内蒙古二连盆地哈达图砂岩铀矿渗出铀成矿作用

[研究目的]哈达图铀矿床是产于二连盆地下白垩统赛汉组上段的一个特大型砂岩型铀矿床，其与传统砂岩铀矿特点不同，矿体呈多层板状，控矿灰色砂体具“两黄夹一灰”特征，传统的渗入（潜水氧化、层间氧化）砂岩型铀成矿理论难以解释，阐明其成因和控矿要素对创新砂岩铀成矿理论与红杂色砂岩中铀矿找矿均具有重大意义。[研究方法]采用野外和室内、宏观和微观相结合，主要包括野外观察、区域地质、构造学、沉积学、岩石学、矿物学、地球化学（元素、有机、同位素）、地震解释和铀矿床学等方法。[研究成果]阐明了矿床矿体、控矿灰色砂体和矿化特征，指出研究区红杂色建造赛汉组上段、二连组和伊尔丁曼哈组为原生氧化建造成因，主含矿层赛汉组上段控矿灰色砂体是深部还原性流体对其再还原的结果，主要受连通深部的断裂构造及相关河道或不整合面控制，属后生改造成因，从成矿铀源、深部渗出流体的形成、铀的迁移和沉淀阐述了砂岩渗出铀成矿作用机制，提出哈达图砂岩铀矿床主要是渗出铀成矿作用形成，建立了相应的渗出铀成矿模式。[结论]发现揭示了红杂色砂岩形成砂岩铀矿一种新的铀成矿作用——渗出铀成矿作用，并由此提出了在红杂色沉积建造中寻找砂岩铀矿“上红下黑、上下连通、红中找灰、灰中找矿”预测评价的新思路，指出针对红杂色沉积建造砂岩铀矿找矿新层位，在找矿空间上可由盆缘拓展到盆中、由浅部拓展到深部。创新点：阐明控矿灰色砂体是深部还原性流体再还原的结果，属后生改造成因；提出了红杂色砂岩形成砂岩铀矿新的渗出铀成矿作用，建立了哈达图砂岩铀矿渗出铀成矿模式；提出了在红杂色沉积建造中寻找砂岩铀矿预测评价的新思路。     

Brackish water faunas from the St Maughans Formation: The Old Red Sandstone section at Ammons Hill,Hereford and Worcester,UK, re-examined

The disused railway cutting at Ammons Hill, Hereford and Worcester, exposes a sequence of beds belonging to the Devonian St Maughans Formation of Lochkovian (Gedinnian) age. The beds are of Old Red Sandstone facies, but contain brackish water faunas. These faunas occur at a level generally considered to be above the level of marine influence that affected the older Raglan Mudstone Formation of mainly Přídolí Series age. The section, described by King in 1934, is now overgrown, but was excavated in 1986 by the British Geological Survey during its survey of the Worcester 1:50000 sheet. The evidence of the section calls for slight amendment of Allen's (1985) model of an interrupted transition from marine deposition in Ludlow time to freshwater deposition in Gedinnian time that was complete by the time of the formation of a regionally extensive calcrete palaeosol, the Psammosteus Limestone. Subsequent transgressive events took place before the establishment of apparently wholly fluvial and floodplain environments.     

Palynofloras from tournaisian lacustrine and tidal sequences in slieve bloom,counties laois and offaly,Ireland

Tournaisian miospore assemblages are used to determine the age of some plant-bearing horizons in the Old Red Sandstone succession of the Slieve Bloom Mountains, Counties Laois and Offaly, Ireland, and the sedimentology and conditions of deposition of the productive lithologies are described. The age of the marine transgression which terminated continental sedimentation is indicated, and the associated depositional environment is discussed. Comparisons are made with other micro- and macrofloras from Ireland, Britain, Canada, the U.S.S.R. and Bear Island.