通过对个旧超大型矿床中变质火山岩岩石矿物和地球化学的研究,该区与铜锡成矿关系密切的火山岩主要为高钛碱性超基性火山岩系列,岩石组合主要有碱性苦橄岩、碱性苦橄质玄武岩和碧玄岩等.大多数样品中SiO2含量变化范围为34.62% ～44.73%, K2O+Na2O含量在2.99% ～7.15%, TiO2含量变化范围为1.83% ～4.0%, 平均含量为3.07%; 富集Nb、Ta、Zr、Hf等高场强元素, Nb含量变化范围为24.9 ～98.1μg/g; 稀土元素表现为平滑右倾的稀土配分模式, δCe和δEu异常不明显.上述特征与洋岛碱性玄武岩类似, 结合相邻地区的构造特征看, 个旧三叠纪沉积盆地原型盆地属于弧后裂谷盆地, 这种弧后裂谷盆地对于大型-超大型块状硫化物矿床的形成是十分有利的成矿地质背景和条件.%The Gejiu superlarge tin polymetallic deposit is located in the southeastern part of Yunnan Province,China, which comprises five separate orefields: the Malage, Songshujiao, Gaosong, Laochang and Kafang orefields. The pre-Triassic and Early Triassic sedimentations were marine source predominated, and shifted to terrestrial source dominated after Early Triassic. Multiple periods or stages of magmatic activities ranging from Proterozoic to Cenozoic along with main tectonic movements were recorded in the area. This paper reports the petrological and geochemical characteristics of the Triassic volcanic rocks which are closely related to the tin and copper mineralization in the Gejiu area. The volcanic rocks, which consist mainly of alkaline picrite, alkaline picritic basalt and basanite, are of alkaline ultrobasic with high content of titanium. The rocks are characterized by SiO2 =34.62％ ～ 44.73％, K2O+Na2O=2.99％ ～7.15％, TiO2 =1.83％ ～4.0％, high HFSE contents. The chondrite normalized REE patterns are smooth right-dipping lines without significant Eu and Ce anomalies, which are similar to those of the typical oceanic island basalt (OIB). Considering the rigional tectonic settings, the Triassic sedimentary basin in the Gejiu area was a backarc rift basin which was a favourable site for the formation of largesuperlarge massive sulfid deposit.
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