Geologic characteristics and potential of bauxite in China

Journal Pre-proofs Geologic characteristics and potential of bauxite in China Li Sun, Shuai Zhang, Shihong Zhang, Jiannan Liu, Keyan Xiao PII: DOI: Reference:

S0169-1368(17)30582-6 https://doi.org/10.1016/j.oregeorev.2019.103278 OREGEO 103278

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Ore Geology Reviews

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Please cite this article as: L. Sun, S. Zhang, S. Zhang, J. Liu, K. Xiao, Geologic characteristics and potential of bauxite in China, Ore Geology Reviews (2019), doi: https://doi.org/10.1016/j.oregeorev.2019.103278

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Geologic characteristics and potential of bauxite in China Li Sun a, Shuai Zhang b*, Shihong Zhanga,b, Jiannan Liu a, Keyan Xiao a a

MlR Key Laboratory of Metallogeny and Mineral Resource Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China b

China University of Geosciences, Beijing 100083, China Corresponding authors: Li Sun, Shuai Zhang E-mail: [email protected];[email protected]

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Abstract: This contribution provides a comprehensive review of the bauxite resources and its potential in China, which is an important part of China National Mineral Resources Assessment Initiative. Bauxite resources in China are concentrated in regions such as Guangxi, Guizhou, Henan, and Shanxi. Bauxite deposits in China can be subdivided into sediment type, accumulation type and lateritic type with the former two types dominating the bauxite resources in China. Based on the established deposit models, and regional prediction models , the integrated information assessment methods based on the deposit model approach was implemented to estimate potential bauxite resources. As a result, 101 prospective areas were defined and their mineral potential was estimated to a maximum depth of 1000m by volumetric method based on geological parameters. The results of this activity indicate that the amount of undiscovered bauxite resources is huge. Five key bauxite mineral provinces dominated by sediment type and accumulation type deposits have been identified and their potential was discussed. Keywords: Bauxite; Mineral potential; Deposit model; Integrated information assessment methods

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1. Introduction The vast majority of aluminum is sourced from bauxite (Jiang et al., 2017; Qi et al., 2013; Sun et al., 2008), and bauxite can also be used for fire retardant, abrasives, chemicals, aluminous cement (Ran, 2012; Wang et al., 2012) and as a source of gibbsite and monohydrate diaspore (Ahmadnejad, 2017; Liao et al., 1991; Patterson, 1973). Various studies have been undertaken on the mineralogy, petrology, geochemistry, protolith, and genesis of bauxite deposits. For example, Bardossy provided a comprehensive review for bauxite genesis and defined lateritic- and karst-type bauxite (Bardossy, 1982, 1990). Blatt (1982) suggested that majority of the world’s bauxite deposits formed via laterization in a warm and humid environment. Other research examined the geochemistry and mineralogy of lateritic bauxites, which provide further insights into their genesis (e.g. Horbe and Anand, 2011; Du et al., 2012; Foley and Ayuso, 2013; Berger and Frei, 2014; Giorgis et al., 2014). As for karst type bauxite, Mongelli (1997) and Öztürk et al. (2002) studied the genesis of the bauxite formation in the southern Aplian block in Italy and in Taurides, Turkey respectively and Temur and Kansun (2006) explained the process of bauxite deposition in Masatdaqqi region of Turkey. Chinese scholars such as Sun et al. (2018), Gao et al. (2015), summarized the studies on bauxite deposits in China and subdivided them into sediment type, accumulation type and lateritic type. Bauxite prospectivity in United States has been assessed by the United States Geological Survey (USGS)1 (Lang et al., 1965; Overstreet, 1964; Renaud et al., 2015).

1

https://minerals.usgs.gov/minerals/pubs/mcs/

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The USGS has also assessed the global bauxite reserves and resources, indicating that over 40 countries contain significant bauxite resources (Liu,2001; Patterson,1967). The 2017 USGS Mineral Commodity Summary for bauxite indicates that globally there are 5.50  1010 to 7.50  1010 tons of bauxite resources, which are distributed in Africa (32%), Oceania (23%), South America and the Caribbean (21%), Asia (18%), and other regions (6%). Total global bauxite reserve is about 28 billion tons in 2016, and is distributed in Guinea (740Mt), Australia (620Mt), Brazil (260 Mt)), Vietnam (210Mt), Jamaica (200Mt), Indonesia (100Mt), and China (100Mt) (Table 1; Fig. 1). A number of bauxite deposits have been discovered and exploited in China. However, the rapid development of aluminum industry has promoted a detailed reestimation of the total bauxite resources in China. This contribution utilized integrated information assessment method based on deposit models and geological parameter volumetric method to estimate the total bauxite resources in China (Xiao et al., 2010a; Ye et al., 2007). Areas with existing mineralization are combined with geological evidence layers to generate regional mineralization potential maps that outline prospective areas for future exploration. The approach involves the extraction of metallogenic information to establish a regional evaluation model, which both facilitate the delineation of prospective areas and estimation of the undiscovered resources by geological parameter volumetric method. Potential mineral resource estimation was conducted at 1:50 000 scale in eastern China and 1:200 000 scale in western China, to a depth of 500m or 1000m below surface. This study provides an up-to-date review of the geology of bauxite deposits and its potential in China, which will promote future bauxite exploration in China. 4

2. Bauxite resources in China A large number of bauxite deposits have been discovered and mined in China. Total bauxite resource is about 1 billion tons. Large and high-grade bauxite deposits are mainly distributed in Shanxi, Guizhou, Henan, and Guangxi Provinces, which account for 87% of the total bauxite resources in China. The main bauxite deposit types in China are the paleo-weathering crust and the karst accumulation type (Sun et al.,2018) with the former commonly rich in metals such as Ga, V and Sc. Late Paleozoic (especially Carboniferous) is the main ore-forming epoch for paleoweathering crust-type bauxite deposits. This type of deposits in South China are mainly hosted in the lower Carboniferous Datang Group overlying the Cambrian-Silurian carbonates and sandy shale, whereas those in northern China are mainly hosted in the lower-middle Carbonaceous Benxi Group overlying the Cambrian-Ordovician carbonates. The Permian Liangshan, Wujianping and Xuanwei Formations (overlying the lower Paleozoic carbonates and siltstone) host some small or middle sized deposits in Guizhou and Chongqing. Small sized bauxite deposits are also associated with upper Permian Formations such as Wujianping and Xuanwei, both of which overlie CarboniferousPermian limestones. Paleocene–Neogene lateritic bauxite deposits in China are derived either from Quaternary basalts or upper Paleozoic carbonates in Hainan and Guangxi. (Gao et al., 2015)

3. Deposit types and mineralisation prospectivity mapping method 3.1. Deposit types

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Different classifications of bauxite deposits have been proposed. For example, Peive (1947) classified bauxite deposits into geosyncline and platform types based on tectonic setting and sedimentary facies. Meanwhile, Vadasz (1951) proposed a threefold classification including lateritic, karst, and mechanical clastic depositional types. Bardossy et al. (1982) and Liao (1991) argued that all bauxite was from laterite derived from weathering processes. For that reason, bauxite deposits can be classified as paleoweathering or paleo-lateritic types. Bauxite deposits in China can be classified into sedimentary, accumulation, and lateritic types based on geological features and ore forming processes (Sun et al.,2018) (Table 2). (1) Sedimentary type Sediment bauxite deposits are mainly distributed in Henan, Shanxi, Guizhou, Guangxi, and Chongqing Provinces. They are normally hosted in the weathering crust of carbonates, and some in sandstone, shale, and basalt. In northern China, bauxite is hosted in a sedimentary sequence comprising eroded limestone, coal seam, clay, bauxite, Febearing clay, hematite, and siderite or pyrite (from top to bottom of the deposit). In Southern China (e.g., Guizhou and Chongqing Provinces), bauxite occur on top of Paleozoic sandstone, sandy shale and basalt. The orebody shape, size, and composition are controlled by the source material and the paleo-topography. This type of deposit could be further divided into the eroded carbonate and eroded clastic sub-types. Examples for sedimentary bauxite deposits are those in Wuzhengdao area, West Henan, Shanxi and Sha’an xi regions.

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For the bauxite prospectivity mapping, host rock lithology and paleo-geography were regarded as basic evidence layers. Lithofacies, ore-bearing formations, depth of orebearing formations and Al:Si ratio are dominated predictors for perspectivity mapping (Fig. 2). (2) Accumulation type Deposits of this type are mainly distributed in Guangxi and Yunnan Provinces, and are likely sourced from the original low-grade sedimentary bauxite deposits. Weathering and leaching of bauxite-bearing formations may have led to the decrease of detrimental elements such as S and Fe. Accumulation-type deposits occurred either on top of the sedimentary bauxite formation or in the neighboring karst depressions (Sun et al.2018). Shapes of individual orebodies are complex and irregular, which reflect the topography of the underlying terranes, and are normally several hundreds to over 2000 m long along strike. The thickness varies from 0.5 to 10m.Ore minerals are dominated by diaspore with minor kaolinite, goethite, hematite, gibbsite, and boehmite. The Al/Si ratios vary from 4 to 15 (average > 10). The Al2O3 and Fe2O3 contents vary from 40 %to 65% and from 16% to 25%, respectively. Examples of this type of deposit include those in Pingguo area of Guangxi and in Guangnan area of Yunnan Province. Basic evidence layers for prospectivity mapping are the Quaternary geologic maps and interpreted remote sensing images. Variables including geomorphology, geochemical anomalies and host rocks are used for perspectivity mapping (Fig.3). (3) Lateritic type

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Deposits of this type are hosted in the weathering crust formed by the weathering and leaching of the underlying carbonates or basalt. Most of these deposits are small and located in the South China coastal region, including Hainan and Guangdong provinces, yet a number of large-size deposits have been recently discovered in central Guangxi. Minerals are dominated by gibbsite with minor limonite, hematite, goethite, iddingsite, kaolinite, and boehmite. The Al2O3 and Fe2O3 contents and Al:Si ratio vary from 30% to 50%, 18% to 25% and 4 to 6, respectively. Ga and Co are commonly enriched in this type of deposits. Examples include those in Penglai area of Hainan and Wenchang area of Guangdong. Basic evidence layers are the Quaternary geologic maps and interpreted remote sensing images. Geochemical anomalies and favorite rock types, such as carbonate and Quaternary basalt are main predictors for mineral perspective mapping. 3.2. Bauxite prospectivity mapping and resource estimation method Mineral prospectivity mapping aims at estimating the probability of mineral occurrence, which mainly involves three steps: (a) Conceptual modeling of the target mineral deposit type,(b) Obtaining the evidence layers and (c) integrating the evidence layers to indicate the probability of mineral occurrence. It can be regarded as

a

complicated systematic project of optimal decision making for mineral exploration under various uncertain conditions, complying with modern metallogeny theories, mineral resource exploration and evaluation. Moreover the introduction of various advanced data mining technologies combined with the knowledge and experiences of professionals would greatly facilitate the process and improve the accuracy of the results. The adopted method for the estimation of regional bauxite mineral resources namely the integrated information assessment methods based on the deposit model (Xiao

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et al., 2010a, 2010b; Ye, 2013; Ye et al., 2007; Zhang et al., 2017), can be concluded as follows: Firstly, compiling the evidence layers and building the spatial database with GIS; Secondly, selecting the proper prediction method based on the research on metallogenic controls including the regional geological setting, tectonics and lithofacies, paleogeography, as well as the in-depth analysis of integrated geological information. Finally, delineating prospective areas, and estimating the total resources of relevant minerals. For bauxite prospectivity mapping, types of deposit-sought determine the evidence layers. For examples, Sedimentary-type bauxite deposits, lithofacies, paleogeography and paleotectonic and sedimentary formations would be priorities as evidence layers. In specific geotectonic facies, the distribution of specific ore-bearing formations should be seriously

considered.

Favorable

metallogenic

areas

in

tectonic

lithofacies,

paleogeographic maps or formation-structure maps should be exactly expressed in sedimentary formation-tectonic maps. For the accumulation and lateritic type, Quaternary geographic and geomorphic maps as key controlling factors are commonly selected as the evidence layers. The traditional volumetric method (Meyer, 1978; Kingston et al.,1978) assumes that the same sized ore-bearing formation should have the same amount of resources. Xiao et al. (2007) applied geological parameters in volumetric method, which improved the accuracy of traditional volumetric method. With the volume of ore-bearing formation in

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the modelling area and its total resource (including predicted resource at depth), orebearing coefficient can be calculated and applied to estimate the undiscovered resources in the exploration targets (Xiao et al., 2010b).And the Ore-bearing coefficient can be depicted as follows: C = W/V V=S×H

(1) (2)

Where C denotes coefficient, W denotes the total resource (both discovered and undiscovered) of the modelling area, and V is the volume of ore-bearing formation in the modelling area. As to the volume V , it can be calculated by the projected area of mineralization (S)and the depth of ore-bearing formation(H), and H can be approximated by both drilling and geophysical inversion. Finally, the estimated resource 𝑄𝑝 can be calculated as follows: 𝑄𝑝 = C × 𝑆𝑝 × 𝐻𝑝 × F Where 𝑄𝑝 is the predicted resource; 𝑆𝑝 and𝐻𝑝

(3) are the area and depth of the

predicted area respectively, both of which can be determined by integrating geological, geophysical and drilling data. F is the similarity factor, which can be calculated by multiple regression analysis on variables such as ore-bearing formation thickness and other variables or by weight of evidence method(Xiao et al.,2010b)The key parameters for estimating predicted resources are the volume of ore-bearing formation and orebearing coefficient. The details of approach for potential resource estimation is illustrated in Figure 4.

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The uncertainties lied in the method mentioned above are mainly derived from the identification of areas and depths of the ore-bearing formations. In practice the uncertainties in the implementation of the method largely depends on the scales of related evidence layers and knowledge of the estimator. A procedure that follows the estimation of predicted mineral resources comprises the determination of: Depth credibility in terms of prediction type; Area credibility according to multi-information;Ore-bearing coefficient determined by the morphology, continuity of ore-body in modeling area. And finally, there is a comprehensive credibility for each target decided by experts.

4. Bauxite distribution and potential resources in China In China, there are 3 223 Mt of bauxite resources, with 3 031 Mt of remaining reserves and 10000 Mt of undiscovered resources. These resources are dominated by sedimentary type, followed by accumulated type and lateritic type (Fig.5). A total of 33 bauxite deposits have been exploited in China, among which 6 are in Henan,4 in Shanxi,8 in Guizhou and 1in Guangxi. A significant amount of research has been undertaken on bauxite ore belts to guide future mineral exploration (e.g., Guo et al., 1987; Mitchell et al., 1981; Routhier et al., 1990; Xie.,1936; Xie et al., 1999; Xiao et al.,2009). Chen et al. (2007) analyzed the bauxite ore belts in China and divided the country into different mineral provinces, zones/belts, sub-belts, and ore fields. A total of 15 bauxite belts are identified in China (Fig. 6). Four mineral provinces of China contain significant bauxite resources, namely the North China platform, Yangtze platform, South China folding system, and the SE China coastal region.

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Bauxite resource was assessed by the integrated information assessment method proposed by Xiao et al. (2017) and 101 targets were delineated as a result. These targets are mainly distributed in Shanxi, Henan, Guizhou and Guangxi, and a few in Yunnan, Sichuan, Shandong, Hunan and Hubei. The exploration targets of central and northern Shanxi and western Henan-southern Shanxi most likely contains >10 000Mt of bauxite resources. The central and northern Guizhou and southern Chongqing regions are favorable for sedimentary-type bauxite formation, and could contain ~2 000Mt of resources. In addition, certain areas in western Guilin and eastern Yunnan are prospective for sedimentary- and accumulation-type bauxites and could contain >1 000Mt of resources. Potential Bauxite have been estimated for 18 administrative provinces down to 500 m or 1,000 m deep below surface. The size of basic prediction unit is about 5  5 mm on the 1:5M geologic map, and the total resource estimated is expressed as contours (Figs. 7 and 8). The potential resources to the depth of 500m shows no obvious increase compared with that to the depth of 1000m, indicating that the bauxite potential does not increase significantly with depth. Details for major bauxite rich provinces/regions are as follows: The Henan region is dominated by sedimentary-type bauxite deposits, and this exercise shows that it contains two areas including Zhanggou–Tongshuyuan area and Wanggou–Fanpo area with resources of >1 000 Mt. In addition, several areas such as Bomiao–Nanlicun and Caojiagou–Shisi with >500Mt of potential resources, and areas such as Yangbiling–Xiyao, Dongyao–Aotou, Mihe–Chendong, and Bailang–Huguoshu with >100Mt of predicted resources. 12

The Guangxi region, dominated by accumulation-type bauxite deposits, contains one area of Jiaomei–Dalong with >500Mt of potential resources, several areas such as Genzhu–Maling and Beigeng–Babiao with >300Mt of potential resources, and some areas such as Wucun–Ludong, Naliu–Gula, northeastern Luxindong–Menggou, and Fengren–Longxiang with >200Mt of potential resources. Areas such as the Kongxiang– Tingliang and Beigeng–north Longqing with >100Mt of predicted resources are also presented in this region, The Shanxi region is dominated by sedimentary-type deposits and contains >900Mt of potential resources in the Tiejiangpu–Yangjiagou area, >400Mt of potential resources in the Sanquan–Taohongpo area, and >100Mt of potential resources in the Tianjiashan– Wangjiagou, Xiyang–Hanwang, Wanghe–Guodao, and Mengxian–Qianzhuang areas. The Guizhou region contains mainly sedimentary-type bauxites with >600Mt of potential resources in the Niunaichong–Maochang area, >300Mt in the Datang– Zhangjiayuan area, and >1 00Mt in the Shanji–Wujiang and Wangjiazhai–Lushan areas. A comparison of existing and potential resources in the main bauxite provinces indicates that the potential resources are three times higher than the existing resources in Henan, two times higher than those in Guangxi and Shanxi, and more than double of those in Guizhou (Fig. 9). This result suggests that these provinces remain to be the foci of future bauxite exploration and mining in China.

5. Conclusions and discussion

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In this exercise the resource distribution, deposit-type classification, and mineral potential estimation method and prospectivity of bauxite-rich provinces are summarized in China and some conclusions are as follows:. Sedimentary type and accumulation type bauxites are the dominant deposit types in China while lateritic type deposits only occur in certain areas such as Hainan and Guangdong provinces The former two types of bauxite will remain to be the target for bauxite exploration and play a major role in bauxite mining. . The metallogenic time of sedimentary bauxite in China concentrate in Carboniferous and Permian, mainly carboniferous. This type of deposit normally occurs in northern China and covered by coal seams. Accumulative bauxite was hosted in pleistocene sequence and therefore it is formed during Quarternary. The potential of these two types accounts for more than 90% of the total potential resources. Bauxite resources in China are relatively concentrated. Mainly distributed in Henan, Shanxi, and Guangxi and Guizhou provinces. Five key bauxite mineral provinces in China have been recognized in this exercise. namely the Baode–Xingxian-Qinyuan area (Shanxi), the Mianchi area (Henan), the Maochang and Wuzhengdao areas (Guizhou), and the Laibin–Binyang–Pingguo area (Guangxi), the former 4 provinces are dominated by sedimentary type deposits while the last one by accumulate type deposits. By means of metallogenic system prediction method of sedimentary minerals, comprehensive information analysis of lithofacies and paleogeography, and volume method, the potential resource of bauxite to the depth of -2000m is 13.56 billion tons. A

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total of 101 exploration targets were delineated and their mineral potential was assessed during this exercise. The exploration should be undertaken in Shanxi, Henan, Guizhou and Guangxi provinces, and the prospecting of laterite bauxite in Guangxi and Hainan provinces should be considered.

Acknowledgements The authors are grateful to two anonymous reviewers for their constructive comments that improved the manuscript. This exercise was jointly supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (grant numbers:2016YFC0600504,2017YFC0601500 and

2017YFC0601501),

number

:41802250)

China and

natural

China

science

Geological

foundation Survey

project Project

(grant (grant

numbers:1212011120140, 1212001103000160910).

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Figure captions Fig. 1. Global distribution of bauxite resources. Fig. 2. Ore -forming process of sedimentary type bauxite deposits Fig. 3. Predictive model for accumulation-type bauxite in Guangxi. Fig. 4. Resource estimation procedure diagram Fig. 5. Distribution of bauxite resources in China. Fig. 6. Location of major bauxite ore zones in China. Fig. 7. Contour map showing the distribution of predicted bauxite resources to a depth of 500 m. Fig. 8. Contour map showing the distribution of predicted bauxite resources to a depth of 1,000 m. Fig. 9. Diagram comparing the proven and predicted resources of the main bauxite mineral regions in China.

Table captions Table 1. World bauxite reserves. Table 2. Summary of the major bauxite deposit types in China.

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Fig.1. Global distribution of bauxite resources.

Fig.2. Ore-forming process of sedimentary type bauxite

23

Fig.3 Predictive model for accumulation type bauxites.

Fig.4 Resource estimation procedure diagram

24

Fig.5. Distribution of bauxite resources in China.

25

Fig.6 Locations of major bauxite ore zones in China.

26

Fig.7 Contour map showing the distribution 500 m.

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Fig.8 Contour map showing the distribution1,000 m.

Fig.9 Diagram comparing proved and predicted resources.

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Table 1. World bauxite reserves. Serial number

country

reserves （megatons）

Percentage of total storage

1

Guinea

7,400

26

2

Australia

6,200

22

3

Brazil

2,600

9

4

Vietnam

2,100

8

5

Jamaica

2,000

7

6

Indonesia

1,000

4

7

China

980

4

8

Guyana

850

3

9

India

590

2

10

Suriname

580

2

11

Saudi Arabia

210

1

12

Russia

200

1

13

Kazakhstan

160

1

14

Other countries

2,960

11

28,000

100

15

World total (rounded)

U.S. Geological Survey, 2017,Mineral Commodity Summaries (U.S. Government Publishing Office, Washing ton, DC,)

https://minerals.usgs.gov/minerals/pubs/mcs/

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Table 2. Overview of the main types of bauxite deposit in China. type

ary

tion

Deposit

Sediment

Accumula

Lateritic

Northwest

Shanbei Tainqiaoze Guangpingshi, Wushi Ayili

North

Xiaoyikee, Gongyizhulingou, Xin'an Zhangyaoyuan, Handan Fengfenghecun, Wangcun, Shan'xi Ke'e, IM Guchengpo

ast

Northe

Benxi niuxintai, Hongyang

Southwest

South

East

Xiuwen Xiaoshanba, Qingzhen Maochang, Tianzhong Laomeishan, Diandong Tiechang, Zunyi Xunjiang, Chongqing Dafoyan, Sichuan Dabaiyan, Leshan Xinhua

Pinggu o Burong, Xiangxi Lijiatian, Hubei Shuangcizi

Ganx i Huibu

Diandong Maijiupin

Pinggu o Nadou, Guixi Liuqiao

Shan dong Hutian

Guizho ng Guigang, Hainan Penglai, Guangdong Wenchang

30

31

a)

Integrated information assessment method based on deposit model applied for the areas prospective.

b)

Potential resource estimated by geological parameter volumetric approach.

c)

Five key areas for future bauxite exploration have been outlined in China.

The authors declare that there is no conflict of interest issue regarding this paper.

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