| 关于德兴斑岩铜矿铜源的初步研究 |
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| 引用本文：.1984.Opper Sources Of The Dexing Porphyry Coppelr Deposit--A Tentatkve Discussion[J].Mineral Deposits,3(2):39~48 |
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| Opper Sources Of The Dexing Porphyry Coppelr Deposit--A Tentatkve Discussion |
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| Abstract:Geochemical studies reveal striking yet regular variations in copper content of the Dexing copper ore field. Instead of being governed by stratigraphic positions and lithologic characters, such variations seem to be intimately related to the distance from the porphyry mass. Rocks lying in excess of 5 km from the igneous body contain fairly stable amounts of copper, averaging 78 ppm; those located l.5-5 km from this body have extremely low copper content (averagely 43 ppm); those lying less than l.5 km from the body have comparatively high copper content (averagely 94ppm); ore bodies and mineralized rocks possess by far the highest copper content (averagely 5476ppm). In inward succession these rocks are named normal field, decreased field or negalively anomalous field, positively anomalous field and mineralized field respectively. Assuming approximately the form of concentric circles with the mineralized field as the center, they make up an integrated geochemical system. The positively anomalous field possesses relatively small area while the negatively anomalous field is comparatively large. The increase or decrease of copper content in positively or negatively anomalous field is negatively proportional to their respective extent. Statistics show that the amount of copper released from the negatively anomalous field (as compared with the copper content of the normal field) roughly equals copper concentration of ore or the amount of copper added to the positively anomalous field. The configuration of this geochemical field of copper as well as its close association with the porphyry and the porphyry copper deposit implies that copper was derived from the decreased field surrounding the ore deposit. Like copper, the concentrations of rock-forming elements, REE and Rb, Sr, F, Cl in selected samples from these fields also show regular variations. Most of these elements have anomalous values in anomalous copper fields. The available δO18 data of the ore field suggest the addition of meteoric water in the ore-forming fluids; δO18 is 1.35‰ at the major mineralization stage, which is much lower than the minimum value of the magmatic water, indicating that ore-forming fluids are dominated by the meteoric water. All this points to the conclusion that the Dexing porphyry copper deposit mainly derived its copper from the country rocks. |
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