川井坳陷砂岩型铀矿含矿地层孢粉组合及古气候意义  

Palynomorph assemblage of ore-bearing strata for sandstone-type uranium deposit in Chuanjing depression and its paleoclimatic significance

作　　者：李成元 薄海军 李钢柱 樊松浩 陈磊 冯杰 周文辉 高琪 何泽宇 LI Chengyuan;BO Haijun;LI Gangzhu;FAN Songhao;CHEN Lei;FENG Jie;ZHOU Wenhui;GAO Qi;HE Zeyu(Hohhot General Survey of Natural Resources Center,China Geological Survey,Hohhot,Inner Mongolia O1oo10,China;Institute of Water Conservancy and Civil Engineering,Inner Mongolia Agricultural University,Hohhot,Inner Mongolia 010010,China)

机构地区：[1]中国地质调查局呼和浩特自然资源综合调查中心,内蒙古呼和浩特010010 [2]内蒙古农业大学水利与土木建筑工程学院,内蒙古呼和浩特010018

出　　处：《地质学报》2023年第4期1262-1277,共16页Acta Geologica Sinica

基　　金：内蒙古自然科学基金项目(编号2021MS04024);中国地质调查局项目(编号DD20211549,12120113071800)联合资助的成果。

摘　　要：为了厘清二连盆地川井坳陷准噶顺地区钻井所揭示的砂岩型铀矿含矿地层的时代,本次对钻孔内煤层及深灰色泥岩样品开展孢粉学研究工作。含矿层孢粉具有Cicatricosisporites-Cyathidites-Abietineaepollenites-Pinuspollenites-Classopollis组合特征,指示地层时代为早白垩世阿普第期—阿尔比期。结合碎屑锆石U-Pb年龄谱分析,认为沉积时期主要物质来源于东南部巴音杭盖凸起的古元古界宝音图岩群,小部分来源于北侧索伦山隆起的蛇绿构造混杂岩组分。对孢粉植被类型、气候带类型、干湿度类型进行统计分析,认为古植被以针叶为主,其次为常绿阔叶林,灌木和草本也有一定数量。松科、紫萁科、卷柏科等孢子和花粉与掌鳞杉科、桫椤科、里百科等热带—亚热带植物孢子和花粉混合,显示古气候为湿润的亚热带气候。虽然,白彦花组向上湿生植物有所增加,但是Classopollis和Jugella等旱生植物数量显著增加、针叶及常绿阔叶林有所减少,表明气候有向半干旱方向发展的趋势。下白垩统白彦花组沉积的泥-砂-泥地层结构稳定,砂体透水性好,含有较高还原组分,为含铀流体的还原沉淀提供了丰富的有机质和良好的保存空间,是一套有利的找矿目的层。In order to clarify the stratigraphic age of ore-bearing of sandstone-type uranium deposit in the Zhungashun area of Chuanjing depression,Erlian basin,coal seam and dark gray mudstone samples in the borehole were collected in this study to carry out palynology research.The sporo-pollen of ore-bearing strata has the characteristics of Cicatricosisporites-Cyathidites-Abietineaepollenites-Pinuspollenites-Classopollis assemblage,which indicates that the stratigraphic age is the Apthian to Albian of Early Cretaceous.Combined with the U-Pb age spectrum analysis of detrital zircons,it is considered that the main sedimentary provenance of the sedimentary period came from the Baoyintu Rock Group of the Bayinhanggai uplift in the southeast,and a small part came from the ophiolite tectonic melange of Solunshan uplift in the north.According to the statistical analysis of palynological vegetation types,climatic zone types and dry-humidity types in the Zhungashun area,the ancient vegetation was dominated by coniferous,followed by evergreen broad-leaved forest,and a certain number of shrubs and herbs.Spores and pollen of Pinaceae,Dicranopteridaceae and Selaginellaceae are mixed with tropical-subtropical plants such as Cephalotaxaceae,Cyatheaceae and Encyclopedia,indicating that the palaeoclimate was humid subtropical climate.Although the number of hygrophytes in the Baiyanhua Formation increased,the number of xerophytes such as Classopollis and Jugella increased significantly,while coniferous and evergreen broad-leaved forests decreased,indicate a trend towards semi-arid climate.The mud-sand-mud stratigraphic structure of the Baiyanhua Formation in the Lower Cretaceous is stable.The sand body with good permeability and high reduction components is a favorable prospecting target layer,which provides rich organic matter and good preservation space for the reduction and precipitation of uranium-bearing fluids.

关 键 词：孢粉组合 碎屑锆石 古植被与古气候 早白垩世 二连盆地川井坳陷 

分 类 号：P619.14[天文地球—矿床学] P532[天文地球—地质学]