煎茶岭金镍矿田构造特征及控岩控矿作用探讨

摘 要]煎茶岭含钴硫化镍矿床已进入开采阶段,金矿正进行外围找矿。因而,查明该金镍矿田构造特征并探讨控岩控矿作用尤为重要。笔者通过解析矿田构造、研究矿床特征及其构造地球化学等以后认为:煎茶岭矿田构造-热事件活动频繁,多期褶皱控制着地层展布,共轭区域韧性剪切带控制着岩体就位;构造地球化学特征表明韧性变形有利于元素的活化,韧脆性变形使元素迁移和富集;区域韧性剪切带和控矿韧脆性剪切带内有大量物质的带入带出,韧脆性控矿剪切带中糜棱岩化蛇纹岩型镍矿石中K₂O、Cr 等元素含量相比区域韧性剪切带内蛇纹质糜棱岩明显减少,而Fe₂O₃ 、FeO、P₂O₅ 、LOI、MnO、SiO₂ 、CaO、Ni 和Co 为带入组分;韧脆性控矿剪切带对金镍矿体的形态、产状和矿石的结构构造有明显的控制作用。因此,煎茶岭金镍矿田岩(矿)石受多期褶皱、区域共轭韧性剪切带和控矿韧脆性剪切带共同控制,金镍矿体表现为韧性剪切带、超基性岩体和花岗斑岩体等酸性岩体(脉) 共同作用的“三位一体冶成矿模式。金矿在共轭韧性剪切带相互交叉部位,绕超基性岩呈“金项链冶分布。镍矿位于以花岗斑岩为核的“σ”型“旋转碎斑系”拖尾内韧脆性剪切带之中。脆性断裂生成较晚,并对地层、岩体和矿体有一定破坏作用。

Structural Characteristics of the Jianchaling Gold-Nickel Orefield and Its Rock-controlling and Ore-controlling Roles

Abstract:The cobalt-bearing sulfide nickel deposit in Jianchaling has entered the exploitation stage and gold-search is undergoing in its peripheral mines. Thus it is an important task to ascertain the structural characteristics and rock-controlling and ore-controlling roles of this orefield. We have analyzed the orefield structure, deposits and tectono-geochemistry. The result shows that this orefield has experienced frequent tectono-thermal events, folds of many periods controlled the stratigraphic distribution, and conjugate regional ductile shear belts controlled the emplacement of rock intrusion. The features of tectono-geochemistry indicate that ductile deformation was favorable to the activation of metallogenic elements, while ductile-brittle deformation promoted element migration and enrichment. Introduction and removal of large-volume materials occurred within regional ductile shear belts and ore-controlling ductile-brittle shear belts. The contents of K₂O and Cr etc. in mylonitized serpentinite-type nickel ores are obviously less than that in regional ductile shear belts, and the elements, such as Fe₂O₃ , FeO, P₂O₅ , L0I, MnO, SiO₂, CaO, Ni, and Co, have been carried into nickel ores. The orecontrolling ductile-brittle shear belts have determined the form, occurrence, ore structure and texture of gold and nickel ore-bodies. So, rocks and ores in the Jianchaling gold-nickel orefield are controlled jointly by folds, regional ductile shear belts and ore-controlling ductile-brittle shear belts, which can be described by a mineralizing model. . The brittle fractures were formed later, and destructed the strata, rock bodies and ore-bodies to some degree.