| 八家子铅锌矿床氢、氧、碳和硅稳定同位素研究 |
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| 引用本文：.1991.Hydrogen, oxygen, carbon and silicon stable isotope studies of the Bajiazi lead-zinc deposit[J].Mineral Deposits,10(2):143~151 |
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| 中文摘要:本文通过对八家子矿床的氢、氧、碳和硅稳定同位素研究，揭示了矿床成矿热液的来源及演化问题。研究表明，成矿热液早期以岩浆热液为主，随着成矿过程的进行加入的大气降水比重越来越大，到晚期可能主要以大气降水为主。热液中碳和硅质的来源早期也是以岩浆来源为主，在成矿过程中演变为岩浆来源和地层来源两者的混合。 |
| 中文关键词:氢氧碳和硅稳定同位素 成矿热液来源与演化 八家子铅锌矿 |
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| Hydrogen, oxygen, carbon and silicon stable isotope studies of the Bajiazi lead-zinc deposit |
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| Abstract:The Bajiazi deposit is located 1n the northern margin of the North China Plaffom. Its host rocks are dolomite with chert bands of Gaoyuzhuang Formation and sandstone of Tahongyu Formation in Middle Proterozoic. Magmatic rocks are widely developed, of which the biotite quartz diorite cropping out in the east of the ore district is intimately related to mineralization. Ore bodies are mainly controlled by NW-trending faults, and might be divided from southeast to northwest into five ore blocks. δ18O values of biotiteq uartz diorite vary significantly, ranging from 8.6‰ to 3.3‰ for whole rock, from 11.2‰ to 9.3‰ for quartz and from 9.8‰ to 5.6‰ for biotite, indicating that the rock body suffered late hydrothemal alteration. The calculatedδ18OH2O of magma is 9.9-8.0‰, suggesting that the magma belongs to high 18O member of the normal magma in Taylor’ s classification. Oxygen and hydrogen isotope compositions of altered minerals and ore minerals vary systematically, and the calculatedδ18OH2O values of hydrother real solution are 9.9-8.0‰(mean 9.1‰)in magma stage, 12.9-7.2‰(mean 9.6‰)in skarn stage, 13.5-9.8‰(mean 11.2‰)in magnetite stage, 7.7-6.9‰(mean 7.4‰) in pyrite-galena-sphalerite stage, 6.9-3.6‰(mean 5.0‰) in galena-sphalerite-barite stage. It is obvious that in the initial stage, the magmatic water served as the main source of ore-forming solution, but in the late stage the meteoric water gradually entered the mineralizing system and played an increasingly important role in ore formation. δ13C values of host dolomite are -6.8- -0.1‰(mean-2.5‰), and those of the calcite veins are-6.9- -2.6‰(mean-4.4‰). δ13C values of CO2 in fluid inclusions of quartz are-8.2‰ and-3.1‰ in the early stage and late stage respectively. The carbon source of hydrotheramal solution is mixed carbon from magma and dolomite in the process of ore formation. The silicon isotope compositions are studied for the first timeδ30Si values of chert from the strata are 2.8-1.7‰, while the value of quartz from biotite quartz diorite is -0.1‰. δ30Si values of quartz in the ore bodies and altered minerals are between the two values and approaches 0.1‰ in the vicinity of the magmatic bodies in the early stage and varies in the range of 1.5-0.7‰ distant from the magmatic bodies in the late stage. These data show that the silicon source is the mixture of magma and chert in the strata. |
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