湘东北临湘地区钾质煌斑岩40Ar-39Ar定年及其地球化学特征
40Ar-39Ar dating and geochemical characteristics of the potassic lamprophyre in Linxiang area, northeastern Hunan
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摘要: 提要：对出露于湘东北临湘地区的煌斑岩脉群进行了同位素年龄测定及岩石地球化学分析。研究表明，煌斑岩的全岩40Ar-39Ar年龄为(119.5±2.2)Ma，形成于早白垩世。岩石地球化学方面，岩石属碱性系列、钾质—超钾质煌斑岩；富集大离子亲石元素(LILE) 和高场强元素( HFSE)；稀土元素分配模式为相似的右倾轻稀土富集型；具有较小的TDMⅡ值（1.5 Ga）和较低的εNd（t）（-7.3）。上述特征暗示煌斑岩物质来源于异常（交代富集）地幔，形成于后造山陆内拉张减薄的构造环境。
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关键词:
- 钾质煌斑岩 /
- 40Ar-39Ar年龄 /
- 地球化学特征 /
- 湘东北
Abstract: Abstract：Isotopic age and geochemical characteristics of the potassic lamprophyre in Linxiang area of northeast Hunan were analyzed in this paper. Its whole-rock 40Ar/39Ar plateau age is (119.5±2.2)Ma, indicating a product of Early Cretaceous. The lamprophyre belongs to the alkaline series and is of potassic-superpotassic nature, with rich large-ion lithophile elements (LILE) and high field-strength elements (HFSE), right oblique chondrite-normalized REE pattern, clear low TDMⅡ value of 1.5Ga and low εNd（t）value of -7.3. These characteristics suggest that the lamprophyre was derived from anomalous (metasomatic enriched) mantle, and was formed in a post-orogenic tectonic setting characterized by lithospheric extension and thinning. -
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