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Tagaung Taung, Dagongshan |
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Myanmar/Burma |
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Ni
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Super Porphyry Cu and Au
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The Tagaung Taung (Dagongshan) lateritic nickel deposit is located ~180 km north of Mandalay in north-central Myanma/Burma, 5 km east of the Irrawaddy (Ayeyarwady) River and 750 km north of Yangoon, #Location: 96° 15'E, 23° 35'N.
The ore deposit is developed over a Mid-Eocene, east-vergent, nappe of Triassic ophiolites that was obducted onto Palaeozoic to Proterozoic basement rocks of the Medial Metamorphic Belt, located immediately to the east of the major Sagaing (or Shan) Fault system. This structure seperates the main Asian (Shan-Thai) cratonic plate in eastern Myanmar/Burma from the younger (Late Cretaceous to Tertiary) orogenic rocks of the Burma Volcanic Arc to the west. The 700 km long, north-south oriented Sagaing fault accommodated dextral transverse displacement as the Indian plate moved northward, subsequent to the initial collision between the Indian and Shan-Thai continental plates in the north between 54 and 49 Ma, although east dipping subduction of the Indian oceanic plate continued into the Tertiary to the present in the south. Displacement on this structure is at least 300 km and possibly >450 km.
The Shan-Thai plate is composed of a slate belt of Siluro-Devonian mica- and graphite-schist, slates and marble, phyllite, and Upper Carboniferous pebbly mudstones. The slate belt widens southwards and occupies all of Myanmar east of the Andaman Sea. East of the slate belt, a fold-thrust belt includes older schists and Cambrian to mid-Devonian non-marine clastics, shelf carbonates and graptolitic shales, and topographically prominent Lower Permian to Upper Triassic carbonates. The middle Jurassic to end-Cretaceous includes at least four successions, partly marine and partly red beds separated by angular unconformities. Further east, Permian limestones and mudstones are absent and the Plateau is underlain by Proterozoic and lower and middle Palaeozoic rocks, with Proterozoic gneiss and marble exposed in a regional antiform. These rocks are variously intruded by Permo-Triassic high level granites to the east, a belt of Cretaceous granite further to the west and Palaeozoic granitic complexes to the north. Much of the western part of the Shan-Thai plate, including the Medial Metamorphic Belt, has undergone early Jurassic and Cretaceous thrusting resulting in complex nappe stacks (Mitchell et al., 1999).
The Medial Metamorphic Belt, which is up to 40 km wide and extends for over 1450 km, from Yangoon to northern Myanma, is developed immediately to the east of the Sagaing Fault System. It represents a continental foreland on the western margin of the Shan-Thai plate, onto which other units were thrust from the west in the Mesozoic and Tertiary. It consists of two metamorphic units, both of probable Proterozoic protoliths: (i) the Mogok belt in the north, which is largely composed of sillmanite gneiss, diopside-phlogopite marble and schist, and (ii) the Kyaukse-Mopalin belt in the south, which comprises layered migmatites, schist and minor marble. Both of these units are intruded by discordant plutons of biotite granite and K felspar megacrystic granite batholiths. Mitchell et al. (1999) suggest the Mesozoic ophiolitic rocks were obducted onto the Shan-Thai margin and were later metamorphosed during east dipping subduction, and then exhumed to the surface prior to dextral shearing along the Sagaing fault.
The Burma Volcanic Arc represents the northward continuation from Indonesia, through the Andaman Islands, of the Sunda-Andaman magmatic arc, and comprise:i). the Indo-Burmese Ranges, which mark the Outer Volcanic Arc, that in the east comprise a succession of mica- and graphite-schists, overthrust by tectonised Upper Triassic turbidites and mudstones, and by ophiolite and amphibolite. The schists form the core of a prominent antiform. To the west the ranges consist of late Upper Cretaceous (Campanian) pelagic limestones and mudstones and Tertiary clastic sedimentary rocks in thrust contact with the Mt Victoria belt; ii). the Inter-Arc Trough, with >10 km of Late Cretaceous to Quaternary sediments; iii). the Inner Volcanic Arc, which consists of a terrestrial acid to intermediate volcanic suite, with local sedimentary basins and Oligocene volcanic and intrusive activity; and iv). the Back Basin filled by a thinner Tertiary sedimentary sequence.
The serpentinised massif in the Tagaung Taung district is covered with a thick weathering mantle of saprolite, limonite, and an allochthonous lateritic surface layer. The nickel content, thickness and physical properties of the mineralisation are all very variable. The bedrock source is composed of Triassic ophiolite, dunite and serpentinised harzburgite and intercalated sedimentary rocks, structurally overlying Proterozoic schist and quartzite. The economic mineralisation occurs over an ultramafic massif that covers and area of 95 sq. km.
The laterite profile comprises:
Lateritic overburden, which averages 4.4 m (may be up to 11 m) in thickness, and contains 0.72% Ni, <1.02% Cr2O3. This kaolinite- and illite-rich surface layer is a mixture of limonite and weathered clayey material, which was probably derived from adjacent rocks. Part of the autochthonous weathering section is contaminated with infiltrated allochthonous surface material which is unlikely to have taken place under the current geomorphic regime. Consequently lateritisation of the serpentinite must have occurred before exposure of the Tagaung Taung in its present form;
Ferruginous, limonite, zone which is 5 to 9 m thick, and averages 1.24% Ni. Three-quarters of the original 20 m-thick layer has been eroded, with only the lower part of that limonite layer preserved. Mineralisation within this remnant zone has a relatively high SiO2 content, and generally contains ~1.24% Ni, which is below the cutoff grade of 1.4% Ni, and hence regarded as uneconomic;
Saprolite zone which is 10 to 50 m thick, and averages 1.41% Ni. The mineable resource averages 8 m in thickness and is developed within the saprolite zone. The principal minerals in this zone are nickeliferous serpentine and smectite with associated chlorite, garnierite, goethite, hematite, illite, kaolinite, limonite and talc. Smectite generally contains less nickel than serpentine;
Serpentinized harzburgite which averages 0.3% Ni.
The lateritic nickel ore deposit is located on the ridge summits in the Tagaung Taung district and contains:
~40 Mt (dry) of nickel-saprolite @ 2.14 % Ni, using a 1.4% Ni cut-off.
The waste:ore ratio = 0.97.
The project, which was developed by the Taiyuan Iron and Steel Group (TISCO) and China Nonferrous Metal Mining Group (CNMC) at a cost of >USD 800 million has a planned mine life from commencement of operations in 2011 to 2031, to produce 85 000 tonnes of nickel-iron, containing 22 000 tonnes of nickel, per annum.
The most recent source geological information used to prepare this decription was dated: 2011.
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.
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Selected References:
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Gardiner, N.J., Searle, M.P., Robb, L.J. and Morley, C.K., 2015 - Neo-Tethyan magmatism and metallogeny in Myanmar - An Andean analogue?: in J. of Asian Earth Sciences v.106, pp. 197-215.
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Schellmann W, 1989 - Composition and origin of lateritic nickel ore at Tagaung Taung, Burma: in Mineralium Deposita v.24 pp. 161–168
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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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