The SHRIMP zircon U-Pb dating was carried out and yielded 287±5 Ma (MSWD = 0.34) and 274±3 Ma (MSWD = 1.35) for the Kalatongke No. 1 and Huangshan- dong Cu-Ni-bearing mafic-ultramafic complexes. These ages a...The SHRIMP zircon U-Pb dating was carried out and yielded 287±5 Ma (MSWD = 0.34) and 274±3 Ma (MSWD = 1.35) for the Kalatongke No. 1 and Huangshan- dong Cu-Ni-bearing mafic-ultramafic complexes. These ages are much more precise than pre-existing rock-mineral Rb-Sr, Sm-Nd and Re-Os isochron ages for the two complexes and constrain the timing of not only the complexes but also the magmatic Cu-Ni sulfide deposits more reliably. It is neces- sary to carefully reevaluate the previous chronological data for the complexes. The Cu-Ni-bearing mafic-ultramafic com- plexes have the ages similar to those of postcollisional A-type granites in the same area, implying that they could be related to the delamination of lithospheric mantle and upwelling and partial melting of asthenospheric mantle in postcollisional setting. Therefore, the Cu-Ni-bearing mafic-ultramafic com- plexes are a direct indicator of vertical growth of the conti- nental crustal in the Central Asian Orogenic Belt.展开更多
The reported new U-Pb age by sensitive high-resolution ion microprobe (SHRIMP Ⅱ) on zircon was obtained from a tuff sample at the basal Doushantuo Formation in the Jiuqunao section, which situated at the western limb...The reported new U-Pb age by sensitive high-resolution ion microprobe (SHRIMP Ⅱ) on zircon was obtained from a tuff sample at the basal Doushantuo Formation in the Jiuqunao section, which situated at the western limb of the Huangling anticline in the Yangtze Gorges in Zigui, Hubei, South China. Eighteen spots of zircons were analyzed and they form two clusters: one includes three spots, with an inherited age of 784+ 15 Ma (MSWD=0.05); the other consists of 15 spots and gives a weighted mean ^206pb/^238U age of 628.3±5.8 Ma (MSWD=0.86). It is the first SHRIMP U-Pb zircon age obtained nearly the base of the Doushantuo Formation of Ediacaran and represents a maximum age of the Doushantuo Formation It also forms an age constraint on the upper limit age of the Nantuo (Marinoantype) glaciation.展开更多
Zircons from two high-pressure granulite samples from the Yushugou ophiolitic terrane, southern Tianshan have been investigated by cathodoluminescence, LAICPMS and ion microprobe (SHRIMP) for their internal textures, ...Zircons from two high-pressure granulite samples from the Yushugou ophiolitic terrane, southern Tianshan have been investigated by cathodoluminescence, LAICPMS and ion microprobe (SHRIMP) for their internal textures, trace elemental compositions and in situ dating. Theweighted mean ages of these two samples are 392±7 and 390±11 Ma, respectively, representing the granulite-facies metamorphic age of the ophiolitic terrane, and indicating that the southern Tianshan ocean initiated its northward subduction since the early Devonian.展开更多
The Nyainqentanglha granite, a batholith with an area of 1500 km^2 in the central Lhasa block, comprises mainly medium-fine-grained biotite monzonitic granite and medium-coarse-grained biotite monzonitic granite. Thei...The Nyainqentanglha granite, a batholith with an area of 1500 km^2 in the central Lhasa block, comprises mainly medium-fine-grained biotite monzonitic granite and medium-coarse-grained biotite monzonitic granite. Their contact relationship suggests that the medlum-fine-grained biotite monzonitic granite was crystallized earlier than the medium-coarse-grained monzonitic granite. A SHRIMP U-Pb dating on zircons from representative samples of the batholith shows that the crystallization age of the medium-fine-grained biotite monzonitic granite is 18.3 Ma and that of the medium-coarse-grained monzonitic granite is 11.01 Ma. The emplacement and crystallization of the Nyainqentanglha granite, the youngest granite batholith ever known inside the Lhasa block, have a close relationship with the collisional orogeny, crustal thickening, plateau uplifting,E-W crustal extension and have a dynamic genetic relationship with the crustal partial melting.展开更多
SHRIMP U-Pb zircon analyses for a gabbro sample from the Garzê ophiolite block yielded a mean 206Pb/238U age of 292±4 Ma, which indicated that the spread- ing time of the Garzê-Litang Tethys was most li...SHRIMP U-Pb zircon analyses for a gabbro sample from the Garzê ophiolite block yielded a mean 206Pb/238U age of 292±4 Ma, which indicated that the spread- ing time of the Garzê-Litang Tethys was most likely at the earliest Permian. Combined with previous studies, we sug- gest that the opening of the Tethys in southwest China was derived from breakup of the East Gondwanaland in the late Paleozoic.展开更多
文摘The SHRIMP zircon U-Pb dating was carried out and yielded 287±5 Ma (MSWD = 0.34) and 274±3 Ma (MSWD = 1.35) for the Kalatongke No. 1 and Huangshan- dong Cu-Ni-bearing mafic-ultramafic complexes. These ages are much more precise than pre-existing rock-mineral Rb-Sr, Sm-Nd and Re-Os isochron ages for the two complexes and constrain the timing of not only the complexes but also the magmatic Cu-Ni sulfide deposits more reliably. It is neces- sary to carefully reevaluate the previous chronological data for the complexes. The Cu-Ni-bearing mafic-ultramafic com- plexes have the ages similar to those of postcollisional A-type granites in the same area, implying that they could be related to the delamination of lithospheric mantle and upwelling and partial melting of asthenospheric mantle in postcollisional setting. Therefore, the Cu-Ni-bearing mafic-ultramafic com- plexes are a direct indicator of vertical growth of the conti- nental crustal in the Central Asian Orogenic Belt.
文摘The reported new U-Pb age by sensitive high-resolution ion microprobe (SHRIMP Ⅱ) on zircon was obtained from a tuff sample at the basal Doushantuo Formation in the Jiuqunao section, which situated at the western limb of the Huangling anticline in the Yangtze Gorges in Zigui, Hubei, South China. Eighteen spots of zircons were analyzed and they form two clusters: one includes three spots, with an inherited age of 784+ 15 Ma (MSWD=0.05); the other consists of 15 spots and gives a weighted mean ^206pb/^238U age of 628.3±5.8 Ma (MSWD=0.86). It is the first SHRIMP U-Pb zircon age obtained nearly the base of the Doushantuo Formation of Ediacaran and represents a maximum age of the Doushantuo Formation It also forms an age constraint on the upper limit age of the Nantuo (Marinoantype) glaciation.
文摘Zircons from two high-pressure granulite samples from the Yushugou ophiolitic terrane, southern Tianshan have been investigated by cathodoluminescence, LAICPMS and ion microprobe (SHRIMP) for their internal textures, trace elemental compositions and in situ dating. Theweighted mean ages of these two samples are 392±7 and 390±11 Ma, respectively, representing the granulite-facies metamorphic age of the ophiolitic terrane, and indicating that the southern Tianshan ocean initiated its northward subduction since the early Devonian.
文摘The Nyainqentanglha granite, a batholith with an area of 1500 km^2 in the central Lhasa block, comprises mainly medium-fine-grained biotite monzonitic granite and medium-coarse-grained biotite monzonitic granite. Their contact relationship suggests that the medlum-fine-grained biotite monzonitic granite was crystallized earlier than the medium-coarse-grained monzonitic granite. A SHRIMP U-Pb dating on zircons from representative samples of the batholith shows that the crystallization age of the medium-fine-grained biotite monzonitic granite is 18.3 Ma and that of the medium-coarse-grained monzonitic granite is 11.01 Ma. The emplacement and crystallization of the Nyainqentanglha granite, the youngest granite batholith ever known inside the Lhasa block, have a close relationship with the collisional orogeny, crustal thickening, plateau uplifting,E-W crustal extension and have a dynamic genetic relationship with the crustal partial melting.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.40472119 and 40172071)the Progranme of Excelent Young Scientists of the Ministry of Land and Resources,the Ministry of Science and Technology of the People's Republic of China(Grant No.2002CB412608)the China Geological Survey(Grant No.200313000057).
文摘SHRIMP U-Pb zircon analyses for a gabbro sample from the Garzê ophiolite block yielded a mean 206Pb/238U age of 292±4 Ma, which indicated that the spread- ing time of the Garzê-Litang Tethys was most likely at the earliest Permian. Combined with previous studies, we sug- gest that the opening of the Tethys in southwest China was derived from breakup of the East Gondwanaland in the late Paleozoic.
