鄂尔多斯盆地西南缘砂岩型铀矿含矿目的层——洛河组砂岩的沉积物源特征

Sediment Source Characteristics of the Target Sandstone Layer for Sandstone-type Uranium Deposit in Southwestern Ordos Basin

鄂尔多斯盆地西南缘洛河组砂岩中见有较好的铀矿化现象,具有较大的铀成矿潜力。文章针对盆地西南缘洛河组砂岩开展了碎屑锆石U-Pb定年及重矿物组合分析,并综合探讨了盆地西南缘洛河组沉积物源特征。研究表明:区内洛河组砂岩碎屑锆石U-Pb年龄主要分布在460~95 Ma、1133~982 Ma、2114~1483 Ma、2719~2230 Ma四个年龄区间,以锆石+赤褐铁矿+磷灰石为主的重矿物组合表示沉积物源可能以中酸性岩浆岩为主。通过与周缘岩体年龄进行对比分析,认为研究区洛河组物源主体来源于盆地北侧华北克拉通北缘地区显生宙、古元古代以及新太古代中酸性岩浆岩及变质岩,同时存在西北侧阿拉善地块与兴蒙造山带的小部分贡献。

Sandstone-type uranium mineralization has been identified in the Luohe Formation in southwestern Ordos Basin,indicating great uranium mineralization potential.Detrital zircon U-Pb dating and heavy mineral assemblage analysis for Luohe Formation sandstones was carried out to constrain the sediment source characteristics.The U-Pb ages of detrital zircons in the Luohe Formation sandstones can be mainly divided into four groups,namely:460~95 Ma,1133~982 Ma,2114~1483 Ma and 2719~2230 Ma.The heavy mineral assemblage of zircon+hematite/limonite+apatite in the Luohe Formation sandstones indicates that the sediment source may be dominated by intermediate acid magmatic rocks.Through the U-Pb age comparison between the detrital zircons from Luohe Formation and the surrounding magmatic rocks,it is suggested that the sediment sources of the Luohe Formation in the study area might be mainly from the Phanerozoic,Paleoproterozoic and Neoarchean intermediate-acid magmatic rocks and metamorphic rocks from the northern margin of the North China Craton to the north of the basin,with small contribution from the Alxa block in the northwest and Xing-Meng orogenic belt in the north.