Introduction

Iron oxide-copper-gold (IOCG) deposits are characterized by abundant low-Ti iron oxide (magnetite and hematite), pervasive hydrothermal alkali (Na/Ca/K) alteration, and an extensional tectonic setting (Hitzman et al. 1992). As these deposits host large resources of uranium, copper, and gold, they have become important exploration targets during the past decades (Hitzman and Valenta 2005; Sillitoe 2012; Zhu 2016).

Although several authors have attempted to establish a general ore deposit model (e.g., Williams et al. 2005; Groves et al. 2010; Porter 2010; Barton 2014), much controversy remains on the genesis of these deposits. For the IOCG deposits in the Gawler craton of South Australia, a fairly restricted episode of mineralization between ~1570 and ~1600 Ma was proposed, related to the magmatism of the Hiltaba Suite and Gawler Range Volcanics (Skirrow et al. 2007). However, in most other areas, protracted mineralization seems to be critical for the formation of IOCG deposits (Barton 2014). The two competing models mainly reflect the inability to accurately and precisely determine the mineralization age of IOCG deposits. In addition, most Precambrian IOCG provinces were affected by multiple tectonothermal events (Barton 2014). Thus, a precise chronometer for IOCG deposits resistant to thermal disturbance is required. Molybdenite usually has high Re and low Os concentrations and can resist high-grade thermal metamorphism (Stein et al. 2001; Stein 2014), which makes it a suitable mineral for dating IOCG mineralization, but the rare occurrence of molybdenite in most IOCG deposits limits its utilization (e.g., Requia et al. 2003; De Haller et al. 2006; Skirrow et al. 2007; Moreto et al. 2015b).

The Lala copper deposit is one of the largest IOCG deposits in the Kangdian copper belt, southwest China, containing 163 Mt ores (@14.4% Fe, 1.02% Cu, 0.02% Mo, 0.17 g/t Au; Zhu et al. 2013; Zhu 2016 and several unpublished reports). During recent fieldwork, we identified three textual types of Mo mineralization in the Lala deposit, i.e., disseminated to massive molybdenite, spotted-patchy molybdenite associated to chalcopyrite-quartz veins in albitite, and late molybdenite in quartz-carbonate veins. Here, we report Re-Os molybdenite ages for each of the three textural molybdenite types, which together with previously reported Re-Os data on banded molybdenite (Chen and Zhao 2012), to constrain the formation of the Lala deposit by multiple episodes of mineralization. We further propose a temporal link between the multiple episodes of mineralization of the Kangdian Copper Belt and the breakup of the supercontinent Nuna.

Geologic setting

The South China Block consists of the ~3.3–2.9 Ga Yangtze Block to the northwest and the ~2.5 Ga Cathaysia Block to the southeast (Fig. 1a). The two blocks consolidated around 860–815 Ma (i.e., Sibao orogeny or Jiangnan orogeny; Li et al. 1995, 2002; Zhao and Zhou 2011; Wang et al. 2007b; Yang et al. 2012; Yao et al. 2014; Zhao 2015). The Yangtze Block has a sparse Archean basement in the northern margin and a widespread Paleoproterozoic folded basement in the western margin (Fig. 1b), whereas the Cathaysia Block has a sparse Paleoproterozoic basement in the northeastern sector but a widespread Neoproterozoic basement in the northern sector (Zhao and Cawood 2012). The Proterozoic strata are unconformably overlain by an unmetamorphosed late Sinian to Cenozoic cover sequence (Yan et al. 2003). The Sibao orogeny resulted in widespread deformation, uplift, and upper greenschist to lower amphibolite facies metamorphism at 860–815 Ma in the Yangtze and Cathaysia Blocks (Li et al. 2002).

Fig. 1
figure 1

a Simplified tectonic map showing the study area in the Yangtze Block. b Regional geologic map of the Kangdian Copper Belt showing major Fe-Cu deposits, Precambrian strata and plutons (modified from Zhao and Zhou 2011)

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The Kangdian Copper Belt is a newly defined world-class IOCG metallogenic province, which extends ~300 km from SW China to N Vietnam in the west margin of the Yangtze Block (Fig. 1b, Greentree 2007; Zhao and Zhou 2011). There are more than 50 IOCG deposits hosted in the late Paleoproterozoic (1.7–1.6 Ga) meta-volcanic and meta-sedimentary sequences, and six large Fe-Cu deposits include the Lala, Xikuangshan, Yinachang, Etouchang, Dahongshan, and Sin Quyen deposits (Zhou et al. 2014). Traditionally, these deposits were thought to be syngenetic volcanogenic massive sulfide (VMS) deposits based on their ore texture and marine volcanic host rock (~1.7–1.6 Ga; Li et al. 1988). Recently, they were thought to be epigenetic IOCG deposits due to abundant low-Ti hydrothermal magnetite, elevated REE and Mo, extensive albite and K-feldspar alteration, and disseminated to massive and veined ores with local hydrothermal breccias (Zhao and Zhou 2011).

The Kangdian Copper Belt contains Proterozoic volcano-sedimentary sequences including the late Paleoproterozoic Hekou, Dahongshan, and Dongchuan Groups (~1.7–1.6 Ga; Greentree and Li 2008; Zhao et al. 2010; Zhao and Zhou 2011; Zhu et al. 2013), and the late Mesoproterozoic–early Neoproterozoic Huili and Kunyang Groups (~1.4–1.0 Ga; Greentree et al. 2006; Geng et al. 2007; Yin et al. 2011; Wang et al. 2012; Chen et al. 2014). These Proterozoic sequences were intruded by Paleoproterozoic (~1.65 Ga) and Neoproterozoic (~860–740 Ma) mafic–felsic intrusions (Zhou et al. 2014). The Sibao orogeny (860–815 Ma) resulted in upper greenschist-lower amphibolite facies metamorphism in the late Paleoproterozoic Hekou, Dahongshan, and Dongchuan Groups, whereas lower greenschist facies metamorphic overprint is visible in the late Mesoproterozoic–early Neoproterozoic Huili and Kunyang Groups.

The Lala Fe-Cu deposit is located in the north of the Kangdian Copper Belt and has six main mining sites including Luodang, Hongnipo, Laoyanghantan, Shilong, Changpuqing, and Laohushan (Fig. 2 and Table 1). The detailed geology of the Lala copper deposit has been described by Chen and Zhou (2012) and Zhu and Sun (2013). The Lala deposit is hosted by the Paleoproterozoic meta-volcano-sedimentary sequences of the Hekou Group (zircon U-Pb depositional age of 1669 ± 6 Ma, Zhu et al. 2013). The Hekou Group is in fault contact with the Huili Group (1.4–1.0 Ga) and is unconformably overlain by the Triassic Baiguowan Formation. The Hekou Group comprises the Baiyunshan and Luodang Formations from the base upward (Fig. 2). The Baiyunshan Formation consists of coarse- to fine-grained siliciclastic and carbonate rocks, whereas the Luodang Formation consists of sodic lava and pyroclastic rocks (Zhu et al. 2013).

Fig. 2
figure 2

Geological map of the Lala area showing the main mining sites

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Table 1 Tonnages and grades of six main mining sites of the Lala deposit
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The orebodies of the Lala deposit occur principally as stratiform, stratoid, and lentoid in accordance with the strike of host rocks and locally occur as veins crosscutting the host rocks. The host rocks are mainly biotite quartz schist, two-mica quartz schist, garnet-biotite quartz schist, and magnetite-quartz albitite of the Luodang Formation and are locally intruded by a diabase-gabbro dike (zircon U-Pb: 1657 ± 21 Ma; Chen et al. 2013b) and granite porphyry (zircon U-Pb: 1657 ± 15 Ma; Song 2014). The diabase-gabbro dike and granite porphyry are all hydrothermally altered but without clear relationship with orebodies. Locally, breccias occur in the Lala deposit and are generally associated with orebodies. The clasts of breccias are pink with low roundness and mainly consist of albite, whereas the matrices of the breccias consist of biotite and chlorite largely replaced by chalcopyrite and pyrite. Most breccias are deformed and predated metamorphism (Chen and Zhou 2012). Both orebodies and their host rock underwent greenschist-facies metamorphism at 860–815 Ma (Greentree 2007; Zhou et al. 2014) and were foliated and folded along NS-trending axes and cut by later north-northwest faults.

The paragenetic sequence includes six stages based on the macro- and micro-textural relationships of mineral assemblages of different ores from the Lala deposit (Zhu et al. 2009; Chen and Zhou 2012; Song 2014; and this study) (Fig. 3). Mineral assemblages of stage I to stage V are foliated and metamorphosed, whereas mineral assemblages of stage VI are unmetamorphosed. Stage I (pre-ore pervasive Na alteration) consists mainly of albite and minor amphibole, tourmaline and/or scapolite replacing the host rocks. Stage II (magnetite stage) comprises magnetite, K-feldspar, and apatite, and minor actinolite and chlorite with sparse disseminated chalcopyrite and pyrite. Stage III (polymetallic-disseminated/massive magnetite-sulfide stage) is characterized by abundant magnetite, chalcopyrite, pyrite, pyrrhotite, carbonate minerals, and quartz with minor molybdenite, fluorite, apatite, K-feldspar, biotite, and muscovite; native gold and silver occur locally. Stage IV (banded magnetite-sulfide stage) has a mineral assemblage of oriented pyrite-chalcopyrite-molybdenite, magnetite, carbonate minerals, REE minerals, and quartz with local bornite, native gold, native silver, hematite, titanite, and allanite. Stage V (sulfide vein stage) is dominated by chalcopyrite, pyrite, carbonate, and quartz with variable biotite, muscovite, fluorite, pyrrhotite, bornite, molybdenite, native gold, silver, and REE minerals. The final quartz-carbonate vein stage (stage VI) has minor molybdenite and displays extensive hematite alteration in the country rocks; REE minerals and pyrite occur locally. The sulfide veins of stage V crosscut the host rocks and Fe-Cu ores of stage II to stage IV, whereas the late quartz-carbonate veins of stage VI crosscut host rocks and Fe-Cu ores of stage II to stage V. Iron ore mineralization predominantly occurs as massive and disseminated oxide and oxide-sulfide assemblages in stages II, III, and IV, whereas Cu-Mo sulfide mineralization primarily occurs as disseminated-massive and banded sulfides of stages III and IV, with minor sulfide veining in stage V. Therefore, the disseminated to massive ores of stage III and banded ores of stage IV represent the principal IOCG mineralization, the veined ores of stage V represent minor IOCG mineralization, and the veins of stage VI represent hydrothermal overprint or metamorphic remobilization.

Fig. 3
figure 3

Paragenetic sequence of mineralization and alteration in the Lala deposit (compiled from Zhu et al. 2009; Chen and Zhou 2012; Song 2014 and this study)

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Sampling and analytical methods

In the Lala deposit, molybdenite is present in four paragenetic stages: (1) Stage III fine-grained molybdenite distributed within disseminated to massive magnetite-chalcopyrite-pyrite ore (Fig. 4d–f), (2) stage IV molybdenite-chalcopyrite bands up to several millimeters thick (Fig. 4g–i), (3) stage VI fine-grained molybdenite within late quartz-carbonate veins with the width of several to 20 cm in thickness (Fig. 4h–i), and (4) sparse stage V coarse-grained (~2–8 mm) spotted-patchy molybdenite in sulfide-quartz veins associated with quartz albitite (Fig. 4g). Fifteen samples, with five replicates (0308-1-2, 0308-2-2, 0101-1-2, 0101-2-2, 0109-2), were collected from the Luodang open-pit in the Lala deposit for Re-Os molybdenite geochronology. The samples include nine stage VI vein stage samples (0102–0110), four stage III disseminated to massive samples (0308-1–0308-4), and two stage V spotted-patchy samples (0101-1 and 0101-2).

Fig. 4
figure 4

Photographs of four types of molybdenite samples from the Lala deposit (a–c). Massive magnetite ore (stage II) (d–f). Disseminated to massive Cu-Mo ore (stage III). Chalcopyrite replaces molybdenite and some chalcopyrite overgrows molybdenite (g–i). Banded Cu-Mo ore (stage IV): chalcopyrite replaces molybdenite and molybdenite overgrows chalcopyrite (j). Spotted-patchy molybdenite ore (stage V): molybdenite in quartz albitite (k–l). Molybdenite-quartz vein (stage VI): late molybdenite-quartz-carbonate vein crosscutting the disseminated-massive Cu ores. Mineral abbreviations: Cp chalcopyrite, Mo molybdenite, Mt magnetite, Py pyrite, Qrt quartz, Ab albite, Cc calcite, Fr fluorite

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Molybdenite Re-Os isotope analyses were carried out in the Re-Os Laboratory, National Research Center of Geoanalysis, Chinese Academy of Geological Sciences (CAGS, Beijing). All molybdenite separates were produced and analyzed using the procedures described by Du et al. (2004). About ~0.001 to 0.05 g separates were crushed and ground to less than 200 mesh. Precisely weighed powders were loaded into Carius tubes, together with 185Re and 190Os mixed spikes, and digested by reverse aqua regia. The tube was heated in an oven at 200 °C for about 24 h. Upon cooling, the bottom part of the tube was kept frozen, the neck of the tube was broken, and the contents were poured into a distillation flask and the residue was washed out with 40 ml of MQ water. Osmium was separated as OsO4 by distillation at 105–110 °C and was trapped by Milli-Q water. During distillation, the reverse aqua regia acted as oxidizer. The residual Re-bearing solution was saved in a 150-ml Teflon beaker for Re separation. The Os isotope ratio was determined using an inductively coupled plasma mass spectrometer (TJA X-series ICP-MS). During the entire procedure, the Chinese reference standard GBW 04435 (HLP molybdenite) was used to estimate accuracy and precision. The procedural blanks and standard deviation for Re and common Os are 2.2 ± 1.1 and 0.7 ± 0.1 pg, respectively.

Results

Re-Os data of 15 samples are shown in Table 2. The stage III disseminated to massive samples have moderate Re and Os concentrations (187Re ranging from 66.87 to 74.40 ppm, and 187Os ranging from 1475.6 to 1638.8 ppb) and model ages range from 1294 ± 19 Ma to 1323 ± 19 Ma with an average of 1306 ± 8 Ma (MSWD = 1.1, n = 6). The stage V spotted-patchy molybdenite in sulfide veins also has low Re and Os concentrations (187Re ranging from 4.34 to 4.94 ppm and 187Os ranging from 66.0 to 80.0 ppb) but variable model ages. The small sample aliquants (1 and 21 mg) yield model ages ranging from 907 ± 14 to 929 ± 13 Ma with an inaccurate average age of 919 ± 140 Ma (MSWD = 5.3, n = 2), whereas the larger sample aliquants (~50 mg) yield identical model ages of 974 ± 14 and 982 ± 14 Ma with an accurate average age of 978 ± 10 Ma (MSWD = 0.62, n = 2). The large error of the average age from the small sample aliquants is due to the decoupling of Re and Os within coarse-grained molybdenite (Stein et al. 2003; Selby and Creaser 2004), whereas the large sample aliquants can overcome decoupling of Re and Os within coarse-grained molybdenite (Selby and Creaser 2004; Stein 2006). The ages of the larger sample aliquants are similar to molybdenite Re-Os ages obtained by Wang et al. (2007a). Thus, combined with molybdenite Re-Os ages reported by Wang et al. (2007a), we recalculate the weighted mean model ages of stage V molybdenite as 988 ± 8 Ma (MSWD = 1.3, n = 7). The stage VI vein samples have high Re and Os concentration (187Re ranging from 53.31 to 125.10 ppm and 187Os ranging from 755.0 to 1755.0 ppb) and model ages ranging from 831 ± 12 to 844 ± 12 Ma with an average of 835 ± 4 Ma (MSWD = 0.66, n = 10) and an isochron age of 830 ± 10 Ma (MSWD = 1.2). We interpret the weighted mean model ages of 1306 ± 8, 988 ± 8, and 835 ± 4 as representing the depositional ages of stage III molybdenite, stage V molybdenite, and stage VI molybdenite, respectively (Fig. 5).

Table 2 Re-Os isotope data for molybdenite from the Lala copper deposit
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Fig. 5
figure 5

Weighted averages of Re-Os molybdenite model ages for the Lala deposit. Data of stage IV molybdenite are from Chen and Zhou (2012). Errors are 2σ

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Discussion

Timing of multiple mineralization events at Lala

Our Re-Os data, together with those reported by Wang et al. (2007a), Chen and Zhou (2012) and Song (2014), indicate that there were at least four hydrothermal events in the Lala deposit. The stage III disseminated-massive molybdenite samples yield Re-Os ages of the first ore-forming hydrothermal event (1306 ± 8 Ma), which produced the disseminated to massive molybdenite-chalcopyrite-magnetite ores, and this age overlap with the chalcopyrite Re-Os age of 1290 ± 38 Ma by Zhu and Sun (2013) and with the zircon U-Pb age of early Huili volcanism nearby the Lala deposit (Yin et al. 2011). The stage IV banded molybdenite samples yield Re-Os ages of the second ore-forming hydrothermal event (1086 ± 6 Ma), which produced the banded molybdenite-chalcopyrite ores (Chen and Zhou 2012; Song 2014), and this age is supported by the allanite U-Pb age of 1067 ± 41 Ma (Chen and Zhou 2014) and zircon U-Pb age of the late Huili volcanism (Geng et al. 2007; Yin et al. 2011). The stage V spotted-patchy molybdenite samples define the third ore-forming event (988 ± 8 Ma), which produced the sulfide-quartz veins, and this age is within error of the average molybdenite Re-Os age of 993 ± 7 Ma reported by Wang et al. (2007a). The stage VI veined molybdenite samples define the fourth and barren hydrothermal event (835 ± 4 Ma), which produced the late molybdenite-quartz-carbonate veins. The last molybdenite mineralization was roughly coeval with the metamorphism of the Sibao orogeny (860–815 Ma, Greentree 2007; Yang et al. 2012; Zhou et al. 2014) and REE-U redistribution (880–850 Ma, Chen and Zhou 2014; 824 ± 15 Ma, Song 2014; Chen and Zhou 2015). Overall, the main IOCG mineralization (Fe-Cu) formed in the first and second hydrothermal event, REE mineralization formed in the second hydrothermal event but was redistributed in the fourth hydrothermal event (Chen and Zhou 2015), and Mo mineralization formed at all four hydrothermal events.

Comparison with other IOCG systems

The Fe-Cu deposits in the Kangdian Copper Belt display extensive Na-Ca-K alteration and local brecciation and contain low-Ti iron oxides (magnetite and hematite) and chalcopyrite as primary minerals, with economic Au, Ag, Co, U, and REE by-products (Greentree 2007; Zhao and Zhou 2011). These features are in common with other typical IOCG deposits worldwide (Williams et al. 2005; Groves et al. 2010; Porter 2010). However, the precise timing of the IOCG ore-forming processes in the Kangdian Copper Belt were unclear. Recently, some scientists used Re-Os and U-Pb isotopes to precisely date the hydrothermal events of the Kangdian Copper Belt. Zhao et al. (2013) reported molybdenite Re-Os ages of 1654 ± 7 Ma for magnetite ores, and molybdenite Re-Os ages of 1451 ± 6 Ma for hydrothermal veins from the Yinachang deposit. Hou et al. (2015) obtained a chalcopyrite Re-Os age of 1648 ± 14 Ma for Cu-Fe ores from the Yinachang deposit. Li and Zhou (2015) reported a monazite U-Pb age of 842 ± 9 Ma for REE ores from the Yinachang deposit. Song (2014) obtained a magnetite Re-Os age (ca. 1325 Ma) for magnetite ores and chalcopyrite Re-Os age of 1083 ± 45 Ma for copper ores from the Dahongshan deposit. Zhao et al. (2017) reported a hydrothermal zircon U-Pb age of 1653 ± 18 Ma for stockwork chalcopyrite-magnetite ore, a pyrite Re-Os age of 1026 ± 22 Ma for discordant quartz-carbonate-sulfide veins, and a Re-Os age of 830 Ma for molybdenite within foliated meta-arenite. Zhou et al. (2014) argued that the Kangdian IOCG province may have undergone three mineralization events at 1.66, 1.45, and 1.05 Ga and one post-ore tectonothermal event in the Neoproterozoic (~780–870 Ma).

Our new data record four hydrothermal events in the Lala deposit. Therefore, there were five hydrothermal events in the Kangdian Copper Belt, including three main mineralization events at 1.65, 1.30, and ~1.09–0.99 Ga and two less important or local hydrothermal/mineralization overprint events at 1.45 and 0.83 Ga (Fig. 6).

Fig. 6.
figure 6

Summary of geochronological data showing the timing of magmatism, metamorphism, hydrothermal events, and mineralization for the Kangdian Copper Belt (zircon U-Pb: Zhou, et al. 2002; Geng et al. 2007; Yin et al. 2011; Wang et al. 2012; Yang et al. 2012; Chen et al. 2013b; Zhu et al. 2013; Chen et al. 2014; Song 2014; Zhao et al. 2017, and our unpublished data; chalcopyrite Re-Os: Zhu and Sun 2013; Song 2014; Hou et al. 2015; pyrite Re-Os: Zhao et al. 2017; molybdenite Re-Os: Wang et al. 2007a; Chen and Zhou 2012; Zhao et al. 2013, 2017, and this study; allanite U-Pb: Chen and Zhou 2014; monazite U-Pb: Li and Zhou 2015; pyrite Rb-Sr: Zhao et al. 2013; uraninite U-Th-Pb: Song 2014; biotite and muscovite Ar-Ar: Greentree 2007; Zhou et al. 2014)

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Although Hitzman et al. (1992) initially proposed that the most of the sulfide ore postdated Fe oxide formation associated with regional sodic alteration for many IOCG deposits, precise geochronological data for multiple episodes of mineralization were not available until recent studies in some IOCG provinces, e.g., the Fennoscandian Shield (Smith et al. 2009), the Central Andes (Chen 2010), and the Mount Isa Inlier (Duncan et al. 2011). Furthermore, precise U-Pb ages of hydrothermal zircon from four IOCG deposits at Lyon Mountain Granite, Adirondack Highlands in New York State, show that Fe mineralization was episodic (Valley et al. 2009). More recently, Re-Os isotopic data demonstrate that the Cu mineralization may also have formed from multiple hydrothermal episodes, and some IOCG provinces even formed over large intervals of 100 My or more (e.g., Mount Isa Inlier, Duncan et al. 2011; Kangdian, Zhou et al. 2014; Carajás, Moreto et al. 2015a, b). Our Re-Os molybdenite dates, together with previously reported data, provide robust evidence for the multiple nature of hydrothermal mineralization at the Lala deposit. These age data also indicate that young Neoproterozoic hydrothermal events possibly produced local but potentially important Mo-U-REE mineralization.

Possible link between mineralization and supercontinent cycles

The formation of some ore deposits related to convergent and collisional processes (e.g., orogenic Au, volcanic-hosted massive sulfide, Mississippi Valley-type Pb-Zn, epithermal Au-Ag, porphyry deposits) correlates well with the assembly of supercontinents (Cawood and Hawkesworth 2015), whereas others relate to intra-continental settings and divergent margins (e.g., diamond, Ni-Cu-PGE, and sediment-hosted stratiform Cu deposits) during the breakup of supercontinents (Groves and Bierlein 2007). Most IOCG deposits are located in intra-continental settings and/or divergent margins and may have formed in extensional settings (Hitzman et al. 1992). Therefore, IOCG deposits may also be correlated with the breakup of supercontinents (Porter 2010; Chen et al. 2013a). Groves et al. (2010) further suggest that the formation of giant Precambrian IOCG deposits was related to extensive mantle underplating that impacted on buoyant metasomatized subcontinental lithospheric mantle. Consequently, the underplate and associated high-temperature metamorphism and magmatism acted both as heat engines, driving fluid circulation over large volumes of the crust, and as ore-forming fluid and metal sources during the breakup of supercontinents (Porter 2010).

The Nuna (or Columbia) supercontinent consolidated at 2.2–1.8 Ga, stabilized at 1.8–1.6 Ga, then fragmented from 1.6 Ga to 1.2 Ga, and eventually broke up at 1.0 Ga (Bradley 2011; Kaur and Chaudhri 2014; Pehrsson et al. 2015; Condie et al. 2015). Cawood and Hawkesworth (2015) point out that the timing of Mesoproterozoic IOCG deposits corresponds with the breakup of Nuna (1.6–1.0 Ga) but not with the assembly of Rodinia (1.3–1.0 Ga). The Mesoproterozoic IOCG deposits include Swan in Cloncurry (1.35 Ga, Duncan et al. 2011), Boss-Bixby in SE Missouri (1.45 Ga, Porter 2010), and Blackbird in the Idaho cobalt belt (ca.1.37 Ga, Aleinikoff et al. 2012). It is generally accepted that the Yangtze Block was part of the Nuna supercontinent (Zhu et al. 2013; Chen et al. 2013b; Zhou et al. 2014). The ~1.65–1.00 Ga IOCG mineralization (see compilation in Fig. 6) may provide evidence for a temporal link between the formation of these IOCG deposits in the Kangdian Copper Belt and the breakup of the Nuna supercontinent. At least four pieces of evidence also show that the western margin of the Yangtze Block was located in an extensional rift setting during the late Paleoproterozoic-Mesoproterozoic as follows: (1) the western margin of the Yangtze Block flanks the Yangtze continent and is underlain by a continental basement (Li et al. 1988; Zhou et al. 2014); (2) the geochemistry of the Mesoproterozoic (~1.7–1.0 Ga) mafic-felsic igneous rocks shows features of intra-continental rift magmatism (Geng et al. 2007; Yin et al. 2011; Chen et al. 2013b, 2014); (3) the sedimentary rocks of the Hekou, Dahongshan, Huili, Julin, and Kunyang Groups (~1.7–1.0 Ga) were deposited in a rifted passive margin (Li et al. 1988; Zhao et al. 2011); and (4) there are many stratiform sediment-hosted Cu deposits formed in the Mesoproterozoic (Tangdan: 1432 ± 19 Ma, Huang et al. 2013; Heiqing: 1359 ± 15 Ma, our unpublished data).

Conclusions

We identify four hydrothermal events in the Lala deposit. The main IOCG mineralization formed in two stages in the Mesoproterozoic at 1.30 to 1.09 Ga, respectively, and local hydrothermal events overprinted the Fe-Cu ores at 0.99 and 0.83 Ga. Our results also indicate that the Lala deposit formed from multiple, protracted hydrothermal events over several hundred million years. The first three Mesoproterozoic mineralization events are related to intra-continental rifting and suggest a link between IOCG mineralization in the Kangdian IOCG metal province and breakup of the supercontinent Nuna; the last Neoproterozoic hydrothermal event is related to the Sibao orogeny which culminated with the amalgamation of the Yangtze Block with the Cathaysia Block.