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In the "Central Uplift" of Qiangtang, Northern Tibet, a large scale of mafic dyke swarms extended in E-W direction. Zircon SHRIMP U-Pb dating on two representative samples of diabase dyke yield weighted mean ages of 284 ± 3 Ma and 302 ± 4 Ma, respectively, suggesting they emplaced in the Late Carboniferous to Early Permian. Zircon 176Hf/177Hf ratios range from 0.282852 to 0.283041, with ϵHf(f) values of +12.1 to +12.2 and Hf modal (TDM) ages of -440-460 Ma. These data indicate that these mafic dykes were mainly derived from the depleted mantle. In addition, geochemical data suggest that these mat ic dyke swarms are of intra-plate origin. Therefore, the mafic dyke swarms represent products during the extensional process associated with the opening of the Paleo-Tethys Ocean in the area. [ABSTRACT FROM AUTHOR]

The Bangong Lake ophiolite is located in the westernmost part of the Bangong Lake-Nujiang River suture zone. It is a tectonic mélange consisting of numerous individual blocks of peridotite, pillowed and massive lavas and mafic dykes with SSZ-type ophiolitic geochemical affinity formed at the end of a Wilson circle. The SHRIMP U-Pb ages of the co-magmatic zircon domains from one gabbroic dyke (Sample 01Y-155) range from 162.5±8.6 Ma to 177.1±1.4 Ma with an average of 167.0±1.4 Ma (n = 12, MSWD = 1.2), suggesting that the subduction of the Bangong Lake Neo-Tethyan Ocean started before the Middle Jurassic. It is inferred that the tectonic transform from spreading to subduction of the Neo-Tethyan Ocean began before the Middle Jurassic in the Bangong Lake area. [ABSTRACT FROM AUTHOR]

SHRIMP U-Pb zircon dating was carried out for the Daohugou Biota near Ningcheng of Inner Mongolia and for lavas overlying or underlying salamander-bearing strata at Reshuitang in Lingyuan of West Liaoning. The results suggest that the Daohugou Biota occurred at an interval from 168 Ma to 164 – 152 Ma. Both the Daohugou Biota and the salamander-bearing fossil assemblage are the same biota and thus developed from 168 to 152 Ma, i.e. from late Middle Jurassic to the early Late Jurassic. The Daohugou Biota-bearing rocks, resting on the Jiulongshan Formation in disconformity and being overlain in unconformity by Late Jurassic Tuchengzi Formation and Early Cretaceous rocks containing the Jehol Biota, are mainly composed of volcanic-sedimentary rocks in a normal sequence. It is recommended that the Daohugou Biota and the related stratigraphy should be correlated with the Tiaojishan Formation (Lanqi Formation in West Liaoning) or its synchronous rocks. It is suggested that the Daohugou Biota and the Jehol Biota would be neither taken into one biota nor considered as the earliest elements of the Jehol Biota. The Daohugou Biota and the related rocks and the Yixian Formation were respectively formed in different periods of volcanic-sedimentary tectonics. [ABSTRACT FROM AUTHOR]

Alkali-feldspar syenites from the Maomaogou area of Huili County in Panxi of Sichuan Province, SW China are sodium alkaline rocks, the minerals of which are mainly composed of calcic ferroaugite, ferroamphibole and biotite. Most of the zircons (>80%) selected for SHRIMP U-Pb dating are magmatic compound zircons and they have relict inner cores and growing outer shells. The age of zircon SHRIMP U-Pb dating is 224±8 Ma, suggesting that the Maomaogou alkali-feldspar syenite was formed in the late Triassic period. At the same time, two old age periods of relict cores of zircon are determined, they are the Archean age (2692–2818 Ma) and Neoproterozoic age (622–691 Ma), respectively. These periods indicate that the cores derived from the crystal basement. Furthermore, the Archean age of zircon provides the first reliable SHRIMP U-Pb zircon dating evidence of >2.8 Ga basement in the Xikang-Yunnan Axis of southwest China. [ABSTRACT FROM AUTHOR]

Presents an analyzation about the use of the in situ zircon U-Pb dating method of LA-ICPMS. Consideration of the investigation of a 31 Ma old SHRIMP U-Pb age of the Yongsheng nepheline syenite from southern Jilin Province under different spot sizes; Reference to how the obtained ages are comparable with that of SHRIMP in both accuracy and precision; Findings that the age is also identical to that of the Yinmawanshan gabbro from the Liaodong Peninsula within error; Trend for both the Yongsheng nepheline syenite and the Yinmawanshan gabbro to represent the youngest known exposed intrusions in northeastern and even eastern China; Indication from the results that the Eocene mantle-derived magmatic underplating, and the rapid crustal uplifting of this region since 30 Ma; How the analyses also document extremely high LREE concentrations and relatively flat REE patterns for the zircons from the Yongsheng nepheline syenite, which represent a new type of zircon REE pattern.

Presents the in situ analysis of oxygen isotopes carried out by ion microprobe for zircons from localities of HP-UHP metamorphic rocks including eclogites in the Dabie-Sulu terrane. Significance of zircon isotopes in archeological dating; Possibility to trace zircon value with a particular geological time or event for complicated evolution of given rocks; Interest from international geoscientists of the Dabie-Sulu terrain for its coesite and diamond-bearing eclogites.

Discusses the Zircon SHRIMP uranium-lead dating for the Cangshuipu volcanic rocks and its implications for the lower boundary age of the Nanhua strata in South China. Occurrence of the continental volcanic rocks and volcaniclastic sedimentary conglomerates of the Cangshuipu Formulation in Yiyang of Hunan Province; Configuration of the strata in the Yiyang region; Representation of the lower boundary with a younger age than previously reported.