| 内蒙赤峰红花沟金矿稳定同位素研究 |
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| 引用本文：.1990.Stable isotope studies of the Honghuagou gold deposit in Chifeng County, Inner Mongolia[J].Mineral Deposits,9(3):257~269 |
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| 中文摘要:本文通过对红花淘金矿铅、硫、氧、氧等稳定同位素研究，及微量金，铅、铀、稀土元素的研究指出，成矿物质主要来源于太古代变质岩及其重熔产物，成矿溶液主要来源于大气降水，强调了大气降水在成矿物质辽移、富集过程中的作用。建立了矿源层、构造、热源三位一体的成矿模式。 |
| 中文关键词:稳同位素 大气降水 稀士模式 红花沟金矿 |
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| Stable isotope studies of the Honghuagou gold deposit in Chifeng County, Inner Mongolia |
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| Abstract:The Honghuagou gold deposit is located within the Yunwushan uplift on the northern flank of the Inner Mongolian anteolise and also lies at the intersection of the Chifeng-Chaoyang structural belt with the Chifeng-Longhua structural belt. Archeozoic amphibolites, amphibolite gneisss and various sorts of migmatite crop out in the orefieid, and Upper Jurassic volcanic rocks are distributed extensively. Magmatic rocks are not widely developed, and are dominoted by intermediate-acid dykes, of which tile pre-ore diorite porphyrite is intimately related to mineralization. Orebodies (occurrences)are mostly distributed in Archeozoic metamorphic rocks and controlled by NNW-SN trending faults, belonging to gold-bearing quartz vein type deposit. Metallic minerals are mainly pyrite with small amounts of chalcopyrite and galena. Ore grade is closely associated with contents of sulfides. Archeozoic amphibolitic metamorphic rocks contain abundant gold(10.7ppb). The pre-ore diorite porphyrite also contains rather high gold(6.4ppb); REEpattern suggests that is was formed as a result of partial(10%) melting of amphibolitic metamorphic rocks. The ores certain quite low radiogenic lead, and the single stage model ages are old (within the range of 1700-1800 Ma), indicating that lead was derived from an uranium-deficient area and characterized by multi-stage evolution. The whole rock lead isotope composition of the granite porphyry on the southern side of the ore district is quite similar to the ore lead, and the granite porphyry was formed by remelting of Archeozoic amphibolites. Amphibolite is poor in uranium(0.24 ppm), rich in gold and exhibits multistage evolutionary history, in addition, gold in amphibolite is most readily extracted and activated by hydrothermal fluids. It is therefore conceivable that amphibolite and its remeltlng products might have been the parent rock of lead and the initial source bed of gold. Sulfur isotope composition is rather uniform in the ore deposit, and the overwhelming majority of samples are within the narrow limits of 3.5-4.5‰, suggesting the unity of sulfur source and the stability of physicochemical condition. Whole rock δ34S values amphibole and pre-ore diorite porphyrite are respectively 2.9 and 3.1‰, which are fairly consistent and within the distributton range ofδ34S values of the ore deposit, implying their sanguinity and their genetic connection with the ore sulfur. δ34S values of pyrite in the ore veins gradually increase from the depth upwards, but tend to decrease progressively in the middle.δ18O values of quartz in ore veins vary insignificantly, mostly within the range of 11.5-12.5‰; vertically, δ18O values of quartz andδ34S values of pyrite show similar variation regularityδ18O values of ore fluids are in the range of 0.8-5.9‰, distant from theδ18O ranges of magmatic water and metamorphic water but close to theδ18O range of meteoric waterδD values of quartz inclusions also exhibit characteristics of meteoric water(-85.5-109.7‰). Calculation shows that ore fluids were formed through hydrogen-oxygen isotope exchange between the initial meteoric water(δD)=-96‰, δ18O=-23‰) and the pre-ore diorite porphyrite and amphibolite at 200-250℃, with the ratio of water/rock being 0.3 or so. The vertical variations in δ34S values of pyrite in ore veins and δ18O values of quartz must have resulted from the upward decrease in ore-forming temperature, the unceasing addition of fresh meteoric water, the progressive rising of fO2 values and the remarkable decrease in δ34S and δ18O values of the whole system due to the appearance of SO42- in the upper part of the ore veins. |
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