阿尔泰造山带青河地区哈巴河群变质岩地球化学特征及稀有金属背景值研究

Geochemical Characteristics of Metamorphic Rocks and Metallogenic Potential of Rare Metals in the Habahe Group of the Qinghe Area in the Altai Orogenic Belt

新疆阿尔泰造山带是我国重要的稀有金属成矿带。区内众多的稀有金属矿化伟晶岩被认为是地壳深熔的产物,区域上大量发育的哈巴河群变质岩被认为是潜在的物源。青河地区广泛分布哈巴河群变质岩,但该套地层能否通过深熔作用提供适量的成矿物质尚不清晰。本文对采自该套地层的岩石样品开展了岩石学、矿物学及地球化学等研究。样品主、微量元素组成分析结果表明,青河地区哈巴河群变质岩的原岩主要为泥砂质沉积岩,沉积碎屑主要来自酸性弧物源,碎屑成熟度较差,经历了简单的沉积循环。哈巴河群上亚群和下亚群的稀有金属背景值较中亚群高,且相对富集Li、Rb、Cs。部分熔融程度对稀有金属元素在熔融体中富集很重要,小比例的部分熔融有利于稀有金属元素在初始熔体中富集。

The Altai orogenic belt is an important rare metal metallogenic belt. Many rare metal mineralized pegmatites in this area are thought to be products of the anatexis of crustal materials in which metamorphic rocks of the Habahe Group widely distributed in the region could be the potential source materials. The metamorphic rocks of the Habahe Group are widely distributed in the Qinghe area. However, it is not clear yet whether the anatexis of this stratum could provide adequate amount of metallogenic materials to the metallogeny of rare metals. In this work, we systematically collected rock samples from this stratum, and carried out their related petrological, mineralogical and geochemical studies. The major and trace element composition characteristics of samples show that the protoliths of metamorphic rocks were mainly pelitic-arenaceous sedimentary rocks and their sedimentary clasts, mainly sourced from acidic arc rocks, were of poor maturity and had experienced a simple depositional cycle. The upper and lower subgroups of the Habahe Group in the Qinghe area have relatively high rare metal background values comparing to the middle subgroup, and are relatively enriched in Li, Rb, and Cs. The degree of partial melting is very important for the enrichment of rare metals in the melt, and a small proportion of partial melting is beneficial to the enrichment of rare metal elements in the initial melt.