地质力学学报2011，Vol.17Issue(3)：274-285,12.
内蒙古赤峰北部晚侏罗世中酸性火山岩地球化学特征
GEOCHEMICAL CHARACTERISTICS OF UPPER JURASSIC INTERMEDIATE-GRANITIC VOLCANIC ROCKS FROM NORTHERN CHIFENG, INNER MONGOLIA
摘要
Abstract
Upper Jurassic intermediate-granitic volcanic rocks from northern Chifeng lie in Mongolia Paleo-uplift, the northern margin of the North China Craton. The lava mainly consists of rhyolite, andesite and augite andesite. The geochemical study for intermediate-granitic volcanic rocks suggests that the SiO2 is in 50. 74% -58. 82% , Al2O3and K2O + Na2O range from 15. 32% -17. 17% and 4. 89% ~ 7. 05% , Mg* changes from 0. 13 to 0. 39, which belong to Sodium and Calc-alkaline series. Geochemical results for rhyolite indicate that the SiO2 are in 74. 68% ~ 74. 86% , Al2O3and K2O + Na2O range from 12. 09% ~ 13. 13% , Mg'changes from 0. 13 to 0. 39 and they belong to Calc-alkaline series or Shoshonitic series. The trace elements analysis for intermediate volcanic rocks demonstrate the insignificantly Eu anomalies (Eu*/Eu =0. 94 ~ 1. 12) and intense fractionation between LREE and HREE, [ ( La/Yb) N= 9. 6 ~ 16. 09 ]. The primitive mantle-normalized spider diagrams are characterized by LILE enrichment and HFSE depletion, especially an obviously negative Nb-Ta anomalies, and obviously positive Pb anomalies. Rhyolite has the similar characteristics and is characterized by a significantly negative Eu anomalies, [ ( La/ Yb)N =7.86 ~10.05]. Based on the previous studies, we infer that intermediate volcanic rocks formed under the stretching and thinning environment. With geothermal gradient increasing and atmosphere upwelling, andesitic magma resulted from partial melting of enriched lithospheric mantle.关键词
中酸性火山岩/晚侏罗世/岩石圈地幔/伸展减薄/赤峰北部Key words
intermediate-granitic volcanic rock/ Upper Jurassic/ lithospheric mantle/ stretching and thinning/ northern Chifeng分类
天文与地球科学引用本文复制引用
郝彬,杨欣德,张明洋,谢乘飞..内蒙古赤峰北部晚侏罗世中酸性火山岩地球化学特征[J].地质力学学报,2011,17(3):274-285,12.基金项目
中国地质调查局“内蒙古1∶50000炒米房幅(K50E006017)、土城子幅(K50E006018)、新开地幅(KS0E007017)、大黑水幅(K50E007018)区调”项目. （K50E006017）
