摘要
山西大同新生代时期的玄武岩可划分为两大类型:大同西北部的碱性玄武岩与东南部的拉斑玄武岩。对大同地区玄武岩进行了岩石学及地球化学分析,通过对比其间的差别,得出两地区的玄武岩岩浆来自不同的幔源区,并概括出了二者各自的岩石学特征。在地球化学方面,采用了Mg同位素作为化学示踪剂来研究大同盆地的岩浆作用过程。结果显示:两区域的玄武岩样品均为显微斑状结构,但在长石、贵橄榄石等矿物的含量与比例上差异较大;两地区的稀土元素分配曲线在斜率上也有明显差异,据此也比较得出两区岩浆熔融程度的相对强弱;此外,大同地区的Mg同位素含量明显偏低,δ^(25) Mg质量分数在-0.36‰~-0.11‰之间,δ^(26) Mg质量分数在-0.69‰~-0.21‰之间,轻于正常地幔标准。通过研究玄武岩冷却结晶后的岩石学性质和地球化学性质来推断出深部地幔的地球化学演变过程,并以Mg同位素含量特征为主要研究方向,讨论其岩石成因,重点确定出地幔源区性质,为研究整个华北地区新生代玄武岩的成因机制、化学组成等因素提供了更好的参考。
Basalt in the Cenozoic period in Datong,Shanxi can be divided into two types:alkaline basalt in the northwest and tholeiite basalt in the southeast.Petrological and geochemical analyses were carried out on the basalts in Datong area.As known from the differences between them,the basalt magma in the two regions come from different mantle source regions.Their respective petrology characteristics were summarized.In terms of geochemistry,Mg isotope was used as a chemical tracer to further study the magmatism process in Datong Basin.The results show that the basalt samples in both regions are micro-porphyritic,but the content and proportion of minerals such as feldspar and precious olivine vary greatly;the distribution curves of rare earth elements in the two regions are also significantly different in slope.The relative strength of the magma melting in the two regions was also compared.In addition,the Mg isotope content in Datong area is obviously low,the δ^(25) Mg value is between-0.36‰~-0.11‰,and the δ^(26) Mg value is between -0.69‰~-0.21‰,which is lighter than the normal mantle standard.From the geological and geo chemical properties of the basalt after cooling crystallization the geochemical evolution of deep mantle was inferred.The content of Mg isotopic features was used as the main research direction to discuss its genesis and determine the nature of the mantle source region.This research provides reference to understand the cause mechanism,chemical composition,and other factors of Cenozoic basalts in north China.
作者
李小琴
聂鑫
白卓娜
刘鸿福
冯志强
LI Xiaoqin;NIE Xin;BAI Zhuona;LIU Hongfu;FENG Zhiqiang(College of Mining Engineering,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《太原理工大学学报》
CAS
北大核心
2021年第2期219-225,共7页
Journal of Taiyuan University of Technology
基金
山西省高等学校科技创新资助项目(2019L0199)。
