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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(t) 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 mafic dyke swarms are ofintra-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.
In the “Central Uplift” of Qiangtang, Northern Tibet, a large scale of mafic dyke swarms extended in EW 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, they were emplaced in the Late Carboniferous to Early Permian. Zircon 176Hf / 177Hf ratios range from 0.282852 to 0.283041, with εHf (t) 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 mafic dyke swarms are ofintra-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.