Sediment-hosted Pb-Zn Deposits in Southwest Sanjiang Tethys and Kangdian Area on the Western Margin of Yangtze Craton

The western margin of Yangtze Craton is known as a significant sediment-hosted base-metal aggregate cluster,especially for Pb-Zn deposits in China,e.g.Jinding,Daliangzi,Tianbaoshan, Kuangshanchang and Qinlinchang deposits.In comparison with the classic MVT deposits in the world, based on the basic geology of the sediment-hosted Pb-Zn deposits,this paper focuses on temporal-spatial distribution of this deposit to further discuss its large scale mineralization and tectonic evolution history.In the SW Sanjiang Thethys,Jinding deposit is typically thrust fault-controlled and hosted mainly in the sandstones and breccia-bearing sandstones,whereas MVT-type deposits are controlled by lithology and faulting/fracturing with a strong preference for carbonate-hosted rocks.Most importantly,Jinding Pb-Zn deposit differs from the other types of sediment-hosted Pb-Zn deposits in which it was formed in a strongly deformed foreland basin within a continental collision zone.In the Kangdian area,the sediment-hosted Pb-Zn deposits were formed in the extensional basin on the side of the continental orogenic belt along the Yangtze Craton.Compared with classic MVT deposits,the Pb-Zn deposits in the Kangdian area belong to MVT deposits.This paper is significant not only for interpretation of the genesis of sediment-hosted Pb-Zn deposits but also for exploiting large base metal deposits in large sedimentary target areas.

Organic Geochemistry of Sedimentary Rock-hosted Disseminated Gold Deposits in Southwestern Guizhou Province, China

Sedimentary rock-hosted disseminated gold (SRHDG) deposits in the Youjiang-Nanpanjiang Basin, southwestern Guizhou Province are commonly hosted by the same fold crests that commonly contain a remarkable amount of organic material. The total organic carbon (TOC) contents of the ores and host rocks are usually less than 1%. The reflectance of vitrinite and pyrobitumen in the ores and the host rocks ranges from 1.5% to 4.5%, often in the range of 2% to 3%. In the Lannigou deposit, the reflectance of vitrinite and pyrobitumen in the ores is usually somewhat higher than those within the host rocks, indicating a hydrothermal impact on the organic matter in the altered host rocks. On the contrary, the estimated maximum paleotemperatures of the Getang and Zimudang deposits are higher than the homogenization temperatures of the fluid inclusions in the ores, signifying that the organic matter maturation predated Au mineralization. No correlation between the organic matter contents and Au concentrations were recognized in the ores. However, the most striking observation is that there is a positive correlation between the S2 (a parameter of Rock-Eval analysis), Au and As contents of the ores in the Lannigou deposit. Organic matter maturation and migration is apparent from the TOC vs. HCI diagram. Furthermore, group analysis of the dichloromethane extractable organic component of the ores and host rocks shows that the maturation degree of the organic matter in the ores is slightly higher than that of the host rocks in the Lannigou gold deposit. However, the compositions of their alkanes, steranes and terpenes, which serve as biomarkers, are quite similar; this suggests that the organic matter found in the ores and host rocks has a common marine source. Organic matter probably contributed to the preconcentration of Au in the host rocks. Hydrocarbons in the system, on the other hand, clearly contributed to the emplacement of the gold mineralization through thermal sulfate reduction. Organic matter in the solution might have increased the potential of the hydrothermal solution to transport Au.

Dynamic processes of ore-forming fluid and the localization of orebody: case study on the sediment-hosted gold deposits of southwestern Guizhou, China

1 Geological setting and occurrence features of the sediment-hosted gold deposits OVER 100 sediment-hosted gold deposits and occurrences of southwestern Guizhou lie near the sonthemedge of the Yangtze craton, which is composed of crystalline rocks of Proterozoic age, overlain mainly byPaleozoic and Lower to Middle Triassic shallow-marine platform and reef facies carbonates that gradesouthward and eastward into a thick section of interbedded siltstones and turbidite sandstones. Clasticdeposits were from the Yunkai Old Land and the Jiangnan Old Land respectively. The rocks were foldedand faulted during the Yanshanian orogeny, 190-65 Ma ago. Mineral deposits were mainly located inthe breccia horizon at the base of the Longtan Formation of Upper Permian, underlain by the massive graylimestone of Lower Permian with a karst unconformity, and the high-angle fault zones in the Triassicargillaceous limestone interlayered with shale, arkose, and fine-grained turbidite sandstone. No

Mineralization of sediment-hosted ore deposits in reef-chert suite in China

THE reef-chert suite, named by Chen, mainly consists of four types of rocks, with reef carbonate in thelower part, fine detrital rocks in the upper part, chert beds with ore bodies in the intermediate, and synchronous volcanic rocks either in this sequence or in the same sequence in the neighboring district. It isformed as a fixed and ordered suite in space and time, and is the comprehensive product of normal sedimentary process, biological process in extensional basin, hydrothermal sedimentary process near basinbase and magmatic process in the deep of lithosphere in the special geological setting. Many of thesediment-hosted ore deposits usually occur in such a suite in China, such as Dajiangping pyrite deposit,Shuikoushan lead-zinc ore deposit, Changkeng gold-silver deposit, Dachang cassiterite-lead-zinc ore deposit, Xikuangshan stibium ore deposit, Changba-Lijiangou lead-zinc ore deposit, Baiyunebo