| 鄂尔多斯盆地早白垩世含铀岩系的新发现及其层序地层 |
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| 引用本文： | 张天福,苗培森,程先钰,王少轶,李建国,程银行,奥琮,张云.鄂尔多斯盆地早白垩世含铀岩系的新发现及其层序地层[J].大地构造与成矿学,2020(4):633-647. |
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| 作者姓名： | 张天福 苗培森 程先钰 王少轶 李建国 程银行 奥琮 张云 |
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| 作者单位： | 中国地质调查局天津地质调查中心;中国地质调查局铀矿地质重点实验室;中国地质科学院勘探技术研究所 |
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| 基金项目： | 国家重点研发计划项目(2018YFC0604200);中国地质调查局项目(DD20190813);国际地球科学计划(ICGP675);国家重点基础研究发展计划项目(2015CB453000)联合资助。 |
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| 摘 要： | 鄂尔多斯盆地天环坳陷南部白垩系洛河组及环河华池组为新近突破的含铀岩系新层位,笔者充分利用测井、岩心及地震资料,对本区钻井所揭露的下白垩统层序界面特征及沉积类型进行系统分析。结果表明:天环坳陷内下白垩统整体为一套干旱“红层”,发育旱谷、风成沙丘、丘间及沙漠湖等沉积类型,组成了一个典型的沙漠沉积体系。伴随着坳陷基底的抬升和下沉,在地层记录中出现了2次显著的湖侵,并显示出旋回性沉积的特点,在早白垩世地层中识别出4个三级层序和2个二级层序,三级层序具有从旱谷粗碎屑沉积到沙丘及沙漠浅湖细粒沉积的相序组构。Rb、Sr含量的垂向变化指示在早白垩世整体干旱的气候下存在相对暖湿期,在此背景下水成和风成沉积有序叠置控制了含(隔)水层在空间上的有序分布。SQ2层序中的巨厚泥岩层和石膏夹层构成了区域性隔挡层,而SQ1层序中的风成砂岩则成为深部含烃流体充注的最优层位,Fe^2+/Fe^3+垂向变化显示叠加改造后的灰色风成砂体可成为具有强还原性的潜在铀储集层。泾川铀矿床及外围找矿的不断突破使其成为中国第一个以风成砂为主要储集层的砂岩型铀矿床,它的首次发现进一步拓展了鄂尔多斯盆地深部找矿空间。
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| 关 键 词： | 鄂尔多斯盆地 天环坳陷 早白垩世 沙漠沉积 层序地层 砂岩型铀矿 |
Stratigraphic Characteristics of a Newly Discovered Uranium-bearing Stratum in the Lower Cretaceous,Ordos Basin |
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| ZHANG Tianfu,MIAO Peisen,CHENG Xianyu,WANG Shaoyi,LI Jianguo,CHENG Yinhang,AO Cong,ZHANG Yun.Stratigraphic Characteristics of a Newly Discovered Uranium-bearing Stratum in the Lower Cretaceous,Ordos Basin[J].Geotectonica et Metallogenia,2020(4):633-647. |
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| Authors: | ZHANG Tianfu MIAO Peisen CHENG Xianyu WANG Shaoyi LI Jianguo CHENG Yinhang AO Cong ZHANG Yun |
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| Institution: | (Tianjin Center,China Geological Survey,Tianjin 300170,China;Key Laboratory of Uranium Geology,China Geological Survey,Tianjin 300170,China;Institute of Exploration Techniques,Chinese Academy of Geological Sciences,Langfang 065000,Hebei,China) |
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| Abstract: | The Cretaceous Luohe and Huanhehuachi Formations are two new uranium-bearing horizons which have recently been recognized in the Tianhuan Depression in the southwestern margin of the Ordos Basin.The characteristics of sequence interface and sedimentary types in the Lower Cretaceous were systematically analyzed on the bases of logging,core and seismic data.The results show that the Lower Cretaceous strata in the Tianhuan Depression are marked by a set of arid red beds.Several types of sedimentary subfacies can be discerned in this set of arid red beds:arid valleys,eolian dunes,interstitial hills,desert lakes,etc.These types of sedimentary subfacies constitute a typical desert system.The strata show characteristics of cyclic deposition with two significant lacustrine transgressions which may have been controlled by the rise and fall of the base of the depression.Four third-order sequences and two second-order sequences could be discerned in the lower series of Cretaceous,and these third-order sequences are formed by a succession of“coarse sediments of the alluvial system-fine sediments of dune or shallow desert lake”.The vertical changes of Rb and Sr contents indicate that there are several relative warm and wet periods in the overall arid climate in the Early Cretaceous.In this background,the ordered superposition of sedimentary and eolian deposits control the spatially ordered distribution of the aquifer and aquiclude.The extremely thick mudstone layer and gypsum interlayer in SQ2 sequence constitute the regional aquiclude,which makes the eolian sandstone in the SQ1 sequence to be the optimal horizon filled with hydrocarbon-containing fluid.The vertical changes of Fe^2+/Fe^3+indicate that the superimposed gray aeolian sand body may be a potential strong reductive uranium reservoir.The prospecting in the Ordos Basin has led to the discovery of the Jingchuan uranium deposit,the first sandstone-type uranium deposit in the aeolian sand body.This discovery will further expand the prospecting space for uranium mineralization in the Ordos Basin. |
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| Keywords: | Ordos Basin Tianhuan depression Early Cretaceous desert deposit sequence stratigraphy sandstone-type uranium |
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