应用ICP-MS研究黔西南地区构造蚀变体稀土元素地球化学特征

Application of ICP-MS to Study REE Geochemistry of Structure Alteration Rocks in Southwestern Guizhou Province,China

构造蚀变体(SBT)是沉积作用、构造作用和热液蚀变的综合产物。SBT作为黔西南地区金、锑、萤石等矿产的重要就位空间,金锑矿成矿与其密切相关。近年在黔西南地区发现了丰富的金资源量,关键在于SBT体系的提出及与之为核心的成矿模式的建立和应用。本文应用电感耦合等离子体质谱法(ICP-MS)分析了黔西南台地相区典型矿床的SBT样品,揭示稀土元素的地球化学特征。结果表明,不同矿区SBT的ΣREE=49.55×10^(-6)~271.72×10^(-6),含量变化较大,LREE/HREE=5.62~13.59,轻重稀土分馏明显,轻稀土富集;SBT对北美页岩和CI球粒陨石标准化配分模式图均表现为轻稀土富集的右倾型、"四分组"效应明显、强烈热液作用,为同一体系的产物;大厂至戈塘一线显示高的正铕异常,推测有两个方向含矿热液在此汇聚。本文系统对比了黔西南地区SBT稀土元素地球化学特征,反映该区成矿流体来源及演化,为本区微细浸染型金矿的成矿预测提供了依据。

The structure alteration rocks（named as SBT） is the product of sedimentation, tectonization, and hydrothermal alteration. It is the major body hosting many ore deposits such as gold,antimony,and fluorite in Southwest Guizhou.Recently establishment and application of a metallogenic model based on the SBT made a significant breakthrough in gold prospecting in Southwest Guizhou.Inductively Coupled Plasma-Mass Spectrometry（ICP-MS） was used to determine REE concentrations of SBT samples from several typical ore deposits in Southwest Guizhou.The results show that：（1） ΣREE concentrations of SBT from different locations are variable,ranging from 49. 55 × 10^（-6）to 271. 72 × 10^（-6）（in Table 1）.（2） The SBT is enriched in LREE,with LREE / HREE ranging from 5. 62 to 13. 59（in Table 1）.The REE patterns normalized to North American shale and chondrite display enrichment of LREE and distinct ‘Four grouping＇effect,indicating that they are the products of the same hydrothermal process（in Fig. 2-Fig. 4）. The strongly positive europium anomalies in the Getang—Dachang area suggest the convergence of two hydrothermal ore fluid systems with different directions in this region. This study characterized the REE content and its distribution in SBT from Southwest Guizhou Province,which is crucial for understanding the origin and evolution of ore-forming fluids,and provides guidance for gold prospecting in Southwest Guizhou Province.