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Geodynamic evolution
It is generally accepted that the South China Block was constructed through a Neoproterozoic amalgamation of the Yangtze Block and the Cathaysia Block with the Jiangnan Orogen as the suture zone between them (Figs. 2-2 and 2-3a), although the precise time of the amalgamation is still controversial from 1.0 Ga to 0.8 Ga (Li et al., 2002, 2003, 2007b, 2008, 2009, 2014b; Wang and Li, 2003; Shu et al., 2006a, 2011; Zhou et al., 2006b;
Wang et al., 2007a; Cawood et al., 2013; Yao et al., 2014a). After the collision of the Yangtze Block and the Cathaysia Block, the South China Block experienced a regional-scale extension during Late Neoproterozoic which led to the formation of rift basins that contain a set of siliciclastic sediments coeval with bimodal volcanic rocks (800 – 690 Ma; Fig. 2-3b) (Wang and Li, 2003; Shu et al., 2011; Li et al., 2014b). Then the Cathaysia Block underwent a stable intraplate neritic-bathyal depositional stage from Sinian to Early Paleozoic (690 – 460 Ma; Fig. 2-3c) during which thick siliciclastic sediments were formed (Shu et al., 2014) without volcanic magmatism and any evidence for the input of mantle-derived materials.
In Phanerozoic, the South China Block mainly experienced three tectonothermal events, i.e., Early Paleozoic, Triassic, and Jurassic-Cretaceous events, which were generally referred to as “Caledonian or Kwangsian”, “Indosinian”, and “Yanshanian” movements by Chinese geologists, respectively (Ting, 1929; Hsu et al., 1960, 1963a, 1963b; Ren, 1991; Hua and Mao, 1999; Zhou and Li, 2000; Hua et al., 2003, 2005; Wang et al., 2005a, 2010, 2011a, 2013; Zhou et al., 2006a; Chen et al., 2010, 2013). The Early Paleozoic tectonic movement was commonly recognized according to the presence of a conspicuous unconformity between the Middle Devonian and Silurian strata, pervasive shortening deformation, and high-grade metamorphism (Grabau, 1924; Ting, 1929; Lin et al., 2008; Faure et al., 2009; Charvet et al., 2010; Li et al., 2010, 2016, 2017; Charvet, 2013; Wang et al., 2013; Shu et al., 2015). It is now commonly interpreted as an intracontinental orogeny due to the lack of ophiolitic rocks, accretionary complexes, volcanic rocks with arc affinities, and the input of mantle-derived components in granitic magmatism (Faure et al., 2009; Charvet et al., 2010; Li et al., 2010; Charvet, 2013; Wang et al., 2013; Shu et al., 2015). Three competing tectonic models have been proposed to explain the origin of the Early Paleozoic orogeny, i.e., (1) northwestward intracontinental subduction of the northwestern Cathaysia Block beneath the southeastern Yangtze Block (Fig. 2-4a; Faure et al., 2009), (2) northwestward intraplate overthrusting of the northwestern Cathaysia Block atop the southeastern Yangtze Block (Fig. 2-4b; Li et al., 2010), and (3) combined northwestward underthrusting of an inferred East China Sea Block and southeastward underthrusting of the Yangtze Block both beneath the Cathaysia Block (Figs. 2-3d and 2-4c; Shu et al., 2014, 2015). This tectonic event was constrained in chronology by newly grown mica 40Ar/39Ar dating at 450 – 390 Ma with contemporaneous anatectic granites dated at 460 – 390 Ma (Shu et al., 1999, 2015; Charvet et al., 2010; Shu, 2012; Li et al., 2016, 2017). During Late Paleozoic from 390 Ma to 240 Ma, the South China Block underwent a stable intraplate carbonate depositional stage in a littoral-neritic environment resulting in the formation of a series of limestone, dolomite, and clastic rocks (Fig. 2-3e; Shu et al., 2006b, 2008, 2009).
Triassic is the main period for the development of the South China tectonic framework (Faure et al., 2016a, 2017). The Triassic tectonic movement was initially recognized due to the Late Triassic (Norian) angular unconformity of conglomerate and sandstone overlaying folded and metamorphosed rocks in Vietnam of the Indochina Block (Deprat, 1914, 1915; Fromaget, 1932, 1941). In South China, the Triassic event is recorded as a regional Late Triassic unconformity, folding, thrusting, ductile shearing, metamorphism, and granitic magmatism (Wang et al., 2005a, 2013; Lin et al., 2008; Shu et al., 2008, 2015; Zhang and Cai, 2009; Chu et al., 2012a, 2012b; Faure et al., 2016a, 2016b, 2017; Li et al., 2016, 2017). An Alps-type collision model (Fig. 2-4d) was proposed by Hsü et al. (1988, 1990) to explain the origin of this tectonic event based on interpreting the Banxi Group as a Mesozoic ophiolitic mélange. However, subsequent studies revealed that the Banxi Group is composed of a Neoproterozoic turbidite sequence (Gu et al., 2002; Wang and Li, 2003; Wang et al., 2007a). Although it is now widely accepted that the Triassic tectonic movement in the South China Block is an intraplate deformation event (Lin et al., 2008; Shu et al., 2008, 2015; Chu et al., 2012a, 2012b; Faure et al., 2014), the geodynamic mechanism of this event is still disputed with the following models: (1) flat-slab subduction model of the palaeo-Pacific plate (Figs. 2-4e and 2-5a–d) proposed by Li and Li (2007), (2) intraplate oblique convergence of the Yangtze Block and the Cathaysia Block (Fig. 2-4f) proposed by Wang et al. (2005a), and (3) collision of the South China Block with the Indochina Block and/or the North China Block (Figs. 2-4g and 2-6a–b) (Lepvrier et al., 2004; Faure et al., 2008; Cai and Zhang, 2009; Wang et al., 2013; Shu et al., 2015; Li et al., 2016). Wang et al. (2013) emphasized that the interaction between the South China Block and the surrounding blocks/plates provided the first-order driving force for the Triassic intracontinental deformation across the South China Block. The third tectonic model is becoming more and more popular than the former two, however, the influence of the palaeo-Pacific plate subduction during Triassic is still uncertain (Wang et al., 2013).
During Late Mesozoic (Jurassic-Cretaceous), the South China Block was dominated by an extensional tectonic regime, which is demonstrated by the occurrence of abundant granitoid rocks with an evident input of juvenile mantle-derived components, the wide distribution of extensional basins, the existence of extensional tectonomagmatic associations, the extensional information recorded by magma emplacement processes, and the absence of compressional deformation structures (Shu and Zhou, 2002; Shu et al., 2006b, 2009; Shu, 2012; Wang and Shu, 2012; Wang et al., 2013; Wei et al., 2014a, 2014b, 2016). Zhou and Li (2000) firstly proposed the model of palaeo-Pacific plate subduction with changing angles (Fig. 2-7) to understand the origin of the large-scale Late Mesozoic granitic magmatism in Southeastern China. A combination of the palaeo-Pacific plate subduction induced back-arc extensional setting, asthenosphere upwelling, basaltic magmas underplating, and crustal anatexis is thought to be the key mechanism for the generation of these Late Mesozoic granitoid rocks (Shu and Zhou, 2002; Zhou et al., 2006a). A transition of regional tectonic regime from the Tethysian domain to the palaeo-Pacific domain is suggested to occur in Early-Middle Jurassic (Shu and Zhou, 2002; Zhou et al., 2006a; Shu, 2012). Li and Li (2007) interpreted the Late Mesozoic granitoid rocks as a result of postorogenic magmatism induced by slab foundering and retreating in their flat-slab subduction model of the palaeo-Pacific plate (Fig. 2-5e and f). Wang et al. (2013) pointed that the post-orogenic collapse after the Triassic compressive deformation and the back-arc extension resulted from the westward subduction of the palaeo-Pacific plate probably jointly controlled the Early-Middle Jurassic tectonic regime of the South China Block (Fig. 2-6c), and the palaeo-Pacific plate subduction and the blocking with the Indochina Block to the southwest and the North China Block to the north might dominate the tectonic regime of the South China Block since Late Jurassic (Fig. 2-6d). However, the geophysical study on granite emplacement mechanism carried out by Liu et al. (2018) revealed that the Late Jurassic Qitianling pluton in South China was formed during a period of tectonic quiescence. Therefore, the Jurassic tectonic setting in South China remains a subject of controversy that need to be solved by further studies.
Multiple-aged granitoids and volcanic rocks
The outcrop area of the multiple-aged granitoids in the South China Block is about 169,690 km2, in which the Neoproterozoic, Early Paleozoic, Late Paleozoic, Triassic, Jurassic, and Cretaceous granitoids occupy about 9,950 km2, 22,110 km2, 1,480 km2, 23,230 km2, 61,460 km2, and 51, 460 km2, respectively (Fig. 2-8; according to a recently revised version of the map from Sun, 2006). In addition, the Jurassic and Cretaceous volcanic rocks have outcrop areas of 1,170 km2 and 89,620 km2, respectively (Fig. 2-8; Zhou et al., 2006a). These multiple-aged granitoids and volcanic rocks in the South China Block respectively have unique spatial distributions, chronological features, structural characteristics, mineralogical and geochemical compositions, and relations with tectonic events.
The Neoproterozoic granitoids mostly occur as peraluminous granite batholiths along the southeastern margin of the Yangtze Block in southern Anhui, northern Jiangxi, southern Hubei, and northern Guangxi Provinces (Fig. 2-8), such as the Xucun, Jiuling, Motianling, and Yuanbaoshan granites. They were partially deformed as gneissoid granites and coexist with a set of slightly earlier formed Neoproterozoic island-arc volcanic-sedimentary sequence (Zhou, 2003; Sun, 2006). These Neoproterozoic granites generally contain aluminum-rich minerals, such as cordierite, muscovite, tourmaline, and garnet, and are considered as S-type granites (Li et al., 2003; Zhou, 2003). Some Neoproterozoic I-type granitoids also appear in 2006 and Zhou et al., 2006a).
the South China Block, such as the Huangling complex in western Hubei Province (Fig. 2-8) which is comprised of dominant Na-rich tonalite-trondhjemite-granodiorite association and minor K-rich calc-alkaline intrusions (Li et al., 2003). The Neoproterozoic granitoids were mostly formed at ca. 830 Ma and were derived from partial melting of various crustal sources with different influences by juvenile mantle-derived components (Li et al., 2003; Zhou, 2003; Sun, 2006; Yao et al., 2014a; Zhang et al., 2016a; Wang et al., 2017a; Xiang et al., 2018). Li et al (2003) introduced a model of mantle plume beneath South China to interpret the origin of these Neoproterozoic granitoids, however, it is now more accepted that the generation of these Neoproterozoic granitoids was related to the amalgamation of the Yangtze and Cathaysia Blocks and its post-orogenic extension (Zhou, 2003; Sun, 2006; Yao et al., 2014a; Wang et al., 2017a).
Table of contents :
Chapter 1. Introduction
1.1. Research background and scientific problems
1.1.1. Research background
1.1.2. Scientific problems
1.2. Topic selection and research contents
1.2.1. Topic selection
1.2.2. Research contents
1.3. Research methodology and technical route
1.3.1. Research methodology
1.3.2. Technical route
1.4. Workload and research achievements
1.4.1. Workload
1.4.2. Main findings and innovations
Chapter 2. Geological setting
2.1. South China
2.1.1. Geodynamic evolution
2.1.2. Multiple-aged granitoids and volcanic rocks
2.1.3. Polymetallic mineralization
2.2. Nanling Range
2.2.1. Middle-Late Jurassic ore-bearing granitoids
2.2.2. Middle-Late Jurassic skarn deposits
Chapter 3. Geology of the Tongshanling-Weijia area
3.1. Stratigraphy
3.2. Structures
3.3. Magmatism
3.4. Mineralization
Chapter 4. Different origins of the Cu-Pb-Zn-bearing and W-bearing granitoids
4.1. Introduction
4.2. Petrography of granitoids
4.2.1. Tongshanling granodiorite porphyry
4.2.2. Dioritic dark enclaves
4.2.3. Tongshanling granite porphyry
4.2.4. Weijia granite porphyry
4.3. Sampling and analytical methods
4.4. Results
4.4.1. Zircon U-Pb age
4.4.2. Zircon Hf isotope
4.4.3. Whole-rock major elements
4.4.4. Whole-rock trace and rare earth elements
4.4.5. Whole-rock Sr-Nd isotopes
4.5. Discussion
4.5.1. Timing of granitoids
4.5.2. Degree of fractionation
4.5.3. Petrogenesis
4.5.4. Sources of the Cu-Pb-Zn-bearing and W-bearing granitoids
4.5.5. Genetic model of the Cu-Pb-Zn-bearing and W-bearing granitoids
4.6. Summary
Chapter 5. Reworked restite enclave
5.1. Introduction
5.2. Tongshanling granodiorite and its microgranular enclaves
5.3. Petrography
5.3.1. Tongshanling granodiorite
5.3.2. Microgranular enclaves
5.4. Analytical methods
5.5. Analytical results
5.5.1. Plagioclase
5.5.2. Amphibole
5.5.3. Biotite
5.5.4. Zircon
5.6. Discussion
5.6.1. Textural evidence
5.6.1.1. Residual materials
5.6.1.2. Vestiges of magma reworking
5.6.2. Compositional evidence
5.6.2.1. Magmatic amphibole
5.6.2.2. Metamorphic amphibole
5.6.2.3. Magma reworked metamorphic amphibole
5.6.2.4. Zircon and plagioclase
5.6.2.5. Biotite
5.6.2.6. Residual materials in the granodiorite
5.6.2.7. Geochemical signatures
5.6.3. Geothermobarometry
5.6.3.1. Temperature
5.6.3.2. Pressure
5.6.4. The model for reworked restite enclave
5.7. Petrogenetic implications
Chapter 6. Magma emplacement-induced structural control on skarn formation
6.1. Introduction
6.2. Regional structural analysis
6.2.1. Normal fault
6.2.2. Contact zone
6.3. Deposit geology
6.3.1. Endoskarn
6.3.2. Exoskarn
6.3.3. Sulfide-quartz vein
6.4. Sampling and analytical methods
6.5. Results
6.5.1. RSCM thermometry
6.5.2. EBSD mapping
6.5.3. Garnet composition
6.6. Discussion
6.7. Summary
Chapter 7. Zonation and genesis of the Tongshanling Cu-Mo-Pb-Zn-Ag skarn system
7.1. Introduction
7.2. Deposit geology
7.2.1. Tongshanling Cu-Pb-Zn deposit
7.2.1.1. Proximal endoskarn
7.2.1.2. Proximal exoskarn
7.2.1.3. Distal skarn
7.2.1.4. Sulfide-quartz vein
