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Kanbauk |
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Myanmar/Burma |
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Sn W
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The Kanbauk skarn W-Sn deposit is located in southern Myanmar, ~50 km north of Dawei and ~320 km SSE of Yangon (#Location 14° 34' 57"N, 98° 1' 24"E).
The deposit lies within the Myanma section of the Southeast Asian tin belt, the setting of which is detailed in the "South-east Asian Tin-Tungsten Belt, Thailand, Myanma/Burma, Malaysia, Indonesia" record. It falls within the Sn and W bearing, 180 to 15 Ma Western Granitoid Province of the belt, as distinct from the Sn-dominant deposits in the 227 to 201 Ma Main Range and 289 to 220 Ma Eastern granitoid provinces mostly in Malaysia and Thailand to the east (Mitchell, 2018). In the Dawei region of southern Myanmar, the Western Granitoid Province comprises three granite belts, namely the Coastal, Central and Frontier belts from the west to the east, occurring as NNW-SSE trending elongated batholiths in a structural zone parallelling the regional strike of the Mergui Group, which is known as the Slate belt in Myanmar (Mitchell et al., 2012). This group comprises a thick upper Carboniferous to lower Permian succession of slaty mudstone and pebbly wacke with subordinate limestones and quartzites, probably deposited in a glacio-marine, rift-related environment on the margin of Gondwana (Stauffer and Lee, 1986; Ridd and Watkinson, 2013). Within this region of placer tin deposits, primary mineralisation is also found at locations such as Hermyingyi, Wagone, Bawapin, Pagaye, Pulatto and Kalonta, with fossil tin placer deposits at Heinda all within the Central belt (Mitchell, 2018) where the primary Sn-W mineralisation is predominantly hosted by biotite and two-mica granites (Clegg, 1994). The Coastal belt is characterised by biotite granites with minor hornblende-bearing granodiorite. In the northeastern section of this Coastal belt, medium- to coarse-grained aplogranites, the Kanbauk W-Sn(-F) deposit, and other minor prospects. In the Frontier belt, several W-Sn deposits occur along the border between Myanmar and Thailand, including the Pilok deposit, where W-Sn
mineralisation is predominantly hosted by alkali-feldspar aplite granite (Lehmann et al., 1994; Zhao et al., 2023).
The Kanbauk skarn altered W-Sn deposit is located within the north-south, placer hosting Heinze Chaung Channel, where mining commenced in 1916, primarily as an alluvial tin mining area under the British controlled Messrs Redcliff Company. Subordinate Sn-W bearing quartz veins cut the Mergui Group meta-sediments in the western section of the mine site, and was the subject of small-scale hard-rock production up to the end of World War I. Although the skarn outcropped, it was shown on maps in the reports by Griffiths (1917) and Coggin Brown and Heron (1923) as 'blue rock' or 'basic rock', and not recognised as actual skarns. The potential economic significance of cassiterite, scheelite, and fluorite in these skarns was not addressed until Savitar’s initial evaluation of the project in 2016 (Zhao et al., 2023).
Granites are predominantly exposed to the south and west of the Kanbauk mine site. At least two types of granites have been indicated: i). coarse grained biotite granite and ii). subordinate fine grained muscovite granite. The Mergui Group in Kanbauk occurs as variably hornfelsed siltstones and impure sandstones, generally with shallow dips of ~40°W. These rocks are normally strongly altered, and are cut by quartz and skarn veins. The location of the Heinze Chaung channel is strongly influenced by a major NW-trending fault, which is subparallel to the regional structure. Limestone identified during mineral exploration in the Heinze Chaung channel is mostly covered by Quaternary sedimentary rocks, and is indicated to extend over a distance of at least 16 km along the channel and south of the Kanbauk mining district (Zhao et al., 2023). This unit may be part of the Mergui Group but may alternatively be considered to be correlated with the middle Permian limestone in Moulmein, about 150 km north of Kanbauk, where it lies unconformably above the Mergui Group (Mitchell, 2018).
The skarn alteration at Kanbauk is masked by tin placers at the surface. It occur to the west of marble beds and to the east is in fault contact with the Mergui Group metasediments. This fault contact dip at 70 to 80°W, with a projected surface thickness ranging from 40 to 80 m. Some drill core intersections exhibit interbedding of skarn-altered marble and impure calc-silicate hornfels, whilst skarn veins extend into the metasediments with late fluorite and scheelite. The eastern contact between the skarn and marbles is irregular and poorly defined, with the adjacent marble cut by veins containing skarn minerals and carbonate fluid-escape veins in multiple crosscutting orientations. Gossan in the north of the mining area, is considered to be the oxidised distal sulphide bearing skarn altered rocks, whilst a set of NE-trending faults truncate or displace the southern end of the Kanbauk skarn. Locally, WNW-ESE faults and fractures dominate, and wolframite-cassiterite bearing quartz veins appear to be related to these structures (Zhao et al., 2023).
Early mineralogy studies indicate a prograde skarn stage with massive anhydrous mineral assemblages, mainly comprising garnet and pyroxene, and a retrograde skarn altered suite of hydrous and sulphide mineral either overprinting or forming veinlets cutting prograde alteration. On a deposit scale, the prograde skarns generally exhibit a typical outward zonation from red to green garnet to pyroxene toward the marble contact. Wollastonite-pyroxene-vesuvianite assemblages are found adjacent to massive garnet skarns. Toward the western contact with metasediments, there is an increased predominance of pyroxene with bands of garnet-pyroxene skarn alteration. Scheelite is essentially ubiquitous in both the prograde and retrograde skarns, although the retrograde assemblages have the highest W and Sn grades. Magnetite-rich skarns with wrigglite texture are locally evident, typically containing abundant fluorite and disseminated scheelite, generally overprinting garnet but predating retrograde assemblages. During the retrograde stage, garnet altered skarns were overprinted by assemblages of epidote and carbonate, whilst pyroxene skarns were overprinted by dark green actinolite. Cassiterite is found in late retrograde stages and is associated with carbonate veins and amphibole-chlorite alteration. Sphalerite, galena, pyrrhotite, chalcopyrite and molybdenite are found in retrograde skarns and associated veins. Some quartz veins contain cassiterite and wolframite in the hornfelsed metasediments of the Mergui Group in Tin Valley, west of the mine site, but no clear crosscutting relationships with skarns are observed (Zhao et al., 2023).
Zhao et al. (2023) report LA-ICP-MS U-Pb dating of skarn related minerals from the mineralised zones has returned ages as follows: i). Typically subhedral to euhedral garnet grains from massive prograde skarns, with both sector and oscillatory zoning, composed of 15 to 23% andradite, 55 to 67% grossularite and 16 to 30% pyralspite and contain 0.08 to 306 ppm U, had a lower intercept 206Pb/238U age of 56.0 ±1.5 Ma. ii). Subhedral to anhedral cassiterite grains from retrograde veinlets with U contents from 110 to 12 000 ppm had a lower intercept of 206Pb/238U age of 54.2 ±1.7 Ma.
Reserves/Resources
Initial ore reserve estimates of skarn altered mineralisation indicate >100 Mt of ore with reported grades of 0.17% WO3, 0.26% Sn and 15.4% CaF2, potentially making it one
of the largest W-Sn skarn deposits in the Southeast Asian tin belt (Zhao et al., 2023).
The most recent source geological information used to prepare this decription was dated: 2023.
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.
Kanbauk
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Selected References:
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Zhao, W.W.,Zhou, M.-F. and Dudka, S., 2023 - In situ U-Pb dating of garnet and cassiterite from the Kanbauk W-Sn(-F) skarn deposit, Dawei region, southern Myanmar: new insights on the regional Sn-W metallogeny in the Southeast Asian Tin Belt: in Econ. Geol. v.118, pp. 1219-1229. doi:https://doi.org/10.5382/econgeo.5002.
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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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