云南香格里拉九龙区橄榄辉石岩块中单斜辉石环带的研究

Research of the Clinopyroxene Zoning Phenomenon from the Basic-Ultrabasic Rocks in Jiulong Area,Shangri-La County,Yunnan Province, China

云南香格里拉县九龙一带出露的橄榄辉石岩侵位于峨眉山玄武岩,或呈断块夹持于构造破碎带中。岩相学研究发现,单斜辉石环带结构发育,主要为韵律环带和正环带两种,但吉丁和海西失吉地样品的环带规律性不明显。环带微区的探针成分分析及对比研究表明,安南样品的环带为同一碱性-过碱性系列岩浆多次脉冲补给的产物,其高碱度表现为更高的钙含量、更不饱和的硅和更明显的成分环带,离子的类质同象替代方式、Al-Ti含量的指向性以及温压计算结果反映其形成于温度压力较高的环境;吉丁和海西失吉地样品为富碱的拉斑玄武系列经不明显的分异,形成于活动陆缘低温低压的环境,可能为甘孜—理塘结合带的残余产物。

In Jiulong area,Shangri-La County,Yunnan Province,China,olivine pyroxenite intruded into Emeishan Basalt Formation and is constrained by faults.Petrologic studies show that clinopyroxene develops zone texture,including rhythm zone and orthozone,except the samples from Jiding and Haixishijidi areas.Micro-field analysis of the zones suggests that the sampling zones in Annan Area can supply alkaline-ultra alkaline magma derived from same source.The higher the Ca content,the higher the unsaturated.Patterns of ionic isomorphism,indexes and t-p calculation of Al-Ti suggest that Annan olivine pyroxenite formed in high t-p environment.However,olivine pyroxenite from Jiding and Haixishijidi Areas are uncompleted differentiation of alkaline-rich tholeiitic basalt magma and formed in low t-p environment at the active continent margin.Olivine pyroxenite from Jiding and Haixishijidi areas are speculated to be the relics of Gaze-Litang suture belt.