郯庐断裂带晚中生代富碱侵入岩Nd、Sr、Pb同位素特征及源区性质探讨

郯庐断裂带是中国东部一条巨大的深大断裂带,它纵切华北克拉通、扬子克拉通、兴蒙-吉黑造山带和大别-苏鲁造山带四个大地构造单元,特别是在该断裂带出露许多晚中生代富碱侵入岩体,构成一条长达近2000km的富碱侵入岩带.本文是在前人研究基础上首次从大尺度对整个郯庐断裂带富碱侵入岩的Nd、Sr、Pb同位素做了比较系统深入的研究,发现四个大地构造单元的富碱侵入岩具有明显不同的Nd、Sr、Pb同位素特征,暗示四大构造单元富碱侵入岩的源区性质差别较大:兴蒙-吉黑造山带晚中生代富碱侵入岩源于和亏损地幔有成因联系的年青地壳(εNd(t)为ft.,平均值 2.25);华北克拉通、扬子克拉通和大别-苏鲁造山带三大构造单元晚中生代富碱侵入岩都主要源于EMI型富集地幔(εNd(t)均为负值).但是这三大构造单元岩石圈地幔富集程度差别较大.大别-苏鲁造山带岩石圈地幔相对富集程度最高(εNd(t)平均值为-17.06);华北克拉通次之(εNd(t)平均值为-10.03);扬子克拉通岩石圈地幔富集程度最低(εNd(t)平均值为-6.41).本文认为大别.苏鲁造山带岩石圈地幔相对最富集的原因可能是在早中生代扬子克拉通陆壳向华北克拉通深俯冲之后的折返过程中,因压力释放有利于熔/流体的形成、析出和向上交代并改造华北岩石圈地幔使之成为富集地幔.

Nd, Sr and Pb isotopic geochemistry of late-Mesozoic alkaline-rich intrusions from the Tanlu Fault zone: evidence of the magma source

Tanlu Fault Zone,a large deep fault zone in eastern China,cuts four tectonic units (the North China Craton,the Yangtz Craton,the Hinggan-Inner Mongolia-Jilin-Heilongjiang orogenic belt and the Sulu-Dabie orogenic belt) straight.It is well known that there is a nearly 2000 kilometer-long alkali-rich intrusive rock belt composed of many late-Mesozoic alkaline-rich intrusions in this zone.Based on the pioneers' research,a systematic and thorough geochemical study on their Nd,Sr and Pb isotope is presented in t...