碳酸岩岩浆演化过程中REE富集与分异的研究进展及碳酸岩中的矿物学分带

稀土元素(REE)作为"三稀资源"之一,是中国重要的战略性矿产资源,碳酸岩型稀土矿床是世界稀土的主要来源.成矿碳酸岩的岩浆演化以及稀土元素的富集和分异机理一直是碳酸岩型稀土矿床研究的热点和难点,国内外学者对碳酸岩的岩浆起源、岩浆演化过程中稀土元素富集与分异的机理进行了大量的研究与探讨,但仍存在较多的争议,限制了碳酸岩型稀土元素成矿理论的发展及国内外碳酸岩型稀土矿床的找矿勘查工作.文章重点对稀土成矿碳酸岩的起源、岩浆演化过程及在此过程中REE的富集与分异行为进行了详细的文献调研和评述,同时,基于笔者在冕宁牦牛坪稀土矿床前期的研究工作和最新发现,认为碳酸岩中普遍存在矿物学分带,它是岩浆演化过程的最佳记录,是不同成分矿物结晶分异作用的体现.对牦牛坪稀土矿床碳酸岩的矿物学分带特征及其中的熔体、熔流体和流体包裹体进行了初步描述与探讨,以期为研究碳酸岩的岩浆演化、岩浆-流体转化过程及稀土元素的富集与分异机理提供新的思路,促使对稀土碳酸岩矿物学分带及其对REE富集与分异的研究引起更多的关注和重视.

A review of REE enrichment and fractionation mechanism during magma evolution of ore-forming carbonatite and significance of mineral zonation in carbonatite

Rare earth elements (REE), one of the "three rare resources", is an important strategic mineral resource in China, in which carbonate-related REE deposits are the main source of REE in the world. The magma evolution of ore-forming carbonatitite and the REE enrichment and fractionation mechanism during the magma-fluid evolution process constitute a hot and difficult issue in the study of carbonatite-related REE deposits. Although a lot of research and discussion on the magma origin of carbonatite and the mechanism of enrichment and fractionation of REE have been carried out by domestic and foreign geologists, there are still more controversies, which limits the development of carbonatite-related REE mineralization theory and the prospecting work of carbonatite-related REE deposits. In this paper, the source, magma evolution, as well as the enrichment and fractionation mechanism of REE during the process are reviewed and summarized. Meanwhile, based on the previous research work and the latest discoveries in the Maoniuping REE deposit of Sichuan Province, southwest China, we considered that carbonatite commonly has mineral zonation, which is the best record of magma evolution process and the reflection of the crystallization differentiation of different mineral components. In this paper, mineral zonation of carbonatite in Maoniuping REE deposit and the melt, melt-fluid and fluid inclusions were preliminarily described and discussed. This study could provide a new insight into the understanding of the magma evolution and magmatism-fluids exsolution as well as the enrichment and fractionation of REE, and lead researchers to pay more attention to the mineralogical zonation of REE bearing carbonatite and its significance in the study of REE enrichment and differentiation