内蒙古正蓝旗羊蹄子山-磨石山钛矿区硅质岩地球化学特征及沉积环境意义  

Geochemical characteristics of siliceous rocks in Yangtizishan-Moshishan anatase ore district,Zhenglanqi County,Inner Mongolia,with implications for sedimentary environment

作　　者：丰成友[1] 赵一鸣[1] 李大新[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037

出　　处：《矿床地质》2008年第4期483-493,共11页Mineral Deposits

基　　金：国家自然科学基金(编号:40773038);内蒙古自治区地质勘查项目(编号:05-1-TK01)的联合资助

摘　　要：文章通过详细的野外地质调查和系统的岩石化学、稀土元素、微量元素及硅、氧同位素等研究,探讨了羊蹄子山-磨石山钛矿区无矿白色硅质岩和富钛硅质岩的成因及形成地质构造环境。研究结果表明,呈厚层状产出的无矿白色硅质岩具较高的SiO2、Al2O3含量及Al/(Al+Fe+Mn)、Al2O3/(Al2O3+Fe2O3)比值,稀土元素总量很低,其北美页岩标准化配分模式为向右倾的曲线,无明显铈异常和铕异常,表明其形成于受陆源影响的大陆边缘构造环境;赋矿岩系中薄层状富钛硅质岩的TiO2、Fe2O3、Cu、V含量较高,但Al/(Al+Fe+Mn)、Al2O3/(Al2O3+Fe2O3)比值较低,稀土元素总量较高,北美页岩标准化曲线为明显左倾型-平坦型,具弱的负铈异常,表明其形成于洋脊及附近环境。两种硅质岩的δ30Si值为变化较小的负值,与热水沉积和某些生物成因硅质岩的硅同位素组成相似,两者的δ18O值范围和平均值均相似。两类硅质岩的成因及形成构造环境不同,富钛硅质岩的地球化学特征表明,该矿床的形成与本区元古宙海底火山热液喷流作用有关。Based on detailed field geological survey and comprehensive studies of major and trace elements as well as silicon and oxygen isotopes, the authors have discussed in this paper the origin and tectonic environment of the thick-bedded and anatase-rich siliceous rocks in the Yangtizishan-Moshishan anatase ore district, Inner Mongolia. The results show that the white thick-bedded siliceous rocks have high contents of SiO2 and Al2O3 and high ratios of Al/（Al＋ Fe＋ Mn） and Al2O3/（Al2O3＋ Fe2O3）. The ∑REE are low, and the North American shalenormalized REE patterns are characterized by enrichment of LREE and absence of Eu and Ce anomalies, which suggest that the white thick-bedded siliceous rocks might have been formed in the continental margin environment and affected significantly by terrigenous constituents. The anatase-rich siliceous rocks have high contents of TiO2, Fe203, Cu and V but low Al/（Al＋ Fe＋ Mn） and Al2O3/（Al2O3 ＋ Fe2O3） ratios. The ∑REE are high, the North American shale-normalized REE patterns are obviously characterized by left-oblique to flat styles of curves and slight negative Ce anomalies, implying that they might have been formed in an oceanic ridge environ-ment. The slightly negative δ^30Si values of both thick-bedded and anatase-rich siliceous rocks are similar to those of hydrothermal and biogenic siliceous rocks. The ranges and mean values of 8180 values are similar. On the whole, the thick-bedded and anatase-rich siliceous rocks have different origins and sedimentary environments. This deposit was most likely formed by the Proterozoic volcanic exhalative process, as evidenced by petrochemical and geochemical characteristics of the anatase-rich siliceous rocks.

关 键 词：地球化学 硅质岩 钛矿床 主元素和微量元素 构造环境 羊蹄子山-磨石山 内蒙古 

分 类 号：P618.47[天文地球—矿床学]