Glass melt inclusion in clinopyroxene from Linqu Cenozoic basalt,Shandong Province,China  

作　　者：ZHANG Hongfu Eizo Nakamura ZHANG Jin Ishikawa Akira 

机构地区：[1]State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China [2]Institute for Study of the Earth's Interior, Okayama University at Misasa, Tottori 682-0193, Japan

出　　处：《Chinese Science Bulletin》2006年第15期1869-1876,共8页

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.40534022 and 40225009).

摘　　要：Cenozoic basalts from the Linqu County, Shandong Province, China entrain some clinopy- roxene crystals, of which many contain abundant glass melt inclusions. These melt inclusions are ex- tremely irregular in shape with most grain sizes in a range of 10-50 μm and coexist with low-Mg# olivines, labradorites and Ca-rich potassium feldspars. In-situ major and trace element analyses show that the glass melt inclusions are high in alkalis (Na2O+K2O > 10 wt%), SiO2 (>54 wt%), CaO and FeO (>4 wt%), but low in MgO (Mg# < 20), and have LREE enrich- ments ((Ce/Yb)cn = 11.6-16.4) and apparently posi- tive Eu anomalies (Eu/Eu* > 2), thus having phonoli- tic compositions. The compositional features of cli- nopyroxene crystals, glass melt inclusions and their coexistent minerals suggest that these melt inclu- sions were exotic melts in clinopyroxenes trapped prior to their entrainment in the host basalt. The dis- covery of these melt inclusions provides a new ap- proach to further investigating the evolution of Meso- zoic lithospheric mantle beneath the southeastern North China Craton.Cenozoic basalts from the Linqu County, Shandong Province, China entrain some clinopyroxene crystals, of which many contain abundant glass melt inclusions. These melt inclusions are extremely irregular in shape with most grain sizes in a range of 10-50 μm and coexist with low-Mg^# olivines, labradorites and Ca-rich potassium feldspars. In-situ major and trace element analyses show that the glass melt inclusions are high in alkalis （Na2O＋K2O 〉 10 wt%）, SiO2 （〉54 wt%）, CaO and FeO （〉4 wt%）, but low in MgO （Mg# 〈 20）, and have LREE enrichments （（Ce/Yb）cn = 11.6-16.4） and apparently positive Eu anomalies （Eu/Eu^＊ 〉 2）, thus having phonolitic compositions. The compositional features of clinopyroxene crystals, glass melt inclusions and their coexistent minerals suggest that these melt inclusions were exotic melts in clinopyroxenes trapped prior to their entrainment in the host basalt. The discovery of these melt inclusions provides a new approach to further investigating the evolution of Mesozoic lithospheric mantle beneath the southeastern North China Craton.

关 键 词：新生代 玄武岩 斜辉石 玻璃熔体 地壳资源 山东 

分 类 号：P58[天文地球—岩石学]