The Xigaze ophiolite crops out in the central segment of the Yarlung Zangbo suture zone,southern Tibet(Fig.1).It is characterized by large amounts of ultramafic units with minor mafic rocks.The mafic rocks consist of ...The Xigaze ophiolite crops out in the central segment of the Yarlung Zangbo suture zone,southern Tibet(Fig.1).It is characterized by large amounts of ultramafic units with minor mafic rocks.The mafic rocks consist of gabbros,展开更多
The nature(i.e., sub-oceanic, sub-arc or subcontinental) of ophiolitic mantle peridotites from the eastern Neo-Tethyan domain in southern Tibet has been hotly debated. This uncertainty limits our understanding of the ...The nature(i.e., sub-oceanic, sub-arc or subcontinental) of ophiolitic mantle peridotites from the eastern Neo-Tethyan domain in southern Tibet has been hotly debated. This uncertainty limits our understanding of the history and evolution of the eastern Neo-Tethys Ocean. Here we present petrological, geochemical and Re-Os isotopic data for the mantle peridotites from the Dazhuqu ophiolite in the central segment of the Yarlung Zangbo suture zone, southern Tibet. Samples collected include both spinel lherzolites and spinel harzburgites. The lherzolites have spinel Cr~# [Cr/(Cr + Al), ~ 0.3–0.4] comparable to those of typical abyssal peridotites. In contrast, the harzburgites have spinel Cr~#(~0.3–0.7) overlapping with the ranges of both abyssal and fore-arc peridotites(Day et al., 2017;Parkinson and Pearce, 1998);two samples have spinel Cr~# higher than 0.6, which is probably ascribed to intense melt-rock interactions. Clinopyroxene trace element modeling indicates that the Dazhuqu mantle peridotites have experienced 0–6% garnetfacies melting followed by 10% –18% melting in the spinel stability field. This is similar to the degree of garnet-facies melting inferred for many abyssal peridotites(Hellebrand et al., 2002) and implies deep initial melting(> 85 km), which distinguishes the Dazhuqu mantle peridotites from fore-arc peridotites(commonly <80 km in origin). The Dazhuqu peridotites have unradiogenic 187 Os/188 Os of 0.11836–0.12922, which are commonly lower than the recommended value of primitive upper mantle(PUM)(Meisel et al., 2001). All but one samples yield relatively younger Re depletion ages(TRD = 0.06–0.81 Ga) with respect to the only one sample having an older TRD age of 1.66 Ga. Re-Os isotopes and highly siderophile element(HSE) compositions of the Dazhuqu peridotites are similar to those of abyssal peridotites(Day et al., 2017) and the Oman southern massifs(Hangh?j et al., 2010) but are distinct from noncratonic sub-continental lithospheric mantle(SCLM) xenoliths and sub-arc mantle. We emphasize the similarity between the Dazhuqu and Oman ophiolites, both representing Neo-Tethyan oceanic lithosphere and implying ridge–trench collision.展开更多
Ophiolites along the E-W trending Yarlung-Tsangpo Suture(YTS),which separates the Indian plate from the Eurasian plate,have been regarded as relics of the NeoTethyan Ocean.The Xigaze ophiolite in the central YTS
Based on petrological and geochemical characteristics such as rock assemblage, petrogeochemistry, Sr-Nd isotope, zircon U-Pb age, and Hf isotope, we studied geochronological framework, magma types, source characters, ...Based on petrological and geochemical characteristics such as rock assemblage, petrogeochemistry, Sr-Nd isotope, zircon U-Pb age, and Hf isotope, we studied geochronological framework, magma types, source characters, and petrogenesis of different stages of magmatism of the granitic rocks from the Gangdese batholith in southern Tibet. The magmatic activities of the Gangdese batholith can be divided into three stages. The Mesozoic magmatism, induced by northern subduction of Neotethyan slab, was continuously developed, with two peak periods of Late Jurassic and Early Cretaceous. The Paleocene-Eocene magmatism was the most intensive, and resulted from a complex progress of Neotethyan oceanic slab, including subduction, rollback, and subsequent breakoff. And the Oligocene-Miocene magmatism was attributed to the convective removal of thickened lithosphere in an east-west extension setting after India-Asia collision. Isotopically, zircons from these granitic rocks are characterized by positive εHf(t) values, suggesting that the magmatic source of the Gangdese batholith might be an arc terrane, which was accreted to the southern margin of Asia during Late Paleozoic. Therefore, the chronological framework and Hf isotopic characteristics of the Gangdese batholith are distinct from the granitic rocks in adjacent areas, which can be served as a powerful tracer in studying source-to-sink relation of sediments during the uplift and erosion of Tibetan Plateau.展开更多
文摘The Xigaze ophiolite crops out in the central segment of the Yarlung Zangbo suture zone,southern Tibet(Fig.1).It is characterized by large amounts of ultramafic units with minor mafic rocks.The mafic rocks consist of gabbros,
基金financially supported by the National Natural Science Foundation of China(grants 41673038,41521062)the Key Research Program of Frontier Sciences from CAS(QYZDB-SSW-DQC032)the Open Fund Project of State Key Laboratory of Lithospheric Evolution(201707)
文摘The nature(i.e., sub-oceanic, sub-arc or subcontinental) of ophiolitic mantle peridotites from the eastern Neo-Tethyan domain in southern Tibet has been hotly debated. This uncertainty limits our understanding of the history and evolution of the eastern Neo-Tethys Ocean. Here we present petrological, geochemical and Re-Os isotopic data for the mantle peridotites from the Dazhuqu ophiolite in the central segment of the Yarlung Zangbo suture zone, southern Tibet. Samples collected include both spinel lherzolites and spinel harzburgites. The lherzolites have spinel Cr~# [Cr/(Cr + Al), ~ 0.3–0.4] comparable to those of typical abyssal peridotites. In contrast, the harzburgites have spinel Cr~#(~0.3–0.7) overlapping with the ranges of both abyssal and fore-arc peridotites(Day et al., 2017;Parkinson and Pearce, 1998);two samples have spinel Cr~# higher than 0.6, which is probably ascribed to intense melt-rock interactions. Clinopyroxene trace element modeling indicates that the Dazhuqu mantle peridotites have experienced 0–6% garnetfacies melting followed by 10% –18% melting in the spinel stability field. This is similar to the degree of garnet-facies melting inferred for many abyssal peridotites(Hellebrand et al., 2002) and implies deep initial melting(> 85 km), which distinguishes the Dazhuqu mantle peridotites from fore-arc peridotites(commonly <80 km in origin). The Dazhuqu peridotites have unradiogenic 187 Os/188 Os of 0.11836–0.12922, which are commonly lower than the recommended value of primitive upper mantle(PUM)(Meisel et al., 2001). All but one samples yield relatively younger Re depletion ages(TRD = 0.06–0.81 Ga) with respect to the only one sample having an older TRD age of 1.66 Ga. Re-Os isotopes and highly siderophile element(HSE) compositions of the Dazhuqu peridotites are similar to those of abyssal peridotites(Day et al., 2017) and the Oman southern massifs(Hangh?j et al., 2010) but are distinct from noncratonic sub-continental lithospheric mantle(SCLM) xenoliths and sub-arc mantle. We emphasize the similarity between the Dazhuqu and Oman ophiolites, both representing Neo-Tethyan oceanic lithosphere and implying ridge–trench collision.
文摘Ophiolites along the E-W trending Yarlung-Tsangpo Suture(YTS),which separates the Indian plate from the Eurasian plate,have been regarded as relics of the NeoTethyan Ocean.The Xigaze ophiolite in the central YTS
基金Supported by Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KZCX2-YW-Q09-06)National Natural Science Foundation of China (Grant No. 40721062)
文摘Based on petrological and geochemical characteristics such as rock assemblage, petrogeochemistry, Sr-Nd isotope, zircon U-Pb age, and Hf isotope, we studied geochronological framework, magma types, source characters, and petrogenesis of different stages of magmatism of the granitic rocks from the Gangdese batholith in southern Tibet. The magmatic activities of the Gangdese batholith can be divided into three stages. The Mesozoic magmatism, induced by northern subduction of Neotethyan slab, was continuously developed, with two peak periods of Late Jurassic and Early Cretaceous. The Paleocene-Eocene magmatism was the most intensive, and resulted from a complex progress of Neotethyan oceanic slab, including subduction, rollback, and subsequent breakoff. And the Oligocene-Miocene magmatism was attributed to the convective removal of thickened lithosphere in an east-west extension setting after India-Asia collision. Isotopically, zircons from these granitic rocks are characterized by positive εHf(t) values, suggesting that the magmatic source of the Gangdese batholith might be an arc terrane, which was accreted to the southern margin of Asia during Late Paleozoic. Therefore, the chronological framework and Hf isotopic characteristics of the Gangdese batholith are distinct from the granitic rocks in adjacent areas, which can be served as a powerful tracer in studying source-to-sink relation of sediments during the uplift and erosion of Tibetan Plateau.
