鄂尔多斯盆地北部延安组沉积学特征与成矿潜力分析

Sedimentary Characteristics and Metallogenic Potential of Yan’an Formation in the North of Ordos Basin

鄂尔多斯盆地北部广泛沉积延安组,随着铀矿勘查工作的不断深入,延安组已成为研究区重要的产铀层位。通过对野外露头及钻孔岩心的系统研究,运用层序地层学与沉积学原理,建立延安组分层标志,分析其沉积体系特征,并结合砂体、氧化带发育特征,分析评价延安组铀成矿潜力。结果表明,延安组的重要标志层是延安组含煤岩系及其内部的主要煤层,据此将延安组自下而上划分为Ⅰ~Ⅴ岩段(J_(2)y^(1)~J_(2)y^(5))5个成因地层单元;Ⅰ岩段和Ⅱ岩段下段为曲流河沉积体系,Ⅱ岩段上段到Ⅴ岩段沉积环境演变为曲流河三角洲相;延安组Ⅰ岩段发育有利铀成矿的铀储层和氧化带,同时发现较好的铀矿化线索,成矿潜力巨大。

The Yan’an Formation was widely deposited in the north of Ordos Basin.With the expanding of uranium exploration,Yan’an Formation has become an important horizon in the research area.Stratification markers of Yan’an Formation were established by systematic studying the outcrops and drilling cores,characteristics of the sedimentary system,sand bodies.The oxidation zones and uranium metallogenic potential were also evaluated for the Yan’an Formation.The results showed that the main stratigraphic criterion was the coal-bearing series and main coal seam,and the Yan’an Formation was divided from bottom to up into MemberⅠ~Ⅴ(J_(2)y^(1)~J_(2)y^(5));MemberⅠand the lower part of MemberⅡare the products of meandering river sedimentary system,the upper part of MemberⅡto MemberⅤwere the sediments from meandering river to meandering river delta;MemberⅠof Yan’an Formation developed the oxidation zone and uranium reservoir that are good for uranium mineralization,and some uranium mineralization were identified in Yan’an Formation,which suggest there is great metallogenic potential in Yan’an Formation.