摘要
选择处于钦杭带中段的湖南江永回龙圩煌斑岩作为研究载体,通过地球化学特征探讨其蕴含的构造意义。回龙圩煌斑岩SiO_2含量48. 58%～52. 62%,Na_2O+K_2O为5. 41%～6. 30%,K_2O/Na_2O值为1. 54～1. 86,属钾质钙碱性煌斑岩。其稀土总量ΣREE为(168. 72～186. 61)×10^(-6),LREE/HREE平均为9. 0,δEu为0. 87～0. 95,δCe为0. 90～0. 94,具轻稀土富集、重稀土亏损、轻微的Eu、Ce负异常的特点;微量元素Zr、Hf、Nb、Ti、Th、Ce、K、Rb为负异常,正异常的元素有U、Ba、Pb。研究认为,回龙圩煌斑岩来源于富集地幔,在中侏罗世中晚期燕山运动的NWW向挤压转为拉张过程中沿断裂上升侵位,岩浆在经历了板块俯冲导致部分熔融和少量分离结晶后形成的,在成岩过程中没有发生明显的地壳混染作用。
The Huilongxu lamprophyry,located in the middle of Qinzhou-Hangzhou belt,is chosen as the reseach carrier to explore its structural significance through geochemical characteristics.It belongs to the potash calc-alkaline lamprophyre(SiO 2=48.58%-52.62%,Na 2O+K 2O=5.41%-6.30%,K 2O/Na 2O=1.54-1.86).TheΣREE ranges from 168.72×10-6 to 186.61×10-6,the average of LREE/HREE is 9.0,which has the characteristics of light rare earth enrichment,heavy rare earth deficiency and Eu,Ce slight negative anomaly(δEu=0.87-0.95,δCe=0.90-0.94).The trace elements Zr,Hf,Nb,Ti,Th,Ce,K,Rb are negative anomaly,and the elements with positive anomaly are U,Ba,Pb.It is considered that the Huilongxu lamprophyre was originated from the enriched mantle,and emplaced along the NWW fault made by Yanshanian movement during middle and late Jurassic.After plate subduction,the magma was formed by partial melting and a few of separation-crystallization.There is no obvious crustal contamination during the diagenetic process.
作者
梁恩云
陈迪
邹光均
熊苗
LIANG En-yun;CHEN Di;ZOU Guang-jun;XIONG miao(Hunan Institute of Geological Survey,Changsha 410116,China)
出处
《桂林理工大学学报》
CAS
北大核心
2018年第4期640-646,共7页
Journal of Guilin University of Technology
基金
中国地质调查局地质调查项目(DD20160032-17)
关键词
煌斑岩
地球化学特征
构造意义
钦杭带中段
江永
lamprophyre
geochemical characteristics
tectonic significance
Qinzhou-Hangzhou belt
Jiangyong
