The lithospheric mantle beneath the North China Craton changed dramatically in its geophysical and geochemical...
ZHANG HONG-FU~(*++),SUN MIN~(++),ZHOU MEI-FU~(++),FAN WEI-MING~*, ZHOU XIN-HUA~* & ZHAI MING-GUO~* * Laboratory of Lithosphere Tectonic Evolution,Institute of Geology and Geophysics, Chinese Academy of Sciences,P.O.Box 9825,Beijing 100029,P.R.China ++ Department of Earth Sciences,The University of Hong Kong,Pokfulam Road,Hong Kong
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.
