Geochemical Characteristics and Sedimentary Environment of Silicalites in Manduhu Area,Inner Mongolia
Abundant radiolarian-bearing silicalites are identified in Devonian strata in Manduhu area, Inner Mongolia.Based on the field and petrological study, the geochemical characteristics of silicalite are synthetically analyzed in this paper.There eleven silicalite samples contain much lower SiO2 (70.42-82.50 wt.%) contents and SiO2/A12O3 ratios (4.76-8.42) comparing with the pure silicalite (e.g., SiO2>90%, SiO2/A12O3=80-1400), suggesting that the silicalite has high proportion of terrigenous argillaceous sediments.The Al/(Al+Fe+Mn) ratios (0.62-0.92) and Ce/Ce* ratios (0.75-0.99) according to the features of organosedimentary silicalite.In addition, the average δCe value (0.89), Th/Sc and Th/U radios (0.27-0.79 and 2.72-5.79, respectively) of the studied silicalite are similar to those of silicalite located near continental margin.Combination of geochemical discriminative diagrams of Al-Fe-Mn,Fe2O3/TiO2-Al2O3/(A12O3+Fe2O3), (La/Ce)N-Al2O3/(Al2O3+Fe2O3), La-Th-Sc and Th-Sc-Zr/10, the Manduhu silicalite is considered to be formed in abyssal sedimentary environment along the continental margin.Compared with the regional geology, the Siberian plate had been subducting under the North China plate at late Devonian, and the active divergent continental margin should be formed at back-arc area.Thus the Manduhu silicalite is the product of the extensional back-arc basin.
silicalite geochemistry late Devonian Manduhu
TENG Xuejian LIU Yongshun CHENG Yinhang
Tianjin Center of Geological Survey,CGS,Tianjin 300170 China
国际会议
第十八届凯洛林国际地质学术研讨会(The 18th Kerulien International Conference on Geological)
石家庄
英文
45-51
2013-09-20（万方平台首次上网日期，不代表论文的发表时间）