Ore genesis of the unusual Talate Pb–Zn(–Fe) skarn-type deposit, Altay, NW China: constraints from geology, geochemistry and geochronology DENG-FENG LI 1,2 , LI ZHANG 1 * , HUA-YONG CHEN 1 , YI ZHENG 1,3 , PETE HOLLINGS 4 , CHENG-MING WANG 1,2 and JING FANG 1,2 1 Key Laboratory of Mineralogy and Metallogeny, Chinese Academy of Sciences, Guangzhou, China 2 Graduate University of Chinese Academy of Sciences, Beijing, China 3 Department of Earth Sciences, Sun Yat-sen University, Guangzhou, China 4 Department of Geology, Lakehead University, Thunder Bay, Ontario, Canada The Talate ore field is located in the Abagong polymetallic metallogenic belt of the Altay Orogen, NW China. Lenticular ore bodies occur in the Kangbutiebao Formation, a package of intermediate-felsic marine volcanic rocks and terrigenous clastic sedimentary-carbonate rocks. Skarn alteration (mainly garnet) is present in both ore and wall rocks, especially the carbonate rocks. The mineral assemblages and cross- cutting relationships of veins allow the alteration and mineralization process to be divided into four stages. From early to late, these are the early skarn (E-skarn), the late skarn with quartz–magnetite veins (QM), the quartz–sulphide (QS) and the quartz–carbonate (QC) assemblages. Quartz crystals are important gangue minerals in the latter three stages, in which four distinct compositions of fluid inclusions are identified based on petrography, microthermometry and laser Raman microspectroscopy, namely aqueous inclusions (W-type), pure CO 2 inclusions (PC-type), CO 2 -rich inclusions (C-type) and daughter mineral-bearing inclusions (S-type). Microthermometric data and laser Raman analyses show that the quartz crystals from the QM stage contain all four inclusion types, with the W-type being predominant. Homogenization temperatures range between 271 and 426 °C. The salinities of the W- and C-type fluid inclusions range from 0.5 to 22.4 wt.% NaCl eqv., whereas the S-type fluid inclusions in the QM stage range from 31 to 41 wt.% NaCl eqv. Daughter minerals in the fluid inclusions include halite, sylvite, pyrite and calcite. Quartz from the QS stage (main mineralization stage) contains the W-, C- and PC-type inclusions, which are homogenized at temperatures of 204–269 °C, with salinities of 0.2–15.6 wt.% NaCl eqv. Only W-type fluid inclusions have been identified in the QC stage. These yielded homogenizing temperatures of 175–211 °C and salinities of 1.1–9.9 wt.% NaCl eqv. The C-type fluid inclusions of the main (QS) mineralization stage yield trapping pressures of 107–171 MPa, corresponding to a depth of 4–6 km. The sulphur isotope values (À1.7‰ and À6.6‰) imply that the QS stage may not be directly associated with the early skarn (À7.4‰) and quartz–magnetite stages (À4.8‰ and À5.0‰), though the QS stage is probably dominated by magmatic-hydrothermal fluids. 40 Ar/ 39 Ar isotope plateau ages of 227.6 and 214.1 Ma for biotite separated from the QM and QS stages are significantly younger than the host Kangbutiebao Formation (ca. 410 Ma). The Talate Pb–Zn(–Fe) deposit is interpreted to be an unusual skarn-type system formed in a continental collision orogeny. Copyright © 2014 John Wiley & Sons, Ltd. Received 20 November 2013; accepted 15 April 2014 KEY WORDS Pb–Zn(–Fe) deposit; fluid inclusion geochemistry; sulphur isotope; 40 Ar/ 39 Ar geochronology; Chinese Altay 1. INTRODUCTION Skarn-type (or contact metasomatic) deposits occur through- out the world and have been mined for a variety of elements (Fe, W, Cu, Pb, Zn, Mo, Ag, Au, U, REE, F, B and Sn). Over the past two decades, large numbers of skarn-type deposits have been discovered all over the world (Sato, 1980; Shelton, 1983; Meinert et al., 1997; Lu et al., 2003; Baker et al., 2004; Chen et al., 2007; Shi et al., 2009; Yang et al., 2013a). Although the majority of the deposits are found in lithologies containing at least some limestone, they can form in most rock types, including shale (Einaudi and Burt, 1982; Meinert, 1983; Jamtveit and Andersen, 1993), sandstone (Takeuchi, 1994; Forster et al., 2004; Ganino et al., 2008), granite (Watters, 1958; El-Sharkawi and Dearman, 1966; Romer and Soler, 1995), basalt (Kunzmann, 1999) and komatiite (Meinert, 1992). Distinguishing between reworked deposits with skarn alteration and primary skarn deposits in metamorphic terranes is sometimes difficult but is essential for establishing genetic models. Reworked deposits may form prior to regional metamorphism or magmatism, and many *Correspondence to: L. Zhang, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, P.O. Box 1131, Tianhe District, Guangzhou 510640, Guangdong, China. E-mail: zhangli@gig.ac.cn Copyright © 2014 John Wiley & Sons, Ltd. GEOLOGICAL JOURNAL Geol. J. 49: 599–616 (2014) Published online 26 May 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/gj.2570