摘要
南太行山符山和东冶角闪闪长岩岩体的精细SHRIMP锆石U-Pb定年和元素-同位素地球化学研究表明:符山角闪闪长岩体形成于126.7±1.1Ma,东冶角闪闪长岩体形成于125.9±0.9Ma,与区内基性侵入岩和北太行地区侵入杂岩具有相似的形成年龄,表明晚中生代(±130Ma左右)太行山地区经历了与华北陆块同期的重要构造岩浆事件。区内闪长质岩石SiO_2=54.84％～65.75％,MgO=1.31％～3.89％,K_2O+Na_2O=6.53％～11.40％,mg值=0.36～0.58,(La/Yb)_(cn)=9.86～22.77,(Gd/Yb)_(cn)=1.51～2.00;Eu/Eu=1.00～1.23,以富集LREE、LILE元素和明显亏损Nb-Ta、Zr-Hf-Ti等高场强元素为特征。^(87)Sr/^(86)Sr(t)=0.705363～0.706165,ε_(Nd)(t)=-13.8～-16.8,源自于EMI型富集岩石圈地幔,可解释为新生地幔底侵物质熔融后经过结晶分异作用的产物。与华北克拉通内部其他地区一样,早白垩世南太行山地区处于软流圈上涌的岩石圈伸展构造背景。
The geochronological and geochemical data of the Mesozoic dioritic rocks from the southern Taihang Mountains provide an insight into the understanding of the nature of the Mesozoic lithospheric mantle beneath the North China interior. The Fushan and Dongye hornblende-diorites, the representative for the Mesozoic dioritic intrusions in the region, yield the SHRIMP zircon U-Pb ages of 126.7 +/- 1.1 Ma and 125.9 +/- 0. 9 Ma, respectively. The ages are consistent with those of the North Taihang Mountains and other areas in the North China Block interior. These dioritic rocks have SiO2 = 54. 8 similar to 65. 8%, MgO 1. 31% similar to 3.89%, K2O + Na2O = 6.53% similar to 11.40%, mg-number = 0. 36 similar to 0. 58, (La/Yb)(cm) = 9.86 similar to 22.77, ( Gd/Yb)(cm) = 1.51 similar to 2.00; Eu/Eu* = 1.00 similar to 1.23. They are enriched in LILEs and LREEs, depleted in HFSEs, and are characterized by Sr-87/(86) Sr(t) = 0.705363 similar to 0.706165, epsilon(Nd)(t) = - 13. 8 similar to16. 8 with an affinity to EMI-like source. Such characteristics suggest that they were most likely originated from an EMI-like lithospheric mantle. Mesozoic lithospheric extension might induce the melting of the enriched lithospherie mantle in response to the asthenosphere uprising for generating these dioritic rocks in the region.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2004年第5期1253-1262,共10页
Acta Petrologica Sinica
基金
国家自然科学基金(40303005
40334039)
中国科学院知识创新项目(GIGCX-03-0
KZCX1-102)
