摘要
内蒙古达茂旗阿拉格敖包地区位于华北板块北缘增生带。对区内英云闪长岩岩石地球化学研究表明：岩石具有较低的w（SiO2）（68．71％～70．53％）和较高的伽（Al2O3）（13．82％～14．42％），贫碱（训（Na2O＋K2O）-5．69％～6．37％）、富钠贫钾（Na2O／K2O-6．29～9．40）的特点，A／CNK值为0．98～1．26，显示铝弱饱和；岩石稀土总量较低（89．2×10^-6～132．94×10^-6），轻重稀土分馏不明显[（La／Yb）N-2．75～4．573，具有弱的负铕异常和负铈异常；相对富集不相容元素Rb，Th，U，LREE，亏损Ba，Ta，Nb，sr，P，Ti等高场元素；属准铝质-弱过铝质低钾I型花岗岩。分析表明，荚云闪长岩总体经历了较低程度的部分熔融和结晶分异，源区为下地壳基性岩部分熔融，同时混有地壳物质；构造环境为内陆造山环境，指示华北板块与西伯利亚板块在二叠纪末已完全闭合，英云闪长岩是在造山后的伸展环境下，地幔上涌与地壳中具有洋壳性质的岩石相互作用而形成，具有岛弧花岗岩性质，为滞后型岩浆岩，代表了岩浆来源具有壳幔混合的特征。
A Lage Obo region of the Inner Mongolia is located in the northern margin accretion of the North China plate. Geochemical study of the local tonalite rocks shows that the rocks are of low w（SiO2） （68.71%-70.53%）,high w（Al2O3） （13.82%-14.42%）,low alkali （w（Na2O＋ K2O）=5.69%-6. 73%） and rich sodium poor potassium （Na2O/K2O=6.29-9.40）. A/CNK value ranges from 0.84 to 1.26, which sh＇owing weak aluminum saturation. In addition, the total rare earth of the rocks are lower （89.2 × 10^-6 -132.94 × 10^-6） and the fractionation of LREE is not obvious [（La/Yb）N =2. 75-4.57）],indicating that the rocks have weak negative Eu anomalies and negative Ce anomaly. Comparative enrichment of incompatible elements, such as Rb, Th, U, LREE and depletion of Ba, Ta,Nb, Sr, P, Ti demonstrates that the tonalite rock belongs to the metaluminous-weak peraluminous low potassium tholeiitic I-type granites. Tonalite rocks experienced a lower degree of partial melting and crystallization differentiation and the source region is the partial melting of the lower crust mixed with crustal material with the tectonic setting of inland orogenic environment, indicating that the North China plate and the Siberian plate were completely closed at the end of the Permian. Tonalite rocks were formed by interaction of upwelling mantle and oceanic crust in the post-orogenic extensional environment.
出处
《矿物岩石》
CAS
CSCD
北大核心
2015年第2期51-59,共9页
Mineralogy and Petrology
基金
中国地质调查局项目(12120113075800
12120113057300)
