Recognition of the latest Permian to Early Triassic Cu–Mo mineralization on the northern margin of the North China block and its geological significance Jian-min Liu a, ⁎, Yue Zhao a , Ya-li Sun b , Dun-peng Li a , Jian Liu a , Bai-lin Chen a , Shuan-hong Zhang a , Wei-dong Sun b a Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China b Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China abstract article info Article history: Received 25 March 2009 Received in revised form 30 July 2009 Accepted 31 July 2009 Available online 11 August 2009 Keywords: Cu–Mo mineralization Latest Permian to Early Triassic Northern margin of the North China block Re–Os dating Zircon U–Pb age In this paper, we present newly obtained molybdenite Re–Os ages for the Chehugou copper–molybdenum deposit and the Yuanbaoshan molybdenum mineral locality from the Chifeng area on the northern margin of the North China block, combined with U–Pb zircon ages of the host granites. The Re–Os isochron age of six molybdenite samples from the Chehugou deposit is 257.5 ± 2.5 Ma and one molybdenite sample from the Yuanbaoshan locality yields a Re–Os model age of 248.0 ± 2.7 Ma. These ages clearly indicate the signature latest Permian to Early Triassic Cu–Mo or Mo mineralization that has not been previously recognized. Zircon LA-ICP-MS U–Pb dating shows that the host granites of the Chehugou deposit and Yuanbaoshan locality formed in the Late Devonian (376 ± 3 Ma) and Late Permian (269 ± 3 Ma), respectively, and is not of Jurassic age, as previously thought. The latest Permian to Early Triassic Cu–Mo mineralization is likely related to extension due to final closure of the Paleo-Asian Ocean and amalgamation of the Mongolian arc terranes with the northern North China block. The establishment of a latest Permian to Early Triassic age for mineralization should encourage renewed exploration aimed at the discovery of new Mo or Cu–Mo resources along the northern margin of the North China block. © 2009 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction The Chifeng area, located in the eastern part of the northern margin of the North China block (NCB), is one of the most important ore clusters in eastern China. It hosts several major gold deposits (e.g. Honghuagou, Zhuanshanzi, Lianhuashan), one major lead and zinc deposit (e.g. Xiaoyingzi) and one major Mo (Fe) deposit (e.g. Xiaojiayingzi), as well as a series of small and medium size gold, lead and zinc and copper–molybdenum deposits (Fig. 1B). Over the past few decades, most of these deposits have been exploited and some investigations focused on the geology of these deposits have been carried out (BGMRIMAR, 1984; Wang et al., 1992; Zhang et al., 1993; Cui et al., 2000; Zhao et al., 2007). Most of these previous studies attributed the mineralization of these deposits to magmatic activities and fault systems formed during Jurassic and Early Cretaceous time due to lithospheric thinning and crustal extension in east China (Cui et al., 2000; Wu et al., 2002, 2005). Intensive exploration in the past three years has led to not only the newly discovered Mo deposits (e.g. at Nianzigou and Yuanbaoshan areas), but also to an increase in Cu–Mo or Mo resources from the existing Cu–Mo or Mo deposits (e.g. at Xiaodonggou and Chehugou, etc). Just as in the previous studies, these newly discovered Cu–Mo or Mo deposits were also considered to be formed during the Jurassic and Cretaceous and this notion was only supported partly by Re–Os ages in some cases. Nie et al. (2007) reported a Re–Os age of 135.5 ± 1.5 Ma for molybdenite from the Xiaodonggou Mo deposit. Dai et al. (2009) reported a Re–Os isochron age of 165.5 ± 4.6 Ma for the molybdenite from the Xiaojiayingzi Mo deposit, and Zhang et al. (2009d) reported a Re–Os age of 154.3 ± 3.6 Ma for the molybdenite from the Nianzigou Mo deposit. Our recent research on the Chehugou Cu–Mo deposit and the Yuanbaoshan Mo locality, however, yields ages of latest Permian and Early Triassic for some Cu–Mo or Mo mineralization on the northern NCB. Furthermore, the newly obtained zircon U–Pb ages indicate that emplacement of the host granites from the Chehugou and Yuan- baoshan areas occurred during Late Devonian and Late Permian respectively, and not Jurassic as previously thought. Our finding has important implications on the geodynamic process associated with these important ore deposits of the Late Paleozoic to Early Mesozoic ages. Recent geological and geochronological data have revealed that the northern margin of the NCB was strongly affected by the Paleo- Asian tectonic system (e.g., Davis et al., 2001; Xiao et al., 2003) and the late Paleozoic to Early Mesozoic evolution of the northern NCB, surrounding regions and related mineralization are closely related to that of the Central Asian Orogenic Belt (Xiao et al., 2003; Zhang et al., Gondwana Research 17 (2010) 125–134 ⁎ Corresponding author. No. 11 South Minzudaxue Road, Haidian District, Beijing 100081, China. Tel.: +86 10 6848 6764; fax: +86 10 6842 2326. E-mail address: liujianmin@vip.sina.com (J. Liu). 1342-937X/$ – see front matter © 2009 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2009.07.007 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr