摘要
郯庐断裂带东侧的皖东地区上第三系花果山组和桂五组玄武岩,是我国东部大陆新生代玄武岩带中,尚未作详细地球化学研究的少数岩区之一。本文报道了该岩区22个样品的常量元素和稀土等20多种微量元素的丰度,以及其中11个样品的Nd,Sr,Pb同位素组成,比较系统地揭示了该大陆玄武岩套的地球化学特征。依据同位素和元素地球化学的制约,讨论了该岩套的成因及其地幔源区的性质和过程。该岩套来源于具EMI型大洋玄武岩地幔端元特征的不均一的大陆岩石圈地幔,该源区曾受地幔交代(或微量元素富集)作用的影响,具有开放条件下多阶段演化的特征。
The basalt terrain of the Neogene Huangguoshan and Guiwu Formations of eastern Anhui on the east side of the Tancheng-Lujiang fault belt is one of a few Ce-nozoic basalt terrains in eastern China for which detailed geochemical study has not been conducted. This paper reports the abundances of more than 20 trace elements of 22 samples and the Nd, Sr and Pb isotopic compositions of 11 samples from the eastern Anhui basalt terrain.The basals from eastern Anhui belong to normal alkali basalt series, composed of alkali olivine basalt (AOB), olivine basalt (OB), and olivine tholeiitic basalt (OTB), in terms of the CIPW normative compositions and total alkali-silica (TAS) diagram as well as the concentrations of sodium and potassium.The geochemical charactristics of the basalts are as follows: (1) the enrichment of LREE and highly incompatible elements,(2) the wide variation of Nd, Sr and Pb isotopic compositions,(3) EMI type signature of Nd and Sr according to the isotope system for oceanic basalts, and(4) the contrast between the wide variation of Nd isotopic compositions and the relative consistency of Sm/Nd ratios.The eastern Anhui alkali basalts were derived from the heterogeneous continental lithospheric mantle, which was affected by mantle metasomatism shortly before the formation of basalt melt.The discovery of EMI-type eastern Anhui Neogene basalts is very useful for understanding the geochemistry and petrogenesis of Cenozoic basalts in the area and eastern China.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1995年第2期156-168,共13页
Acta Geologica Sinica
基金
国家自然科学基金(编号 49173167)
关键词
玄武岩
地球化学
成因
上第三纪
continental alkali basalt, EMI-type mantle end-component, eastern Anhui
