摘要
吉林敦化—密山断裂带北段琵河口—黄泥河镇之间新发现有多处的霓辉粗面岩,岩石以普遍富含碱性矿物霓辉石为特点,均呈整合接触覆盖于船底山期碱性玄武岩之上,具高位喷发、低位充填特点,全岩K--Ar年龄测定结果 (25. 64±0. 53 Ma、27. 36±0. 45 Ma、28. 45±0. 56 Ma、28. 55±0. 43Ma、28. 63±0. 45 Ma、28. 65±0. 61 Ma)属渐新世。地球化学数据显示,霓辉粗面岩SiO_2质量分数均值为59. 05%,富碱、高钾,亏损大离子亲石元素(Sr、Ba、V、Cr),富集高场强元素(Nb、Ta、Hf、Zr)和轻稀土元素(LREE),∑REE含量很高,具有右倾型稀土分配型式,显示明显Eu负异常。研究表明,霓辉粗面岩是由碱性玄武质岩浆经强烈分离结晶作用形成的,揭示该区渐新世处于一种强烈的拉张环境,幔源岩浆经历了由碱性玄武岩-碱性粗面岩的演化过程。
Aegirine trachytes were newly recognized in northern Dunhua--Mishan fault belt,between the Bahekou and Huangnihe towns,Jilin Province. Aegirine trachytes are characterized by enrichment in alkaline minerals represented by aegirine,conformably overlying the alkaline basalt of Chuanfishan Period. Whole-rock K--Ar isotopic dating reveals ages of 25. 64 ± 0. 53 Ma,27. 36 ± 0. 45 Ma,28. 45 ± 0. 56 Ma,28. 55 ± 0. 43 Ma,28. 63 ±0. 45 Ma and 28. 65 ± 0. 61 Ma,which belong to Oligocene. The geochemical analysis shows average SiO2 content of 59. 05 % for the aegirine trachytes,with high alkaline and enriched K2O contents. They are depleted in LILEs( Sr,Ba,V,Cr) and enriched in HFSEs( Nb,Ta,Hf,Zr) and LREE,with high ∑REE abundances,right-inclined REE distribution patterns and obvious negative Eu anomalies. Integrating all the results,it is indicated that the aegirine trachytes were derived from strongly fractioned crystallization of alkaline basaltic magma,under an intensive extensional setting during Oligocene and the mantle-derived magma evolved from alkaline basalt to aegirinetrachyte.
作者
邸新
贾海明
于宏斌
聂立军
DI Xin;JIA Hai-ming;YU Hong-bin;NIE Li-jun(Survey of Regional Geological & Mineral Resources of Jilin Province ,Changchun 130022,China;Geological Survey of Jilin Province , Changchun 130102,China)
出处
《世界地质》
CAS
2018年第4期1047-1057,1084,共12页
World Geology
基金
中国地质调查局项目(1212011120732)
关键词
敦密断裂带
霓辉粗面岩
玄武岩
地球化学
K-AR年龄
Dunhua-Mishan fault belt
aegirine trachyte
geochemistry
whole-rock K-Ar isotopic age