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    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.
    天山-阿尔泰东部地区海西晚期后碰撞铜镍硫化物矿床-主要特点及可能与地幔柱的关系 [查看] 毛景文、FrancoPIRAJNO、张作衡、柴凤梅、杨建民、吴华、陈世平、程松林、张长青
    天山—阿尔泰东部地区是中国重要的铜镍成矿区，近年来针对区内的铜镍矿床和相关岩体的研究不断取得进展，找矿也取得了一系列新突破，已经探明了十几个矿床和矿点。笔者基于以往研究成果，结合目前地质勘查和找矿评价的新进展，比较详细地全面总结了后碰撞铜镍硫化物矿床的基本特点、成矿规律和成矿过程，并建立了描述性成矿模型。这些矿床沿一组平行的走向近东西的深大断裂分布，与成矿有关的镁铁质—超镁铁质杂岩体一般不大于5km2，小的可为一个岩墙。矿化分两种类型：通道型和熔离型。成矿时代为298～270Ma，为中亚成矿带大规模成矿期的组成部分，形成于后碰撞伸展阶段。与这组铜镍硫化物矿床有关的镁铁质—超镁铁质杂岩体可能是早二叠世大面积喷溢岩浆的残留根部或通道部分，可能与地幔柱活动有关。另外，针对区内的地质特征，结合以往找矿的成功经验，对区内进一步的找矿工作提出了一些设想和建议。
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