煤中火山灰蚀变粘土岩夹矸（Tonstein）在煤层和地层对比、同位素定年、岩浆和区域地质演化、成煤环境、寻找稀有金属矿床、煤炭质量评价等方面发挥重要作用。西南晚二叠世煤中发育不同性质的Tonstein（基性、酸性和碱性），基性和碱性Tonstein在世界其他地区罕见，不同性质Tonstein的元素和矿物组成各异。项目将以西南若干煤矿区的晚二叠世煤中Tonstein为典型实例，深入分析火山灰、岩浆和热液活动、煤系基底特征、物源供给、煤盆地升降规律、聚煤环境、煤相、生物有机质、风化氧化等诸地质背景因素，查明不同性质Tonstein中元素和矿物的来源、赋存状态和空间分布规律，建立不同性质Tonstein的地球化学和矿物学判识标志，揭示各种影响Tonstein中元素和矿物富集、分异的地质和地球化学因素及其内在联系，从而阐明不同性质Tonstein中元素和矿物分异机理。

The tonsteins derived from air-borne material of pyroclastic origin in coal play an important role in identifying and correlating coal seams and coal-bearing strata, radiometric age determination, magmatic and regional geological evolution, coal-forming depositional environment, searching for rare metal ore deposits, and coal quality evaluation. Different tonsteins (basic, acid, and alkaline) are well-developed in the Late Permian coals in southwestern China, among of which the basic and alkaline tonsteins are rare in other areas of the world. The different tonsteins have different elemental and mineral compositions and associations. The different tonsteins in the Late Permian coals from some coal mines of southwestern China will be takes as typical cases for the study of fraction mechanisms of elements and minerals in the tonsteins. A couple of geological factors will be carefully studied: these include volcanic ashes, magma and hydrothermal activities, the bases of the coal-bearing strata, the sediment sources, coal basin evolution, coal-forming depositional environment, coal facies, organism, and weathering and oxidations. Accordingly, the sources, modes of occurrence, and distribution of elements and minerals in different tonsteins will be revealed; the geochemical and mineralogical identification indicators for different tonsteins will be built; the geological and geochemical factors that have affected the enrichment and fractions of elements and minerals in different tonsteins and their relations will be deeply investigated.