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    Timing of skarn deposit formation of the Tonglushan ore district, southeastern Hubei Province, Middle–Lower Yangtze River Valley metallogenic belt and its implications [查看] GuiqingXie、JingwenMao、HaijieZhao、KetaoWei、ShangguangJin、HuijunPan、YufuKe
    The Tonglushan ore district in theMiddle–Lower Yangtze River Valleymetallogenic belt includes the Tonglushan Cu–Fe, the Jiguanzui Au–Cu, and the Taohuazui Au–Cu skarn deposits. They are characterized by NE-striking ore bodies and hosted at the contact of Triassic carbonate rocks and Late Mesozoic granitoid deposits. New Sensitive High-Resolution Ion Microprobe (SHRIMP) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA–ICP-MS) zircon U–Pb,molybdenite Re–Os, and phlogopite 40Ar–39Ar ages indicate that these skarn deposits formed between 140.3±1.1 and 137.3±2.4 Ma. These dates are identical to the zircon U–Pb ages for host quartz diorites ranging from 140±2 to 139±1 Ma. These results confirm that both skarn mineralization and related intrusions were initiated during the Early Cretaceous. The high rhenium contents (261.4–1152 μg/g) of molybdenites indicate that ametasomaticmantle fluidwas involved in the ore-forming process of these skarn ore systems. This conclusion is consistent with previously published constraints from sulfur, deuterium, and oxygen isotope compositions, and the geochemical signatures, and Sr–Nd isotopic data of the mineralization-hosting intrusions. Geological and geochronological evidence demonstrates that there were two igneous events in the Tonglushan ore district. The first resulted in the emplacement of quartz diorite during the Early Cretaceous (140±2 to 139±1 Ma), and the second is characterized by the eruption of volcanic rocks during the mid-Early Cretaceous (130±2 to 124±2 Ma). The former is spatially, temporally and genetically associated with skarn gold-bearing mineralization (140.3±1.1 to 137.3±2.4 Ma). The recognition of these two igneous events invalidates previous models that proposed continuous magmatism and associated mineral deposits in the Middle–Lower Yangtze River Valley metallogenic belt.
    SHRIMP U–Pb (zircon), Ar–Ar (muscovite) and Re–Os (molybdenite) isotopic dating of the Taoxikeng tungsten deposit, South China Block [查看] ChunliGuo、JingwenMao、FrankBierlein、ZhenghuiChen、YuchuanChen、ChuanbiaoLi、ZailinZeng
    The Taoxikeng tungsten deposit is located in the Jiangxi Province in the southern part of China, and is one of the largest wolframite quartz-vein type tungsten deposits in the country. The deposit is situated in Sinian(Neoproterozoic) to Permian strata at the contact with the buried Taoxikeng Granite. Sensitive High Mass Resolution Ion Microprobe (SHRIMP) zircon U–Pb analysis of the granite has yielded dates of 158.7±3.9 and 157.6±3.5 Ma, which are interpreted as the emplacement age of the granite. Molybdenite separated from ore-bearing quartz-veins yields a Re–Os isochron age of 154.4±3.8 Ma, and muscovite separated from greisen between the granite and country rocks yields 40Ar/39Ar plateau ages of 153.4±1.3 and 152.7±1.5 Ma.These dates obtained from three independent geochronological techniques constrain the ore-forming age of the Taoxikeng deposit and link the ore genesis to that of the underlying granite. The Taoxikeng deposit is an example of a Jurassic regional-scale tungsten–tin ore-forming event between 160 and 150 Ma in the Nanling region of the South China Block. The deposit's strikingly low rhenium contents (4.9 to 13.0×10−3 μg/g) in molybdenite suggests that the ore was derived from a crustal source. This conclusion is consistent with previously published constraints from S, D and O stable isotopes, Sr–Nd systematics, and petrogenetic interpretations of spatially related granites.
    Pyrrhotite Re–Os and SHRIMP zircon U–Pb dating of the Hongqiling Ni–Cu sulfide deposits in Northeast China [查看] LinsuLü、JingwenMao、HongboLi、FrancoPirajno、ZuohengZhang、ZhenhuaZhou
    The Hongqiling (HQL) magmatic Ni–Cu sulfide deposits (Jilin Province, NE China) are located at the southern margin of the eastern Xing'an–Mongolian Orogenic Belt (XMOB) of the eastern Central Asian orogenic belt(CAOB), situated between the Siberian Craton (SC) and the North China Craton (NCC). The HQL ore-bearing mafic–ultramafic intrusions intrude into the metamorphic rocks of the lowermost Huangyingtun Formation of the Hulan Group (HLG), whose lithology is herein identified as a hornblende–zoisite gneiss. SHRIMP zircon U–Pb dating for the HLG, country rock of the HQL deposits, indicated a maximum deposition age of 272.2±4.3 Ma (95% confidence level, MSWD=2.6, n=14).Six pyrrhotite samples separated from massive Ni–Cu sulfide ores of the Fujia (No. 7) deposit yielded a Re–Os isotopic isochron age of 208±21 Ma (95% confidence level, MSWD=2.4, n=6), indicating that the oreformation age was Late Triassic. Re–Os isotope analyses showed an initial 187Os/188Os ratio of 0.315±0.050.The γOs values ranged from+137 to+161 with an average of+151, indicating that its ore-forming materials were mainly derived from mantle with possibly b30% crustal Os contamination. Large scale magmatic Ni–Cu mineralization in eastern Jilin occurred in post-collisional tectonic setting in the Late Triassic.Our new results suggest that the ages of the Ni–Cu sulfide deposits in the CAOB within China tended to become younger from west to east, as manifested by the Late Caledonian (~440 Ma), through the Late Hercynian (300–265 Ma) to the Late Indosinian (225–200 Ma). Such variation could reflect the gradual closure and post-collisional orogeny between the SC and the NCC from west to east.
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