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Badaguan |
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Inner Mongolia, China |
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Cu Mo
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Super Porphyry Cu and Au
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The relatively small Badaguan porphyry Cu-Mo deposit is located ~100 km NE of Manzhouli City, and ~130 km NE of the Wunugetushan deposit in Nei Mongol (Inner Mongolia), northeastern China.
(#Location: 49° 58' 59"N, 119° 8' 18"E).
Regional Setting
The Badaguan deposit is located within the Erguna Terrane of the Central Asian Orogenic Belt, between the Mongol-Okhotsk Suture to the NW and the NE-SW trending Derbugan Fault which is immediately to the SE of the deposit. The latter fault is part of the continental scale Irtysh Fault and marks the southeastern margin of the Erguna Terrane, within 10 to 150 km of the Russian border to the NW. As such, it marks the southeastern margin of a relatively narrow strip of the mineralised Erguna Terrane in China. This strip has been referred to as the Derbugan metallogenic belt in China where it also includes the major Wunugetushan porphyry Cu-Mo deposit to the SW of Badaguan; the smaller Babayi and Taipingchuan porphyry Mo-Cu deposits, ~40 km to the SW and ~400 km to NE respectively; and the epithermal/vein Jiawula Pb-Zn-Ag, Chaganbulagen Ag-Zn-Pb and Erentaolegai Ag deposits ~200 km to the SW. However, other porphyry and volcanic hosted Cu-Au, Mo, U and Au deposits are also found to the NE in Russia, between the international border and the Mongol-Okhotsk suture.
The geological setting in the vicinity of the Badaguan deposit includes a basement of Palaeoproterozoic metamorphic rock; Neoproterozoic sedimentary sequences and biotite-K feldspar granite, quartz-monzodiorite and granodiorite; Devonian andesite porphyrite, rhyolite and other volcanic rocks, Carboniferous and Permian hornblende granodiorite, quartz diorite, porphyritic granite, biotite monzogranite and monzonitic granite and gneissic granite; Triassic gneissic granodiorite and biotite monzogranite rocks; Jurassic granitic porphyry, diorite and biotite monzogranite. These sequences are overlain to the SE by Lower Cretaceous volcanic and sedimentary rocks which comprise basalt, trachybasalt, trachyandesite, dacite and tuff of the Great Xing'an Range Large Igneous Province.
Geology
The principal country rocks in the immediate deposit area comprise (after Kang et al., 2018; Mi et al., 2017; Gao et al., 2016), from the base:
• Middle-Upper Devonian Daminshan Group, exposed in the southwestern and northern parts of the deposit area, mainly rhyolitic porphyry, rhyolitic tuff, andesitic porphyry and plagioclase hornblende schist;
• Carboniferous to Permian sedimentary and volcanic rocks, which are less abundant, but are widely distributed in the southeastern part of the deposit area, where they are mainly composed of felsic crystal-tuff which underwent thermal metamorphism associated with subsequent magmatic activity;
• Permian granitic complex composed of an early granite, followed by granitic porphyry and granodioritic porphyry;
• Middle to Late Triassic intrusive complex composed of granite, K eldspar granite, biotite granite, quartz diorite-, granite- and diorite-porphyries and ore-bearing porphyry which are described as quartz-diorite porphyry by Gao et al. (2016) and granodiorite porphyry by Kang et al. (2018). The granite was the first to be intruded in this area, followed by the granitic porphyry and then the quartz-diorite/granodioritic porphyry.
The granite, which occurs in the western and northern parts of the deposit area, is grey to light pink, has a medium to coarse grained porphyroid texture, and contains perthite, plagioclase, quartz and biotite. The granitic porphyry crops out in the centre of the deposit area over an area of ~1.3 km2, and has been dated at 237.8 ±3.0 Ma (U-Pb zircon; Mi et al., 2017). It is light grey, has a porphyritic texture, contains K feldspar, plagioclase and quartz phenocrysts. The granitic rocks have undergone significant post-magmatic tectonism and has a weakly gneissic or schistose structure that is partly defined by melanocratic minerals such as biotite and that obscures some of the primary igneous relationships.
The mineralised granodioritic porphyries are exposed in two sections of the deposit area, designated the No. I and No. II stocks. These stock are elongate ENE-WSW, have maximum lengths of 1.5 and 2.5 km, and crop out over areas of 0.3 and 1.9 km2, respectively. They are dark grey, has a porphyritic texture, contain plagioclase, quartz and minor K feldspar phenocrysts, and have a weakly gneissic or schistose structure that is partly defined by melanocratic minerals such as biotite. The granodiorite porphyry has been dated at 229.6 ±1.4 Ma (U-Pb zircon; Mi et al., 2017) and 226.7 ±2.4 Ma (Re-Os; Mi et al., 2017). These intrusions belong to the voluminous Late Triassic to Early Jurassic magmatism of the Erguna Terrane (Tang et al., 2014; Zhang et al., 2014).
Structure
Well-developed NE-SW and NW-SE trending faults are found within the Badaguan district. The former are more prominent, with lengths of 1 to 10 km occurring as equally spaced parallel structures. In contrast, the NW-SE trending set are less well developed and have lengths of only 2 to 3 km. These faults controlled the location of Indosinian Triassic magmatism, with the granodioritic porphyry intruded at the intersection of the two fault sets, whilst numerous veins occur parallel to the faults (Mi et al., 2017).
Mineralisation
Mineralisation is found near the upper sections of the granodiorite porphyry and in faults along the contact between the granodiorite porphyry and the surrounding rocks. The granitic rocks have undergone significant post-magmatic tectonism and has a weakly gneissic or schistose structure that is partly defined by melanocratic minerals such as biotite and that obscures some of the primary igneous relationships (Mi et al., 2017; Gao et al., 2016.
Hydrothermal alteration is well developed, with four distinct hydrothermal alteration zones recognised from the centre of the mineralised porphyry stock, outwards: i). quartz-sericite; ii). sericite; iii). sericite-propylitic; and iv). propylitic alteration. There are four distinct mineralised assemblages, representing a gradation from a central Mo-Cu, through a median Cu to a distal Pb-Zn zone, which correspond to the hydrothermal alteration zones, as follows (Kang et al., 2018; Mi et al., 2017; Gao et al., 2016):
• pre-mineral, barren K feldspar ±quartz alteration zone in the centre of the deposit and is pervasive throughout the interior of the granodiorite porphyry;
• molybdenite-chalcopyrite, closely associated with quartz-sericite alteration, with ore minerals of molybdenite, chalcopyrite and pyrite, occurring as veinlets and disseminations and represents the bulk of the copper and molybdenite mineralisation in the deposit. The quartz-sericite alteration zone extends for 1 to 1.5 km to the NE and pervades the granodiorite porphyry;
• chalcopyrite, which is related to a poorly defined sericite alteration zone outward from the quartz-sericite interval, reflected by an increase in Cu sulphides and corresponding decrease in the proportion of molybdenite;
• pyrite, predominantly in the sericite-propylitic alteration zone surrounding the molybdenite and chalcopyrite core of the deposit; and
• galena-sphalerite mineralisation distributed in the propylitic chlorite-epidote-calcite ±quartz alteration assemblage, although lead and zinc grades are too low to be of economic interest. The propylitic alteration zone is mainly within the peripheral wall-rocks of the the granodiorite porphyry stock where it is irregularly developed, gradually weakening with increasing distance outward.
• post-mineral (?) phreatic breccia, comprising porphyry clasts, hydrothermal quartz and pyrite cement occurs in the intermediate to upper region of the granodiorite porphyry.
• supergene secondary oxides including limonite-hematite-malachite-azurite.
Molybdenite occurs in quartz veinlets, whilst copper is found a disseminated to densely disseminated accumulations within the altered granodiorite porphyry. As such, the mineralization is zoned outwards from a quartz-Mo core to disseminated Cu bodies. More than 18 Mo orebodies and 16 Cu orebodies had been delineated by 2018 (Kang et al., 2018). These orebodies dip at angles ranging from 34 to 51° and extend to depths of from 95 to 400 m, with lengths and thicknesses ranging from 140 to 1000 m and 2.0 to 50 m respectively.
The mineral assemblages, which vary in relative proportions across the deposit as detailed above, are dominated by molybdenite and chalcopyrite, with lesser sphalerite, magnetite, galena, limonite, malachite and azurite. Gangue minerals, again varying across the deposit, include quartz, plagioclase, K feldspar, hornblende, biotite, sericite, epidote, anhydrite, calcite, fluorite and chlorite. The ore textures are subhedral to anhedral, granular, cataclastic, kinked, radial and flaky, with various replacement textures. I addition to the dominant veins and disseminations, the ore styles also include reticulate, densely disseminated and massive.
Reserves/Resources
Differences in available published reserve/resource figures may represent the growth in size with additional testing, and include:
Reserve of 0.042 Mt of contained Cu @ 0.44% Cu and 0.0087 Mt of contained Mo @ 0.06% Mo (Zeng et al., 2016, after Shen, et al., 2010):
An explored reserve of 17.1 Mt of Cu and Mo ore at an average grade of 0.44% Cu and 0.055 % Mo (Gao et al., 2016, after Chen, 2010);
Reserves of 0.2579 Mt of contained Cu @ 0.27% Cu and 0.042 Mt of contained Mo @ 0.032% Mo, which would equate to 95 and 130 Mt of ore respectively (Mi et al., 2017).
The most recent source geological information used to prepare this decription was dated: 2018.
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.
Badaguan
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Selected References:
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Gao, B., Zhang, L., Jin, X., Li, W., Chen, Z. and Zhu, M., 2016 - Geochronology and geochemistry of the Badaguan porphyry Cu-Mo deposit in Derbugan metallogenic belt of the NE China, and their geological significances: in Int J Earth Sci (Geologische Rundschau), v.105, pp. 507-519. doi 10.1007/s00531-015-1261-4.
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Kang, Y., She, H., Lai, Y., Wang, Z., Li, J., Zhang, Z., Xiang, A. and Jiang, Z., 2018 - Evolution of Middle-Late Triassic granitic intrusions from the Badaguan Cu-Mo deposit, Inner Mongolia: Constraints from zircon U-Pb dating, geochemistry and Hf isotopes: in Ore Geology Reviews v.95, pp. 195-215. doi.org/10.1016/j.oregeorev.2018.02.013.
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Mi, K., Liu, Z., Li, C., Liu, R., Wang, J. and Peng, R., 2017 - Origin of the Badaguan porphyry Cu-Mo deposit, Inner Mongolia, northeast China: Constraints from geology, isotope geochemistry and geochronology: in Ore Geology Reviews v.81, pp. 154-172. dx.doi.org/10.1016/j.oregeorev.2016.09.029
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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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