黄河三角洲贝壳堤的铅同位素特征

LEAD ISOTOPIC CHEMISTRY OF SHELLS IN THE CHENIERS IN THE YELLOW RIVER DELTA

依据黄河三角洲王子岛海滩潮间带活贝壳和黄河三角洲贝壳堤中贝壳样品的铅同位素记录,初步探讨渤海湾南部最近6000多年来海水铅同位素变化特征及其环境意义,发现:①黄河三角洲贝壳堤中贝壳的铅同位素变化较大,206Pb/204Pb范围在18 207～18 648之间,平均值18 470;207Pb/204Pb在15 36～15 757之间,平均值15 619;208Pb/204Pb在37 947～38 945之间,平均值38 599。②渤海湾南部1 5～2 0kaBP海水放射性成因稳定铅同位素206Pb、207Pb、208Pb相对于现在王子岛海滩潮间带海水亏损。③总体上讲,渤海湾南部4 5～6 0kaBP海水放射性成因稳定铅同位素相对于1 5～2 0kaBP的富集。④黄河三角洲贝壳堤中多数贝壳样品的铅同位素分布在海洋沉积物的范围内,但少数样品分布异常,其206Pb/204Pb、207Pb/204Pb、208Pb/204Pb偏低,可能是受陆地或相邻海区的玄武质中铅的输入的影响。

Based on the lead isotopic records of shells in the cheniers in the Yellow River Delta, it is found that lead isotopes have changed in ancient seawater in the south Bohai Bay since 6 kaBP. The 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb range from 18 207 to 18 648, from 15 36 to 15 757 and from 37 947 to 38 945 respectively The averages are 18 470, 15 619 and 38 599 respectively. Stable lead isotopes of most of ancient seawater shells in the cheniers in the Yellow River Delta are in the lead isotopic composition ranges of normal marine sediments. And only a few are out of the ranges. The radiogenic stable lead isotopic compositions change with the input of lead from basalt.