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Geochemical and Hf–Nd isotope data of Nanhua rift sedimentary and volcaniclastic rocks indicate a Neoproterozoic continental flood basalt provenance [查看] Xuan-CeWang、Zheng-XiangLi、Xian-HuaLi、Qiu-LiLi、Qi-RuiZhang

Geochemical and Hf–Nd isotope studies of Neoproterozoic sedimentary and volcaniclastic rocks in the Nanhua Rift Basin, South China, demonstrate that their source provenances contained large proportions of mafic rocks and various amounts of granites. A significant proportion of the studied Neoproterozoic rift sedimentary and volcaniclastic rocks have initial εNd(t) values higher than those of Neoproterozoic granites, but fall within the range of ca. 825–750 Ma basaltic rocks. Their initial εNd(t) values correlate with ratios of La/Sc, La/Cr, La/V, La/Co and La/Ni. The Nd isotope and trace element data, in combination with existing in-situ U–Pb and hafnium–oxygen isotope data fromthe detrital zircon grains indicate a dominant ca. 825–800 Mamafic provenance. Furthermore,the studied samples formed a linear array and plot within the field defined by the remanent of ca. 825–810 Ma continental flood basalts in the Hf–Nd isotopic space. Thus, the inferred large proportions of mafic rocks in the source provenance of the Neoproterozoic rift sedimentary and volcaniclastic rocks likely signify an eroded continental flood basalt province, similar to that reported for the Neoproterozoic sedimentary rocks in Australia. This work thus provides further evidence for the possible once existence of a common large igneous province between South China and eastern Australia as adjacent parts of the supercontinent Rodinia.

Baogutu Porphyry Cu-Mo-Au Deposit, West Junggar, Northwest China Petrology, Alteration, and Mineralization [查看] PINGSHEN、YUANCHAOSHEN、HONGDIPAN、JINGBINWANG、RUIZHANG、YUNXIAOZHANG

Baogutu is the first porphyry Cu-Mo-Au deposit discovered in West Junggar, Xinjiang, China. It is part of the Central Asian orogenic belt. Baogutu is associated with a Carboniferous intrusive complex that was emplaced into lower Carboniferous volcano-sedimentary sequences of the Baogutu and Xibeikulasi Groups. The intrusive complex is made up of main stage equigranular to porphyritic diorites and quartz diorites, and minor late stage diorite porphyries. Intrusive activity occurred at about 325 Ma based on U-Pb (SHRIMP) analyses of zircons. The main stage diorites host the bulk of the Cu-Mo-Au mineralization at Baogutu. They have been overprinted by three alteration assemblages, including an early potassic (biotite) assemblage that occurs in the center of the deposit. A propylitic assemblage surrounds the potassic zone concentrically. Both of these alteration assemblages have been overprinted locally by phyllic alteration (quartz-sericite-pyrite), which is associated with the highest Cu-Mo grades. Mineralized and hydrothermally cemented breccias have disrupted the main stage diorites. The late stage diorites have undergone moderate potassic alteration and contain weak Cu mineralization.Matrix-rich breccias with very weak mineralization have cut the intrusive complex and disrupted the orebody. Re-Os dating of molybdenite indicates that mineralization occurred at about 310 Ma.

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