| 贺兰山中南段奥陶系米钵山组的沉积环境与构造背景分析 |
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| 关键词:Helan Mountain Miboshan Formation turbuitide trace element geochemistry sedimentary environment |
| 基金项目:国家重点基础研究发展计划(973计划)项目“多种能源矿产共存成藏(矿)机理与富集分布规律”(编号: 2003CB214600) |
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| Element Geochemistry and Depositional Setting of Ordovician Miboshan Formation in Central-Southern Helan Mountain |
| The Ordovician Miboshan Formation widely distributed in the Helan Mountain is comprised of a series of detrital rocks interbedded with argillaceous rock and carbonate rock, with the development of flysch bedding and typical turbidite Bouma sequence. The average SiO2 and Al2O3 content of sandstone is 75.18% and 6.26%~ 14.36%, respectively, and TiO2/MnO and K2O/Na2O ratios range respectively from 3.05 to 58.00 and from 0.63 to 9.13. In addition, the content of SiO2 in shale ranges from 68.77% to 77.50%, the TiO2/MnO ratio is high, ranging from 21.30 to 51.00, while the Al2O3/MnO ratio is higher than 450.00. The content of Na2O is relatively low, being lower than 0.01 in some samples. The content of K2O is relatively high, ranging from 3.05 to 4.03. The content of TiO2 and CaO is close to the normal level. The total content of REE in sandstone is relatively high, ranging from 144.80×10-6 to 170.57×10-6. The LREE/HREE ratio is 9.68~16.49, and δ Eu is 1.01~1.31, exhibiting weak positive Eu anomaly. There exists no or only very weak negative Ce anomaly. The abundances of such trace elements in sandstone as Ni, V, Cu, Pb, Ba and, especially, Cr are much higher than their Clarke values in the Earth’s crust. The abundances of Sr and ore-forming elements like Zn and Ga are lower than their Clarke values in the Earth’s crust. The V/(V+Ni) ratio and Ce/La ratio are also high. All these data show that the sedimentation of this area occurred in a reducing, moist and hot environment, characterized by continental deposition. A variety of related diagrams suggest that the source material was formed in continental island arc belts and active continental margins. |
| HUANG Xi-feng,QIAN Zhuang-zhi,LU Dong-xia,WU Wen-kui,WANG Cheng,LU Yan-jun.2009.Element Geochemistry and Depositional Setting of Ordovician Miboshan Formation in Central-Southern Helan Mountain[J].Acta Geoscientica Sinica,30(1):65-71. |
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