Geochemical Characteristics of Cenozoic Jining Basalts of the Western North China Craton: Evidence for the Role of the Lower Crust, Lithosphere, and Asthenosphere in Petrogenesis

  • Author(s): Kung-Suan Ho, Yan Liu, Ju-Chin Chen, Chen-Feng You , and Huai-Jen Yang
  • DOI: 10.3319/TAO.2010.06.28.01(TT)
  • Keywords: K-Ar dating, Sr-Nd-Pb isotope, Petrogenesis, Cenozoic Jining basalts, Western North China Craton
  • Citation: Ho, K. S., Y. Liu, J. C. Chen, C. F. You, and H. J. Yang, 2011: Geochemical characteristics of Cenozoic Jining basalts of the western North China Craton: Evidence for the role of the lower crust, lithosphere, and asthenosphere in petrogenesis. Terr. Atmos. Ocean. Sci., 22, 15-40, doi: 10.3319/TAO.2010.06.28.01(TT)
Abstract

The Jining volcanic field located in the southern margin of the Mongolian plateau and the western North China Block consists of four rock types: quartz tholeiite, olivine tholeiite, alkali olivine basalt and basanite. These rocks have a wide range of K-Ar ages from ~36 to < 0.2 Ma. The early volcanism was voluminous and dominated by flood-type fissure eruptions of tholeiites, whereas the later phase was represented by sparse eruptions of basanitic lavas. Thirty-six samples analyzed in this study show a wide range in SiO2 contents from 44% ~ 54%. They all are sodium-rich and high-Ti basalts that, however, show marked isotopic variations between two end-members: (1) tholeiites that have higher 87Sr/86Sr of 0.7048 ~ 0.7052, and lower εNd of -0.8 to -2.4 and Pb isotope ratios (206Pb/204Pb of 16.9 ~ 17.2, 207Pb/204Pb of 15.3 ~ 15.4 and 208Pb/204Pb of 37.1 ~ 37.7); and (2) basanites that have lower 87Sr/86Sr of 0.7035 ~ 0.7044, and higher εNd of +1.3 to +4.9 and Pb isotope ratios (206Pb/204Pb of 17.7 ~ 18.0, 207Pb/204Pb of 15.4 ~ 15.5 and 208Pb/204Pb of 37.8 ~ 38.2). Alkali olivine basalt that occurs as a subordinate rock type is geochemically similar to the basanites, but isotopically similar to the tholeiites, characterized by the highest 87Sr/86Sr ratio among the three basaltic suites, coupled with a low Nb/U value (~33).

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