ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    霞石岩成因机制研究:以山东霞石岩为例

    Study on the Formation Mechanism of Nephelinite- Take Shandong Nephelinites as the Example

    • 摘要:
      目的 霞石岩是一种少见的强碱性火山岩,主要产生于大陆裂谷、洋岛以及大火成岩省。世界上大多数的霞石岩与碳酸岩共生,具有与OIB相似的地球化学特征。目前,关于霞石岩的岩石学和地球化学已有大量研究,一般认为其能解释地幔性质和演化特征,但目前霞石岩的成因及其与碳酸岩的成因关系尚存争议,阻碍了对地幔源区性质和交代过程熔流体性质的理解。
      方法 笔者选取山东地区代表性的且有一定研究基础的碣石山、栖霞大方山两地霞石岩进行岩石学和全岩主、微量元素地球化学分析,并根据实验岩石学研究结果对霞石岩母岩成分进行相关计算。
      结果 研究显示,山东霞石岩起源于10%~40%碳酸岩+橄榄岩的低程度(3%~5%)部分熔融,而且原始母岩浆可能经历碳酸岩–硅酸岩熔体的液态不混溶,才能产生山东霞石岩的主、微量元素地球化学特征以及霞石岩–碳酸岩共生的现象。
      结论 笔者计算出的原始母岩浆具有典型金伯利岩的地球化学特征,其研究可能对金伯利岩岩浆的起源具有重要启示意义。

       

      Abstract:
      Objective‌ Nephelinite is a rare type of strong alkaline volcanic rock mainly found in continental rift environments, oceanic islands, and large igneous provinces. Most of the world's nephelinites are associated with carbonatites and have similar geochemical characteristics to OIBs. Despite numerous studies on the characteristics and formation environments of nephelinite, the genesis of nephelinite and its relationship with carbonatite rock are still controversial, constraining the understanding of nature of mantle source and characteristics of metasomatic agents.
      Methods  The petrology, and whole-rock major- and trace elemental analysis was carried out on the nephelinites in Jieshi Mountain and Qixia Dafang Mountain in Shandong Province, and the composition of the primary magma is calculated according to the experimental petrological research results.
      Results  The results suggested that the Shandong nephelinite originates from low degree (3%~5%) partial melting of 10%~40% carbonatite + peridotite. In addition, the primary magma has undergone the liquid immiscibility of the carbonate-silicate melt, which can match well with the major and trace elements characteristics and the symbiosis of the nephelinite in Shandong Province.
      Conclusion  It's also found that the calculated primitive magma has similar geochemical characteristics to that of typical kimberlite; thus, the author's study might have important implications for the origin of kimberlite magma.

       

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