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Recognition of a Middle–Late Jurassic Arc-Related Porphyry Copper Belt

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Recognition of a Middle–Late Jurassic Arc-Related Porphyry Copper Belt https://doi.org/10.1130/G48615.1 Manuscript received 11 May 2020 Revised manuscript received 9 November 2020 Manuscript accepted 17 November 2020 © 2021 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 26 January 2021 Recognition of a Middle–Late Jurassic arc-related porphyry copper belt along the southeast China coast: Geological characteristics and metallogenic implications Jingwen Mao1,2*, Wei Zheng2, Guiqing Xie1,2, Bernd Lehmann3 and Richard Goldfarb1 1 China University of Geosciences, Beijing 100083, China 2 MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China 3 Mineral Resources, Technical University of Clausthal, 38678 Clausthal-Zellerfeld, Germany ABSTRACT significant exploration potential for world-class Recent exploration has led to definition of a Middle–Late Jurassic copper belt with an ex- resources. tent of ∼2000 km along the southeast China coast. The 171–153 Ma magmatic-hydrothermal copper systems consist of porphyry, skarn, and vein-style deposits. These systems developed REGIONAL GOLOGY OF THE along several northeast-trending transpressive fault zones formed at the margins of Juras- SOUTHEAST CHINA COASTAL BELT sic volcanic basins, although the world-class 171 Ma Dexing porphyry copper system was The southeast China coastal area is geologi- controlled by a major reactivated Neoproterozoic suture zone in the South China block. cally located along the edge of the Cathaysia The southeast China coastal porphyry belt is parallel to the northeast-trending, temporally block, which amalgamated with the Yangtze overlapping, 165–150 Ma tin-tungsten province, which developed in the Nanling region in craton along the Qinhang suture zone ca. 1.1– a back-arc transtensional setting several hundred kilometers inboard. A new geodynamic- 0.9 Ga (Chen et al., 1991) to form the South Chi- metallogenic model linking the two parallel belts is proposed, which is similar to that char- na block (Fig. 1). The Cathaysia block consists acterizing the Cenozoic metallogenic evolution of the Central Andes. of a Precambrian basement overlain by Sinian to early Mesozoic sedimentary and late Mesozoic INTRODUCTION the active trench in an apparently irregular pat- continental clastic and volcanic cover. There are Ore deposits can be used as markers of geo- tern. Therefore, most workers have historically two important northeast-striking transpressive dynamic evolution, as initially recognized for considered the deposits to have formed in an faults in the eastern part of the Cathaysia block: porphyry copper deposits by Sillitoe (1972), and intraplate rift setting (Guo et al., 1982; Pirajno the Zhenghe-Dapu and the Changle-Nan’ao later generalized by Mitchell and Garson (1981) and Zhou, 2015; Zhou et al., 2015). Some re- faults. The Zhenghe-Dapu fault is regarded as and Sawkins (1984). One of the classic examples searchers, however, have proposed a relation- a translithospheric strike-slip fault, dividing the is the Central Andes, where Cenozoic porphyry ship to the oblique subduction of the Izanagi Cathaysia block into two units (Fig. 1), locally copper deposits in Chile are representative of or paleo–Pacific plate beneath the interior of known as the Interior Cathaysia and the Coastal an active continental margin setting, and the the South China block (Qi, 1990; Zhou et al., Cathaysia blocks. The newly recognized Middle Bolivian tin belt is indicative of a back-arc set- 2006; Mao et al., 2013). If this were the case, to Late Jurassic southeast China coastal cop- ting. Both metal belts formed in specific and then one must consider whether there exists a per porphyry belt is located along and close to relatively narrow time windows at the 10 m.y. recognizable Mesozoic arc along the Eurasian these two major fault systems. Pre-Devonian scale related to the regional stress field, which continental margin; such arcs typically host basement, late Paleozoic–Middle Triassic clastic was modulated by periods of flat-slab subduc- copper-rich porphyry and related ore systems. and carbonate rocks, and late Mesozoic conti- tion (James and Sacks, 1999; Kay et al., 1999; Data from our recent field investigations, cou- nental volcanic rocks are the major rock types Lehmann, 2004). pled with previous data from numerous work- intruded by the porphyry systems (Zhao et al., However, the tectonic setting of the major ers, confirm that there is clearly a Middle to 2015). There are numerous variably eroded late tin-tungsten province in the Nanling region of Late Jurassic porphyry copper belt along the Mesozoic volcanic edifices in the belt, includ- southeast China has remained puzzling. The southeastern continental margin of China asso- ing stratovolcanoes and volcanic domes and re- tin and tungsten deposits are mainly of Mid- ciated with the subduction of the Izanagi plate lated intrusive rocks, which mainly formed at dle to Late Jurassic age, a time period locally during that time. The regional metal polarity 140–85 Ma within an extensional regime (Chu known as early Yanshanian. Many of the de- of tin-tungsten ores in the back-arc and copper et al., 2019). Lesser igneous activity is recorded posits formed more than 1000 km inward from ores in the main arc integrates the mineral de- during the time period of 170–140 Ma, which posits of southeastern China into a comprehen- was characterized by a compressional regime *E-mail: [email protected] sive global metallogenic framework and reveals (Chu et al., 2019). Local and relatively small CITATION: Mao, J., et al., 2021, Recognition of a Middle–Late Jurassic arc-related porphyry copper belt along the southeast China coast: Geological characteristics and metallogenic implications: Geology, v. 49, p. 592–596, https://doi.org/10.1130/G48615.1 592 www.gsapubs.org | Volume 49 | Number 5 | GEOLOGY | Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/49/5/592/5273400/592.pdf by guest on 25 September 2021 Figure 1. Map showing Jurassic porphyry–skarn–hydrothermal vein copper deposits in the southeast China coastal belt (continental arc set- ting) and the tin-tungsten (W-Sn) province of the Nanling region (dashed red ellipse) in a back-arc setting. exposures of Jurassic volcanic and hypabyssal gin. Through detailed field investigations in the Andean belt because of the greater degree of intrusive rocks dated at 172–152 Ma (Table S1 coastal area over the past 10 yr, it has been rec- erosion in the older southeast China belt. The in the Supplemental Material1) are recognized ognized that there are dozens of copper-rich por- deposits have an age range from 171 Ma to within the southern, northwestern, and western phyry, skarn, and polymetallic vein deposits as- 153 Ma (mostly Re-Os ages on molybdenite) margins of the younger Cretaceous volcanic sociated with small magmatic centers of Middle and are coeval with the related granitic rocks cover (Fig. 1). It is these remnant igneous cen- to Late Jurassic age (Fig. 1). These discoveries ranging from 172 to 152 Ma (U-Pb on zircon; ters that host the copper mineralization. put the historic giant porphyry copper district see Table S1), which include quartz diorite por- of Dexing in a new light, where rather than an phyry, granodiorite porphyry, granodiorite, and FEATURES OF THE MIDDLE–LATE isolated ore district of uncertain tectonic affin- minor monzogranite. The host rocks of the ore JURASSIC SOUTHEAST CHINA ity, it could now be viewed as part of a partly deposits and their associated intrusions are var- COASTAL PORPHYRY COPPER BELT eroded Andean-style magmatic-hydrothermal ied. Qiguling (165 Ma), Potoumian (164 Ma), South China is well known for the excep- metallogenic belt. Chadi (165 Ma), Mang’eling (166 Ma), and tionally metal-rich Late Jurassic Nanling tin- Didougang (166 Ma) at the southwestern end tungsten province, in what we would interpret Geology of the Copper Belt of the belt are copper-rich skarn occurrences here as a back-arc setting (Fig. 1; more detailed The porphyry copper deposits are mainly in the Yangchun Basin (Fig. 1). They occur at information is provided in the Supplemental in the southern and northwestern parts of the the contact between Jurassic granodiorite plu- Material; Mao et al., 2013, 2019). The discov- Coastal Cathaysia block, as well as west of the tons and Upper Devonian carbonate rocks. The ery of the 161 Ma Xinliaodong porphyry copper extensive Cretaceous volcanic rock cover with- Zhongqiuyang (162 Ma), E’di (169 Ma), Guan- deposit associated with granodiorite porphyry in the block. Only a few deposits, such as the tian, Xinliaodong (161 Ma), Gutian (162 Ma), in eastern Guangdong Province in 2010 (Fig. 1; Dingjiashan and Fengyan Cu-rich polymetallic and Honggoushan (156 Ma) porphyry copper Wang et al., 2014) gave rise to the speculation deposits (Fig. 1), are exposed in a tectonic win- prospects are hosted in Late Jurassic intrusive that there may possibly be a Jurassic arc-related dow surrounded by younger Late Jurassic–Cre- rocks and their country rocks of Lower Jurassic copper porphyry belt near the continental mar- taceous volcanic rocks. siltstone and Upper Jurassic volcanic rocks. Ma- The Jurassic copper deposits in the southeast jor Pb-Zn-Cu skarn orebodies at both Fengyan China coastal belt comprise a spectrum from and Dingjiashan are mainly hosted in Protero- 1Supplemental Material. Appendix S1, Figures S1– S4, and Table S1. Please visit https://doi.org/10.1130/ porphyry to skarn and to epithermal vein types. zoic carbonate rocks and are spatially associated GEOL.S.13530608 to access the supplemental material, The latter veins are less abundant and economi- with minor late Jurassic subvolcanic dikes. The and contact [email protected] with any questions. cally less significant than in the well-studied northernmost part of the belt hosts the major Geological Society of America | GEOLOGY | Volume 49 | Number 5 | www.gsapubs.org 593 Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/49/5/592/5273400/592.pdf by guest on 25 September 2021 Dexing porphyry copper district with a total gram (Fig.
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