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    苏北柳泉地区煌斑岩地球化学特征及岩石成因

    Geochemical characteristics and petrogenesis of the lamprophyres in Liuquan area of northern Jiangsu Province

    • 摘要: 柳泉地区是苏北地区煌斑岩的集中分布区,与之相伴的还有金伯利岩和橄榄玄武玢岩。通过研究该区煌斑岩的岩石学及岩石地球化学特征,进一步探讨其岩石成因及构造环境。研究表明:柳泉地区煌斑岩为同源岩浆演化的产物,整体属于钾质碱性煌斑岩,具有低硅、富铁镁钛的特点,大离子亲石元素和轻稀土元素相对富集,高场强元素和重稀土元素相对亏损。柳泉地区煌斑岩形成于中—新生代太平洋板块俯冲、岩石圈减薄的构造背景下,起源于深75~100 km、受俯冲沉积物改造形成的富集岩石圈地幔源区,经含角闪石石榴石二辉橄榄岩部分熔融,并沿构造薄弱带上侵至地壳浅部形成的。

       

      Abstract: The Liuquan area is the concentrated distribution area of lamprophyres in northern Jiangsu, accompanied by kimberlites, olivine basaltic porphyrites and so on. By studying the petrology and lithogeochemical characteristics of lamprophyres in the area, the petrogenesis and tectonic setting are discussed further in this paper. The results show that the lamprophyres are the product of comagmatic evolution, belonging to potassium alkaline series, characterized by low Si and rich Fe, Mg, Ca and Ti, enrichment of LILEs and LREEs, and depletion of HSFEs and HREEs generally. They are formed under the background of Meso-Cenozoic Pacific plate subduction and lithospheric thinning, originating from the enriched lithospheric mantle source formed by subducted sediments at a depth of about 75~100 km, with the nature of low-degree partial melting of amphibole garnet-bearing lherzolite intruding into the shallow crust along the tectonic weak zones.

       

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