3.8.1.1 Resources and Reserves

Lead and zinc mineral resources are abundant in China. The cumulative explored reserves (metal content; the same hereinafter) as of 1997 were 45.3583 million tons of lead and 110.078 million tons of zinc. The available retained reserves as of 1997 were 35.3069 million tons of lead, of which 11.5691 million tons were industrial reserves (categories A+B+C reserves; the same hereinafter), and 92.5664 million tons of zinc, of which 33.852 million tons were industrial reserves.

3.8.1.2 Characteristics of Resources

By the end of 1997 there had been 730 lead occurrences and 768 zinc occurrences in China. Their reserves were explored in 28 provinces, autonomous regions and municipalities. Ten provinces and autonomous regions had more than 1.5 million tons of retained lead reserves; they are (in order of decreasing reserves) Yunnan, Guangdong, Inner Mongolia, Gansu, Jiangxi, Hunan, Sichuan, Guangxi, Shaanxi and Qinghai. The total sum of the lead reserves of the ten provinces and regions account for 80% of the national total. Thirteen provinces and autonomous regions contributed more than 2 million tons of retained zinc reserves; they are (in order of decreasing reserves) Yunnan, Inner Mongolia, Gansu, Guangxi, Guangdong, Hunan, Sichuan, Hebei, Jiangxi, Shaanxi, Qinghai, Zhejiang and Fujian. The total sum of the zinc reserves of the 13 provinces and regions make up 90% of the national total. The distribution of lead-zinc deposits and reserves and status of the main occurrences in China are shown in Fig. 3.8.1 and Table 3.8.1.

The percentages of lead and zinc reserves in the eastern, central and western economic regions are as follows (according to the retained reserves as of 1997): in the eastern coastal region, lead 37.2% and zinc 26.9%; in the central region, lead 21.3% and zinc 29.9%; in the western region, lead 41.5% and zinc 43.2%.

China's lead-zinc resources have the following characteristics:

1) The occurrences are widespread, but reserves are chiefly concentrated in several provinces and regions. At present lead and zinc resources have been found and explored in 28 provinces, regions and municipalities. In terms of the degree of concentration and retained reserves, they are mainly concentrated in six provinces and regions. The provinces and regions with combined lead and zinc reserves >8 million tons are (in order of decreasing reserves): Yunnan, Inner Mongolia, Gansu, Guangdong, Hunan and Guangxi, with their combined reserves accounting for 64% of the national total lead and zinc reserves. In terms of their distribution in the above-mentioned three economic regions, they are mainly concentrated in the western region, where the lead and zinc reserves make up 41.5% and 43.2% respectively.

2) Most reserves occur in large and medium-sized deposits and ore types are complex. Among more than 700 lead-zinc occurrences in China, large and medium-sized deposits contribute 81.1% of lead reserves and 88.4% of zinc reserves. The ore types are highly varied. The principal ore types are lead sulfide ore, zinc sulfide ore, lead oxide ore, zinc oxide ore, lead-zinc sulfide ore, lead-zinc oxide ore and mixed lead-zinc ore. There are more lead-zinc deposits and copper-zinc deposits mined mainly for zinc, but less lead-zinc deposits mined mainly for lead and still less deposits mined exclusively for lead.

3) In lead-zinc deposits the mineral composition is complex and there are many associated components that have great value in total use. Most deposits contain the elements Cu, Fe, S, Ag, Au, Sn, Sb, Mo, W, Hg, Co, Cd, In, Ga, Se, Tl, Sc etc. In some deposits the ore mined contains as many as more than 50 elements. Particularly, in the past two decades, through an integrated exploration and a study of the material composition of ore, it has been verified that many lead-zinc deposits have a higher silver content and become lead-zinc-silver deposits or silver-lead-zinc deposits. Their silver reserves account for over 60% of the national total. The production of silver recovered during mining, dressing and smelting of such ores makes up 70 to 80% of the national total. There are also fairly considerable gold reserves and production.

4) There are more low-grade ore and less high-grade ore, more ore with complex textures and structures and mineral composition and less ore with simple textures and structures and mineral composition. In the producing deposits, the average grade of lead and zinc is 3?74%, the zinc grade being higher than the lead grade, with a lead/zinc ratio=1:2.5 (the ratio abroad is 1:1.2). The mineral composition of the ores is complex and some dressed ores contain up to over 30 minerals. Some ores with complex textures and structures and very fine grain size belong to the refractory ore type, causing difficulty in ore dressing.

China's lead-zinc deposits have the following geological characteristics£º

1) Lead-zinc deposits are distributed relatively concentratedly in time and space. China's lead-zinc deposits were mainly formed in the Yanshanian and the multi-stage compounding metallogenic epoch. According to the statistics of the Explanatory Notes to the Endogenic Metallogenic Map of China, of the metallogenic epochs of the lead-zinc deposits, the Precambrian takes up 6%, the Caledonian 3%, the Hercynian 12%, the Indosinian 1.3%, the Yanshanian 39%, the Himalayan 0.7%, and the multi-stage compounding metallogenic epoch 38%. In terms of spatial distribution, the superlarge, large and medium-sized deposits that have been explored now are chiefly concentrated in the western Yunnan, Sichuan-Yunnan, West Qinling-Qilian, Langshan (Inner Mongolia)-Da Hinggan and Nanling metallogenic provinces.

2) Regional faults and downfaulted basins or depressions resulting therefrom obviously control the distribution of lead-zinc ore zones, ore fields and ore deposits. The distribution of some superlarge and large deposits (fields) found in China up to the present is essentially related to them.

3) Lead-zinc deposits controlled by folds are common too. The deposits occurring in anticlines, synclines and monoclines account for 70%, 14% and 13% respectively.

4) The element (mineral) assemblages in deposits are complex. Few deposits are mined for lead or zinc alone, and most deposits, especially large and superlarge deposits, are synthetic ore deposits. For example, the Xicheng superlarge ore field, Gansu, is marked by a lead-zinc-silver-gold assemblage; the Fankou superlarge lead-zinc deposit, Guangdong, a lead-zinc-silver-sulfur-mercury assemblage; the Kangjiawan deposit of the Shuikoushan ore field, Hunan, a lead-zinc-silver-gold assemblage; the Taolin deposit, Hunan, a lead-zinc-silver and fluorite assemblage; the Jinding superlarge deposit, Yunnan, a lead-zinc-silver-cad-

Table 3.8.1 Summary of main lead-zinc occurrences of China¢Ù(metal reserves, t)

¢Ù In the Chinese edition 128 occurrences are listed in the table, while in the English edition only relatively large deposits (or fields) are listed and their serial Nos. are the same as in Fig. 3.8.1.¢Ú According to the Criteria for the Size Classification of Mineral Deposits promulgated by the China National Mineral Reserves Committee in 1987, large lead-zinc deposits are defined as those containing lead or zinc reserves > 500,000 tons; deposits of medium size, lead or zinc reserves 100,000 to 500,000 tons; and small deposits, lead or zinc reserves < 100,000 tons.

mium-thallium-strontium assemblage; the Qixiashan deposit, Jiangsu, a lead-zinc-silver-sulfur-manganese assemblage; the Dongshengmiao superlarge deposit, Inner Mongolia, a pyrite and lead-zinc assemblage; the Yinshan deposit, Jiangxi, a lead-zinc-gold-silver assemblage. The material compositions of the deposits are very complex, including 35 elements and 77 minerals. The occurrence of these synthetic ore deposits (field) reflects that China's lead-zinc deposits were formed in complex and highly varied environments and are the product of synthetic mineralization. Some deposits become multi-source and multi-stage composite ore deposits.

5) There is a relatively full range of ore deposits that have their own distinctive characteristics. The basic geological characteristics of various types of deposit are given in Table 3.8.2.

6) The metallogenic environments and distribution of main types of deposit (field) show certain regularities. Most of the metallogenic environments of widespread and giant carbonate rock type deposits (fields) occur in platforms, while some of them in miogeosynclines. Restricted sedimentary basins are more favorable for the formation of carbonate rock type lead-zinc deposits than open sedimentary basins. Ore-bearing strata in Southern China are mostly the upper Sinian, Devonian and Carboniferous; whereas those in Northeast China, the Middle Proterozoic and Cambrian-Ordovician.

Mudstone-fine clastic rock type lead-zinc deposits (fields) mostly occur in a miogeosynclinal flyschoid sedimentary environment in fold belts, and the deposits are large and occur in swarms and zones.

Marine volcanic type lead-zinc deposits are mainly developed in Paleozoic-Triassic geosynclinal fold belts of western China.

Granite, skarn, porphyry and continental volcanic type lead-zinc deposits in eastern China are mostly the product of Meso-Cenozoic magmatism and were formed to a large extent under the influence of Meso-Cenozoic crustal movements.

Sandy conglomerate type lead deposits (fields) have two subtypes. One subtype is lead-zinc deposits hosted in continental red beds. Most of them are restricted in fluvial and deltaic facies strata of Meso-Cenozoic downfaulted basins. Their host rocks are chiefly conglomerate and sandstone, arkose, as well as marl and mudstone, with gypsum and celestite beds. The deposits are mainly distributed in western China, e.g. the superlarge Jinding sandy conglomerate type lead-zinc deposit in western Yunnan. The other subtype is the lead-zinc deposits hosted in littoral or paralic sandy conglomerate, which are scarcely found in China now and not large in size.