金伯利岩演化过程及金刚石含矿性评价的研究进展

Progresses and Perspectives of Research of the Evolution of Kimberlite and Evaluation for Diamond Potential

金伯利岩是研究地幔动力学过程、探讨岩石圈演化等深部重大科学问题的有效载体,也是揭示金刚石这一稀缺矿产资源的形成环境、成因、来源及找矿实践等最为重要的研究对象之一。长期以来,由于受到研究手段、研究思路等的限制,对金伯利岩相关研究的核心与瓶颈性关键基础科学问题,即"金伯利岩的初始岩浆组成"、"金伯利岩的演化过程及其意义"、"金伯利岩的金刚石含矿性评价"等知之甚少,这极大地制约了人们对金伯利岩及其相关深部过程意义等方面的深入了解。例如,基于高压熔体模拟实验、基质矿物、细小同源包裹体及金伯利岩筒边部隐晶质物质的研究,可以有效分析金伯利质岩浆的初始组成特征,但却难于有效甄别金伯利质岩浆的源区特征,难于有效区分地幔同化/混染作用、流体分异以及就位期间的脱玻化作用等对岩浆的影响等;由于缺乏再结晶及(或)再生长矿物在微成分、微结构方面的系统研究报道,难于有效精准分析金伯利质岩浆组成的变化规律及脱气作用的影响,揭示金伯利质岩浆的演化过程;尽管根据共生矿物组合、橄榄石的含水性等可用于评估金伯利岩的金刚石含矿性,但存在指标体系过于简单、数据积累少等方面问题。理论上,从微区(微米级、纳米级)的角度,对金伯利岩各组成结构单元中矿物等的微成份、微结构进行系统研究,可以更为精准地提取金伯利质初始岩浆组成、演化过程等方面的信息,因此对含金刚石与不含金刚石的金伯利岩的微组构进行精细研究,可以为有效重建金伯利质岩浆的演化机制、深入揭示其对深部过程的响应等奠定科学基础。同时,也可以在对已知金刚石矿区研究的基础上,建立用于金刚石初始品位预测和保存潜力分析的模型,以实现有效评价未知金伯利岩区的含矿性的目的。

Kimberlite is an effective vector for researches and discussions on mantle dynamics process, litho- sphere evolution and other major scientific problems, which plays an important role in revealing the forming envi- ronment, origin, source and prospecting of diamond. Currently, the developing research process of Kimberlite is still hampered by several key scientific problems, such as the evolution and the significance of the Kimberlite, eval- uation for diamond potential and so on. Based on high-pressure melt simulation experiments, researches about ma- trix mineral, fine syngenetic inclusion （cognate xenofith？） and cryptocrystalline in the margin area of Kimberlite pipe, it seems that the initial composition features of Kimberlitic magma can be effectively analyzed. However, these experiments and researches are not only difficult to identify source characteristics of Kimberlitic magma effi- ciently, but also difficult to distinguish those effects on magma from which is assimilation/contamination, tluid frac- tionation or devitrification. Lacking of systematic research reports about reerystallization and （or） regrowth mineral on micro-composition and micro-structure, it is hard to efficiently and accurately analyze the changes and degassing effects in Kimberlitic magma, so far as to reveal the process of Kimberlitic magma evolution. Although Kimberlite diamond potential can be evaluated based on mineral assemblage, water content of olivine, there still exist some kinds of problems, like the index system being too simple, and the data accumulation being too little. Carrying out the fine micro-fabric studies between diamond-beating Kimberlite and non diamond-bearing one can establish the scientific foundation for rebuilding the Kimberlitic magma evolution mechanism effectively and reveal the response to deep geological process. Meanwhile, on the basis of known diamond mines, a model for initial grade prediction of diamond and analysis of preservation potential can be set up to realize final purpose to evaluate the diamond poten- tial in unknown Kimberlite areas in effect validity.