湘东北蕉溪岭富钠煌斑岩地球化学特征
Petrological and geochemical characteristics of sodium-rich lamprophyres from Jiaoxiling in northeast Hunan province
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文摘
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湘东北蕉溪岭富钠煌斑岩是产于陆内拉张环境的一组特殊的岩石类型,包括闪斜煌斑岩、棕闪煌斑岩、闪辉正煌岩等。在岩石化学组成上,SiO_2为45.78%-48.42%,K_2O+Na_2O为5.05%-6.56%,属于碱性玄武岩系列,岩石以富集Na_2O、TiO_2、<FeO>、MgO,尤其以富钠为特征,K_2O/Na_2O平均值为0.41,在煌斑岩分类中属于钠质碱性煌斑岩。岩石∑REE较高,富LREE,不出现铕负异常,δEu平均值为1.04。岩石Rb-Sr等时线年龄为136.61Ma。岩石微量元素组成具有洋岛玄武岩(OIB)型特征,HREE明显亏损,不出现Ta、Nb、Ti的亏损以及LILE富集不明显,表明岩浆源区与岛弧环境无关,并且地壳物质混染程度很低。~(87)Sr/~(86)Sr初始比值0.705308~0.705366,ε_(Nd)(t)为+3.5~+3.8,~(143)Nd/~(144)Nd初始比值0.512639-0.512654,具有较为均一的洋岛玄武岩(OIB)地幔源区性质,并且位于地幔排列线附近。推测区内存在地幔柱构造环境,岩石的形成是在软流圈地幔上涌条件下导致深剖地幔部分熔融产物,富钠碱性煌斑岩应具有其自身岩浆源。 |
其他语种文摘
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The lamprophyres occurring at Jiaoxiling area in northeastern Hunan Province are special types of lamprophyres within continental plate, which include kersantite, barkevite lamprophyre, spessartite and garganite. The contents of SiO2 are 45.78%~48.42%, K_20 + Na_20 are 5.054%~6.56%, they all belong to alkalic series. The characteristics of rocks are rich in Na_2O> TiO+2, <FeO>, MgO, especially in sodium, K_2O/Na_2O = 0.41, which show that the rocks belong to sodium-rich alkali lamprophyres (agpaitic lamprophyres) in lamprophyre classification. The whole-rock Rb-Sr isochron age of the lamprophyres in Jiaoxiling area is 136.61Ma. The rocks have relatively high 2REE, no Eu negative anomalies (δeu = 1.04). Trace elements show that the rocks have characteristics of oceanic island basalt(OIB). HREE was depleted, but Ta> Nb, Ti were not depleted and LILE was very obviously not rich which shows that the magma source not occurred in island arc and the crustal assimilation was very limited. The initial ~(87)Sr/~(86)Sr isotope ratio of the lamprophyres is 0.705308~0.705366. The Initial ~(143)Nd/~(144)Nd isotope ratio is 0.512639 ~ 0.512654 andε_(Nd)(t) = +3.5 ~ +3.8. Those accord with the nature of OIB magma source and locate near the mantle array line. Geochemistry of the lamprophyres expresses the asthenosphere mantle diapirism and existing mantle plume. The agpaitic lamprophyre has special magma source. It was the product of part melting of mantle source controlled by asthenosphere mantle diapirism in the tectonic setting of mantle plume. |
来源
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岩石学报
,2002,18(4):459-467 【核心库】
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关键词
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富钠碱性煌斑岩
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地球化学特征
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洋岛玄武岩
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蕉溪岭地区
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岩石化学
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地幔
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地址
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1.
中国科学院地球化学研究所, 矿床地球化学开放研究实验室, 贵阳, 550002
2.
吉林大学地球探测科学与技术学院, 长春, 130026
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语种
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中文 |
文献类型
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研究性论文 |
ISSN
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1000-0569 |
学科
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地质学 |
基金
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中国科学院知识创新工程项目
;
中国科学院贵阳地球化学研究所矿床地球化学中国科学院重点实验室基金
;
中国科学院边缘海地质与古环境开放实验室基金项目
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文献收藏号
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CSCD:1365456
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