Pb isotope geochemistry of lead, zinc, gold and silver deposit clustered region, Liaodong rift zone,northeastern China

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【出版日期】2005-04-10

【刊名】Science in China(Series D:Earth Sciences)

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As one of the important deposit-clustered regionsof China, the Liaodong (eastern Liaoning Province)rift zone contains many large lead, zinc, gold, boron,magnesite and talc ore deposits with a long mininghistory. Recently, large-scale Xiaotongjiapuzi gold andGaojiapuzi silver deposits were discovered in the re-gion. Much work on the origin of these deposits hasbeen carried out, however, the discrepancy on the ageand the metal source of the deposits still rem- discuss the metamorphic age of the marble of theains[1—3]1,2). A study on the formation age and the Dashiqiao Formation from the Qingchengzi ore field,source(s) of the ore-forming materials will help with a the geochemical characteristics of the Pb isotopesdeep understanding of the ore-forming process and from various ore deposits and possible source(s) of thefurther prospecting. ore-forming metals. Lead isotopes are powerful in not only delineat- 1 Geologic settinging the evolution history of the crust[4] but also tracing The Paleoproterozoic Liaodong rift zone (fig. 1)the source of the ore-forming material and the origin is developed on the Archaean North China craton.of the deposits[5—8]. Extensive Pb isotopic studies have Thick Paleoproterozoic Liaohe Group deposited in thebeen performed for the deposits from the Qingchengzi rift zone. The lower part of the Liaohe Group, con-ore field and the Beiwagou deposit[2, 9—15] . However, sisting of the Yujiapuzi and Langzishan Formations,the early data produced in the 1960s and 1970s were consists of volcano-clastic rocks, the middle part, thenot precise enough[15] and, therefore, a new run of Pb Dashiqiao Formation, carbonate rocks, and the upperisotopic study is necessitated. part, the Gaixian Formation, clastic and pyroclastic rocks. Depositions in the rift zone have experienced We report in this paper the Pb isotopic composi- the metamorphism from greenschist facies to amphi-tions for the Xiqueguo lead-zinc deposit, Zhenzigou bolite facies, forming amphibolite, granulite, schistzinc-lead deposit and Gaojiapuzi silver deposit from and marble.the Qingchengzi ore field as well as for the Beiwagouzinc-lead deposit. Based on the Pb isotopic ratios we In the late stage of development of the rift zone at Fig. 1. A sketch map of the Proterozoic Liaodong rift zone with locations of the deposits (modified after Wang and Qu, 2000[16]). 1) Wei, M., Geological characteristics and the origin of gold and silver deposits from the Qingchengzi ore field (ed. Geological Survey ofChina), Symposium on Regional Geology and Metallogeny of Liaoning and Jilin provinces, Shenyang, 2001, 137-145. 2) Liu, G. P., Deng, Y. C., Zhou, G. X., Discussion on the type and the exploration of deposits from the Qingchengzi ore field (ed. GeologicalSurvey of China), Symposium on Regional Geology and Metallogeny of Liaoning and Jilin provinces, Shenyang, 2001, 19-23. Pb isotope geochemistry of Pb, Zn, Au, Ag deposit in Proterozoic Liaodong rift zone 469the Mid-Late Paleoproterozoic, the crust was melted, gentite, native silver and pyrargyrite. The wall rockforming Na-rich granite, such as Shuiquan, Lianshan- alteration includes silicification, carbonation andguan, Shijialing and Dadingzi bodies. The Dadingzi sericitization. Besides lead and zinc, the associatedbiotite plagiogranite with a gneissic texture gives a silver is also economically important1).K-Ar age of 1740-1621 Ma[2]. The formation of the The Zhenzigou is a typical lode-type Zn-Pb de-granite was associated with thrusting and napping. posit. The ore bodies are strictly controlled by theTectonism and magmatism in the period stimulated the bedding and occur within the marble of the Dashiqiaotransportation of ore-forming elements and formation Formation and in amphibolite, biotite schist andof the ore deposits. banded graphite-bearing marble close to the contacts Strong tectonism and magmatism occurred in the between those rocks and the marble. No wall rock a

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