华北板块西南缘河西堡中酸性侵入岩岩石地球化学和环境演化特征  

Geochemical and Environmental Characteristics of Hexipu Medium-acid Intrusive Rocks in the Southern Margin of North China Plate

作　　者：丑永魁 张翔[1] 马永东[1] 杨涛[1] 王玉玺[1] CHOU Yongkui;ZHANG Xiang;MA Yongdong;YANG Tao;WANG Yuxi(Geological Survey of Gansu Province, Lanzhou 730000, Gansu, Chin)

机构地区：[1]甘肃省地质调查院,甘肃兰州730000

出　　处：《西北地质》2018年第2期57-68,共12页Northwestern Geology

基　　金：中央财政出资的基础地质研究类项目"J48E009001(西坡幅);J48E010001(河西堡幅);J48E011001(东寨乡幅)1:5万区域地质调查项目(2001GB13)"

摘　　要：河西堡中酸性侵入岩体位于华北板块西南缘龙首山和祁连山造山带的结合部,岩性为细粒石英闪长岩、中细粒花岗闪长岩、中粗粒似斑状花岗闪长岩、中粗粒似斑状二长花岗岩,均具有富钾、硅,贫铝、钙、镁和负Eu异常,富含稀土铀、钍矿物等特点。稀土元素配分模式呈轻稀土富集型;地球化学特征显示SiO_2、ΣREE、ΣLREE/ΣHREE、La/Yb逐渐增高和δEu增大的演化趋势,^(87)Sr/^(86)Sr的变化范围为0.706 0~0.707 8,岩体由早期的I型逐渐过渡为I-S到S型,反映构造环境由块体挤压至碰撞造山的过程。结合区域资料,认为加里东早期北祁连向华北板块俯冲形成沟弧体系,在挤压作用下导致北祁连走廊过渡带与龙首山在加里东中期碰撞造山,碰撞造山作用于加里东晚期终止,较为系统的反映了龙首山造山带的构造演化过程。The Hexipu medium-acid intrusive rock is located at the intersection area between the Qilian orogenic belt and the Longshou mountain of the southwestern margin of North China Carton,which is composed of fine grained quartz diorite,medium-fine grained granodiorite,mediumcoarse grained porphyritic granodiorite and medium-coarse grained porphyritic monzogranite.The Hexipao granitic plutons are enriched in K and Si,but depleted in Al,Ca and Mg,having weakly negative Eu anomalies.Chondrite-normalized REE patterns show that all samples are enriched in LREEs.TheδEu values of the ploutons are rising with the increasing of the SiO2,ΣREE,ΣLREE/ΣHREE and La/Yb.The ^87Sr/^86 Sr ratios of all samples vary from 0.706 0 to 0.707 8,these plutons have been transited from early I type to I-S type to S type,showing a complete process of transiting from plate compression to collisional orogeny.Combined with the regionalgeological data,the results show that the North Qilian was subducted into the North China craton in Early Caledonian to form a trench-arc-basin system,the compression was led to the midCaledonian collisional orogeny between the North Qilian and Longshou mountain,and this collisional stage was terminated in Late Caledonian,systematically reflecting the tectonic evolution of the Longshoushan orogenic belt.

关 键 词：中酸性侵入岩 河西堡 弧后扩张 碰撞造山 

分 类 号：P588.121[天文地球—岩石学]