摘要
华北地台北部燕辽地区发现一批三叠纪(245—195Ma)碱性或偏碱性杂岩体。这些杂岩体均贫硅,绝大多数富含铁、镁、钾、磷和稀土等不相容微量元素。^(87)Sr/^(86)Sr初始值为0.7055—0.7057,它们可能源自被交代蚀变的上地幔。结合燕辽地区三叠系的分布及构造形变的研究,表明该地区三叠纪存在构造岩浆活动带,它是本地区印支运动的重要表现。
A number of alkaline and subalkaline igneous complexes were discovered in the Yan-Liao area in the northern part of the North China platform. These complexes were formed during the Triassic age according to their isotopic ages (245—190 Ms). The geochemical features of the complexes are as follows: (1) SiO_2 is undersaturated or very unsaterated; (2) most of the complexes are rich in Fe, Mg and K (K/Na=1.1—30.7), and the content of P_2O_5 is in the range of 1.50—3.86 wt.％; (3) incompatible elements such as Rb, Ba, U and Sr are abundant; (4) the complexes are characterized by ΣREE=210—3367×10^(-6), a high LREE/HREE ratio ((La/Yb)_(cn)=11.8—123.6) and a linear REE pattern without Eu anomalies in the chondrite-normalized abundance plot; (5) the initial ^(87)Sr/^(86)Sr of ratios of the complexes range from 0.7055 to 0.7057.
Petrological, major and trace element geochemical, and Sr and O isotope data indicate that the magma that generated the igneous complexes might have originated in the altered upper mantle, Judging by the distribution of the Triassic formation and their characters of tectonic deformation of the region there should have existed a tectono-magmatic zone in the Yan-Liao area in the Triassic time. This serves as an important evidence for the existence of the Indosinian movement in this area.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1992年第2期108-121,共14页
Acta Geologica Sinica
关键词
碱性
杂岩体
地球化学
燕辽地区
alkaline and subalkaline complexes, geochemical, Yan-Liao area.
