The Wenyu copper polymetallic deposit, with proven reserves of about 0.23 Mt Cu, 394 t Ag and 0.04 Mt Pb, is located in the central part of the Lancangjiang volcanic rock belt （Fig. l a）, which is one of the most po...The Wenyu copper polymetallic deposit, with proven reserves of about 0.23 Mt Cu, 394 t Ag and 0.04 Mt Pb, is located in the central part of the Lancangjiang volcanic rock belt （Fig. l a）, which is one of the most potential copper polymetallic exploration areas in SW China.展开更多
In view of the importance of mafic dyke swarms and their contribution to current scientific problems relating to South China,herein,we present the findings of studies on twenty–five representative mafic dykes croppin...In view of the importance of mafic dyke swarms and their contribution to current scientific problems relating to South China,herein,we present the findings of studies on twenty–five representative mafic dykes cropping out in Hunan Province and Guangxi Zhuang Autonomous Region,within the southern Wuling Mountain gravity lineament,China.These results include new zircon LA-ICP-MS U-Pb age,whole rock geochemical,Sr-Nd-Pb isotopic,and zircon Hf isotopic data for these dykes.The dykes formed between 131.5±1.2 and 121.6±1.1 Ma,and have typical doleritic textures.They fall into the alkaline and shoshonitic series,are enriched in light rare earth elements(LREE),some large ion lithophile elements(LILE;e.g.,Rb,Ba,and Sr),Th,U,and Pb,and are depleted in Nb,Ta,Hf,and Ti.Moreover,the dolerites have high initial 87 Sr/86 Sr ratios(0.7055–0.7057),negativeεNd(t)and zirconεHf(t)values(-14.8 to-11.9,-30.4 to-14.9),and relatively constant initial Pb isotopic ratios(that are EM1-like,16.77–16.94,15.43–15.47,and 36.84–36.92 for 206 Pb/204 Pb,207 Pb/204 Pb,and 208 Pb/204 Pb,respectively).These results indicate that the dykes were likely derived from magma generated through low-degree partial melting(1.0%–10%)of an EM1-like garnet–lherzolite mantle source.The parental magmas fractionated olivine,clinopyroxene,plagioclase,and Ti-bearing phases with negligible crustal contamination,during ascent and dyke emplacement.Several possible models have been proposed to explain the origin of Mesozoic magmatism along the Wuling Mountain gravity lineament.Herein we propose a reasonable model for the origin of these mafic dykes,involving the collision between the paleo-Pacific Plate and South China,which led to subsequent lithospheric extension and asthenosphere upwelling,resulting in partial melting the underlying mantle lithosphere in the Early Cretaceous,to form the parental magmas to the WMGL mafic dykes,as studied.展开更多
The contents of major element composition of the phenocrysts and the matrix glass as well as the spinel inclusions and the melt inclusion in the phenocrysts of the basalt dredged from Station 133 of the Okinawa Trough...The contents of major element composition of the phenocrysts and the matrix glass as well as the spinel inclusions and the melt inclusion in the phenocrysts of the basalt dredged from Station 133 of the Okinawa Trough are determined by electron microprobe. The results show that the basalt is a dor- galite consisting of phenocrysts of bytownite, chrysolite, clinopyroxene and magnetite as well as labradorite microcrystal, matrix glass and a few bits of broken vein quartz. Glassy melt inclusion and chromohercynite or chrompleonaste exist in bytownite and chrysolite. The formation of the spinels is re- lated to partial melting of mantle. The melt inclusions stand for a primary alkali dorgalitic magma, whose composition corresponds to olivine gabbro. The basaltic magma was generated from partial melting of spinel-lherzolite of the upper mantle and evolved in a process of 'alkali dorgalitic magma-trachy- basaltic magma-basdaltic trachytic magma-trachytic magma'. Assimilation and hybridization of crustal material may exist during magma upwelling in every evolutionary stage.展开更多
Coronitic microstructures have been used to interpret the late-stage solidification history of igneous rocks and to constrain the corresponding chemical and/or physical changes.Coronas with three shells were also reco...Coronitic microstructures have been used to interpret the late-stage solidification history of igneous rocks and to constrain the corresponding chemical and/or physical changes.Coronas with three shells were also recognized in the Miaowan olivine norite,Yangtze Craton,South China.In our study,orthopyroxene intergrowth with vermicular magnetite in the inner shell is in optical continuity with magnetite-free orthopyroxene in the middle shell.In the outer shell of brown amphibole remaining magnetite-free orthopyroxene inclusions sporadically occur.Meanwhile Mg#values of orthopyroxene(76–80)in the inner and middle shells are basically consistent with olivine(78–81).In this paper,we propose a multi-stage genetic model for the formation of coronas in the Miaowan olivine norite.In the first stage,the magnetite-free orthopyroxene shell formed through reaction between primocrystal olivine with the residual Si-rich melt at 990–1053℃and 6.2–6.5 kbar.In the second stage,the orthopyroxene-magnetite symplectite shell formed when primocrystal olivine reacted with the late-stage residual Fe-rich melt promoted by high oxygen fugacity condition at 927–1035℃and 6.0–6.5 kbar.In the third stage,the brown amphibole shell formed as the presence of residual hydrous melt and replaced the middle shell at 821–900℃and 5.5–6.0 kbar.展开更多
基金financially supported by the China State Mineral Resources Investigation Program (Grant No.12120114013701 and 1212011120608)
文摘The Wenyu copper polymetallic deposit, with proven reserves of about 0.23 Mt Cu, 394 t Ag and 0.04 Mt Pb, is located in the central part of the Lancangjiang volcanic rock belt （Fig. l a）, which is one of the most potential copper polymetallic exploration areas in SW China.
基金supported by the National Natural Science Foundation of China(grant,41573022)。
文摘In view of the importance of mafic dyke swarms and their contribution to current scientific problems relating to South China,herein,we present the findings of studies on twenty–five representative mafic dykes cropping out in Hunan Province and Guangxi Zhuang Autonomous Region,within the southern Wuling Mountain gravity lineament,China.These results include new zircon LA-ICP-MS U-Pb age,whole rock geochemical,Sr-Nd-Pb isotopic,and zircon Hf isotopic data for these dykes.The dykes formed between 131.5±1.2 and 121.6±1.1 Ma,and have typical doleritic textures.They fall into the alkaline and shoshonitic series,are enriched in light rare earth elements(LREE),some large ion lithophile elements(LILE;e.g.,Rb,Ba,and Sr),Th,U,and Pb,and are depleted in Nb,Ta,Hf,and Ti.Moreover,the dolerites have high initial 87 Sr/86 Sr ratios(0.7055–0.7057),negativeεNd(t)and zirconεHf(t)values(-14.8 to-11.9,-30.4 to-14.9),and relatively constant initial Pb isotopic ratios(that are EM1-like,16.77–16.94,15.43–15.47,and 36.84–36.92 for 206 Pb/204 Pb,207 Pb/204 Pb,and 208 Pb/204 Pb,respectively).These results indicate that the dykes were likely derived from magma generated through low-degree partial melting(1.0%–10%)of an EM1-like garnet–lherzolite mantle source.The parental magmas fractionated olivine,clinopyroxene,plagioclase,and Ti-bearing phases with negligible crustal contamination,during ascent and dyke emplacement.Several possible models have been proposed to explain the origin of Mesozoic magmatism along the Wuling Mountain gravity lineament.Herein we propose a reasonable model for the origin of these mafic dykes,involving the collision between the paleo-Pacific Plate and South China,which led to subsequent lithospheric extension and asthenosphere upwelling,resulting in partial melting the underlying mantle lithosphere in the Early Cretaceous,to form the parental magmas to the WMGL mafic dykes,as studied.
基金This work was supported by the Youth Oceanic Science Foundation of State Oceanic Administration of China under contract!No. 94-2
文摘The contents of major element composition of the phenocrysts and the matrix glass as well as the spinel inclusions and the melt inclusion in the phenocrysts of the basalt dredged from Station 133 of the Okinawa Trough are determined by electron microprobe. The results show that the basalt is a dor- galite consisting of phenocrysts of bytownite, chrysolite, clinopyroxene and magnetite as well as labradorite microcrystal, matrix glass and a few bits of broken vein quartz. Glassy melt inclusion and chromohercynite or chrompleonaste exist in bytownite and chrysolite. The formation of the spinels is re- lated to partial melting of mantle. The melt inclusions stand for a primary alkali dorgalitic magma, whose composition corresponds to olivine gabbro. The basaltic magma was generated from partial melting of spinel-lherzolite of the upper mantle and evolved in a process of 'alkali dorgalitic magma-trachy- basaltic magma-basdaltic trachytic magma-trachytic magma'. Assimilation and hybridization of crustal material may exist during magma upwelling in every evolutionary stage.
基金financially supported by the National Key Research and the Development Program of China(No.2016YFC0600502)the National Natural Science Foundation of China(No.41502046)the Geological Survey Project of China(No.DD20160030)
文摘Coronitic microstructures have been used to interpret the late-stage solidification history of igneous rocks and to constrain the corresponding chemical and/or physical changes.Coronas with three shells were also recognized in the Miaowan olivine norite,Yangtze Craton,South China.In our study,orthopyroxene intergrowth with vermicular magnetite in the inner shell is in optical continuity with magnetite-free orthopyroxene in the middle shell.In the outer shell of brown amphibole remaining magnetite-free orthopyroxene inclusions sporadically occur.Meanwhile Mg#values of orthopyroxene(76–80)in the inner and middle shells are basically consistent with olivine(78–81).In this paper,we propose a multi-stage genetic model for the formation of coronas in the Miaowan olivine norite.In the first stage,the magnetite-free orthopyroxene shell formed through reaction between primocrystal olivine with the residual Si-rich melt at 990–1053℃and 6.2–6.5 kbar.In the second stage,the orthopyroxene-magnetite symplectite shell formed when primocrystal olivine reacted with the late-stage residual Fe-rich melt promoted by high oxygen fugacity condition at 927–1035℃and 6.0–6.5 kbar.In the third stage,the brown amphibole shell formed as the presence of residual hydrous melt and replaced the middle shell at 821–900℃and 5.5–6.0 kbar.
