蒙古查干苏布尔加(Tsagaan Suvarga)大型斑岩型铜钼矿床含矿蚀变岩常量、微量和稀土元素地球化学特征及意义

Geochemical Characteristics and Significance of Major Elements, Trace Elements and REE in Mineralized Altered Rocks of Large Scale Tsagaan Suvarga Cu-Mo Porphyry Deposit in Mongolia

蒙古Tsagaan Suvarga大型斑岩型铜钼矿床围岩蚀变类型主要有网脉状硅化、泥化、石英-绢云母化、钾硅酸岩化和青盘岩化。从热液成矿中心向外的矿化蚀变分带特征为含铜网脉状硅化蚀变带→含铜泥化带→含铜钼石英-绢云母化带→含铜钼钾硅酸岩化带→青盘岩化带。早期为钾硅酸岩化带,中期为石英-绢云母化和硅化,晚期为泥化带和碳酸盐化(方解石)。含矿蚀变岩明显受不同级次构造-裂隙带控制,北东向和北西向裂隙带可能是斑岩成矿热液体系的运移通道。随着接近循环热液成矿体系的成矿中心和硅化不断增强,REE,LREE和HREE含量降低,轻和重稀土元素之间分异程度增强;轻和重稀土元素之间分异程度与硅化-钾硅酸盐化之间关系具有指数关系。随着(Na2O+K2O)含量逐渐增高,从负Eu异常→无Eu异常→正Eu异常→明显正Eu异常,说明Eu异常受循环热液成矿体系的碱交代程度控制明显,因此,正Eu异常、轻和重稀土元素之间分异程度明显及其相关围岩蚀变特征是寻找与蒙古Tsagaan Suvarga斑岩型铜钼矿床类似的找矿预测指标。

The alteration types of the large scale Tsagaan Suvarga Cu-Mo porphyry deposit mostly comprise stockwork silification, argillization, quartz-sericite alteration, K-silicate alteration and propylitization. The mineralized and altered zoning from hydrothennal metallogenic center to outside successively consists of Cu bearing stockwork like silification zone, Cu bearing argillized zone, Cu-Mo bearing quartz-sericite alteration zone, Cu-Mo bearing Ksilicate alteration zone and pmpylitization zone. The Ksilicate alteration occurs in early phase, quartz-sericite alteration in middle phase, and argillization and carbonatization （calcite） in final phase. Ore bearing altered rocks obviously are controlled by structure and crack zones of different scale, NE and NW crack zones of which are probably migration pathway of hydrothennal ore-forming solution of porphyry. While circulatory hydrothermal ore-forming center approaches with continual enhancement of silification, REE, LREE and HREE decrease, and fractionation between LREE and HREE becomes high. The fractionation between LREE and HREE has exponential relation with extent of silification and K-silicate alteration. Negative Eu anomaly, normal Eu, positive Eu anomaly and obviously positive Eu anomaly in turn appear with Na2O ＋ K2O increase gradually. This indicates that Eu anomaly is visibly controlled by alkaline metasomatism of circulatory hydmthermal ore-forming system, and therefore such characteristics as positive Eu anomaly, obvious fractionation between LREE and HREE, special wall rock alteration are some metallogenic prognostic indications for finding other deposits like Tsagaan Suvarga in Mogolia.