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Yangtze River Belt - Chengchao, Tieshan, Jinshandian, Tongshankou, Tongloshan, Fengshan, Longqiao, Shaxi, Xinqiao, Dongguashan, Shizishan, Fenghuangshan, Anjing, Magushan, Qiaomaishan, Gushan, Makou, Baixiangshan, Longshan, Hemushan, Zhongjiu
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Latest addition on 14_Apr_2024 is the   Shaxi   porphyry Cu-Au deposit.
NOTE: This record provides an overview of the tectonics, geology and mineralisation of the Middle to Lower Yangtze River Valley Metallogenic Belt, followed by descriptions of individual districts and deposits, which is a work in progress with additions being inserted as information is accessed.

The Middle to Lower Yangtze River Valley Metallogenic Belt extends over a 30 000 km2, flattened 'S-shaped', generally NE-SW aligned interval of ~700 km, from the western margin of Jiangsu province, through Anhui, the northernmost tip of Jiangxi into Hubei, almost to Wuhan. It hosts a range of ore deposits and mineralised systems that include:
Stratabound and transgressive, intrusion related skarn altered Fe-Cu-Au-Mo-W deposits formed between 148 and 135 Ma in carbonate host beds, distributed between the i). Ningzhen district, mostly in Jiangsu, near Nanjing in the north; ii). in the Tongling, Anqing-Guichi and Nanling-Xuancheng ore fields in Anhui, in the centre of the belt, near Tongling, e.g., Xinqiao, Dongguashan, Shizishan, Fenghuangshan, Anjing, Magushan and Qiaomaishan; and iii). in the southwestern extremity, partially in Jiangxi, but predominantly in Hubei in the Jiurui and Edong ore fields, e.g., Tongloshan and Tongshankou (both near Daye). These deposits occur in areas of uplift and are related to 156 to 137 Ma intrusions of high-K calc-alkaline granitoids comprising diorite, quartz diorite and granodiorite.
Skarn Fe-Cu deposits in carbonate units that are largely restricted to the Edong ore cluster, to the SW in Hubei, associated with similar >135 Ma intrusives as for the preceding deposits.
Iron-skarn deposits in carbonate units, but related to intrusions of between 133 ±1 and 129±2 Ma. These deposits are also predominantly located in the Edong ore cluster,to the SW in Hubei, and include the Chengchao, Tieshan and Jinshandian deposits.
Magnetite-apatite deposits, predominantly in the Cretaceous Luzong and Ning-Wu volcanic fault basins in the northern two thirds of the belt, e.g., the Luohe, Gushan, Makou, Baixiangshan, Longshan, Hemushan, Zhongjiu and Taipingshan deposits. Mineralisation was deposited between 134.9 and 122.9 Ma, associated with 126.5 to 124.8 Ma A-type granitoids and 135 to 123 Ma shoshonitic series volcanic rocks. The igneous suite consists of pyroxene diorite porphyry, diorite porphyry, syenitic granite porphyry and their eruptive equivalents.
Porphyry Cu-Au and Cu-Mo deposits such as the ~128 Ma Cretaceous Shaxi deposit in the Mesozoic Luzong volcanic basin which is located in the central part of the Middle to Lower Yangtze River Valley Metallogenic Belt, and is described below. Another example is the ~140 Ma Tongshankou porphyry mineralisation directly related to one of the skarn copper - molybdenum deposits, which is located further to the SW in the Edong Mining District on the south western extremity of the belt.

  The Middle to Lower Yangtze River Valley Metallogenic Belt (subsequently abbreviated to the 'Yangtze River Belt') is located over section of the northern fringes of the Yangtze Craton, and lies to the east of the Qinling-Dabie-Sulu Orogen which separates the North China and Yangtze cratons (see regional setting image below). The southwestern segment of the Yangtze River Belt lies to the SW of the NW-SE trending Xiangfan-Guangji fault that defines the southern margin of the Qinling-Dabieshan Orogenic Belt to the north, and appears to have been terminated to the west by the NW-SE Ma-Tuan Fault. The bulk of the main arm of the belt however, is bounded to the west by the major NNE-SSW trending transform structure, the sinistral Tan Lu Fault, which juxtaposes it with the Qinling-Dabieshan Orogenic Belt. This same structure truncates and offsets the Qinling-Dabieshan Orogen by up to 500 km as the Sulu Orogen to the north on its east side. The attenuated trailing edge of the Sulu Orogen which parallels the Tan-Lu Fault separates the Yangtze River Belt from the North China Craton before swinging more NE-SW on the Jiaodong Peninsular. Both the Qinling-Dabieshan and Sulu orogens are characterised by UHP metamorphic assemblages. The northern extremity of the Yangtze River Belt turns east west following the similar rotation of the main Sulu Orogen to the north. To the south, the main arm of the belt is limited by the composite, curvilinear, east-west to SW-NE trending,Yangxin-Changzhou Fault.

  See the Regional Setting section of the East Qinling Mo Belt record and accompanying images for an overview of the setting of the Yangtze River Belt and the location of structures etc., mentioned above.

The basement to and sequences of the Yangtze River Belt comprise four packages, as follows:

Pre-Sinian (pre-Late Neoproterozoic) basement rocks occur on either side of the belt, i.e., to the NW and SE:
  - Northwestern margin - which are represented by the Dabie Massif of the Qinling-Dabie Orogen to the west of the Tan Lu Fault (and north of the Xiangfan-Guangji Fault) and those of the Sulu Orogen in the north. Both suites are predominantly only in structural contact with the younger rocks of the belt. Both are largely composed of high and ultra high pressure (HP and UHP) metamorphic rocks resulting from the continent-continent collision between the North China and Yangtze cratons (Huang, 1978; Wang et al., 1995; Cong, 1996). Following complete subduction of the intervening oceanic crust, the Yangtze Craton was underthrust below the former to depths of more than 120 km, as is evident from the occurrence of microdiamonds in eclogites (Xu et al., 1992). Following post-collisional relaxation, exhumation of deep rocks from over 200 km depths was deduced from exsolution minerals in eclogitic garnet (Ye et al., 2000). Sm-Nd mineral isochron and U-Pb zircon dating suggests that the continental collision and UHP metamorphism occurred between 240 and 220 Ma in the Early-Middle Triassic in the Dabie Massif (Ames et al., 1993; Li et al., 1993; Chavagnac and Jahn, 1996; Hacker et al., 1998; Zheng et al., 2002; Liu et al., 2004). Upper amphibolite to granulite facies gneisses of the Dabie Massif have also been dated at ~195 Ma in the Lower Jurassic (
40Ar/39Ar; Wang et al., 2002). Age data from the Sulu Orogen indicate an initial prograde metamorphic event at 247 to 244 Ma (Liu et al., 2006, 2007) followed by peak eclogite facies metamorphism at 240 to 215 Ma (e.g., Tang et al., 2008) and exhumation at 215 to 205 Ma (e.g., Liu et al., 2007; Leech and Webb, 2013).
Setting of Yangtze River Belt
  The HP and UHP metamorphosed rocks of the Neorchaean to Palaeoproterozoic (2820 to 2413 Ma) Dabie Group of the eastern Qinling-Dabie Orogen range from eclogite and orthogneiss suites to granulite and amphibolite gneisses and marble formed from supracrustal protoliths (Liu and Liou, 2011; see description of Dabie/Tongbai Complex in the East Qinling Mo Belt record.
  The metamorphic rocks of the Sulu UHP belt are mainly amphibolite facies granitic gneisses, with subordinate coesite-bearing eclogites as well as ultramafics, 1994), marbles, pelitic schists and meta-granitoids. The UHP metamorphic rocks occur as sporadic lenticular bodies in the regional granitic gneisses. Most eclogite lens margins are retrograded to amphibolite, revealing a significant amphibolite facies overprint following UHP metamorphism. These rocks were buried to similar depths to those of the Dabie Massif and have similar ages of formation (Yang et al., 2005). Late Jurassic (160 to 150 Ma) and Early Cretaceous (130 to 125 Ma) high-K calc-alkaline granitic rocks are widely distributed in the Sulu Orogenic belt (Wang et al., 1998; Zhang et al., 2003).
  Within the Dabie Massif, these HP and UHP metamorphic rocks are confined to Archaean to Proterozoic sequences, whilst in the Sulu Orogen they also overprint protoliths as young as Middle to Late Triassic (Wang et al., 2019). In the Dabie Massif, they grade southward into, or are structurally juxtaposed with Palaeo- to Mesoproterozoic greenschist phyllite and slate intercalated with metaspilite-keratophyre and are overlain by Neoproterozoic greenschist facies marine clastic and carbonate rocks intercalated with felsic volcanic rocks, dolostone-quartz schist, biotite-albite schist, epidote-albite-quartz schist, dolostone-albite-quartz schist and phosphorous- and manganese-bearing carbonate rocks, intercalated with amphibolite.
  - Southeastern margin - comprising the Yangtze Craton, where older Archaean to Palaeoproterozoic crystalline basement is largely concealed by discordantly overlying cover sequences of Neoproterozoic Sinian conglomerate, tillite, dolostone, shale and chert.

Sinian to Early Triassic submarine sedimentary cover - The Yangtze River Belt was a stable fault bounded trough from the Cambrian to the Early Triassic, and was filled by shallow marine facies carbonate and clastic rocks (Xu, 1985). Sinian clastic rocks and dolostone are conformably overlain by Cambrian and Ordovician siltstone and shale with intercalated dolomitic limestone and marl, whilst the succeeding Silurian succession is characterised by thick quartz sandstone, arkose intercalated with shale, marl and dolostone. Deposition was halted during the Late Silurian and Devonian, as the basin was uplifted with a positive relief. Renewed subsidence during the Late Devonian resulted in deposition of terrigenous clastic rocks comprising thick beds of quartz sandstone, sandstone and basal conglomerate, coal seams and hematite-rich layers, passing conformably upwards into Carboniferous littoral facies carbonate rocks. Permian sedimentary rocks occur extensively throughout the whole belt, commencing with interbedded marine and terrigenous facies carbonate rocks, intercalated with some silicic, marl, Ca-rich shale, sandstone, siltstone and coalbearing sedimentary rocks (Zhai et al., 1992). These are overlain by littoral to shallow marine facies carbonates, intercalated with carbonaceous shale.
  The overlying Lower Triassic sequences include shallow marine to littoral dolostones, limestone and minor gypsum-bearing rocks. The Middle Triassic includes interbedded marine dolostone, marl, limestone and terrigenous marl and siltstone, overlain by Upper Triassic terrigenous argillaceous siltstone, fine-grained sandstone with coal seams, and local sandstone hosted copper mineralisation.   In the south of the Yangtze River Belt the total Cambrian to Middle Triassic strata comprise >6000 m of shallow-marine carbonates, clastic rocks, shale and sandstone.
  During the Middle to Upper Triassic, whilst these stable platform sedimentary rocks were being deposited, the Yangtze Craton was colliding with and under-thrusting the North China Craton, producing a very unstable strongly uplifted terrane. This suggests the two contrasting tectonic regimes were separated by a considerable interval at this stage and juxtaposed by later structural reorganisation. It is likely the platformal sedimentary sequence was deposited over the stable Yangtze Craton well to the south of the collision zone, and translated northward on the eastern side of the regional Tan-Lu sinistral strike slip fault zone, which was initiated at 233 ±6 to 225 ±6 Ma in the Upper Triassic (dates from Wang, 2006; Zhang and Dong, 2008). This was the first stage of five main periods of activity on the fault. During this period it acted as a transform separating south vergent subduction in the Qinling-Dabie Orogen from that on the Shandong Peninsular, while attenuating the trailing edge of the latter along the fault's eastern margin. Both zones separated by this structure underwent UHP metamorphism during subduction. The second stage of activity from 220 to 190 Ma in the Lower Jurassic, and was a sinistral strike-slip stage, initially accommodating the differential movement during the 215 to 205 Ma relaxation of the underthrust Yangtze Craton margin. This period resulted in sinistral displacement of ~145 km, which was absorbed to the west by an E-W striking thrust system in the hinterland area of the Dabie orogenic belt. During this period, the Tan-Lu Fault propagated northward through the whole of North China and Northeast China (Zhang and Dong, 2008). This was followed by a hiatus in activity along the Tan-Lu Fault.

Lower Jurassic to Cretaceous - Reactivation of the Tan-Lu Fault zone, initiated the third stage of movement at ~160 Ma in the Upper Jurassic (muscovite from mylonite at two widely separated locations along the fault;
40Ar/39Ar plateau ages; 162 ±1 to 156±2 Ma, Wang, 2006; 161 ±3, Sun et al., 2008). This third stage persisted from the Middle to Late Jurassic to earliest Early Cretaceous and resulted in transpressive strike-slip motion, accompanied by the lithospheric and crustal thickening of the eastern North China Block and development of the broader Tan-Lu fault system. The Lower Cretaceous, from ~140 to 130 Ma saw a period of transition from transpression to transtension (e.g., Wang et al. 2019) that corresponded to the fourth stage which resulted in crustal extension and intracontinental rifting, rapid mechanical delamination and thinning of previously thickened lithosphere and resultant asthenospheric upwelling in the North China, middle and lower Yangtze River and the Qinling-Dabie orogenic belt (Xue et al., 2015; Zhang and Dong, 2008). This tectonic regime change was influenced by the relative motion of the Pacific and Eurasian plates (Xue et al., 2015).
  During the Lower Jurassic to Cretaceous a number of fault-bound continental sedimentary and then volcano-sedimentary basins were developed along the Yangtze River Belt, filled by a sequence that commenced with Jurassic lacustrine- and swamp-facies sandstone, siltstone and shale overlain by a volcaniclastic unit.
  While these basins were being filled, and prior to deposition of the main Cretaceous volcanic sequence, the first of two overlapping magmatic events was underway, predominantly represented by intrusive activity. This involved a widespread suite of high-K calc-alkaline mafic to intermediate to felsic I-type granitoids (Pei and Hong, 1995; Xie et al., 2008; Zhou et al., 2007), comprising gabbro, diorite, quartz diorite and granodiorite, or magnetite-series granitoids (Ishihara, 1977). These were emplaced between 156 and 137 Ma (Hou and Yuan, 2010; Lou and Du, 2006; Xie, 2009; Yan et al., 2009; Zhang et al., 2003; Zhou et al., 2008) in the Upper Jurassic to Lower Cretaceous, during the period of transpression. These intrusions are predominantly found in fault uplifts within the belt, external to the main Jurassic to Cretaceous volcanic basins and were coeval with porphyry and porphyry-skarn Cu-Mo and/or Au mineralisation.
  The second magmatic event resulted in an extensive Lower and Middle Cretaceous succession predominantly composed of lavas and volcaniclastic rocks with ages that range from 135 to ~124 Ma (SHRIMP zircon U-Pb; Zhang et al., 2018). These rocks were deposited during the transtensional event, and occurred in a string of volcanic basins that developed progressively northward from the Jinniu Basin in the southwestern extremity of the belt, through the Huaining, Luzong, Fangchang and Ningwu basins towards the northeastern extremity of the belt. These volcanic rocks were accompanied by the coeval emplacement of two intrusive suites that are exposed in the volcanic basins, namely,
  i). subvolcanic rocks within the Cretaceous volcano-sedimentary basins, mainly pyroxene diorite porphyry, diorite porphyry and syenitic granite porphyry, which like their volcanic equivalents described below, are considered to be alkali-rich and shoshonitic. They are predominantly of 135 to 127 Ma in age and are related to iron mineralisation (Wang et al., 1996); and
  ii). A-type granitoids that consist of 126 to 123 Ma quartz syenite, syenite, quartz monzonite, alkaline granite and corresponding phonolitic volcanic rocks (Fan et al., 2008; Ni et al., 1998; Tang et al., 1998) which are accompanied by weak gold and uranium mineralisation.
  The fault controlled Jurassic to Cretaceous basins and associated magmatism were emplaced during continued sinistral translation on both the Tan-Lu Fault and on parallel structures to the SE. Whilst the stable platform Middle to Upper Triassic sequence in the Yangtze River Belt was deposited some distance from the present relative location adjacent to the Dabie Massif, as detailed above, by the Cretaceous the two terranes were close to their current relative position and Cretaceous intrusions in both are comparable, although possibly offset further by subsequent sinistral and later dextral displacement. As such, the intrusions and related porphyry/skarn Mo-Cu mineralisation are probably a peripheral continuation of the same intrusive event that produced the Qinling and Dabie Molybdenum Belts.
  The Lower Cretaceous volcanic sequences in the principal basins were as follows:
  - The Jinniu (or Jin-Niu) Basin sequence comprises >2000 m of shoshonitic volcanic rocks, including andesite, rhyolite, trachyte, trachytic basalt, basaltic andesite, welded breccia and tuff, which dating suggests are 130 to 124 Ma in age. The rocks show a bimodal distribution in composition, with dominant rhyolite and dacite, and subordinate basalt and basaltic andesite. The mafic rocks are moderately enriched in large ion lithophile elements (LILE) (e.g., Ba, Th, U, and Pb) and light rare earth elements (LREE), and are characterized by negative Nb, Ta, and Ti anomalies, and relatively high TiO
2 (0.72 to 2.06%) and Nb (9.20 to 26.5 ppm) contents. Overall, the felsic rocks have geochemical characteristics, and Sr-Nd-Pb signatures, and in situ zircon Hf isotopic compositions similar to those of the mafic rocks. Compared with the mafic rocks, the felsic rocks are characterised by enriched and variable concentrations of LILE and REE and negative Eu anomalies, as well as a wide range of radiogenic Nd-Pb isotopic values. These features indicate that the genesis of felsic magma in the Jinniu basin is consistent with extensive fractional crystallization and large amounts of crustal contamination from an evolved mafic magma (SiO2 = ~ 55%). These data are interpreted to be evidence that Early Cretaceous volcanic rocks in the Yangtze River Belt developed in an extensional tectonic regime (Xie et al., 2011).
  The sequence within the basin has been divided into the Majiashan, Lingxiang, Dasi (which is 128±1 Ma) and Taihe formations from bottom to top (Zhang et al., 2018). The basin lies within the larger Edong District which has undergone extensive plutonic magmatism, generating six major 50 to 200 km
2 batholiths that range from granite to quartz diorite to minor gabbro, intruding Devonian to Lower Triassic sedimentary rocks and dated between 152 and 132 Ma (Zhang et al., 2018). The NW-SE aligned Edong District is separated from, and juxtaposed with the main NE-SW elongated main section of the Yangtze River Belt by the Tan-Lu Fault. To the north it has underthrust the Dabie Massif below the reverse Xiangfan-Guangji Fault (XGF), whilst to the west it is terminated by the sinistral Ma-Tuan Fault.
  - The Luzong (or Lu-Zong) Basin covers an area of ~1030 km
2, and lies in the centre of the Yangtze River Belt, both longitudinally and across strike. The basin contains widespread shoshonitic volcanic rocks and igneous intrusions. The lithostratigraphy commences with the Middle Jurassic Luoling Formation which comprises terrigenous clastic sedimentary rocks that are progressively and unconformably overlain by volcanic rocks of the Longmenyuan, Zhuanqiao, Shuangmiao and Fushan formations that are exposed in a synclinal structure. Each is separated by an unconformity and represents a separate volcanic cycle that started with eruptive facies, followed by increasing lava flows and ended with volcano-sedimentary facies. The volcanic rocks are composed of 21% basaltic, 26% basaltic-trachyandesitic, 44% trachyandesite and 9% trachyte (Yu and Bai 1981; Deng et al., 1992), deposited between 136 and 124 Ma (Yuan et al., 2011), with ages of 132 ±1 and 131 ±1 Ma yielded by rocks from the Longmenyuan, Zhuanqiao formations respectively (SHRIMP zircon U-Pb; Xue et al., 2015).
  - The Ningwu (or Ning-Wu) Basin is partially filled by up to 2700 m of shoshonitic continental volcanic rocks that are intruded by cogmagmatic subvolcanic to plutonic rocks, and is bounded by NNE-SSW and NW-SE trending faults. The basement to the volcanic basin is dominated by Triassic and Jurassic sedimentary rocks. The volcanic sequence of the basin which rests on this basement is divided from bottom to top into the Longwangshan (~ 20% volcanic rocks, ~510 m thick), Dawangshan (~70% volcanic rocks and the thickest unit at ~1000 m), and the Gushan and Niangniangshan formations each with ~5% volcanic rocks and thicknesses of 285 and 880 m respectively. The upper Niangniangshan formation differs from the other units in that it is predominantly composed of nosean phonolite (Zhou et al., 2011). Each of these four units is unconformable with the rest, which constitute four eruptive-accumulative cycles. Each cycle commenced with explosive volcanic activity, followed by more effusive eruptions, and ended with volcanic sedimentation. The volcanic rocks comprise andesitic volcanic breccias, brecciated lavas, sedimentary volcanic breccias and lava, which are intercalated with tuffaceous siltstone. They four formations listed above yield consistent Early Cretaceous ages of 134.8 ±1.8, 132.2 ±1.6, 129.5 ±0.8, and 126.8 ±0.6 Ma, respectively (Zircon LA-ICP-MS U-Pb; Zhou et al., 2011). Intrusions within the basin include diorite porphyrite and gabbro-diorite that are all dated at ~130 Ma (Fan et al., 2010), between the ages of the Dawangshan and Gushan formations, and are mostly geochemically similar to the volcanic rocks of the Dawangshan Formation. These intrusions are overprinted by granodiorite that was emplaced between 127 and 123 Ma (Fan et al., 2010), similar in age to the Gushan and Niangniangshan formations (Zhou et al., 2011). The magmatic activity and geochronological framework of volcanic rocks within the basin, particularly those of the Niangniangshan Formation, has been interpreted by Yan et al. (2009) to indicate that from ~130 Ma progressively dynamic deep processes in the Lower Yangtze River Belt commenced a transformation of tectonic setting from compression to extension.
  - The Fanchang (or Fan-chang) Basin is similarly divided into four volcanic cycles, the Zhongfencun, Chisha, Kedoushan and Sanliangshan formations dated at 134.4 ±2.9, 131.3 ±1.8, 130.8 ±2.2 and 128.1 ±3.1 Ma respectively (Zhou et al., 2011), although Liu et al. (2016) dates the Zhongfencun Formation at 132.1 ±1.5 Ma (zircon LA-ICPMS U-Pb). The volcanic rocks include basalts, trachytes and rhyolites (Liu et al., 2016). As is the case in the other Cretaceous volcanosedimentary basins of the Yangtze River Belt, the volcanic rocks in the Fanchang Basin constitute a bimodal magmatic suite, with a significant compositional gap (from 50% to 63% SiO
2) between the mafic and felsic members (Luo et al., 2013). The bimodal suite is moderately enriched in LILEs, and has negative Nb, Ta and Ti anomalies, and are significantly enriched in LREEs. Luo et al. (2013) conclude the basalts were likely generated from a parental magma derived from enriched lithospheric mantle with minor assimilation of crustal material. They also suggest from simulations that the felsic magma was produced by the mixing of 5 to 20% lower crustal anatectic melts with an evolved mafic magma (~48% SiO2), accompanied by extensive clinopyroxene, plagioclase, biotite and Fe-Ti oxide fractionation.

Upper Cretaceous to Cenozoic - The overlying Upper Cretaceous comprises a sequence of red bed clastic sedimentary rocks including conglomerate, sandy conglomerate, sandstone and siltstone, intercalated with minor andesite, basalt and thin layers of gypsum. These are overlain by an extensive Tertiary cover sequence of conglomerate, sandstone, basaltic tuffaceous breccia, lava and agglomerate (Mao et al., 2011).
  The fifth and final stage of activity on the Tan-Lu Fault was from the Late Cretaceous to Paleocene, and resulted in dextral strike-slip motion predominating, and a number of pull-apart basins being formed along and at both sides of the Tan-Lu fault zone (Zhang and Dong, 2008).


  The Middle to Lower Yangtze River Valley Metallogenic Belt ('Yangtze River Belt') has been divided into eight mining districts or deposit clusters, which from SW to NE are as follows, with the key representative deposits within each, as are described to date:
Edong District -   Chengchao Fe Skarn deposit;   Tieshan Fe Skarn deposit;   Jinshandian Fe Skarn deposit;   Tongshankou Porphyry/Skarn Cu-Mo deposit;   Tongloshan Cu-Mo Skarn deposit;
Jirui District -   Fengshan Cu-Mo deposit;   Jilongshan and Fengsandong porphyry/skarn gold-copper, and   Caojiashan and Zhulintang carbonate hosted gold deposits of the Fengshan ore field;
Anqing-Guichi District - No deposit descriptions yet completed;
Luzong District -   Longqiao Fe Skarn deposit;  Shaxi porphyry Cu-Au deposit;
Nanling-Xuancheng District - No deposit descriptions yet completed;
Ningwu District - No deposit descriptions yet completed;
Ningzhen District - No deposit descriptions yet completed.


  The Edong District contains a cluster of Fe, Fe-Cu-(Au), Cu-Au and Cu-Mo-(W) skarn or porphyry deposits and occurrences (Shu et al., 1992; Zhai et al., 1992; Xie et al., 2015). A zoning of mineralisation from SE to NW of W-Cu-Mo → Cu-Mo → Cu → Fe-Cu → Fe has been recognised, mainly controlled by ENE trending faults (Shu et al., 1992). The exposed stratigraphy is mainly of Palaeozoic and Mesozoic in age and includes Triassic carbonate rocks which are the predominant hosts to the skarn deposits (Shu et al., 1992; Pan and Dong, 1999). The district also includes the Lower Cretaceous Jinniu volcano-sedimentary basin as described above. Intrusive rocks are dominated from north to south by the Echeng, Tieshan, Jinshandian, Yangxin, Lingxiang and Yinzu batholiths which are composed of diorite, granodiorite, quartz diorite, monzonitic granite and granite. These batholiths formed between the Late Jurassic and Early Cretaceous (Li, J.W., et al., 2009, 2014; Xie et al., 2008, 2011, 2012; Zhu et al., 2017) in two episodes of magmatism and mineralisation (Xie et al., 2013), namely: i). granodiorite, granite porphyry stocks and diorite emplaced between 147 and 136 Ma with associated Cu-Mo-W porphyry-skarn deposits, Cu-Fe and Fe-Cu skarn deposits formed between 144 and 143 Ma; and ii). diorite, monzonitic granite and granite emplaced between 133 and 127 Ma with associated Fe skarn deposits formed between 133 and 130 Ma (Li et al., 2019). Key deposits include:

Chengchao Fe Skarn deposit

  Chengchao is located in the northern part of the Edong deposit cluster hosted by sedimentary rocks that include the Early Triassic Daye Formation limestone, dolomitic limestone and evaporites, and the Middle Triassic Puqi Formation sandstone and muddy siltstone. Along their contact with the intrusions, these sedimentary rocks have been transformed into marble and hornfels. Outcropping of the Triassic evaporites are found in the western section of the Chengchao deposit and are mainly composed of anhydrite. Some of these evaporites have been remobilised to form purple to light-purple hydrothermal anhydrite.
  The sedimentary rocks were intruded by granitic rocks and diorite to the north and south of orebodies respectively. The granitic rocks include porphyritic quartz monzonite, monzonitic granite and granite (Li, W., et al., 2014; Yao et al., 2015) that belong to different phases of the Echeng composite batholith. Of these, the volumetrically largest intrusions are the porphyritic quartz monzonite and monzonitic granite. The diorite is composed of ~65% plagioclase, ~20% hornblende, ~10% biotite and ~5% K feldspar, and has been dated at 129 ±2, 131 ±1 and 133 ±1 Ma (zircon U-Pb; Xie et al., 2012; Hu et al., 2017 and Li et al., 2019 respectively), whereas Yao et al. (2015) obtained an age of 140 ±1 Ma (LA-ICP-MS zircon U-Pb). The porphyritic quartz monzonite is composed of phenocrysts including ~15% plagioclase and ~10% K feldspar set in a groundmass of ~30% plagioclase, ~30% K feldspar and ~15% quartz. The monzonitic granite, which has been dated at 129 ±1 Ma (LA-ICP-MS zircon U-Pb; Ding et al., 2018), contains ~40% plagioclase, ~35% K feldspar, ~20% quartz and ~5% biotite. The granite has ~50% K feldspar, ~15% plagioclase, ~30% quartz and ~5% biotite and has been dated at 127 ±2 to 129 ±1 Ma (LA-ICP-MS zircon U-Pb; Xie et al., 2012; Yao et al., 2015; Hu et al., 2017). Combined mineralogical, geochemical and Sr-Nd-Pb isotope studies suggest these intrusive rocks were derived from mixtures of an enriched mantle-derived mafic magma and a lower crust-derived felsic magma (Xie et al., 2008; Li et al., 2014).
  The Chengchao deposit comprises >100 NW striking magnetite bodies within a 2300 x 800 m zone, with 7 of these, denoted as I to VII inclusive accounting for 95% of the total resource (Shu et al., 1992). The individual bodies mostly occur at the contacts between intrusions and sedimentary rocks, as both endo- and exo-skarn zones, many in narrow bands of Daye Formation sandwiched between granitic and dioritic bodies. Two mineralisation types are recognised: i). massive (>80 vol.%) magnetite with minor skarn minerals or sulphides; and ii). disseminated mineralisation containing 30 to 80 vol.% magnetite within a gangue of skarn minerals (Li et al., 2019).
  Hydrothermal alteration associated with mineralisation has been divided intofive paragenetic stages (Li et al., 2019), as follows:
Stage I - Na-K alteration - was widespread, characterised by albite and K feldspar within both dioritic and granitic rocks, with more intensely altered intrusives converted to a reddish brown colour. K feldspar veins/veinlets from 0.3 to 2 cm thick are developed within the intrusive rocks.
Stage II - prograde skarn is intensely developed within diorite, porphyritic quartz monzonite and monzonitic granite, as well as in the sedimentary rocks of the Daye and Puqi formations. Prograde skarn occurs as both endo- and exoskarn over a NW-SE directed interval of at least 2 km and is characterised by an assemblage that primarily includes pyroxene and garnet. Within the granitic rocks, endoskarn commonly occurs as stockworks and veins which vary from a few to a few tens of centimetres in thickness. The endoskarn within the diorite, which is pyroxene-dominated, also occurs as stockworks/veins, with vein widths ranging from 1 to 10 cm. Exoskarn is developed in a parallel adjacent zone with a broadly similar mineralogy, although the garnet and pyroxene proportions vary. Garnet dominated skarns are mostly found in the northwest, while those that are predominantly pyroxene occur throughout the length of the skarn altered zone (Li et al., 2019).
  Three generations of garnet have been recognised, all of which have been crosscut or replaced by magnetite. Garnet-1 is found in the exoskarn zone, with a euhedral to subhedral texture and is 50 to 200 µm in size. Garnet-2 is widely distributed in both the endoskarn and exoskarn, occurring as 20 to 500 µm anhedral to subhedral, grey to red-brown grains that are overprinted by the red-brown Garnet-3. Garnet-3 occurs as 0.4 to 2.5 cm thick veins/veinlets carrying 50 to 300 µm subhedral to anhedral grains. Pyroxene assemblages comprise 100 to 500 µm anhedral to subhedral grains that are widespread in both the endoskarn and exoskarn, where they coexist with Garnet-2 and are replaced by subsequent retrograde skarn minerals (Li et al., 2019).
Stage III - retrograde skarn accompanies development of the main Fe mineralisation of which magnetite is the dominant ore mineral. The retrograde gangue assemblage that coexists with magnetite in both disseminated and massive ores mainly consists of phlogopite, amphibole, epidote and chlorite which replace or infill the prograde garnet and pyroxene skarn assemblages in endo- and exoskarn. Phlogopite grains coexisting with magnetite are euhedral to subhedral and vary from 200 to 1500µm in size. Amphibole grains vary from 800 to 2000 µm in size, and are widespread, coexisting with magnetite, chlorite, epidote and phlogopite. The abundance of epidote and chlorite, when compared to phlogopite and amphibole, is relatively small. There are 2 generations of epidote; Epidote-1, which occurs as 100 to 1000 µm subhedral to anhedral grains, coexisting with magnetite in the disseminated mineralisation, may be distinguished from Epidote-2 which coexists with anhydrite in stage IV. Chlorite occurs between the magnetite grains and coexists with phlogopite.
  Multiple generations of magnetite have been distinguished. Three generations, Magnetite-1 to -3, are developed in the massive ores, whilst four generations are recognised in the magnetite-bearing garnet-dominated exoskarn. In contrast, the disseminated mineralisation is generally only enriched in Magnetite-1. The first three generations of magnetite commonly coexist with the hydrous minerals within the skarn. Magnetite-4 grains either coexist with anhydrite or replace pyrite, suggesting precipitation during the late sulphate-sulphide stage (Li et al., 2019).
  Magnetite-1 occurs as 100 to 1500 µm euhedral to anhedral grains, some of which have pseudomorphically replaced garnet. Magnetite-2 has well-developed oscillatory zoning textures, with individual zones ranging from 50 to 100 µm. Magnetite-3 commonly encloses Magnetite-1 and Magnetite-2. Magnetite-3 grains range in size from 20 to 400 µm. Acicular Magnetite-4 grains surround earlier generations of magnetite, with lengths of up to 1000 µm, whilst anhedral Magnetite-4 grains are <50 µm in size (Li et al., 2019).
Stage IV - sulphate-sulphide is represented by widely distributed anhydrite and pyrite, as well as minor epidote (Epidote-2), garnet (Garnet-4) and magnetite (Magnetite-4). Massive light purple to purple hydrothermal anhydrite assemblages that range from 0.1 to several millimetres occur within the intrusions and skarns. Garnet-4 grains enclose magnetite and chlorite. Pyrite and anhydrite veins often infill between magnetite grains, whilst minor amount of Magnetite-4 replaces pyrite (Li et al., 2019).
Stage V - carbonate, predominantly calcite, which occurs as massive assemblages that infill between magnetite grains, represents the latest hydrothermal fluid event.

The deposit is quoted a having a total Fe reserve of 280 Mt, almost half of which is at grades of >53 wt.% Fe (Yao et al., 1993).

Tieshan Fe Skarn deposit

  The Tieshan deposit is located ~11 km south to SSW of Chengchao within the Edong Mining District of southeastern Hubei Province. The exposed sequence in the area surrounding the deposit includes the Upper Permian Dalong and Longtan formations; carbonates of the Early Triassic Daye Formation; sandy-shale of the Middle Triassic Puqi Formation; coal-bearing sandy-shale of the Jurassic Wuchang Formation; arenite of the Ziliujin Formation; and volcanic and pyroclastic rocks of the Lingxiang and Dasi formations. Exposed rocks in the immediate deposit area comprise the Dalong, Longtan and Daye formations. Widespread Jurassic to Cretaceous intermediate- felsic intrusions occur within the district (see the Chengchao summary above).
  Mineralisation at Tieshan is related to the 140 to 136 Ma Early Cretaceous Tieshan intrusive complex syenodiorite, diopside-diorite, monzodiorite, granodiorite and quartz diorite with minor gabbro which intrudes Daye Formation marine carbonates. The deposit comprises six lenticular or podiform orebodies (named Tiemenkan, Longdong, Jianlinshan, Xiangbishan, Shizishan and Jianshan) which are predominantly located along the marble-quartz diorite contact. Metallic minerals are mainly magnetite with minor pyrite, chalcopyrite, pyrrhotite and hematite. Gangue minerals mainly include diopside, garnet, phlogopite, amphibole, chlorite and calcite. Wall rock alteration is locally well developed, the main types including skarn, sodic, potassic, silicic, carbonate and chlorite (Qu et al., 2012).
  Mineralisation at the Tieshan Fe-(Cu) deposit has been divided into four stages by Hu et al. (2017):
Stage I - skarn development, mainly prograde garnet and diopside with minor epidote. Diopside is mostly replaced by retrograde phlogopite along its margins or within fractures;
Stage II - magnetite deposition, representing the main Fe mineralisation stage. Magnetite is commonly intergrown with retrograde phlogopite, whilst amphibole veins crosscut magnetite and diopside, suggesting that amphibole is also retrograde and post-dates Fe mineralisation. Locally, phlogopite and amphibole are chlorite altered.
Stage III - quartz-sulphide in which the main Cu mineralisation takes place, mainly comprising quartz, pyrite, chalcopyrite and minor pyrrhotite, with pyrite and chalcopyrite veins crosscutting magnetite.
Stage IV - carbonate, dominated by calcite, chlorite and hematite. Magnetite is commonly crosscut by calcite veins, and replaced by hematite along fissures.

  The Tieshan Fe-(Cu) deposit has proved reserves of ~160 Mt of contained Fe at a grade of 53% Fe [i.e., in 300 Mt of ore], and 0.67 Mt of Cu at a grade of 0.58% Cu [i.e., in 115 Mt of ore], accompanied by economic by-product Co, Ni, Au and Ag (Yao et al., 1993).

Jinshandian Fe Skarn deposit

  The Jinshandian cluster of deposits is located ~12 km SW of Tieshan, within the Edong Mining District of southeastern Hubei Province. The deposit is composed of six large and 94 small skarn altered magnetite bodies along the NW to WNW striking fault that follows the contacts between quartz diorite or granite (to quartz monzonite) and Triassic sedimentary country rocks. The I and II orebodies are the most important, accounting for 96% of the total Fe reserve of the deposit (Shu et al., 1992). The WNW trending, 2.7 km long I orebody, to the west, has a long, strip-like shape at surface, with a width varying from 0.2 to 84 m, persisting to a depth of from 179 to 970 m (Yao et al., 1993). The intruded country rocks are dolomite and dolomitic marble interbedded with mudstone of the Early Triassic Daye Formation, and the sandy shale, mudstone, siltstone and hornfels intercalated with carbonate rocks of the Middle Triassic Fuxi Formation (Xie et al., 2012).
  The mineralisation-related intrusions at Jinshandian are dominantly quartz diorite and granite. The quartz diorite has an intermediate to fine texture (0.1 to 2.2 mm) and comprises ~55% plagioclase, ~18% K feldspar, ~15% quartz and ~10% hornblende with accessory zircon, magnetite and apatite. The granite is developed deeper than 300 m underground and is fine-grained texture (0.01 to 0.9 mm) and is composed of ~25% K feldspar, ~40% plagioclase, ~25% quartz, and minor hornblende and biotite, with accessory zircon, titanite and magnetite (Xie et al., 2012).
  Ore minerals are dominantly magnetite with lesser hematite and pyrite, and minor pyrrhotite, siderite, chalcopyrite and sphalerite. Gangue minerals are mainly diopside, phlogopite, serpentine, tremolite, scapolite, calcite and dolomite with minor tremolite and anhydrite. The gangue assemblage is characterised by a range of magnesian skarn minerals, hornfels, epidote, chlorite and albite, which overprinted the granitic intrusions and host sedimentary rocks. Diopside-, diopside-phlogopite-, phlogopite- and serpentine-skarn are extensively developed along the contact between the intrusions and the carbonates of the Daye Formation, whilst hornfels occur in the Middle Triassic clastic rocks. Skarn Fe mineralisation is dominantly associated with phlogopite-, diopside-phlogopite- and diopside-skarn (Fu et al., 2008). Magnetite and phlogopite are frequently intergrown. On the basis of crosscutting relationship and mineral assemblages, four mineralisation stages have been recognised: i). skarn development, ii). magnetite deposition at between 480 and 400°C in three alteration and mineralisation skarn zones, outward from the granitoid contact, a). porous massive magnetite, b). disseminated diopside-magnetite, and c). banded diopside-scapolite magnetite, iii). sulphide emplaced at ~300°C, and iv). carbonate at Jinshandian (Fu et al., 2008).
  The quartz diorite and granitic intrusive phases have been dated at 127±2 Ma and 133±1 Ma respectively (U-Pb zircon; Zhu et al., 2017), whilst hydrothermal titanite and phlogopite from the skarn indicate that Fe mineralisation also formed at ~131 to 128 Ma, but with an additional 118 Ma hydrothermal event recorded by phlogopite (U-Pb and
40Ar-39Ar; Zhu et al., 2017). These dates suggest that at least two hydrothermal events took place in the Jinshandian ore cluster. Based on these and other dates from the broader Edong district, two regional magmatic-hydrothermal events are recognised after 135 Ma. The older of these was between 131 and 127 Ma which coincides with the ~131 Ma formation age of magnetite-apatite deposits in the Jinniu volcano-sedimentary basin, and a younger episode between 122 and 118 Ma post-dating emplacement of the ca. 126 Ma A-type granite and syenite in the eastern part of Middle-Lower Yangtze River region. A detailed comparison between the Fe skarn deposits and magnetite-apatite deposits suggests that these two deposit types not only share similar alteration assemblages and association with the evaporites within the ore-forming systems, but also may have formed during the same Early Cretaceous magmatic-hydrothermal event (Zhu et al., 2017).

  Proved reserves at Jinshandian have been quoted as 128 Mt ore at an average grade of 42.3 wt.% Fe (Zeng et al., 2019). In addition, cobalt can also be recovered as by-products, although Cu and Au are absent (Shu et al., 1992).

Tongshankou Porphyry / Skarn Cu-Mo deposit

  This deposit is located ~15 km S of Jinshandian and is the subject of the separate Tongshankou record.

Tongloshan Cu-Mo Skarn deposit

  This deposit is located ~13 km NE of Tongshankou and is the subject of the separate Tongloshan record.


  The Jiurui District lies to the SE and SW of the Edong and Anqing-Guichi districts respectively. The NE-SW Tan Lu Fault lies between the Jiurui and Edong districts. The sub-parallel Yangxin-Changzhou Fault passes through the SE corner of the Jiurui District. The Jiurui district contains porphyry, skarn and strata-bound Cu-Au-Mo mineralisation, with a total of 13 individual deposits having been distinguished in the district, including the four largest, the Wushan Cu-Au, Chengmenshan Cu-Au-Mo, Fengshan Cu-Mo and Jilongshan Au-Cu deposits. Major structures in the district include a series of NW-trending Triassic Indosinian faults and WNW- to NNE-trending folds and faults, which were superimposed on the NW-trending Yangtze deep fracture zone that separates the North and South China Blocks. Late Jurassic to Early Cretaceous Yanshanian intrusions are only exposed in the Jiurui district as small, generally <1.5 km
2 stocks and dykes, and are mainly distributed along the faults or at fault-fault and fault-fold axis intersections. The principal intrusive rocks are granodiorite porphyry and quartz diorite porphyry, with minor diorite, quartz porphyry, monzogranite and granite porphyry. These intrusions are characterised by the occurrence of crypto-explosive breccias (e.g. at the Chengmenshan, Fengshan, Yangjishan and Dingjiashan deposits). The diorites, quartz diorite and granodiorite porphyries have been dated between 135 and 205 Ma (biotite K-Ar), whilst the quartz porphyries are invariably younger and have ages between 98 and 120 Ma (whole-rock K-Ar; Pan and Dong, 1999). Key deposits include:

Fengshan Cu-Mo deposit.

  The Fengshan mineralisation is located in the western section of the Jiurui district, and is spatially associated with the 149 to 138 Ma Fengshan granodiorite porphyry stock (whole rock and biotite K-Ar; Shu et al., 1992). The deposit mainly comprises porphyry and skarn-type mineralisation, hosted both within the Fengshan granodiorite and proximal to it's contact with the Lower Triassic limestone and dolomite of the Daye Formation. The Fengshan granodiorite is exposed over an area of 1.26 km
2 and trends NWW as an oval shape in plan that has dimensions of 2.2 km in length and a maximum width of 800 m. In cross section it resembles a mushroom-shaped pipe, pitching to the south. It has a porphyritic texture and is rich in phenocrysts that include white plagioclase, K feldspar, quartz, biotite and hornblende, set within a fine-grained matrix of similar minerals. It has the characteristic of calc-alkaline intrusive stocks. It contains abundant accessory minerals, mainly magnetite, apatite, zircon and titanite, which are found as both phenocrysts and in the matrix (Shu et al., 1992). The structure is simple, including several east-west striking faults, that are interpreted to have had a strong influence on the emplacement of the granodiorite (Li et al., 2010; Mao et al., 2011; Pan and Dong, 1999; Xie et al., 2007, 2011). Shu et al. (1992) record an average composition of the granodiorite as 63.39 wt.% SiO2, 15.02 wt.% Al2O3, 2.21 wt.% MgO, 3.71 wt.% K2O, 3.41 wt.% CaO, 1.82 wt.% Fe2O3, and 2.5 wt.% FeO.
  The composite Fengshan Cu-Mo deposit is composed of a large number of individual ore bodies in different areas. Of these the No. 1, No. 501 and No. 558 are the largest and account for 90% of the total reserve (Zhai et al., 1992). The No. 1 ore body, the largest of the three, is located along the southern contact between the Fengshan stock and the Lower Triassic carbonates. It is >800 m long at surface, 30 to 40 m thick, and extends for ~400 m down dip. The No. 501 ore body, lies along the north contact between the Fengshan stock and the Lower Triassic carbonates, and >1500 m long, 8 to 15 m thick and persists for >500 m down dip. These two represent the main and typical skarn orebodies. The No. 558 ore body, which is concealed, is located in the northwest part of the Fengshan stock and occurs in the hanging wall of the No. 501 ore body. It includes a crypto-explosive breccia pipe, with characteristics characteristic of porphyry mineralisation, and is ~50 m from the north contact with the intrusion. It is >200 m long, 25 to 40 m thick and the ore grade is highest in the thicker breccias.
  Potassic and phyllic alteration dominate within the mineralised intrusion, whilst propylitic and argillaceous assemblages are limited (Shu et al., 1992). Phyllic altered rocks are most closely associated with Cu mineralisation. These alteration zones tend to overlap. Potassic alteration is mostly confined to the central part of the granodiorite intrusion, and is represented by assemblages of K feldspar (orthoclase), biotite, quartz and magnetite. It is typically characterised by mm-to cm-scale K feldspar veins, K feldspar selvages around stockwork quartz veins, and sparse disseminations of biotite. Sulphide minerals are rare, with minor disseminated pyrite. Phyllic alteration is the most extensive and economically significant, occurring in association with veins and abundant disseminations of quartz and sulphides, commonly accompanied by chlorite where adjacent to the potassic alteration. The mineral assemblage includes sericite, quartz, pyrite, molybdenite, chalcopyrite and bornite. Argillic alteration is only locally developed in the upper levels of the deposit, and comprises sericite, quartz, and calcite (Shu et al., 1992). Propylitic alteration, is rarely recognised in the Fengshan deposit. Wang et al. (2014) summarise the alteration patter, as a potassic alteration core to the granodiorite, overprinted by a zone of phyllic alteration, passing out to skarn alteration, serpentinite alteration and the largely unaltered carbonate. Early stage of skarn is characterised by anhydrous silicate minerals, such as garnet and diopside, whilst he late stage typically comprises hydrous silicate minerals, such as tremolite, epidote, actinolite and phlogopite. Shu et al. (1992) recognised four ore types, namely porphyry, skarn, breccia and marble ores. The porphyry and skarn mineralisation are the principal ore types. Breccia ore is located in crypto-explosive breccia pipes, with mineralisation in both the breccia clasts and the matrix. The clasts include skarn, porphyry and marble. Marble ore is located in marbles or serpentinized marbles near the contact zone, and it is represented by massive/veinlets of chalcopyrite and pyrite and belongs to skarn mineralisation.
  The Fengshan deposit has reserves of ~38 Mt @ 1.38 wt.% Cu for 0.52 Mt of contained Cu, as well as 6 Kt Mo with an average grade of about 0.109 wt.% Mo (Liu and Qian, 2001).

The information in this Fengshan description is drawn from Wang et al. (2014).

See also the
Fengshan ore field - Jilongshan, Fengsandong, Caojiashan, Zhulintang record which describes other mineralisation surrounding the Fengshan intrusion.

More Deposit descriptions to be added.


Deposit descriptions to be added.


  This district is centred on the Mesozoic Luzong volcanic basin which is located in the central part of the Middle to Lower Yangtze River Valley Metallogenic Belt, and is described above. It contains Upper Triassic marine and terrigenous clastic and carbonate rocks and Middle to Lower Jurassic continental clastic sedimentary rocks, intruded by abundant Mesozoic shoshonitic volcanic rocks (Ren et al., 1991; Sun et al., 1994; Wang et al., 2006; Xue et al., 2010). The latter comprise (from oldest to youngest) the Luoling, Longmenyuan, Zhuanqiao, Shuangmiao and Fushan formations (Zhou et al., 2011), exposed as a ring-shaped basin, with the youngest Fushan Formation in the centre and the Longmenyuan Formation around the outer rim. Apart from the Middle Jurassic Luoling Formation which comprises terrigenous clastic sedimentary rocks, the other four formations are composed of pyroxene trachyandesite, trachybasalt, trachyte and trachyandesite, respectively (Zhou et al., 2008). Major intrusive rock types include diorite, monzonite, granite and syenite (Zhou et al., 2008). Key deposits include:

Longqiao Fe Skarn deposit

  The Longqiao Fe deposit is located in the northern Luzong basin where the exposed stratigraphy mainly comprises the 'basement' Triassic Dongma'anshan, Jurassic Luoling, and Cretaceous Longmenyuan and Zhuanqiao formation, the latter two of which are mainly pyroxene-trachyandesite. The Longqiao Fe deposit is stratabound, and persists to depths of from 50 to 400 m. Mineralisation is hosted in marl, calcite dolomite, breccia limestone, breccia dolomitic limestone and pelitic siltstone of the Dongma'anshan Formation (Tang, 1998; Wu, 1996). The footwall comprises pelitic siltstone of the Dongma'anshan Formation intruded by syenite, whilst the hanging wall mainly comprises pelitic siltstone of the same formation and local Longmenyuan Formation trachyandesite (Zhou et al., 2011). Magnetite ores are massive, disseminated or laminated, and locally occur as breccias enclosing clasts and/or as mesh like matrices of magnetite. Textures within the magnetite include hypidiomorphic-xenomorphic granular, euhedral granular, xenomorphic-granular, skeletal, poikilitic and foliated (Hu et al., 2017). Minor lamellar mineralisation is enclosed by massive magnetite in the upper part of the deposit, interpreted as evidence of sedimentary reworking of part of the deposit late in its development (Ni et al., 1994; Tang, 1998; Wu, 1996). The metallic minerals are predominantly magnetite with minor pyrite, siderite and chalcopyrite. The dominant gangue minerals are diopside, garnet and calcite. Wall rock alteration comprises six alteration zones, from base to top, of hornfels → alkali-feldspar hornfels → skarn → K feldspar-tourmaline → kaolinite-chlorite → K feldspar (Wu, 1996).
  Mineralisation is interpreted to have taken place in two episodes, namely hydrothermal and sedimentary. The hydrothermal event is divided into four stages, namely:
Stage I - skarn development, mainly prograde wollastonite, diopside and garnet with minor K feldspar and tourmaline, and retrograde chlorite, epidote and amphibole. Epidote can seen to crosscut wollastonite.,
Stage II - magnetite deposition accompanied the retrograde skarn development and is the main stage of mineralisation, mainly as massive magnetite. It is closely associated with quartz and hematite with minor tourmaline, serpentine, epidote and chlorite. Magnetite crosscuts barite and is commonly crosscut by late sulphides.
Stage II - sulphide, dominated by pyrite and chalcopyrite, with minor calcite, hematite, chlorite, galena, sphalerite and kaolinite. Chalcopyrite is associated with calcite and hematite.
Stage IV - carbonate, dominated by late carbonate veins crosscutting or infilling between the older minerals such as magnetite and quartz.
  The mineralisation is dated at 147.13 ±1.45 Ma (phlogopite
40Ar-39Ar; Duanet al., 2009).
  The 'sedimentary episode' is mainly composed of siderite, quartz and calcite with minor gypsum, ankerite, hematite, barite and anhydrite and predominantly comprises laminated mineralisation with a light-coloured bands of mainly silicate minerals interspersed with black bands of dominantly magnetite. On a microscopic scale, the siderite is commonly subhedral, colourless, and is locally replaced by skeletal magnetite (Zhou et al., 2011).
  Li et al. (2013) concluded that the mineralisation was initially deposited as an Early-Middle Triassic sedimentary process overprinted by a Cretaceous hydrothermal event. Ren et al. (1991) suggested that the deposit was closely associated with volcanic exhalative sedimentary processes, whereas Ni et al. (1994) argued that the deposit was formed by exhalative sedimentary hydrothermal overprinting on a pre-existing Fe deposit. More recently, Zhou et al. (2011) considered that the deposit to be a skarn-type stratabound mineral system (Hu et al., 2017).

The Longqiao Fe deposit has a Mineral Resource of 120 Mt iron ore @ 44% Fe (Wu, 1996).

Shaxi porphyry Cu-Au deposit

  The Shaxi porphyry Cu-Au deposit is located in the northern part of the Luzong Basin on the outer, western edge of the southern Middle to Lower Yangtze River metallogenic belt, China, and is typical of the porphyry Cu-Au deposits in the belt. The host sequence includes the:
Silurian, Gaojiabian and Fentou formations, which occupy a NNE-SSW elongated anticlinal core in the central part of the deposit. The lower of the two, the Gaojiabian Formation is ~510 m thick and characterised by yellow-green silty shale with locally interbedded mud- stone-siltstone. The ~180 m thick overlying Fentou Formation is dominated by yellowish-orange to greyish green feldspar-quartz sandstone interbedded with yellowish-green siltstone and minor shale.
Jurassic Moshan and Luoling formations are widespread, occurring on both limbs of the anticline, but being most widely exposed to the NW part of the deposit area. The Moshan Formation is approximately 296 m thick and comprises sandy shale, siltstone, shale, and feldspathic sandstone with thin coal seams. The Luoling Formation is >200 m thick and is characterised by a sequence of purple lacustrine siltstone and argillaceous siltstone, interbedded with greyish medium-grained feldspar-quartz sandstone, and local marl lenses.
Cretaceous volcanic rocks of the Longmenyuan and Yangwan formations unconformably overlie the Moshan formation. The Longmenyuan Formation is >500 m thick and consists of volcaniclastic rocks, dominated by andesitic tuff with interbedded andesitic tuff breccia and siltstone. The Yangwan Formation is characterised by conglomerate, fine grained sandstone, and a gypsum bearing silty mudstone up to 290 m thick. The Cretaceous volcanic rocks of the Longmenyuan Formation are dominated by andesite porphyry lavas dated at 137.6 ±3.7 Ma (Tang 2012) and tuff breccias.
Quaternary units, mostly concentrated in the topographic lows of the district.
  Folding and faulting is widespread in the Shaxi district, with pre-Jurassic, NNE-trending, strong, mainly Silurian fold complexes belonging to the Indosinian deformation event, whereas post-Jurassic formations, including the Cretaceous volcanic rocks, are part of the Yanshan deformation event. Local faulting has been subdivided into four sets with E-, NE-, NNE- and NW-trends. The NNE-trending faults are most strongly developed, followed by the NE-set. As with the folding, faulting is best developed in the pre-Jurassic rocks.
  There are numerous Cretaceous intrusions within the district, although the most significant are coarse-grained diorite porphyry (CDP), medium and fine grained quartz diorite porphyry (MDP and FDP), biotite quartz diorite porphyry (BDP), late diorite porphyry, and mafic dykes. The 130.60 ±0.97 Ma coarse-grained diorite porphyry (CDP) are pre-mineralisation and older than the other three, which were emplaced at 129.30 ±1.00 Ma, 127.10 ±1.50 Ma, and 129.46 ±0.97 Ma, respectively (Wang et al., 2014). The medium and fine grained quartz diorite porphyry (MDP and FDP), and biotite quartz diorite porphyry (BDP) are the main hosts to Cu and Au mineralisation, and represent different phases of the quartz diorite porphyry (Wang et al., 2014). The MDP and FDP are distributed over a NNE elongated area of near 7 x 1 km, flanked by narrower widths of the BDP. Some magmatic breccias are locally present present within these intrusives. The BDP, MDP and FDP host most of the ore in the Shaxi Deposit.
  The Shaxi deposit has been subdivided into four mine sections over a length of ~3.6 km (from south to north): Longtoushan, Duanlongjing, Tongquanshan, and Fengtaishan. Of these, the Fengtaishan and Tongquanshan sections contain the bulk of the mineralisation.
  Mineralization predominantly occurs as disseminations and as veins, and has been divided into 4 stages, each characterised by a separate alteration assemblage, as follows:
Stage 1 Potassic core, characterised by K feldspar, biotite, magnetite and lesser quartz, anhydrite and pyrite, occurring as vein selveges, and as pervasive replacements. K feldspar forms a halo around mineralisation as the main alteration mineral. Potassic alteration is best developed in the deeper parts of the quartz diorite porphyries.
Stage 2 Propylitic alteration is found peripheral to the potassic zone, but can also be recognized in the core of the deposit, where vein density is low. It marginally postdates the potassic phase and tends to be weak, only being strong where it is superimposed upon potassic alteration. It is characterised by epidote, chlorite and minor albite, with significant illite, calcite and anhydrite, occurring as disseminations and localised in-fill. Disseminated propylitic alteration occurs as epidote and chlorite replacement of amphibole, plagioclase, hydrothermal biotite and K feldspar. Significant epidote occurs as irregular open space filling.
Stage 3 Phyllic alteration that comprises muscovite, illite, quartz, chlorite, anhydrite, pyrite and minor calcite, and occurs as both vein selveges and as pervasive alteration. The latter is mainly developed in the upper parts of the deposit and locally overprints both the potassic and propylitic stages. Feldspar grains have been altered to fine-grained quartz ±muscovite ±illite, and the groundmass exhibits strong microcrystalline quartz alteration. Amphibole, biotite, and other mafic minerals tend to be altered to chlorite, illite, muscovite and quartz. Other pre-existing minerals are replaced by chlorite, muscovite, illite, quartz and anhydrite.
Stage 4 Argillic alteration is generally restricted to the shallow parts of the deposit, and is characterised by ±muscovite ±illite ±calcite ±clay minerals, and also occurs as both pervasive alteration and vein halos. Where pervasive, the primary mineral assemblage has been completely obliterated and converted to quartz, chlorite, dickite, kaolinite, and other clay minerals. Veins associated with argillic alteration are composed of gypsum ±calcite ±anhydrite ±quartz ±pyrite ±illite ±dickite ±kaolinite.
  The main mineralisation within the deposit occurs as sulphide veinlets in the potassic zone where it is superposed by phyllic alteration. The paragenetic sequence shows that chalcopyrite began to precipitate early, in stage 1, in association with potassic alteration, forming quartz sulphide veins with K feldspar selveges, and reached a peak during the stage 3 phyllic alteration phase, following both the potassic the propylitic stages, and forming chalcopyrite-pyrite ±quartz ±anhydrite ±chlorite ±illite veins that accompanied phyllic alteration.
  Veins associated with K feldspar alteration include stage 1a K feldspar ±quartz, stage 1b barren quartz, stage 1c magnetite ±quartz, stage 1e quartz-K feldspar ±pyrite, stage 1f magnetite-quartz ±anhydrite ±K feldspar ±pyrite, and stage 1 g quartz-pyrite-chalcopyrite ±anhydrite ±bornite ±molybdenite ±K feldspar.
  Veins associated with propylitic alteration are stage 2a epidote ±chlorite ±quartz ±pyrite.
  Veins associated with phyllic alteration include stage 3a chalcopyrite-pyrite ±quartz ±anhydrite ±chlorite ±illite and stage 3b pyrite ±quartz ±anhydrite ±calcite ±chlorite ±illite.
  Veining associated with argillic alteration is stage 4a gypsum ±calcite ±anhydrite ±quartz ±pyrite ±illite ±dickite ±kaolinite.
The Shaxi copper-gold deposit is quoted as having a Mineral Resource of >1 Mt of contained copper and 45 tonnes of gold with ore grades of 0.55% Cu and 0.47 g/t Au (Wang et al. 2020). This would equate to a copper resource of ~180 Mt of ore @ 0.55% Cu. However, the gold ore tonnage would be be 96 Mt of ore. This suggests, the gold resource only relates to part of the deposit.
This Shaxi summary is largely drawn from Wang et al. (2020).


Deposit descriptions to be added.


Deposit descriptions to be added.


Deposit descriptions to be added.


Deposit descriptions to be added.

The most recent source geological information used to prepare this decription was dated: 2020.     Record last updated: 14/4/2024
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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