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Procedia Environmental Sciences 12 ( 2012 ) 978 – 983
2011 International Conference on Environmental Science and Engineering (ICESE 2011) Analysis on Mineralization Geological Conditions of Danchi Metallogenetic Belt, Guangxi, China*
Yongsheng Chenga,b
aSchool of Geosciences and Info-Physics,Central South University,Changsha, Hunan Province, China bChina Tin Group Co., Ltd., Liuzhou, Guangxi Province, China [email protected]
Abstract
The Danchi metallogenetic belt is a very important Non-ferrous base in China. According to the status of resource mining and theory research, this paper analyzed the geological conditions (i. e. stratum, tectonic evolution and magmatism), in order to supply the theory guidance for the prospecting in this district. The exposure strata consists of Devonian, Carboniferous, Permian, Triassic and Quaternary, but Devonian is the key stratum, which there is a close relation with Sn–polymetallic deposits. This area, which experienced three tectonic evolution stages, is situated in the south margin of the Yangtze platform. Because of the affect of the tectonic evolution, it was characterized the special geological conditions and mineralization environment. The main magmatism occurred in the medium and late period of Yanshan, including biotite granite, granite porphyry, quartz diorite and white granite, in the pattern of dykes, rock strain, rock bed commonly. In the whole, the prospecting is rather favorable, in the deep or around of the known deposits.
© 20112011 Published Published by Elsevierby Elsevier B.V. SelectionLtd. Selection and/or peer-review and/or peer-review under responsibility under responsibility of National University of [name of Singapore.organizer]
Keywords :Stratigraphy, Tectonic evolution, Danchi, Guangxi, China
1.Introduction
The Danchi metallogenetic belt is the most important Sn-polymetallic producing district in China, even in the world, where there are some super-large scale ore deposits[1-3], i.e., the Tongkeng ore deposit, the Changpo ore deposit, the Mangchang ore deposit, the Lamo ore deposit, the Kengma ore deposit (Fig.1), and is also an important source of Zn, Pb, Cu, Ag, Sb, In and Cd. The Dachang Sn- polymetallic ore deposit, which is situated in the Danchi metallogenetic belt of Guangxi province, south
* This work is partially supported by the special funds of central college basic scientific research operating expenses (Grant No. 201012200210), China postdoctoral science foundation (Grant No. 20090451105) and the postdoctoral workstation of China Tin Group Co., Ltd. (Grant No. 043010100).
1878-0296 © 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of National University of Singapore. doi: 10.1016/j.proenv.2012.01.374 Yongsheng Cheng / Procedia Environmental Sciences 12 ( 2012 ) 978 – 983 979
China, is one of the largest Sn ore deposits in this world. The Danchi metallogenetic belt, which formed as a NW–SE trough, surrounded by shallow–water carbonate platform from two sides, is situated in the south margin of the Yangtze Platform[4-5]. The trough has an area of 3000 km2 (100 km long and 30km wide).
2.Regional stratigraphy
In the Danchi metallogenetic belt, the exposure strata consist of Devonian, Carboniferous, Permian, Triassic and Quaternary (Table 1)[6-9].
2.1.Quaternary
About 0-50 m thick, composed mainly of slope sediments, eluvium and alluvium, which scattered along the slopes, valleys and caves, and covered the bedrock. In the area of Dachang, Mangchang and Huile, there are the industrial value tin sand deposits.
2.2.Triassic
2023 m thick, exposed only in the middle and lower system, which belongs to the sedimentary regeneration geosyncline, composed of clastic, mudstone with volcanic rocks and carbonate, which is characterized the sedimentary type of clastic turbidite rock, and contacting with the quaternary unconformity.
Fig. 1 Mineralization zoning of the Dachang ore field (compiled from China Nonferrous Metals Industry Corporation, 1987) 1ˉPermian limestone and siliceous; 2ˉCarboniferous limestone; 3ˉDevonian limestone, shale and siliceous; 4ˉParallel unconformity stratigraphic contact; 5 ˉDiorite porphyrite; 6ˉGranite and granite porphyry; 7ˉAnticline axis; 8ˉ Syncline axis; 9ˉFaults; 10ˉTin orebody; 11ˉZn-Cu orebody; 12ˉScheelite veins; 13ˉWolframite veins; 14ˉAntimony veins 980 Yongsheng Cheng / Procedia Environmental Sciences 12 ( 2012 ) 978 – 983
2.3.Permian
About 378-458 m thick, composed mainly of shallow marine carbonate, with little coastal lacustrine coal-bearing sedimentary rocks, contacting with the triassic conformable.
2.4.Carboniferous
About 1391 m thick, composed of limestone, dolomitic limestone for the upper and middle system, which belongs to the shallow shelf depositional environment. In terms of the lower system, it is composed mainly of clastic, which was the coastal sedimentary environment, contacting with the upper stratum parallel unconformity contacting.
2.5.Devonian
Approximately 2138ˉ5000m thick, exposed in the Danchi metallogenetic belt widespread, such as Mayang, Mangchang, Luofu, Dachang, Beixiang, Wuxu, etc, and composed mainly of sandstone, shale, limestone and chert. In this district, Devonian contains plankton fossils, which was called the Nandan- type sediment, contacting with the carboniferous conformable in the whole, but unconformity in local.
Table 1 Simple table of regional stratum in the Danchi metallogenetic belt Thickness System Series Group Code Lithology (m)
Upper Maping C3m Limestone, dolomitic Huanglong C2h Carboniferous Middle 1391 limestone Dapu C2d
Lower Bading C1bd Clastic rock Neritic facies terrigenous Tongchejiang D t 340Д370 3 clastic rock Bean limestone, banded Upper Wuzhishan D w 66Д127 3 limestone
Liujiang D3l 5Д174 Gray black siliceous Black mudstone, argillaceous Luofu D l 206Д519 2 limestone, siltstone Middle Black mudstone, argillaceous Nabiao D n 563ДЇ1791 Devonian 2 limestone, siltstone Mudstone, argillaceous Tangding D t 240ДЇ894 1 limestone Argillaceous limestone, Yilan D1y 20Д35 Lower mudstone, silty mudstone Quartz sandstone, argillaceous Nagaoling D n 412 1 siltstone Quartz sandstone, greywacke Lianhuashan D l Ї287 1 and conglomerate
ķ Upper devonian Consisting of three strata: Tongchejiang Formation, Wuzhishan Formation and Liujiang Formation Tongchejiang Formation (D3t): composed of shallow marine terrigenous clastic deposition. Yongsheng Cheng / Procedia Environmental Sciences 12 ( 2012 ) 978 – 983 981
(a) 3 3 (200 m thick), composed of dark gray thin-bedded mudstones, marl, with intercalated thick- D3 tcˆ bedded siltstone, silty mudstone and shale. (b) 3 2 (60 m thick), composed mainly of black carbonaceous shale. D3 tcˆ (c) 3 1 (80-110 m thick), composed of dark gray-black mudstone, marl, with intercalated limestone, D3 tcˆ calcareous fine sandstone and shale. Wuzhishan Formation (D3): consisting of four strata: 2 4 (a) D3 Z : consisting mainly of big bean limestone, the major axis about 2-5 cm long, the minor axis about 0.5-2 cm long. 2 3 (b) D3 Z : consisting mainly of small bean limestone, about 0.2-2 mm long. (c) 2 2 : consisting mainly of fine banded limestone, about 0.5-2 cm wide of the band, with D3Z disseminated limestone bands and chert bands. 2 1 (d) D3Z : consisting mainly of wide banded limestone, about 2-8 cm wide of the band, with disseminated limestone bands and mudstone bands. Liujiang Formation ( 1 ): composed of the gray-dark gray thin-bedded chert, with intercalated D3lj siliceous shale, siliceous mudstone, with high content of the carbonaceous in local. There are different sizes of calcareous nodules in the chert. ĸ Medium devonian Consist of mudstone, shale and marl, limestone, with intercalated chert, and fine-grained pyrite in the local part. Luofu Formation (D2lf): composed of dark gray-black calcareous mudstone, shale, interbed with gray-dark gray argillaceous limestone, with intercalated sandstone, carbonaceous mudstone, and a little of chert in local. Nabiao Formation (D2nb): composed mainly of gray-black mudstone, shale, with intercalated calcareous nodules, argillaceous limestone, fine-grained sandstone, with plenty of calcium and sandy, even reef limestone locally. Ĺ Lower devonian Tangding Formation (D1t): composed mainly of black mudstone, and organic matter and fine- grained pyrite. Yilan Formation (D1y): composed of dark gray-gray black mudstone, shale, with intercalated muddy siltstone and fine sandstone. Nagaoling Formation (D1n): composed mainly of gray siltstone, with intercalated fine-grained sandstone and gray-black sandy mudstone, which has high content of iron in local. Lianhuashan Formation (D1lh): composed mainly of purple-gray medium-fine quartz sandstone, with intercalated muddy siltstone, silty mudstone and a little shale and sandstone, with high iron content locally.
3.Structural Features
The Danchi metallogenetic belt is situated in the south margin of the Yangtze platform. The belt formed as a NW–SE trough, surrounded by shallow–water carbonate platform from two sides[10-12]. In the whole, it experienced three tectonic evolution stages: continental-continental margin rift stage from proterozoic to early paleozoic, continental-continental margin rift stage from devonian to early permian and back-arc rift stage during late permian and the triassic. 982 Yongsheng Cheng / Procedia Environmental Sciences 12 ( 2012 ) 978 – 983
This belt and the whole northern Guangxi suffered many times of tectonic movement, which leaded to form the different sedimentary basin in the different evolution stage, and characterized the special sedimentary sequence, magmatism and mineralization. This area is a fault depression basin in the north of the Youjiang passive continental margin rift basin in the period of Hercynian-Indosinian.
4.Magmatic rocks
To Danchi metallogenetic belt, the main magmatism occurred in the medium and late period of Yanshan, belonging to shallow-super shallow magmatic rocks, which distributed in the area of Longxianggai , Dachang, Mangchang, in the shapes of dykes, rock strain, rock bed, etc[13-15]. (1) Biotite granite It exposed at the Longxianggai fold of the middle metallogenetic belt, has an area of 200000m2 (1000 m long and 200m wide), which was composed of K-feldspar, plagioclase, quartz, biotite, muscovite, and the accessory minerals of topaz, apatite, tourmaline. It is characterized by the high content of SiO2 (averaging value 72. 84%), alumina saturation, poor in CaO, Fe2O3, FeO, MgO and MnO. (2) Granite porphyry It appeared in the east of the Changpo deposit in the shapes of dyke, which was called the east dyke. In this area, it was about 500-1500 m long, 5-l0 m wide, but it reached 8000 m maximum long, which was SN direction, trending the east, about 70° angle. Granite porphyry contained a little of metallic minerals, such as pyrite, sphalerite, native copper, jamesonite and cassiterite, etc. (3) Quartz diorite It was called the west dyke, exposing in the west of the Changpo deposit discontinuously. One of these come up to the surface, which near the SN trending, 200-500 m long, 2-12 m wide, containing a little of pyrite and marmatite. (4) White granite It exposed at the side of the Longxianggai hidden biotite granite, and filled the fracture and interlaminar fracture, in the shapes of dikes, sills, or rock sticks.
5.Discussion and conclusions
The Danchi metallogenetic belt, where produced plenty of metallic mineral resources, is an important Non-ferrous base in China. There are many favourable geological conditions, such as stratum, tectonic evolution, magmatism, lithofacies palaeogeography, etc. According to the mining status and the geological conditions, there are very great prospecting in this area, special in the deep and around of the known deposits. So, the further geological research is meaningful for the mineral resources development.
6.Acknowledgment
This work was partially supported by grants from the special funds of central college basic scientific research operating expenses (Grant No. 201012200210), China postdoctoral science foundation (Grant No. 20090451105) and the postdoctoral workstation of China Tin Group Co., Ltd. (Grant No. 043010100). Thanks are due to Fan Senkui of China Tin Group Co., Ltd., and Wu Yongtian, Zhang Xusheng, Lan Jiang of the WUYI Mining Company for their kind support during field work.
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