Qinling Molybdenum Belt - Nannihu, Sandaozhuang, Shangfang, Jinduicheng, Shijiawan, Huanglongpu
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The Qinling Molybdenum Belt is located in Shaanxi and Henan Provinces, central China, on the southern margin of the North China Craton/Paraplatform (also known as the Sino-Korean Craton). It contains three clusters of deposits with different characteristics, as described below, and is one of the largest molybdenum provinces in the world.
All three cluster lie within the generally WNW-ESE trending, two part Qinling Orogenic Belt, which lies along the suture between the North China and Yangtze Cratons. This fold belt is divided into the North and South Qinling Fold Belt by the transcrustal Shangnan Suture. The North Qinling Fold Belt, which embraces these deposits, represents the southern active margin of the North China Craton, and comprises a Proterozoic metamorphic complex of meta-greywackes, marbles and meta-tholeiites and an ophiolite suite. The South Qinling Fold Belt is the northern margin of the Yangtze Craton and is composed of a Proterozoic metamorphic complex of paragneiss, marble, tholeiites and alkaline basalt, Cambrian carbonaceous rocks, and Silurian and Devonian sequences.
Jinduicheng (Jinduichen or Jin Dui Cheng) (#Location: 34° 19' 51"N, 109° 57' 17"E) and Shijiawan.
These deposits, which are ~100 km east of Xian, are 5 km apart. They are classic porphyry molybdenum ores, comparable to Climax in Colorado, USA. At the Jinduicheng deposit, mineralisation is associated with a small 1.8 x 0.4 km, Late Triassic, 124±6 Ma granite porphyry stock, located just beyond an apophysis on the south-eastern margin of the 130±5 Ma, >50 x 15 km Laoneushan monzogranite batholith.
The host stratigraphy in the Jinduicheng district comprises, from the base (after Nie, 1994):
Archaean to Palaeoproterozoic Taihua Group - dated between 2.6 and 2.0 Ga (Hu et al., 1986), this ~4000 m thick sequence comprises granulite, amphibolite, amphibole-plagioclase gneiss, biotite-plagioclase gneiss, banded and streaked ptygmatic migmatite and phlogopite-diopside marble, and is only exposed 7 to 13 km north of the Mo deposits.
Mesoproterozoic Tietonggou Formation - a ~2850 m thick sequence, which unconformably overlies the Taihua Group, and is predominantly composed of micaceous quartz schist, schist, schistose quartzite and quartz conglomerate, and is exposed in the SW of the district.
Mesoproterozoic Xionger Group - a ~3900 m thick sequence, which is made up of metaspilite, porphyritic basalt, tuffaceous slate, sericite-phyllite, biotite-quartz schist, with marble lenses.
Neoproterozoic Gaoshanhe Formation - which unconformably overlies the Xionger Group and is composed of quartzite, muddy-sandy slate, conglomeratic quartz sandstone, varicoloured sericite-slate and lenticular dolomite, with lesser intermediate to mafic lavas, sills and dykes.
Neoproterozoic Longjiayuan and Xiongjianshi Formations - comprising ~1500 m of sandy slate, banded chert, tuffaceous slate, banded siliceous dolomite and limestone.
The Jinduicheng and Shijiawan granite porphyry stock intrudes rocks of the Xionger Group, close to the boundary with the overlying arenaceous slates of the Gaoshanhe Formation. The Huanglongpu porphyry stock (see below) is developed within the Gaoshanhe Formation arenaceous slates (Nie, 1994).
The district has undergone multiple deformation and metamorphism since the Mesoproterozoic. The major fold in the district is the east-west oriented Huanglongpu anticline, which hosts the Laoneushan monzogranite batholith in its axis. All three deposits lie on the southern limb of the anticline, within 2 to 5 km of the batholith margin. Faults and fractures trend east-west, ENE to NE, and NW.
The ore deposits comprises disseminated and stockwork Mo mineralisation, hosted by quartz ±K feldspar ±pyrite ±fluorite veins and veinlets, with accessory disseminated magnetite, chalcopyrite, sphalerite, galena, cassiterite, bismuthinite, sericite, biotite, beryl, apatite, topaz and calcite. Both the porphyry stock and enveloping Proterozoic host rocks have been intensely altered to produce ore related silicification and K feldspathisation, passing out into phyllic and propylitic zones. The ore at Jinduicheng, is 25% within the granite porphyry stock and 75% in the country rock. The Jinduicheng deposit had a total production + resource of 910 Mt @ 0.10% Mo, 0.03% Cu (Mutschler, 2000).
Huanglongpu (#Location: 34° 20' 52"N, 110° 01' 31"E).
The Huanglongpu deposit which is ~7 km ENE of Jinduicheng is characterised by Mo-Pb bearing carbonatite vein deposits. At Huanglongpu the vein mineralisation is hosted by Proterozoic andesites and tuffaceous shales. Veins are generally up to 1 m wide and may reach 500 m in length and consist of 50-70% calcite, 30-50% quartz, around 5% microcline, 4.5% barytocelestine and 1% biotite with significant molybdenite, galena and pyrite and subordinate magnetite, hematite, chalcopyrite and sphalerite. Deposits contain around 0.06% Mo.
Molybdenite occurs as disseminated aggregates, as bands or crusts paralleling vein walls and as infillings along calcite and galena cleavage planes. Hydrothermal alteration is limited to the margins of the veins.
Nannihu, Sandaozhuang and Shangfang, Luanchuan County, Henan Province (#Location: 33° 55' 13"N, 111° 29' 45"E).
The Nannihu porphyry molybdenum (-tungsten), Sandaozhuang skarn molybdenum (-tungsten) and Shangfang porphyry-skarn molybdenum deposits, which are some 80 km ESE of the Jinduicheng and Huanglongpu deposits, and 12 km NW of Luanchuan, have total reserves of ~1.9829 Mt of contained Mo at grades of from 0.06% to 0.24%, with an associated 0.7379 Mt of W grading from 0.091% to 0.129% (Li et al., 2004).
The sequence within the Nannihu district includes the Mesoproterozoic Guangdaokou Group banded chert-bearing carbonate rocks, overlain by a thick sequence of medium- and low-grade Neoproterozoic metamorphic shelf clastic and carbonate rocks, comprising the Luanchuan Group, carbonates rocks and trachyte, Taowan Group terrigenous clastic-carbonate rocks, Guandaokou Group marble, and Kuanping Group, marble and basic volcanic rocks.
The major regional faults curve from near east-west, through WNW to NW directions (from west to east), and were formed in the Late Triassic and Early Jurassic (Ren et al., 1998), with a less well developed NE-trend, formed during the Mid to Late Jurassic transition to the tectonic regime of eastern China (Mao et al., 2003). These fault sets vary considerably, but occur in swarms and are concentrated in defined zones. The Nannihu-Sandaozhuang-Shangfang district is sandwiched between the major Luanchuan and Machaoying faults to the south and north respectively.
The major magmatic rocks in the district are Caledonian metagabbro and syenite porphyry, and mid to late Yanshanian intermediate to acid intrusions at Nannihu, Shangfang, Shibaogou, Yuku and Majuan. The host sequences have been extensively metamorphosed into various hornfels and skarn rocks by the Yanshanian intrusions, in particular the marbles of the Sanchuan Formation (altered to diopside-garnet skarns) and the Nannihu Formation sandstones (altered to various hornfels). These intrusive rocks were derived from partial remelting of the lower crust producing I-type granitoids (Wang et al., 1986).
Molybdenum and tungsten mineralisation is associated with small, hypabyssal and near-surface complex stocks of late Jurassic Yanshanian calc-alkaline granite porphyries (Xu et al., 2000).
Mineralisation occurs as stockwork quartz-molybdenite veins within the granite porphyry and disseminated molybdenite within the skarn altered zone. Alteration stages include skarn alteration (described above), potassic (K feldspar-quartz alteration with associated 0.2 to 1 cm veins of dark quartz and molybdenite, and lesser pyrite and fluorite), silicification (quartz-sulphide alteration with 0.5 to 2 cm veins of molybdenite with milky quartz with lesser magnetite and fluorite), phyllic (quartz-sericite-pyrite), zeolite-carbonate (zeolite, quartz and carbonate, with 0.5 to 5 cm veins of molybdenite, clear quartz and lesser calcite and pyrite) and propylitisation (Liu et al., 1988).
The Nannihu and Sanfanggou granite porphyries have SHRIMP zircon U-Pb ages of 157.1±2.9 Ma and 157.6±2.7 Ma respectively (Mao et al., 2005), while the Nannihu-Sandaozhuang and Sanfanggou deposits have a Re-Os isochron age of 141.5±7.8 Ma (Li et al., 2004), the nearby Lengshuibeigou Ag-Pb-Zn deposit has an 40Ar-39Ar plateau age of 137.87±0.39 Ma. These ages show that the granitic porphyries are slightly older than the deposits, and that the porphyries and deposits exhibit different evolution stages of the same tectonic-magmatic-ore fluids system in the same geodynamic setting.
Geochemical studies indicate anomalous halos surrounding granite porphyries, e.g., the Nannihu granite porphyry is accompanied by an anomalous zone that is 40 km long, by 20 km wide with a well-defined outward zonal pattern, from a core of high temperature porphyry-skarn type molybdenum (-tungsten), to an outer zone of medium to low temperature hydrothermal vein type lead-zinc-silver mineralisation. The porphyry-skarn type molybdenum (-tungsten) deposits occur within the core or contact zones of granite porphyries, surrounded by copper-lead-zinc skarn altered and stockwork mineralisation.
The Nannihu porphyry molybdenum (-tungsten) deposit occurs in the Nannihu porphyritic monzogranite and its contact zone with hornfels. It contains a total metal reserve of 6646 Mt of contained Mo grading from 0.06% to 0.20% Mo, and 0.135 Mt of W, at an average grade of 0.099% W.
The Sandaozhuang skarn molybdenum (-tungsten) deposit, mainly hosted in skarn and marble, contains 0.6725 Mt of Mo grading from 0.093% to 0.149% W, and 0.6025 Mt of W grading 0.091% to 0.129% W.
The Shangfang porphyry-skarn molybdenum deposit occurs in the contact zones of the Shangfang porphyry and dolomitic marble of the Meiyaogou Formation of the Neoproterozoic Luanchuan Group. It has a total metal reserve of 0.7158 Mt grading 0.11 to 0.24% Mo, and by-product reserves of 2.5 Mt grading 1.49%S and 81.3 t grading 0.0042% Re (Wang et al., 2008, after Luo et al., 1991).
For detail see the reference(s) listed below.
The most recent source geological information used to prepare this summary was dated: 2008.
Record last updated: 1/9/2013
This description is a summary from published sources, the chief of which are listed below.
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Jinduicheng and Shijiawan
Nannihu, Sandaozhuang and Shangfang
References to this deposit in the PGC Literature Collection:
Nie F J, 1994 - Rare earth element geochemistry of the molybdenum-bearing granitoids in the Jinduicheng-Huanglongpu district, Shaanxi Province, northwest China: in Mineralium Deposita v29 pp 488-498|
Stein H J, Markey R J, Morgan J W, Du A, Sun Y 1997 - Highly precise and accurate Re-Os ages for Molybdenite from the east Qinling Molybdenum belt, Shaanxi Province, China: in Econ. Geol. v92 pp 827-835|
Wang C M, Cheng Q M, Zhang S, Deng J and Xie S, 2008 - Magmatic-Hydrothermal Superlarge Metallogenic Systems - A Case Study of the Nannihu Ore Field: in Journal of China University of Geosciences v.19 pp.391–403|
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