西北地质2017，Vol.50Issue(2)：61-68,8.
可可西里东部地区新生代钾质火山岩地球化学特征
Geochemical Characteristics of Cenozoic Potassic Volcanic Rocks in the Eastern Hoh Xil
摘要
Abstract
The major trace element and rare earth element of potassic volcanic rocks in the studied area have been analyzed in this paper.The results show that these rocks have high SiO2 contents (59.35%~63.85%), alkali content (K2O+Na2O=7.89%~8.47%), K2O/Na2O ratio (K2O/Na2O>1), MgO content (1.76%~2.46%) and Mg# values.In the TAS diagram, these rocks are located in the range of shoshonite series.In the primitive mantle normalized distribution pattern, the incompatible elements of these volcanic rocks present as rightist type, the heavy ion lithophile elements are enriched, and the high field strength elements are relatively depleted.In addition, the pattern exhibits three peak values of Th, La and Pb and three losses groove of Ta, Nb and Ti, indicating that the shoshonite has the characteristics of the intraplate alkali basalt and it has the geochemical characteristics of the arc magma mixed with more crustal material in the magma source area.The total content of rare earth is very high, ΣREE, LREE and HREE vary from 442.44×10-6 to 681.53×10-6, from 425.94×10-6 to 657.26×10-6 and from 12.53×10-6 to 24.27×10-6, respectively, and the LREE/ΣREE ratios range from 0.96 to 0.97, with strong enrichment of light rare earth element.The potassic volcanic rocks exhibit weakly negative Eu (δEu=0.69~0.77), and the La/Sm ratios show an increasing trend with the raising of La content, which indicate that these rocks serve as the products of partial melting, with weak fractional crystallization.The geochemical characteristics of Shoshonitic rocks indicates that, they were formed by the partial melting of mantle materials in the thickened crust continental setting, and these mantle materials were contaminated by oceanic sediments and crust materials, with enrichments of light rare earth elements and large ion lithophile elements.关键词
岩石地球化学/钾玄岩/新生代火山岩/可可西里东部Key words
petrogeochemistry/shoshonite/cenozoic volcanic rock/Eastern Hoh Xil分类
天文与地球科学引用本文复制引用
周维贵,李余生,鲍道亮,郭宇..可可西里东部地区新生代钾质火山岩地球化学特征[J].西北地质,2017,50(2):61-68,8.基金项目
中国地质调查局区域地质调查项目(121201140087、1212011221003)资助 （121201140087、1212011221003）
