西北地质2018，Vol.51Issue(1)：34-43,10.
北祁连扎柯山寒武纪高镁安山岩地球化学及构造动力学特征
Geochemistry of Cambrian High-Mg Andesites in North Qilian and Its Geodynamic Implications
摘要
Abstract
High-Mg andesites are occurred in Zakeshan area,North Qilian,which were formed in Early and Middle Cambrian,with Rb-Sr isotopic age of (516±7) Ma (1σ).These andesites (SiO2=51.45％～59.62％,averaging in 56.33％) have higher MgO contents (MgO contents are 4.85％～9.64％,averaging in 71.44％,Mg# values are 66.68～74.15,averaging in 71.44) than the ones of typical island arc andesite,with enrichment of Cr (21.6× 10-6～476× 10-6,averaging in 196.26×10-6),Ni (14×10-6～102×10-6,averaging in 56.14×10-6) and Na elements,but low Al (Al2O3 =13.22％ ～ 17.37％,averaging in 15.69％),Ca (CaO=2.01％ ～10.33％,averaging in 5.64％) andK (K2O=1.04％～2.79％,Na2O/K2O=0.59～5.0,averaging in 2.36).Meanwhile,these rocks show weakly negative Eu anomaly,they are enriched in Rb,Th and K (LILE),but they are depleted in Sr,Ti,P,Nb and Ta (HFSE),with LREE/HREE ratios ranging from 7.19 to 13.58 (Yb=1.47 × 10-6 ～3.26 × 10-6,Y=11.6 × 10-6 ～22.5 ×10-6).Combined with regional geological setting,the results suggest that high-Mg andesite was formed in island arc setting and was sourced from the partial melting of the peridotites in mantle wedge,which were metasomated by the fluids from subducted sediments and altered oceanic crust.关键词
高镁安山岩/寒武纪/地球化学/构造动力学/扎柯山/北祁连Key words
high-Mg andesite/Cambrian/geoehemistry/geodynamics/Zakeshan area/North Qilian分类
天文与地球科学引用本文复制引用
王晓伟,杨春霞,王玉玺,于漫..北祁连扎柯山寒武纪高镁安山岩地球化学及构造动力学特征[J].西北地质,2018,51(1):34-43,10.基金项目
中国地质调查局“中国矿产地质与成矿规律综合集成和服务(矿产地质志)”项目(DD20160346) （矿产地质志）
