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本文介绍了用电子探针分析采自西南太平洋斑岩矿铜省含矿和无矿岩株中的新鲜、未蚀变岩类的角闪石和黑云母中的大量元素。含矿和无矿岩株的铁镁矿物中不同化学组份变化有明显的区别。薄片签定中这些变化不很明显。无矿岩株中的角闪石明显地呈通常所认为的正常钙碱性岩石系列的变化(即从各个晶体的中心到边缘 Mg/(Mg+∑Fe)比值是变化的或者减少)。含矿岩株中则观察到相反的趋势(即从角闪石晶体的中心向边缘 Mg/(Mg+∑Fe)比值增加)。产于含矿和无矿岩株中的黑云母发现了性质上类似的变化。现有资料表明,化学组份的变化可归因于结晶过程中岩浆内氧逸度(fo_2)的不同。含矿的岩浆系列具有高的 fo_2(结晶过程中 fo_2可能增加),无矿的岩浆系列 fo_2低或是变化的。fo_2高是岩浆期后热液最后结晶产物的特性。利用上述观察结果提出了一种勘查方法。即从远景区快速采集有代表性的样品,接着在实验室研究高fo_2条件下晶出的矿物组合(角闪石+磁铁矿+榍石)标志及其矿物的化学组份变化。与其他找矿方法相比其优点是(1)采样的靶区大(岩株、岩基),(2)能快速确定远景区。这种方法可用于找寻与中-基性钙碱性岩类有关的其他热液型矿床。
In this paper, a large number of elements from amphibole and biotite from fresh and unaltered rock in copper-bearing ore-bearing and non-ore-bearing rocks collected from porphyry copper deposits in the Southwest Pacific are analyzed by electron microprobe. There are obvious differences between different chemical components in iron-magnesium minerals of ore-bearing and non-ore-bearing rock strains. These changes are not obvious when the sheet is signed. The amphiboles in the ore-free rock strains are clearly in the generally accepted variation of the normal series of calc-alkaline rocks, ie, varying or decreasing from the center to the edge Mg / (Mg + ΣFe) ratio of individual crystals. The opposite trend is observed in ore-bearing rock strains (ie, increasing the ratio of Mg / (Mg + ΣFe) from the center to the edge of the amphibole crystal). Biotites produced in ore-bearing and non-ore-bearing rock formations revealed a qualitatively similar change. The available data show that the change of chemical composition can be attributed to the difference of oxygen fugacity (fo_2) in the crystallization process. The ore-bearing magma series have a high fo_2 (fo_2 may increase during the crystallization), and the ore-free magmatic series fo_2 is low or variable. High fo_2 is the characteristic of the final crystalline product of hydrothermal fluids after the magmatic period. Using the above observations, a survey method is proposed. Ie rapid collection of representative samples from distant vantage point, followed by laboratory studies on the mineralogical changes of the mineral assemblages (amphibole + magnetite + gallstone) crystallized under high fo_2 conditions. Compared with other prospecting methods, the advantages of this method are (1) large sampling target area (rock mass and rock foundation), (2) quick determination of the prospect area. This method can be used to find other hydrothermal deposits related to Meso-basic calc-alkaline rocks.