中国北方造山带岩浆铜镍硫化物矿床及其地球动力学背景——以吉林红旗岭矿床为例

The Magmatic Sulphide Cu-Ni Deposits and Their Earth Dynamics Setting in North Orogenic Belt of China:A Case Study of Hongqiling Deposits

中国北方兴蒙造山带东段吉林省中南部产有一系列铜镍硫化物矿床,红旗岭矿床代表的是早三叠纪同造山期与超镁铁质-镁铁质岩浆作用相关的矿床类型.含矿母岩主要是由辉长岩-二辉岩-橄榄辉石岩-辉石橄榄岩等构成的杂岩体和顽火辉石岩超基性岩脉,构成星点状—稀疏浸染状、稠密浸染状、斑杂状、致密块状四种矿石类型.硅酸盐岩石的矿物组合为橄榄石+斜方辉石+单斜辉石+角闪石+斜长石,为钙碱性系列岩石组合类型.岩石化学显示其微量元素富集轻稀土元素和大离子亲石元素Rb、Ba,亏损高场强元素Ti、Nb,相似于俯冲带拉斑玄武岩,可能为幔源岩浆混染地壳物质的结果.同位素年代学证实岩体就位时间约为250Ma左右的早三叠纪,与区域变质和中国北方大面积的同造山花岗岩年龄相似.暗示了含矿岩体的形成和华北板块与西伯利亚板块碰撞造山作用有关,是造山挤压过渡期伸展体制下岩浆作用的产物.

Large amount of geological research indicates that there are series Cu-Ni sulphide deposits in south central Jilin Province, eastern portion of the Xing＇an Mongolian Orogenic belt, North China. Hongqiling Cu-Ni sulphide deposit represents the type related to ultramafic-mafic magmatic processes in the Early Triassic period. The parent rocks for the deposits are consist mainly of mafic-ultramafic complex of gabbro-websterite-olivine websterite lherzolite and dykes of orthopyroxenite, what constituting four types ore with sparse disseminations and sideronitic texture, dense disseminations texture, patched structure and massive structure. The silicate minerals assemblages as olivine ＋ othopyroxenes ＋ clinopyroxenes ＋ amphiboles ＋ plagioclases± phlogophe, similar to the talc-alkaline series rocks. Petrological works has proved that mafic-ultramafic rocks are enriched in LREE and Rb, Ba and depleted in Nb Ti conformed with the subduction related tholeiite, maybe presented a result that parental magma was derived from mantle source and contaminated with the Crust. Isotopic dating confirms that the intrusions were emplaced at about 250Ma, the Early Triassic, being similar to the time of the syn-orogenic granite widely found in North China. It implies that the ore-bearing intrusions are products of magmatic activities under a transition period from extrusion to extension system and was related to the colliding orogeny between the north China plate and the Siberia Plate.