Highly precise 40Ar-39Ar dating results demonstrate that the ages of potash-rich volcanic rocks in western Shandong Province are 114.7 - 124.3 Ma, and that of the lamprophyres is 119.6 Ma. The potash-rich volcanic rocks have relatively high(87Sr/86Sr)i ratios (0.708715 - 0.711418) and distinctly negative εNd values (-11.47 - -17.54), and are enriched in radiogenic lead (206 Pb/204Pb=17.341-17.622, 207Pb/204Pb=15.525-15.538, 208Pb/204Pb = 37.563-37.684). Similarly, the lamprophyres also have quite low εNd values (-11.57 - -19.64). Based on the fact that the Sr, Nd and Pb isotopic compositions of potash-rich volcanic rocks are very consistent with that of the clinopyroxene separates, and by integrating comprehensive analyses of their tectonic settings, and extensive comparisons of the Sr, Nd isotopic compositions with that of the related simultaneous rocks, it is concluded that the potash-rich volcanic rocks and lamprophyres in western Shandong Province were most possibly derived from the partial melting of enriched mantle which was caused by source contamination and metasomatism of subducted continental crustal materials.
|Number of pages||9|
|Journal||Chinese Science Bulletin|
|Publication status||Published - 2002|
- Ar-Ar dating
- Potash-rich volcanic rocks
- Sr-Nd-Pb isotope tracing
- Western Shandong Province