26'26&qu...The area which is being studied is located in northwest of Isfahan, 30 kilometers south of Kashan, and southern section of Qmasar. The longitude of the area of study is 51°19'13"E to 51°26'26"E and its latitude is 33°34'24"N to 33°44'24"N. Based on microscopic observations, modal analysis, and also based on their location in the Streckeisen [QAPF], both the stones of the Qohrud batholitic mass themselves and its enclaves are more in quartz monzonite ranges. Granitoid also have quartz monzonite enclaves. These enclaves are from both microgranular mafic and Autolith types which indicate the mixing of two magmas. At the center of the pluton, there are indications of existence of main magma reservoir and magma mixing. In terms of mineralogy, the granitoid rocks of the area very much resemble I-type. The zoning of the plagioclases is both the normal kind and variation invert and has andesine general composition. The probed biotite sample contains iron and belongs to a granitic sample from the center of the mass. Also, the ranking graph indicates biotite as the source of recrystallization for the analyzed points. The probed biotite sample of the Qohrud area showed formation temperature of 730 degrees centigrade. According to the Rb and Sr contents, the source of the rocks is at depths of 20 to 30 kilometers from the earth’s surface that are depending on the subduction zone. The formation temperature of the specimens of the Qohrud batholithic mass is mostly between 900 to 1000 degrees centigrade. [At] the center of the mass (around Qahrud), the amount of molybdenum is higher than the economic limit.展开更多
Granitoid pluton in the north of Golpayegan is located in10 kmnorth of Golpayegan at SanandajSirjan zone. Dominant rocks of this region include granite, syenite, and gabbro. Granite type is granular with medium to coa...Granitoid pluton in the north of Golpayegan is located in10 kmnorth of Golpayegan at SanandajSirjan zone. Dominant rocks of this region include granite, syenite, and gabbro. Granite type is granular with medium to coarse crystals and its mineralogical composition contains alkali feldspar + quartz + plagioclase + biotite + secondary minerals (opaque + sphene + apatite). Granite rocks have calc-alkaline and?metaluminous to peraluminous nature, relative enrichment of Rb over Sr, and relative enrichment of LILE over HFSE elements. These granites, which are type I, are derived from the melting of metagreywackes and their tectonic setting is of upper continental crust and post-orogenic setting. Gabbroic type is older than other types of the pluton and is granular with medium to fine crystal. Mineralogical composition of these rocks is plagioclase + pyroxene + amphibole + biotite + secondary minerals (opaque). Based on geochemical characteristics of tholeiitic and metaluminous nature, relative enrichment of Ba and Sr elements over Rb, relative enrichment of LILE elements over HFSE, negative anomaly of Nb, Ba, and Ta, and positive anomaly of Pb are observed. Origin of this type is probably from enriched mantle and in-plane tectonic setting.展开更多
文摘The major and trace elements and Sr-Nd-Pb isotopes of Miocene host granitoid rocks and their mafic microgranular enclaves（MMEs） were studied to understand the petrogenesis of MMEs in the Kashan complex, which is part of the Urumieh-Dokhtar magmatic belt（Iran）. The host rocks consist of quartz-diorite and tonalite associated with a dioritic intrusion. The enclaves show microgranular texture and the same mineralogy as their respective host with plagioclase, quartz and biotite. MMEs have a diorite to quartz-diorite composition and show geochemical characteristics mostly between their granitoid host and the diorite intrusion. Chondrite-normalized REE patterns of all samples are moderately fractionated [（La/Yb）N=2.1 to 12.9]. The MMEs display in part small negative Eu anomalies（Eu/Eu＊=0.54 to 0.99）, with enrichment of LILE and depletion of HFSE. The enclaves show emplacement depth of -4 to 6 km which is comparable with the host rocks. Moreover, the Hornblende-plagioclase equilibrium temprature of MMEs yields average temperatures of 795℃ which is slightly higher than the host ones. Identical mineral compositions and Nd-Sr-Pb isotopic features of MME-host granitoid pairs indicate interactions and parallel evolution of MME and enclosing granitoid in the Kashan plutons. Additionally, the geochemical and isotopic investigations of host and dioritic intrusions suggest a common source for their genesis. A thermal anomaly induced by underplated basic magma into a hot crust would have caused partial melting in the lower crust to generate Kashan granitoid rocks.
文摘The KoheSiah Volcanoes are located in the North of Qorveh city in the west of Iran. The KoheSiah volcanoes include several craters bearing domes located in the Kordestan Province, between latitudes 35°23'13.54” to 35°21'26.63”N and longitudes 47°54'38.26”E to 47°56'01.42”E. Based on the petrographic and geochemical analysis, the volcanic rocks in the KoheSiah area are classified as basalt, Alkali basalt, trachy-andesites and mugearite. The studied samples are alkaline with sodic to potasic feature based on Na2O/K2O ratios and belonging to Shoshonite series. Most of the alkaline volcanic rocks in the study area fall in the field of within in plate basalts (WPB) and represent of a mantle metasomatism trend associated with variable degrees in the partial melting of an enriched mantle source.
文摘Given special tectonic and climatic conditions, Iran has the most diverse land-forms and beautiful geological phenomena, which could attract many scientific, adventurous tourists and geological researchers. The present study aims at studying and introducing wonderful geomorphological attractions and numerous geotourism potentials of very hot paradise of the earth, e.g. Dasht-e Lut of Iran, a desert which contains a collection of exclusive desert relieves and geological and geomorphological records of the world. Such unique perspectives as the biggest Nebkhas of the world, the largest Yardangs or Kaluts of the world, the hottest point of the earth, as well as rare species of desert structures such as salt marshes and salt polygons, Gandom Beryan Hill, massive sand dunes, Barchans, clay zones in pretty shapes, saline river , etc., present a vast and diverse extension of geographical beauties and phenomena of the desert. Using library studies, interpretation of satellite images and field studies, this study has been conducted. The results of the studies show that Lut Desert has considerable capability for carrying out complementary studies as well as effect on economic development process in national and international levels. In addition, geotourism development obstacles in Lut Desert are identified, and such solutions as development of ways for access to attractions, erection of geotourism development centers, advertisement and introduction of the desert's attractions, dispatch of guides with tourists, promotion of the region security, extension of accommodations and… for better use of the potentials of the desert, are provided. Furthermore, towards developing the region geotourism, some other fun and exciting activities such as sand skiing, racings and desert rallies, endurance cycling, sun bath, star observation, camel riding and so on, are suggested. Obviously, having various desert attractions and multiple geotourism potentials, Dasht-e Lut has the capability of being considered among global geoparks of UNESCO.
文摘In the west and south-west part of Salafchegan near Zavarian village in Iran (in central Iranian volcano plotonic belt), there are some volcanic rocks. Based on petrography and geochemistry findings, these volcanic rocks are Basalt, Andesite, Tracky-Andesite, Trackyte, Latite, Dacite. Tectono-magmatic diagram Y versus Zr shows the magmatic arc setting and Zr/TiO2 versus Ce/P2O5 diagram contrasts post colligenal magmatic arcs. The HFSE depletion in the MORB spider diagram shows significant volcanic arc magmatism. The high enrichment of Eu, Sr, Th, Rb, Cs, K (LFS elements) and Y, Zr, Hf shows negative anomaly and subduction tectonic setting. Based on MORB, Chondrite and primitive mantle spider diagrams, LREE have enriched to HREE in this area. The results of petrography, geochemistry and tectonic setting studies in this area, indicate that neogene magmatism occurred in post colligenal tectonic setting—subduction of Neo-thetise ocean under central Iranian plate in neogen era.
文摘Kerman region where Sarcheshmeh zone is located includes the end part of Uremia-Dokhtar Zone. Extrusive igneous group in Sarcheshmeh is as follows: 1) andesite and 2) rhyodacite. The group of intrusive igneous rocks includes 1) porphyry granite, 2) porphyry granodiorite, and 3) porphyry diorite. Nochoon mine is located at 4 km of southwest of Sarcheshmeh copper mine and it comprises of a group of extrusive igneous rocks as follows: 1) andesite, and 2) dacite. Based on results of microprobe analysis, pyroxene mineral’s composition in these rocks of diopside and augite indicates amphiboles of composite zone of magnesium hosting type and existing plagioclases in regional rock for labradorite and bitonit composition. The most common compounds are chlorite with formula among antigorite and amosite. Comparison of magnetite mineralization in Sarcheshmeh and Nochoon indicates vein mineralization in Nochoon and disseminated granulation in Sarcheshmeh and particularly concerning to chalcopyrite, Nochoon includes more veins than Sarcheshmeh.
文摘Oblique continent—continent collision between Iranian microcontinent and Arabian plate is the main cause of transpression and transtension regimes in this area. Zagros orogeny in this area resulted in formation of various structures including thrust fault-related folds, dextral and sinistral, strike slip faults, normal fault related to dextral strike slip fault. Thrust faults within the area under study are duplex with general trend of NW-SE and dip toward the north-east with right slip component. Strike slip fault regime acts as tear fault and it is active yet. Therefore, simultaneous presence of thrusts and strike slip faults illustrates convergent dextral transpressional tectonic regime while this transpressional regime accompanied with transtension as well;since normal faults are also seen in alluvium around depression of Sirjan which can be as a result of extension stresses due to strike slip faults activity of the district. The results achieved from geometry and kinematic analysis of west of Sirjan structures indicate that structures of the area have characteristics of internal part of Zagros orogeny.
文摘This paper elucidates the compositional studies on clinopyroxene, plagioclase of basalts to andesitic rocks of Torud area to understand the geotectonic and geothermobarometry conditions.?Early?Eocene-Oligocene calc-alkaline volcanic rocks are exposed around Torud in the Central Iranian zone. Volcanic rocks consist of basaltic, andesite basalt, Tracyandesite, and andesite. Minerals in the volcanic rocks exhibit degrees of disequilibrium features. Plagioclase as dominant mineral in these rocks generally displays oscillatory zoning. Mineral chemistry studies show that clinopyroxenes in the volcanic rocks are diopside, augite and plotted in medium pressure field. The clinopyroxene composition yields the crystallization temperatures 900°C?- 1000°C. The mineral composition indicates that these rocks are formed in a tensional environment.
文摘This paper studies on clinopyroxene, plagioclase of andesitic to dacite rocks of Nochun area to understand the geotectonic and geothermobarometry conditions. Eocene calc-alkaline volcanic rocks are exposed in Nochun that are near the Sarcheshmeh cooper mine. Volcanic rocks consist of andesitic to dacite rocks. Minerals in the volcanic rocks exhibit degrees of disequilibrium features. Plagioclase as dominant mineral in these rocks generally displays oscillatory zoning;sieves or dusty, cores are usually Ca-rich. Petrographic evidence and varying anorthite content (10% to 90%) of plagioclase and temperature estimates of clinopyroxene indicated fractional crystallization condition later than hydrothermal alteration and partial metasomatism occurred. The varying content indicates that the parent’s magma was generated from subalkaline composition and then hydrothermal alteration affected phenocryst minerals and matrix of andesitic to dacite rocks. The equilibration temperatures of clinopyroxene showed (800°C - 1200°C). Thus, in mafic minerals development of sieve textures in plagioclase, reaction rims, zoning and heterogeneity of plagioclase phenocrysts, the resorbed and embayed phenocrysts, unique composition of clinopyroxene phenocrysts;support fractional crystallization at deep reservoir and high pressure condition as an important process in the evolution of these rocks.
文摘The area which is being studied is located in northwest of Isfahan, 30 kilometers south of Kashan, and southern section of Qmasar. The longitude of the area of study is 51°19'13"E to 51°26'26"E and its latitude is 33°34'24"N to 33°44'24"N. Based on microscopic observations, modal analysis, and also based on their location in the Streckeisen [QAPF], both the stones of the Qohrud batholitic mass themselves and its enclaves are more in quartz monzonite ranges. Granitoid also have quartz monzonite enclaves. These enclaves are from both microgranular mafic and Autolith types which indicate the mixing of two magmas. At the center of the pluton, there are indications of existence of main magma reservoir and magma mixing. In terms of mineralogy, the granitoid rocks of the area very much resemble I-type. The zoning of the plagioclases is both the normal kind and variation invert and has andesine general composition. The probed biotite sample contains iron and belongs to a granitic sample from the center of the mass. Also, the ranking graph indicates biotite as the source of recrystallization for the analyzed points. The probed biotite sample of the Qohrud area showed formation temperature of 730 degrees centigrade. According to the Rb and Sr contents, the source of the rocks is at depths of 20 to 30 kilometers from the earth’s surface that are depending on the subduction zone. The formation temperature of the specimens of the Qohrud batholithic mass is mostly between 900 to 1000 degrees centigrade. [At] the center of the mass (around Qahrud), the amount of molybdenum is higher than the economic limit.
文摘Granitoid pluton in the north of Golpayegan is located in10 kmnorth of Golpayegan at SanandajSirjan zone. Dominant rocks of this region include granite, syenite, and gabbro. Granite type is granular with medium to coarse crystals and its mineralogical composition contains alkali feldspar + quartz + plagioclase + biotite + secondary minerals (opaque + sphene + apatite). Granite rocks have calc-alkaline and?metaluminous to peraluminous nature, relative enrichment of Rb over Sr, and relative enrichment of LILE over HFSE elements. These granites, which are type I, are derived from the melting of metagreywackes and their tectonic setting is of upper continental crust and post-orogenic setting. Gabbroic type is older than other types of the pluton and is granular with medium to fine crystal. Mineralogical composition of these rocks is plagioclase + pyroxene + amphibole + biotite + secondary minerals (opaque). Based on geochemical characteristics of tholeiitic and metaluminous nature, relative enrichment of Ba and Sr elements over Rb, relative enrichment of LILE elements over HFSE, negative anomaly of Nb, Ba, and Ta, and positive anomaly of Pb are observed. Origin of this type is probably from enriched mantle and in-plane tectonic setting.
