The Yarlung Zangbo suture zone extends more than2000 km along southern Tibet and marks the boundary between the Indian subcontinent and Eurasia.The Zedong terrane has been not suggested to represent the vestige of suc...The Yarlung Zangbo suture zone extends more than2000 km along southern Tibet and marks the boundary between the Indian subcontinent and Eurasia.The Zedong terrane has been not suggested to represent the vestige of such an intra-oceanic arc developed within the Neo-Tethys Ocean,as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic.In this study,we present detailed geochemical and geochronological data of various types of magmatic rocks widely exposed in the Zedong terrane to constrain the formation age and tectonic setting of the Zedong terrane.We found that the Zedong volcanic rocks belong to high K2O calc-alkaline series,whereas the diabase and gabbro plotted in the low-K calcalkline.The basalt rocks are highly enriched in LREE and LILE,but strongly depleted in HFSE,indicating they were derived from a metasomatized mantle.Both gabbros and diabase have similar N-MORB geochemistry indicates that the cumulates were produced from MOR setting.Zircons from four samples,including the basalt rocks(158-161Ma)are older than the gabbro(131 Ma),certificate the gabbro are as the vein intrude into the basalt rocks.This suggests that the volcanic eruption and plutonic emplacement were coevally developed in the Zedonghave similar positiveεHf(t)values(+2.0 to+15.6)and(+8.6 to+18.4),indicating they were stemmed from similarly depleted mantle sources,same with the gabbro and granitic rocks from the Gangdese arc.Therefore,we proposed that the basalt rocks in the Zedong terrane were formed through partial melting of the mantle wedge metasomatized by slab-released fluids/melts.A part of hydrous basalts were underplated in the thickened lower crust beneath the Zedong terrane,which gave rise to the cumulate and granitic rocks.This suggests that the Zedong terrane represents a slice of the active continental margin developed on the southern margin of the Lhasa terrane as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic,although a possible intra-oceanic arc setting cannot be excluded.展开更多
Diopside and magnetite exsolutions occur as oriented intergrowths within olivine of the lower Cr# dunite in the Dongbo ophiolite, Tibet. The fresh lower Cr# dunite has a mineral assemblage of olivine, spinel and diops...Diopside and magnetite exsolutions occur as oriented intergrowths within olivine of the lower Cr# dunite in the Dongbo ophiolite, Tibet. The fresh lower Cr# dunite has a mineral assemblage of olivine, spinel and diopside.展开更多
The ultramafic massif of Bulqiza, which belongs to the eastern ophiolitic belt of Albania, is the most important area for metallurgical chromitite ores. The massif consists of a thick (〉4 km) rock sequence, with a ...The ultramafic massif of Bulqiza, which belongs to the eastern ophiolitic belt of Albania, is the most important area for metallurgical chromitite ores. The massif consists of a thick (〉4 km) rock sequence, with a generalized profile from the bottom to the top as follows. The tectonite sequence composed mainly of harzburgites with subordinate intercalations of dunites,展开更多
基金funded by grants from the Ministry of Science and Technology of China (Sinoprobe-05-02)the NSF China (Nos. 41502062, 41672046, 41202036)+2 种基金the China Geological Survey (Nos. DD20160023)grants from the Institute of Geology, Chinese Academy of Geological Sciences (J1526)IGCP-649
文摘The Yarlung Zangbo suture zone extends more than2000 km along southern Tibet and marks the boundary between the Indian subcontinent and Eurasia.The Zedong terrane has been not suggested to represent the vestige of such an intra-oceanic arc developed within the Neo-Tethys Ocean,as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic.In this study,we present detailed geochemical and geochronological data of various types of magmatic rocks widely exposed in the Zedong terrane to constrain the formation age and tectonic setting of the Zedong terrane.We found that the Zedong volcanic rocks belong to high K2O calc-alkaline series,whereas the diabase and gabbro plotted in the low-K calcalkline.The basalt rocks are highly enriched in LREE and LILE,but strongly depleted in HFSE,indicating they were derived from a metasomatized mantle.Both gabbros and diabase have similar N-MORB geochemistry indicates that the cumulates were produced from MOR setting.Zircons from four samples,including the basalt rocks(158-161Ma)are older than the gabbro(131 Ma),certificate the gabbro are as the vein intrude into the basalt rocks.This suggests that the volcanic eruption and plutonic emplacement were coevally developed in the Zedonghave similar positiveεHf(t)values(+2.0 to+15.6)and(+8.6 to+18.4),indicating they were stemmed from similarly depleted mantle sources,same with the gabbro and granitic rocks from the Gangdese arc.Therefore,we proposed that the basalt rocks in the Zedong terrane were formed through partial melting of the mantle wedge metasomatized by slab-released fluids/melts.A part of hydrous basalts were underplated in the thickened lower crust beneath the Zedong terrane,which gave rise to the cumulate and granitic rocks.This suggests that the Zedong terrane represents a slice of the active continental margin developed on the southern margin of the Lhasa terrane as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic,although a possible intra-oceanic arc setting cannot be excluded.
基金funded by grants from Sinoprobe-05-02 from the Ministry of Science and Technology of Chinathe NSF China (Nos. 40930313, 40921001, 41202036)+1 种基金the China Geological Survey (Nos. 1212011121263, 12120114061801, 2014DFR2127C)project from Institute of Geology, Chinese Academy of Geological Sciences (J1526)
文摘Diopside and magnetite exsolutions occur as oriented intergrowths within olivine of the lower Cr# dunite in the Dongbo ophiolite, Tibet. The fresh lower Cr# dunite has a mineral assemblage of olivine, spinel and diopside.
基金funded by grants from Sinoprobe-05-02 from the Ministry of Science and Technology of Chinathe NSF China (Nos. 40930313, 40921001, 41202036)+1 种基金the China Geological Survey (Nos. 1212011121263, 12120114061801, 2014DFR2127C)project from Institute of Geology, Chinese Academy of Geological Sciences (J1526)
文摘The ultramafic massif of Bulqiza, which belongs to the eastern ophiolitic belt of Albania, is the most important area for metallurgical chromitite ores. The massif consists of a thick (〉4 km) rock sequence, with a generalized profile from the bottom to the top as follows. The tectonite sequence composed mainly of harzburgites with subordinate intercalations of dunites,