摘要
朱拉扎嘎金矿是近年来在华北地台北缘西段首次找到的以变质沉积岩为主岩的大型金矿床。金矿化主要呈似层状、脉状和透镜体状产在中元古界变质沉积岩地层内。11件硫化物和2件金矿石全岩的δ^(34)S值变化范围为1.1‰～7.1‰。根据硫化物的产状及形成期次判断,成矿热液中的硫同位素基本上达到了平衡,成矿热液的δ^(34)S值为2‰左右,暗示硫的来源主要以深源硫为主,与岩浆活动关系密切。6件金矿石中的硫化物、1件变质沉积岩、2件地层火山岩+5件侵入岩体(脉)的^(206)Pb/^(204)Pb值分别为17.034～17.725、16.971、17.602～17.513和17.492～17.776;^(207)Pb/^(204)Pb为15.297～15.552、15.031、15.436～15.445和15.299～15.564;^(208)Pb/^(204)Pb为36.599～37.489、36.347、37.493～37.623和37.606～37.895。在铅构造模式图中,尽管金矿石Pb同位素投影点分布范围较大,但多数集中于地幔和造山带演化线附近,并与侵入岩铅同位素组成较为接近,反映了铅的来源主要与岩浆活动有关,矿石铅同位素组成可能是侵入岩铅与变质地层中铅混合的结果。S、Pb同位素数据表明,在朱拉扎嘎金矿床,原始地层中的火山岩可能促成了金在地层中的预富集,而海西期大规模的构造—岩浆活动不仅带来了大量的成矿物质,而且使地层中的金活化。
The Zhulazhaga gold deposit is a large-scale deposit first found in the Proterozoic meta-sedimentary rocks along the northern margin of the North China Platform in recent years. The gold mineralization mainly occurs in the Mesoproterozoic meta-sedimentary rocks as layers, veins and lens. The δ34S values of 11 samples of sul-fides and 2 samples of whole rocks of gold ore vary from 1. 1‰~ 7. 1‰. Based on the δ34S values of different sulfides and their formation stages and occurrences, the sulfur isotope fractionation in the ore fluid almost reached the equilibrium, with the δ34S value about 2‰. It means that the sulfur may be derived mainly from deep source related to magmatic activity. The 206Pb/204Pb values of 6 samples of sulfides of the gold ore, 1 sample of meta-sedimentary rocks and 2 samples of volcanic rocks from the strata and 5 samples of intrusive bodies (or dykes) are 17. 034~ 17. 725, 16.971, 17. 602 - 17. 513 and 17.492 - 17.776, respectively; the 207Pb/ 204Pb values 15. 297 - 15. 552, 15. 031, 15. 436 - 15. 445 and 15- 299-15. 564, respectively; 208Pb/204Pb values 36. 599~37- 489, 36. 347, 37. 493 - 37- 623 and 37. 606 - 37. 895, respectively. In the lead-tectonic model , the dots of lead isotopes span the lower crust, mantle and erogenic belt evolution curves, and are mostly located between the mantle and orogenic belt evolution curves. It indicates that the lead is mixed by the intrusives and the strata, with main part from the intrusives. Based on the sulfur and lead isotopic features of the gold ore, it is supposed that the volcanic rocks from the strata might make the gold preconcentrated in the strata. The large-scale Hercynian tectonic-magmatic activity not only brought a large amount of ore-forming materials, but also activated the gold in the strata. When the gold-bearing fluid deposited and concentrated in some favored structures, the gold deposit was formed.
出处
《地质论评》
CAS
CSCD
北大核心
2001年第4期438-445,共8页
Geological Review
基金
国土资源部定向基金科研项目"内蒙古朱拉扎嘎金矿床地质特征和找矿勘查标志研究"
国土资源大调查项目"前寒武纪成矿作用"(编号K1.4-3-1)
