The Shiyaogou deposit is a large molybdenum deposit lately discovered in the East Qinling molybdenum belt. Emplaced along the intersection of the EW-trending Machaoying fault and the NE-trending Jiaoyuan fault,the Shiyaogou deposit has a proven reserve of more than 100,000 tonnes Mo,averaging grade of 0.068%. Mineralization of the deposit consists of quartz-molybdenite veinlets and stockworks which occur in the altered granite porphyry and Proterozoic Xionger Group. Hydrothermal alteration is well developed and is composed of potassic feldspar alteration,silicification,sericitization,and pyritization,typical of porphyry Mo deposits. Five molybdenite-bearing samples of different mineralizing types were selected for precise Re-Os dating,and the results yield Re-Os model ages between 131.3±2.4~134.3±2.6Ma and an isochron age of 135.2±1.8 Ma. The Re contents of molybdenite are (8.242±0.116~30.24±0.24) ×10-6,indicating that they were mainly derived from the lower crust. The age of the Shiyaogou molybdenum deposit is consistent with that of the Yuchiling and Leimengou Mo deposits in the East Qinling molybdenum belt,indicating that porphyry Mo mineralization was driven by the Early Cretaceous lithospheric extension in East China.

Molybdenite

Quartz monzonite

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Sedimentary characteristics and origin of polyhalite in Lop Nur Salt Lake,Xinjiang

Mineralium Deposita (2008)

Cheng Liu Mrl Key

Halite

Potash

Brine

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Zircon SHRIMP U-Pb Dating and Geochemical Characteristics of Late Variscan Granites of the Daitongshan Copper Deposit and Lamahanshan Polymetallic-Silver Deposit, Southern Daxing'anling, China

Mrl Key

Daxing'anling(大兴安岭) area is one of the regions that Phanerozoic granites are extremely developed in NW China. At present, the Hercynian granitoid research lags behind the Mesozoic granitoid research. In this article, we have taken systematic petrochemistry and geochronology researches on the Hercynian granitoids in Daitongshan(代铜山) copper deposit and Lamahanshan(喇嘛罕山) silver polymetallic deposit, which were located at southern section of Daxing'anling metallogenic belt. Zircon SHRIMP U-Pb dating results show that, the granite aplites in Daitongshan and the gneissic granites inLamahanshan were formed at(265±5)–(268±9)Ma and(252±2)–(252.6±3.4) Ma, respectively,which were both the products of late Herynian tectonic-magmatic events. Samples from Lamahanshan are characterized by high SiO2(69.72wt.%–74.65 wt.%), high potassium(3.53wt.%–4.55 wt.%) and low P2O5(0.03 wt.%–0.12wt.%), aluminum saturation index(A/CNK)range from 0.95 to 0.98, Rb, Nd and K are enriched, whereas the elements such as Nb, Ta, P and Ti are depleted, which belong to I-type granitoids. Characteristics of samples from Daitongshan are similar to H-type granitoids. The magmasource may be mostly originated from the lithospheric mantle component which were transformated or affected by the subduction components, and its formation may be closely related with the subduction and orogenesis of the Paleo-Asian Ocean.

Geochronology

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