内蒙古霍各乞矿区含矿富石榴石岩晶体定量化结构分析及其意义

晶体粒度分布（CSD）是定量化分析火成岩和变质岩结构的重要手段。在变质岩中测量的CSD提供了有关变质过程中晶体成核和生长速率、生长时间的定量信息。文章选取内蒙古霍各乞二号矿床含矿富石榴石岩样品中石榴子石晶体为研究对象,在GIS软件和R语言的支持下,应用空间点模式分析、CSD分析、空间最邻近分析、空间多距离分析、Fry分析等综合方法,探讨了晶体空间数据和点空间数据表征的微结构变化特征,将CSD曲线分段变化记录的信息与地质演化历史联系起来。分段的CSD曲线记录了变质事件的叠加。不同形式的晶体粒度分布直接反映了区域变质岩与接触变质岩演化历史的差异。由于接触变质作用的高温阶段持续时间较短,因此产生的CSD曲线是线性的,不受退火的影响。而区域变质作用涉及长时间升温及其之后的冷却阶段,所以最初的线性CSD后来被退火改造为钟形曲线。含矿富石榴石岩样品的核密度和CSD分析结果显示了两个晶体群密度。分析认为一类晶体群可能与造山过程中的区域变质活动有关,另一类晶体群可能与大面积区域变质期后发生在特定位置的岩体侵入迅速升温的接触热变质事件有关。 

Quantitative structure analysis of ore-bearing garnet-rich crystal in the Huogeqi mining area in Inner Mongolia and its significance

Crystal size distribution(CSD) is an important method to quantitatively analyze the structure of igneous rocks and metamorphic rocks. The CSD measured in metamorphic rocks provides quantitative information about crystal nucleation, growth rate and growth time during metamorphism. In this paper, garnet crystals from ore-bearing garnet-rich rock samples from the Huogeqi No. 2 deposit in Inner Mongolia are selected as the research object, supported by GIS software and R language. By using methods of spatial point pattern analysis, CSD analysis, spatial nearest neighbor analysis, spatial multi-distance analysis and Fry analysis, the microstructure variation characteristics of crystal spatial data and point spatial data are discussed. The segmented change record information of CSD curves is linked with the geological evolution history. The results show that the segmented CSD curves reflect the superimposed records of metamorphic events. The grain size distributions of different forms of crystals directly reflect the difference in the evolution history of regional metamorphic rocks and contact deformed rocks. The contact metamorphism involves a short period of high temperature, so the CSD produced is linear and not affected by annealing. The regional metamorphism involves long-term cooling at high temperature, so the initial linear CSD is later annealed and modified to bell shape. The nuclear density and CSD analysis results of ore-bearing garnet-rich samples also show two crystal group densities. It is considered that the differentiation of one crystal group may be related to the regional metamorphism in the orogenic process, while the other may be related to intrusive rocks that occurred in specific locations after regional metamorphism and activation.