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The Houshihua gold deposit is located in Halaheshao Village, 38km southwest of Wuchuan County, Inner Mongolia. Its mineralization age is still a quite controversial subject, which directly restricts the understanding of metallogenic mechanism and regularity. In this paper, we present the results of Re-Os isotopic age of molybdenites sampled from auriferous quartz vein within the Houshihua gold deposit in an attempt to constrain the timing of the mineralization, the tectonic setting in which the deposit was formed and also to provide more evidence for multi-stage Au-Mo mineralization in the northern margin of the North China Craton.

The Hadamengou gold ore field is located in the Agarutai town, about thirty kilometers west of Baotou City, Inner Mongolia. Since the first ore vein was discovered by Gold Branch of the Chinese Armed Police Force in 1986, hundreds of mineralized quartz-potassium feldspar veins have been discovered, with a proven reserve of 100 t gold. However, timing of gold mineralization of this ore field remains controversial due to the lack of precise radiometric dating, significantly hampering a comprehensive understanding in the temporal-spatial distribution and genesis of the gold deposits. Here we present the result of Re-Os isotopic dating of molybdenite sampled from auriferous quartz vein in the Hadamengou gold ore field in an attempt to tightly constrain the timing of gold mineralization and the tectonic setting unbder which the ore field was formed.

The age, petrogenesis and geodynamic implication of Xiaomiaogou granite porphyry dykes in the northern margin of the North China Craton were investigated using geochronology, geochemistry and Sr–Nd–Pb–Hf isotopic data. LA‐MC‐ICP‐MS zircon U–Pb dating yielded the concordant 206Pb/238U weighted mean age of 350.4 ± 1.4 Ma for the dykes, suggesting they were the productions of the Early Carboniferous magmatism in the northern margin of the North China Craton. The granite porphyries display the pronounced A‐type affinities: apart from higher zircon saturation temperature, they are high‐K calc‐alkaline and metaluminous, with high concentrations of K2O + Na2O varying from 7.93 to 8.55 wt.%, incompatible elements (e.g. Zr, Y, Nb and Ce), REEs and 10 000 Ga/Al ratios but less obvious LREE and HREE fractionation. With the lower initial 87Sr/86Sr ratios (0.7055 to 0.7070), negative values of εNd(t) (−7.1 to −4.9) and εHf(t) (−11.2 to −8.0) and old Nd (1505 to 1681 Ma) and Hf (1861 to 2061 Ma) model ages, all the rocks exhibit the similar geochemical compositions to the melts obtained in experimental studies by dehydration melting of meta‐basalts, implying a lower continental crust origin. However, the high Mg# values (47.53 to 53.60) and subcontinental lithospheric mantle‐like εNd(t), εHf(t) and Pb isotopic compositions ((206Pb/204Pb)i = 17.296–17.766, (207Pb/204Pb)i = 15.460–15.490 and (208Pb/204Pb)i = 37.097–37.568) indicate the involvement of melts from subcontinental lithospheric mantle. Combined with the special features of mafic microgranular enclaves occurring within the granite porphyries, mixing of the lower crust and subcontinental lithospheric mantle of the North China Craton is proposed for the genesis of granite porphyry dykes in this study. During the hybrid magma ascending, pronounced fractional crystallization and crustal assimilation may have also occurred. Based on geochemical criteria, the Xiaomiaogou granite porphyries can be classified into A1 group. Characterized by the compositional features of anorogenic granites, an intraplate setting is envisaged for the formation of Xiaomiaogou granite porphyry dykes. Such a tectonic environment may be related to the northward drift of the North China Craton during rifting away from East Gondwana. Copyright © 2016 John Wiley & Sons, Ltd.