内蒙古满都胡地区塔尔巴格特组沉积相及地球化学特征

运用岩性一岩相和地球化学方法对东乌旗满都胡地区中晚泥盆世塔尔巴格特组碎屑岩进行了研究,探讨了其碎屑岩岩相、物源区及地球化学特征,将区内塔尔巴格特组划分为2种沉积相、5种沉积亚相。地球化学分析结果表明:塔尔巴格特组砂岩和泥岩具高SiO2、K20和A12O3/(Na2O+CaO)值,低CaO含量特征,其碎屑物质来源于相对稳定的大陆源区;稀土元素配分曲线具轻稀土富集,重稀土比较平坦,轻重稀土分留明显,砂岩(La/Yb)N=6.66~11.15,平均值为9.01,泥岩(La/Yb)N=4.7~7.39,平均值为6.14,并伴有明显的Eu负异常。在La-Th—Sc、Th—Sc—Zr/10构造环境判别图解中,多数落入被动大陆边缘区域;主量元素构造判别图中也显示具有被动大陆边缘和活动大陆边缘的特征。结合区域分析,笔者认为塔尔巴椿特组碎届岩形成干被动大陆边缘环境。

Sedimentary Faceies and Geochemical Features of the Tarbage Formation in Manduhu Area, Inner Mongoloa

On the basis of the analysis of lithology - lithofacies and geochemical characteristics of clastic rock of the Devonian Tarbaget Fm. in the Manduhu Area, east Ujimqin Qi of Inner Mongolia, the lithofacies, source ar-ea, and geochemistry of the clastic rock have been discussed. There are 2 sedimentary facies, 5 sub-facies to be recognized in it. The geochemical sample texting indicate that the clastic rock is rich in SiO2,1〈220, high A1203/ (Na20+CaO), and low CaO. The fragments are from relatively stable continent. The REE patterns are character-ized by LREE enrichmen, HREE lat, LREE and HREE fractional distillation is obvious. (La/Yb)N =6.66 - 11.15 (average 9.01 )in the standstone, (La/Yb)N=4.7 - 7.39 (average 6.14)in the mud rock with strong negative Eu ab- normily. In both La-Th-Sc and Th-Sc-Zr/10 discriminate diagrams, almost all of the chastic rock plots fall in the passive continental margin field, and the major element discrimination diagram of the clastic sediments show they are from passive continental margin or active continental margin. With the regional geology analysis, the au-thors suggest that the tectonic setting of the clastic rock of the Devonian Tarbaget Fm. is a passive continental margin.