Recent geological study and survey on the scale of 1: 50000 in northern Guangxi have made some advancements: meta-basic-ultrabasic rocks which occured as bedding injection sheets in the Sanrnenjie formation of the Pro...Recent geological study and survey on the scale of 1: 50000 in northern Guangxi have made some advancements: meta-basic-ultrabasic rocks which occured as bedding injection sheets in the Sanrnenjie formation of the Proterozoic Danzhou group and caused contact metamorphism or hydrothermal alteration in adjacent wallrocks, were originated in extensional environment. Basic rocks belong to deep-sea tholeiite. TLe meta-basic -ultrabasic rocks sufferred intense deformation partitioning, resulting in lenticular network which was composed of mylonite zones in highly de formed field and lensoids in less- or non-deformed field. This structural pattern was explained as "melange" or "non-rooted cool intrusion " by previous workers. The deformation partitioning was mainly pure shearing in the early stage plus simple shearing in the later stage. This evolution was closely related to progressive deformation of the Guangxi orogeny.展开更多
Recently discovered intermediate-basic volcanic rocks in the Devonian strata at Dachang, Guangxi Zhuang Autonomous Region are dominated by basalts and andesites. Most of them belong to the calc-alkali and alkali serie...Recently discovered intermediate-basic volcanic rocks in the Devonian strata at Dachang, Guangxi Zhuang Autonomous Region are dominated by basalts and andesites. Most of them belong to the calc-alkali and alkali series. Petrology and geochemistry data indicate that the volcanic rocks may be formed in a continental rift environment. The volcanic rocks are in conformable contact with the overlying and underlying wall rocks, with such typical sedimentary structures as laminated and striped ones, and the host rocks of the volcanic rocks contain lots of marine fossils such as tentaculite. Many pieces of evidence indicate that the eruption environment of the volcanic rocks is a sea-facies one. The volcanic rocks are of the LREE-enrichment type, with high ratios of light rare-earth elements to heavy rare-earth elements. In addition, they display moderately negative δEu anomalies and moderately negative δCe anomalies with a higher degree of LREE and HREE fractionation. Through the Q-cluster analysis of the REE samples, it is indicated that the ores have a closer relation with the layered volcanic rocks, and also possess a certain inheritance-consistency relationship with the layered volcanic rocks. The source of ore-forming materials may be related with volcanism. It is proposed that the ore deposit in the study area should be genetically explained as the result of marine volcano-sedimentary exhalation of hot water and late superposition-reworking.展开更多
The meta-basic volcanic rocks in the Tengtiaohe Zone yield zircon U–Pb ages of 258.8±2.5 Ma and 259.2±1.8 Ma, respectively which agree with the ages of flood basalts of ELIP and are similar to the basaltic ...The meta-basic volcanic rocks in the Tengtiaohe Zone yield zircon U–Pb ages of 258.8±2.5 Ma and 259.2±1.8 Ma, respectively which agree with the ages of flood basalts of ELIP and are similar to the basaltic rocks and komatiites from the Song Da Zone in northern Vietnam. The results suggest that the age of meta-basic volcanic rocks is Late Permian, rather than the Early Permian or Early Carboniferous ages as previously inferred. Most meta-basic volcanic rocks are strongly enriched in LREEs relative to HREEs and display trace element patterns similar to the ELIP high-Ti basalts, and are enriched in LILEs with negative Sr anomalies. Their initial 87^Sr/86^Sr ratios range from 0.705974 to 0.706188 and εNd（t） from-0.82 to-2.11. Their magmas were derived from an enriched and deep mantle source without significant crustal contamination. These meta-basic volcanic rocks formed in ELIP. Therefore, the Tengtiaohe Zone is not an ophiolite zone and can link to the Song Da Zone in northern Vietnam.展开更多
A large number of basic dikes, which indicate an important tectonic-magmatic event in the eastern part of the Central Qilian （祁连） orogenic belt, were found from Maxianshan （马衔山） rock group, Yongjing （永靖） ...A large number of basic dikes, which indicate an important tectonic-magmatic event in the eastern part of the Central Qilian （祁连） orogenic belt, were found from Maxianshan （马衔山） rock group, Yongjing （永靖） county, Gansu （甘肃） Province, China. According to the research on the characteristics of geology and petrology, the basic dike swarms, widely intruded in Maxianshan rock group, are divided into two phases by the authors. U-Pb isotope of zircons from the basic dikes above two phases is separately determined by LA-ICP-MS in the Key Laboratory of Continental Dynamics of Northwest University, China and the causes of formation of the zircons are studied using CL images. The formation age of the earlier phase of metagabbro dikes is （441.1±1.4） Ma （corresponding to the early stage of Early Silurian）, and the age of the main metamorphic period is （414.3±1.2） Ma （corresponding to the early stage of Early Devonian）. The formation age of the later phase of diabase dike swarms is （434±1.0） Ma （corresponding to the late stage of Early Silurian）. The cap- tured-zircons from diabase dike swarms saved some information of material interfusion by Maxianshan rock group （^207pb/206pb apparent ages are （2 325±3）-（2 573 ±6） Ma）, and some zircons from diabase dike swarms also saved impacted information by tectonic thermal event during the late period of Caledonian movement （^206pb/^238U apparent ages are （400±2）-（429±2） Ma）. By combining the results of the related studies, the basic dikes within Maxianshan rock group were considered to be formed in the transfer period, from subductional orogeny towards collisional orogeny, which represents geological records of NW-SE extension during regional NE-SW towards intense compression in the Central Qilian block.展开更多
The geochemistry of the basic volcanic rocks at the south margin of the Qinling orogenic belt (SMQOB) suggests that they were formed in an intraplate tectonic setting. The REE distribution patterns show these rocks ar...The geochemistry of the basic volcanic rocks at the south margin of the Qinling orogenic belt (SMQOB) suggests that they were formed in an intraplate tectonic setting. The REE distribution patterns show these rocks are strongly enriched in LREE with high ΣREE, and their trace elements geochemistry is similar to that of continental flood basalt. All the above evidence suggests that the Caledonian basic volcanic rocks in the SMQOB were tholeiitic basalts formed in an intraplate spreading initial rift tectonic setting. The characteristics of regional geology and geochemistry indicate that there was an intraplate spreading rift tectonic setting between the South Qinling block and the Yangtze block in the Caledonian epoch. The dynamic spreading in this district began in the Early Caledonian and then the intraplate spreading initial rifts were formed in the Late Caledonian. As a result of spreading of the Tethys and geodynamic processes in deep mantle, the Mianlue Huashan oceanic basin was formed between the Qinling block and the Yangtze block in Devonian, and the Qinling microplate was separated from the northern part of the Yangtze plate.展开更多
Based on thermal simulation experiment, interactions between volcanic fluids and source rocks were studied. Gas generations in the dry system and fluid system under different temperatures were analyzed. The results sh...Based on thermal simulation experiment, interactions between volcanic fluids and source rocks were studied. Gas generations in the dry system and fluid system under different temperatures were analyzed. The results showed that the various types of source rocks are similar in composition, containing gaseous C1-C5 hydrocarbons, H2 and CO2 whose gas yields increase with increasing temperature. The gas yield of source rocks of type is Ⅰ the highest, followed by type Ⅱ, and that of source rocks of type is Ⅲ the lowest, indicating that the yield of hydrocarbon gases is related to their hydrocarbon generating potential. Although the generating potential of type is Ⅲ the lowest, it can still be regarded as a useful gas source when it is buried deeply enough. The basic volcanic fluid restrains the generation of gaseous hydrocarbons in different types of source rocks, but promotes the generation of inorganic gases.展开更多
As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element ...As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-NdPb isotopic composition data are presented for volcanic rocks from the Iheya Ridge（IR）, the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in ^87Sr/^86Sr（0.703 862–0.704 884）, ^144Nd/^143Nd（0.512 763–0.512 880） and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle（DM） but extends to the enriched mantle（EMII）, indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts.展开更多
文摘Recent geological study and survey on the scale of 1: 50000 in northern Guangxi have made some advancements: meta-basic-ultrabasic rocks which occured as bedding injection sheets in the Sanrnenjie formation of the Proterozoic Danzhou group and caused contact metamorphism or hydrothermal alteration in adjacent wallrocks, were originated in extensional environment. Basic rocks belong to deep-sea tholeiite. TLe meta-basic -ultrabasic rocks sufferred intense deformation partitioning, resulting in lenticular network which was composed of mylonite zones in highly de formed field and lensoids in less- or non-deformed field. This structural pattern was explained as "melange" or "non-rooted cool intrusion " by previous workers. The deformation partitioning was mainly pure shearing in the early stage plus simple shearing in the later stage. This evolution was closely related to progressive deformation of the Guangxi orogeny.
基金financially supported by the Applied Basic Research Projects(General Program)of Yunnan Province(2011FB015)
文摘Recently discovered intermediate-basic volcanic rocks in the Devonian strata at Dachang, Guangxi Zhuang Autonomous Region are dominated by basalts and andesites. Most of them belong to the calc-alkali and alkali series. Petrology and geochemistry data indicate that the volcanic rocks may be formed in a continental rift environment. The volcanic rocks are in conformable contact with the overlying and underlying wall rocks, with such typical sedimentary structures as laminated and striped ones, and the host rocks of the volcanic rocks contain lots of marine fossils such as tentaculite. Many pieces of evidence indicate that the eruption environment of the volcanic rocks is a sea-facies one. The volcanic rocks are of the LREE-enrichment type, with high ratios of light rare-earth elements to heavy rare-earth elements. In addition, they display moderately negative δEu anomalies and moderately negative δCe anomalies with a higher degree of LREE and HREE fractionation. Through the Q-cluster analysis of the REE samples, it is indicated that the ores have a closer relation with the layered volcanic rocks, and also possess a certain inheritance-consistency relationship with the layered volcanic rocks. The source of ore-forming materials may be related with volcanism. It is proposed that the ore deposit in the study area should be genetically explained as the result of marine volcano-sedimentary exhalation of hot water and late superposition-reworking.
基金supported by National Natural Science Foundation of China(Grant No.41172202,No.41190073 and No.41302178)China Geological Survey(Grant No.1212011121256)+2 种基金National Basic Research Program of China(2014CB440901)the Fundamental Research Funds for the Central Universities to SYSUState Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences in Wuhan(MSFGPMR201402)
文摘The meta-basic volcanic rocks in the Tengtiaohe Zone yield zircon U–Pb ages of 258.8±2.5 Ma and 259.2±1.8 Ma, respectively which agree with the ages of flood basalts of ELIP and are similar to the basaltic rocks and komatiites from the Song Da Zone in northern Vietnam. The results suggest that the age of meta-basic volcanic rocks is Late Permian, rather than the Early Permian or Early Carboniferous ages as previously inferred. Most meta-basic volcanic rocks are strongly enriched in LREEs relative to HREEs and display trace element patterns similar to the ELIP high-Ti basalts, and are enriched in LILEs with negative Sr anomalies. Their initial 87^Sr/86^Sr ratios range from 0.705974 to 0.706188 and εNd（t） from-0.82 to-2.11. Their magmas were derived from an enriched and deep mantle source without significant crustal contamination. These meta-basic volcanic rocks formed in ELIP. Therefore, the Tengtiaohe Zone is not an ophiolite zone and can link to the Song Da Zone in northern Vietnam.
基金This paper is supported by the China Geological Survey (No. 1212010510416)
文摘A large number of basic dikes, which indicate an important tectonic-magmatic event in the eastern part of the Central Qilian （祁连） orogenic belt, were found from Maxianshan （马衔山） rock group, Yongjing （永靖） county, Gansu （甘肃） Province, China. According to the research on the characteristics of geology and petrology, the basic dike swarms, widely intruded in Maxianshan rock group, are divided into two phases by the authors. U-Pb isotope of zircons from the basic dikes above two phases is separately determined by LA-ICP-MS in the Key Laboratory of Continental Dynamics of Northwest University, China and the causes of formation of the zircons are studied using CL images. The formation age of the earlier phase of metagabbro dikes is （441.1±1.4） Ma （corresponding to the early stage of Early Silurian）, and the age of the main metamorphic period is （414.3±1.2） Ma （corresponding to the early stage of Early Devonian）. The formation age of the later phase of diabase dike swarms is （434±1.0） Ma （corresponding to the late stage of Early Silurian）. The cap- tured-zircons from diabase dike swarms saved some information of material interfusion by Maxianshan rock group （^207pb/206pb apparent ages are （2 325±3）-（2 573 ±6） Ma）, and some zircons from diabase dike swarms also saved impacted information by tectonic thermal event during the late period of Caledonian movement （^206pb/^238U apparent ages are （400±2）-（429±2） Ma）. By combining the results of the related studies, the basic dikes within Maxianshan rock group were considered to be formed in the transfer period, from subductional orogeny towards collisional orogeny, which represents geological records of NW-SE extension during regional NE-SW towards intense compression in the Central Qilian block.
文摘The geochemistry of the basic volcanic rocks at the south margin of the Qinling orogenic belt (SMQOB) suggests that they were formed in an intraplate tectonic setting. The REE distribution patterns show these rocks are strongly enriched in LREE with high ΣREE, and their trace elements geochemistry is similar to that of continental flood basalt. All the above evidence suggests that the Caledonian basic volcanic rocks in the SMQOB were tholeiitic basalts formed in an intraplate spreading initial rift tectonic setting. The characteristics of regional geology and geochemistry indicate that there was an intraplate spreading rift tectonic setting between the South Qinling block and the Yangtze block in the Caledonian epoch. The dynamic spreading in this district began in the Early Caledonian and then the intraplate spreading initial rifts were formed in the Late Caledonian. As a result of spreading of the Tethys and geodynamic processes in deep mantle, the Mianlue Huashan oceanic basin was formed between the Qinling block and the Yangtze block in Devonian, and the Qinling microplate was separated from the northern part of the Yangtze plate.
基金financially supported by the National Basic Research Program of China(973 Program)(No.2009CB219306)
文摘Based on thermal simulation experiment, interactions between volcanic fluids and source rocks were studied. Gas generations in the dry system and fluid system under different temperatures were analyzed. The results showed that the various types of source rocks are similar in composition, containing gaseous C1-C5 hydrocarbons, H2 and CO2 whose gas yields increase with increasing temperature. The gas yield of source rocks of type is Ⅰ the highest, followed by type Ⅱ, and that of source rocks of type is Ⅲ the lowest, indicating that the yield of hydrocarbon gases is related to their hydrocarbon generating potential. Although the generating potential of type is Ⅲ the lowest, it can still be regarded as a useful gas source when it is buried deeply enough. The basic volcanic fluid restrains the generation of gaseous hydrocarbons in different types of source rocks, but promotes the generation of inorganic gases.
基金The National Basic Research Program(973 Program)of China under contract No.2013CB429700the National Natural Science Foundation of China under contract Nos 41325021 and 41706052+9 种基金the National Program on Global Change and AirSea Interaction under contract No.GASI-GEOGE-02the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11030302the Special Fund for the Taishan Scholar Program of Shandong Province under contract No.ts201511061the AoShan Talents Program supported by Qingdao National Laboratory for Marine Science and Technology under contract No.2015ASTP-0S17the Innovative Talent Promotion Program under contract No.2012RA2191the Science and Technology Development Program of Shandong Province under contract No.2013GRC31502the Scientific and Technological Innovation Project Financially supported by Qingdao National Laboratory for Marine Science and Technology under contract Nos 2015ASKJ03 and2016ASKJ13the National High Level Talent Special Support Programthe CAS/SAFEA International Partnership Program for Creative Research TeamsQingdao Collaborative Innovation Center of Marine Science and Technology
文摘As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-NdPb isotopic composition data are presented for volcanic rocks from the Iheya Ridge（IR）, the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in ^87Sr/^86Sr（0.703 862–0.704 884）, ^144Nd/^143Nd（0.512 763–0.512 880） and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle（DM） but extends to the enriched mantle（EMII）, indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts.
