| 广东新洲-河台金矿带同位素地球化学研究 |
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| 引用本文：陈好寿,余养成,杨开渠,张伟坚,钟金带,雷禹文.1988.广东新洲-河台金矿带同位素地球化学研究[J].地球学报,10(1):117-137. |
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| 中文摘要:用U-Pb法、Pb-Pb法、Rb-Sr法和K-Ar法测定了新洲矿区合矿围岩的时代,结果表明,金矿围岩形成于688Ma前,之后至少经历了两次明显的地质作用,包括构造活动、变质、混合岩化作用、岩浆活动和成矿作用。铅、硫、碳、氢和氧等稳定同位素数据证明,新洲等金矿成矿物质来自围岩,成矿溶液为变质热液,由新洲向西或沿西南方向有岩浆热液加入。从英德到高要沿吴川-四会断裂带铅同位素组成在空间上具有明显的变化规律,与矿床规模和金品位之间有明显的关系,可作为找矿的标志之一。 |
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| ISOTOPE GEOCHEMICAL STUDY ON THE XINZHOU-HETAI GOLD BELT,GUANGDONG |
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| Abstract:The age of the wall rocks of the gold mineralization has been determined by the U-Pb, Pb-Pb, Rb-Sr and K-Ar methods. A U-Pb concordia diagram of zircon from slightly metamorphosed rocks in Xinzhou yielded two ages: t1 = 2498 ±153151 Ma, and t2 = 688?550 Ma. t1, may be interpreted as the age of the source region of zircon and t2 as that of the wall rocks. Thus, it is considered that the original rocks of the slightly metamorphosed rocks were formed 688 Ma ago and since then they had undergone at least two phases of metamorphism. One took place in the Caledonian movement (with a whole-rock Pb-Pb isochron age of 457 Ma) and the other in the Yanshanian (with a whole-rock Rb-Sr isochron age of 171 Ma and a biotite K-Ar age of 175 Ma). The gold mineralization is related to these metamorphic events.The Pb isotopic composition determined in the Xinzhou and Hetai mining districts and the Nanchong, Yiba and Taoyuan gold mineralization districts varies greatly, showing that the gold has different geneses and sources.The Pb isotopic composition in the Xinzhou mining district is characterized by a high content of radiogenic lead: 206Pb/204Pb= 18.244-21.288, 207Pb/ 204 Pb=15.691-16.574, 208Pb/204Pb = 39.033-43.153, μ-(238U/204Pb) = 9.63-11.14, ω (232Th/204Pb)=39.15-45.10, K1 (232Th/238U) =3.98-4.53 and K3 (Th/U)=3.89-4.38. The isotopic data points lie far away from the growth curve of the upper-crust lead of Doe and Zartman. The Pb isotopic feature in Yuba was similar to that in Xinzhou.The content of radiogenic lead in Hetai, Fengmeng'ao, Nanchong and Taoyuan is lower than that in Xinzhou. In Fengmeng'ao, 206Pb/204Pb= 17.356-19.507, 207Pb/204Pb = 15.408-15.687, 208Pb/204Pb = 37.816, μ = 9.22-9.53, ω = 32.66-38.61,K1 = 3.44-4.41, and K3 = 3.33-4.01. The data fall between the mantle lead evolution curve and the erogenic zone (arc) lead evolution curve. In the Hetai mining district, 206Pb/204Pb = 18.740-19.252, 207Pb/204Pb=15.698 - 15.778, 208Pb/204Pb = 39.138-39.449, μ = 9.61-9.73, ω = 37.31-39.26, K1= 3.83-4.05, and K3 = 3.71-3.92. The data fall between the upper-crust lead curve and the erogenic zone lead curve, and the μ value is similar to that in Nanchong and Taoyuan.The sulfur isotopic composition in Xinzhou and Fengmen'ao is characterized by heavy sulfur type, with δ34S=3.4-15.2‰. The data points lie at the right side of the line zero. δ13(PDB) of the carbonate minerals ranges from -3.7‰ to -10.1‰ and δ18O(SMOW) from 13.1‰ to 16.9‰. The calculated 618OH2O value ranges from 3.6 to 12.6‰- The hydrogen and Oxygen isotopic data of quartz and biotite in the deposit fall in the field of metamorphicwater, dD=-41-10.6‰, δ18Omineral = 7.2-16.4‰ and δ18OH2O=4.7-15.6‰,suggesting that the metamorphic water in the Xinzhou mining district played an important role in the ore-forming process in the Xinzhou mining district.The mineralizations with different scales and grades have different Pb isotopic composions. This feature may serve as an indicator for ore prospecting and assessment. |
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