攀枝花大田地区前震旦纪斜长角闪岩地球化学特征及构造意义

对攀枝花大田地区斜长角闪岩进行了系统的主微量地球化学特征、锆石LA-ICP-MS U-Pb年代学以及Lu-Hf同位素特征研究.结果表明:斜长角闪岩的SiO₂含量为47.88%~50.05%，原岩为亚碱性-碱性玄武岩.斜长角闪岩稀土总量(ΣREE)较高，稀土元素配分模式为轻稀土富集的右倾型，与洋岛玄武岩相似.微量元素原始地幔标准化蛛网图为"隆起"型，与板内玄武岩特征类似.Zr/Nb、Hf/Th等比值均表明其与板内玄武岩类似，而与岛弧玄武岩具有明显的差异.锆石U-Pb定年结果表明岩浆结晶年龄为816.0~833.6 Ma，同期岩浆结晶锆石的ε_Hf(t)值在-6.8~+3.8之间，其岩浆源区为与OIB类似的富集地幔源区且受到了地壳物质的混染.综合上述资料，认为其形成于Rodinia超级地幔柱活动导致的大陆裂谷环境. 

Geochemical Characteristics and Tectonic Significance of the Neoproterozoic Amphibolites from Datian Area,Panzhihua City

The amphibolites are widespread in the Kangding complex in Miyi-Panzhihua area,south Sichuan. The petrological,geochemical,zircon U-Pb dating and Lu-Hf isotope characteristics from the amphibolites in the Datian area have been studied in this work. The results show that:(1) The SiO₂ contents range from 47.88% to 50.05%,falling into the range of subalkaline-alkaline basalt in the discrimination diagrams of TAS and Zr/TiO₂-Nb/Y; (2) The total REE contents (ΣREE) range from 121.59×10-6 to 230.43×10-6,which is characterized by LREE-rich pattern((La/Yb)_N=2.73-7.52) and is similar to oceanic island basalt; (3) The primitive mantle-normalized trace elements spider diagram is similar to that of intra-plate basalt. (4) The ratios of Zr/Nb,Hf/Th indicate that they are similar to intraplate basalt,while have obvious differences with arc basalt; (5) Zircon LA-ICP-MS U-Pb dating demonstrates that the crystallization age of amphiboliteis is 816.0-833.6 Ma,which is contemporary to the large-scale Neoproterozoic mafic magmatism in the west margin of Yangtze block (860-750 Ma),the ε_Hf(t) of zircons is -6.8~+3.8,indicating that the basalts were derived from enriched mantle and has been contaminated by crustal materials. Thus,the amphibolites may formed in the continental rift environment caused by the breakup of Rodinia supercontinent.