摘要
湖南煌斑岩以富集大离子亲石元素和轻稀土元素 ,而亏损高强场元素 (Nb Ta Ti)为特征 ,同位素以高87Sr/ 86Sr、低14 3 Nd/ 14 4 Nd为特征。源区可能为早期俯冲交代的古老岩石圈富集地幔。煌斑岩的侵入是软流圈上涌的结果 ,表明湖南地区于晚三叠世已从岩石圈的挤压阶段开始向岩石圈伸展 减薄阶段转换。
The Anhua-Xupu lamprophyre studied here was formed about 207 Ma or 172 Ma ago. It is characterized by high K 2O/Na 2O ratio (0.84～1.72), high K 2O+Na 2O content (>4.33%～6.41%),low TiO 2 content (0.54%～1.21%), high and variable Al 2O 3 content,strong enrichment of LILE and LREE, and distinct depletion of such HFSE as Nb, Ta and Ti. The isotopic components of the rock are of high 87Sr/ 86Sr and low 143Nd/ 144Nd ratio.The Sr-Nd isotope variation implies that the lamprophyre magma is derived mainly from an EMII metasomatic mantle source with low Nb/Th, La/Yb and Rb/Ba and high Ba/Nb ratios. The source is related to metasomatism of the lithosphere mantle with fluid released from the ancient subducted oceanic crust. The data of chemical elements and isotope geochemistry and an analysis of geological history indicate that the lamprophyre resulted from asthenosphere upwelling and the tectonic deformation in Hunan went into the crust extension-thinning stage in Triassic.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2003年第6期603-610,共8页
Acta Geoscientica Sinica
基金
中国科学院知识创新工程项目 (KZCX2 10 2 )
国家自然科学基金 ( 4 0 2 72 0 92 )
湖南省重点项目 ( 2 0 0 1)的成果
关键词
煌斑岩
地球化学特征
中生代
构造变形
湖南
extension lamprophyre geochemical characteristics Hunan province
