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It has been suggested that the Dupal isotopic anomaly in the mantle can be traced in the Paleozoic ophiolites from the . The Karamaili ophiolite (KO) and Dalabute ophiolite (DO) in the eastern and western corners, respectively, of the Junggar basin in NW China represent remnants of the relatively older (N 350 Ma) Paleo-Asian Ocean (PAO) crust. Thus, these ophiolites can provide additional constraints on the long-term composition and evolution of the Paleozoic suboceanic mantle. We present new major-trace element and Sr, Nd and high-precision Pb isotope data for the basalts, gabbros and a plagioclase separate from the KO and DO. Our results indicate that the PAO crust indeed has a Dupal-like isotopic signature. In detail, all samples have relatively low ε Nd(t) and high 208 Pb/ 204 Pb (t) for given 206 Pb/ 204 Pb (t) ratios (i.e., positive Δ8/4 values), similar to the Dupal isotopic characteristics of Indian Ocean mid-ocean ridge basalts (MORB). The trace element signature of DO mafic rocks is similar to that of normal-and enriched-MORB whereas that of the KO is transitional between MORB and arc basalt. Therefore, the DO mantle domain reflects the PAO asthenosphere and the KO domain additionally shows the influence of the subduction process. Geochemical modeling using Th/Nd as well as Nd and Pb isotopic ratios indicates that up to 2% subduction component had been added to a depleted Indian MORB-type mantle to produce the bulk of KO rocks. The subduction component in the KO rocks consisted of variable proportions of ≤1% partial melt of unradiogenic sediment similar to modern Izu-Bonin trench sediment and hydrous fluid dehydrated from the subducted altered oceanic crust. The Devonian asthenospheric mantle beneath the southern PAO is isotopically heterogeneous, but lends support to the idea that the Dupal isotopic anomaly existed prior to the opening of the Indian Ocean. Finally, plate tectonic reconstruction indicates that the anomaly was present in the Neo-and Paleo-Tethyan oceans in the southern hemisphere and in the southern part of PAO in the northern hemisphere during the late Paleozoic.

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The Guposhan-Huashan district is an important W-Sn-Sb-Zn-(Cu) metallogenic area in South China. It is located in the middle-west segment of the Nanling Range. Granitoids in the Guposhan-Huashan district possess certain properties of A-type or I-type granites. The W-Sn-Sb-Zn mineralization in the district is closely associated with magma emplacement. Two igneous biotite and seven hydrothermal muscovite samples from skarn, veins and greisenization ores were analyzed by Ar-Ar methods. Two igneous biotite samples from fine-grained quartz monzodiorite and fine-grained biotite granite show plateau ages of 168.7 ± 1.9 Ma and 165.0 ± 1.1 Ma, respectively. Seven hydrothermal muscovite samples from ores yield plateau ages as two groups: 165 Ma to 160 Ma and 104 Ma to 100 Ma. These data suggest that the emplacement of fine-grained granitoids in this district is coeval with the main phase magma emplacement, different from previous studies. The W-Sn-Sb-Zn mineralization took place in two stages, i.e. the Middle-Late Jurassic and early Cretaceous. W-Sn mineralization in the Guposhan-Huashan district is closely related to the magmatism, which was strongly influenced by underplating of asthenospheric mantle along trans-lithospheric deep faults and related fractures.