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地质通报  2007 

滇西南昌宁-孟连构造带晚泥盆世枕状玄武岩和层状硅质岩的特征

, PP. 39-747

Keywords: 晚泥盆世洋岛玄武岩硅质岩昌宁-孟连构造带滇西南

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Abstract:

滇西南耿马地区回爱剖面发育有昌宁-孟连构造带最早的枕状玄武岩,与其共生的放射虫硅质岩、硅质泥岩含有晚泥盆世放射虫和牙形石化石。对硅质岩和玄武岩的地球化学研究表明,玄武岩的化学成分具有高P、Ti的特点,轻稀土元素富集,在稀土元素球粒陨石标准化模式图上表现为明显的右倾,微量元素中K、Rb、Ba等大离子亲石元素与Nb、Ta、Zr等高场强元素富集。化学投图结果表明玄武岩形成于洋岛环境。硅质岩的彬(Al+Fe+Mn)比值大部分介于0.5-0.7之间,Al2O3/(Fe2O3+Al2O3)位于0.41-0.8之间,大部分硅质岩的Ce/Ce^*比值小于1,具弱的Ce负异常,总体表现为大陆边缘型硅质岩的特征。这说明研究区晚泥盆世为邻近大陆边缘的洋盆环境,具洋壳性质的昌宁-孟连古特提斯盆地在晚泥盆世已经形成。

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