Chapter 9 Sediment-Hosted Zinc-Lead and Copper Deposits in China

Abstract

Abstract Sediment-hosted Zn-Pb and Cu deposits in China include Mississippi Valley-type (MVT) deposits, clastic-dominated (CD) deposits (also historically called sedimentary-exhalative [SEDEX] deposits by some workers), sandstone-hosted (SSH) Zn-Pb deposits, a few large magmatic-related carbonate-replacement deposits (CRD), and volcanic-hosted massive sulfide (VHMS) deposits that have been mistakenly classified as nonmagmatic-related MVT or CD deposits. There are also areas of China that contain important sediment-hosted copper (SHC) deposits. China is exceptionally endowed with MVT deposits with three of the five largest MVT deposits in the world (Huoshaoyun, Jinding, and Changba-Lijiagou). In contrast, China has one CD deposit (Dongshengmiao) in the top 30 CD deposits in the world. The few SHC deposits are small relative to world-class examples. The largest SHC deposits are located in the Yangtze and the North China cratons and hosted in Proterozoic rocks with indications of massive halokinetic features like those observed in the African copper belt. The MVT ores are most abundant in the Yangtze block, Qinling orogen, and the central and eastern Himalayan-Tibetean orogen. There are many other carbonate-hosted deposits in the North China craton and the Cathaysia block that have been widely classified as MVT or sedimentary-exhalative deposits. These are better classified as CRD or skarn deposits based on their proximity to intrusions, alteration assemblages, trace and minor element signatures, and, in some deposits, the presence of skarns minerals. Numerous sediment-hosted Zn-Pb deposits in China have been traditionally classified as SEDEX or syngenetic deposits based on laminated ore textures and stratiform ores that we interpret to reflect deformation and selective replacement processes rather than synsedimentary ore processes. Only two of these sediment-hosted deposits can be unequivocally classified as CD deposits: Dongshengmiao and Tanyaokou in the Langshan area of the North China craton. They are hosted in a siliciclastic-dominated sequence of a Proterozoic passive margin. The location and genesis of many MVT and SHC deposits in China are directly controlled by evaporites and evaporite facies. Evaporite and evaporite facies had an extremely important role in determining the location of the MVT deposits. The second largest sediment-hosted Zn-Pb deposit in China and fifth largest in Asia, Jinding in the Himalayan-Tibetan orogenic belt, is hosted in a hydrocarbon-reduced sulfur reservoir that formed because of salt diapirism. Other large sediment-hosted Zn-Pb MVT deposits in China that are interpreted to be controlled by structures produced by evaporite diapirism are Daliangzi and Tianbaoshan in the western Yangtze block. The largest Zn-Pb deposit in China is the newly discovered oxidized Huoshaoyun Zn-Pb MVT deposit, also in the Himalayan-Tibetan orogenic belt that is hosted in an evaporite-bearing sequence. The third largest Zn-Pb resource in China is at the Changba-Lijiagou deposit and, together with numerous smaller deposits, define a belt of metaevaporites in a carbonate platform sequence of the northern Yangtze platform. Other evaporite-related MVT ores include the Huize deposits that are hosted in a former Carboniferous evaporite-bearing hydrocarbon reservoir and the extensive Sinian dolostone-hosted Zn-Pb deposits that reflect evaporite dissolution breccias in the Yangtze block. The Tarim craton in northwestern China contains the only significant SSH deposit at Uragen. The ore zone lies in the footwall of an evaporative unit that may have served as a hydrocarbon and reduced sulfur trap. Furthermore, the most significant SHC deposits are hosted in Proterozoic rocks in the North China craton and the Yangtze block that contain extensive halokinetic breccias and structures.