摘要
祁连造山带发育有大面积的中-酸性侵入岩。引胜沟花岗质岩体位于中祁连造山带东段，主要岩性为花岗闪长岩。LA—MC—ICPMS锆石U—Pb测年结果分别为（436．9±5．3）Ma和（453．5±6．9）Ma，表明岩体是早志留世-中奥陶世岩浆活动的产物。根据岩体的地球化学特征不同可分为两组岩石：一组岩石特征为高SiO2，w（SiO2）为71．23％～73．65％，高A／CNK值（1．19～1．39）；镁铁（MF）指数为90-92，长英质（FL）指数为87-92，显示岩浆结晶分异程度较高；W（∑REE）=22．88×10^-6～40．65×10^-6，LREE／HREE比值为1．8～2．63，（Ce／Yb）N比值为1．36～1．95；δEu=0．06～0．49，平均为0．27，负Eu异常较为明显。另一组岩石特征为低SiO2，w（SiO2）为62．35％～63．73％，低A／CNK值（0．93～1．05）；镁铁（MF）指数为81～82，长英质（FL）指数为61-65，与第一组岩石相比，岩浆结晶分异程度较低；w（∑REE）：94．10×10^-6～235．50×10^-6，（Ce／Yb）。比值为1．43-10．49，δEu=0．82～0．92。岩石地球化学特征表明，引胜沟花岗质岩体是祁连造山带由俯冲向碰撞转换的构造环境下产生的，具有壳幔混合的特点。
Yinshenggou granitic pluton is one of the largest plutons in the middle Qilian Mountain. In this paper, we select some samples of pluton to study the geochemical characteristics, and discussed the rock causes and characteristics of tectonic environment. LA-ICPMS zircon U-Pb dating are （436.9±5.3） Ma and （453.5 ±6.9） Ma, indicating that the intrusion is the product of Early Silurian and Middle Ordovician magmatic activities. The intrusion shows 2 different geochemical characteristics. One of the rocks has high SiO2 ,whose content ranges between 71.23%-73.65%,and high A/CNK （1.19-1.39）,with MF value 90 -92,FL value 87 - 92, the magmatic crystallization was highly differentiated. ∑ REE = 22.88× 10^-6- 40.65×10^-6 ,the ratio of ∑LREE/∑HREE is 1.8-2.63,The ratio of CeN/YbN is 1. 36-1. 95.δ（Eu） = 0.06-0.49 is 0.27 on average, negative Eu anomaly. The other rock has low SiO2, whose content ranges between 62.35%-63.73% ,and low A/CNK（0.93-1.05）, with MF value 81-82,FL value 61-65. Contrast with the former rock, the magmatic crystallization was lowly differentiated. ∑REE=94.10× 10^- 6 235.50×10^-6,the ratio of CeN/YbN is 1. 43-10. 49,δ（Eu）=0. 82--0. 92. Comprehensive research shows that Yinshenggou pluton is generated in a tectontic environment when the Qilian orogeny changed from subduction to collision, showing the characteristics of crust-mantle mixed.
出处
《地质科技情报》
CAS
CSCD
北大核心
2016年第4期29-37,共9页
Geological Science and Technology Information
基金
中国地质调查局基础地质调查项目(1212011221044)
关键词
中祁连东段
引胜沟岩体
锆石U—Pb
地球化学
构造环境
壳幔混合
eastern Middle Qilian Mountain
Yinshenggou granitic intrusion
zircon U-Pb
geochemical
tec- tonic environment
crust-mantle mixed
