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

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 extremely irregular in shape with most grain sizes in a range of 10-50 mum and coexist with Iow-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 (Na_2O+K_2O > 10 wt percent), SiO_2 (>54 wt percent), CaO and FeO (>4 wt percent), 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 phonoli-tic compositions. The compositional features of cli-nopyroxene 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 Meso-zoic lithospheric mantle beneath the southeastern North China Craton.