肯尼亚Buru区碳酸岩成因及稀土找矿意义研究
Analysis of Carbonatite Genesis and REE Prospecting Significance in Buru Area, Kenya
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摘要: 位于东非大裂谷的维多利亚湖周边(含肯尼亚Buru区)发现多处碳酸岩,富集稀土元素和其他微量元素,研究其成因及与稀土元素和其他微量元素关系具重要意义.Buru区碳酸岩原始地幔标准化分布曲线与幔源碳酸岩浆相似,显示本区碳酸岩是幔源成因.其杂岩体的性状和典型模式相似,但又有较大的不同,其侵入顺序为超基性岩(变玄武岩)→碱性岩(响岩)→碳酸岩.碳酸岩是在低温低压条件下形成的,为次火山岩相-浅成相.Buru区位于东非大裂谷东支与西支之间,拉张应力环境为幔源碳酸岩上侵创造了条件.碳酸岩是在岩浆晚期分异后形成的,经交代作用后稀土元素和其他微量元素进一步富集.稀土元素和其他微量元素易富集在火成方解石碳酸岩、白云岩等碳酸岩中,为稀土元素和其他微量元素矿床的寻找指明了方向.维多利亚湖周边碳酸岩具良好的找矿前景.Abstract: A number of carbonatites were discovered surrounding the Lake Victoria in Great Rift Valley of East Africa (including Buru area in Kenya). The rock is rich in rare earth elements and other microelements, so it is important to discuss its genesis and relationship with rare earth elements and other microelements. The standardized distribution curve of original mantle of Buru carbonatites is similar to that of mantle-derived carbonatite magma, it is thus suggested that the origin of carbonatite in Buru area is the earth's mantle. Behaviors of miscellaneous rocks are similar to typical mode, but there are many differences too. The order of intrusion is from ultrabasite (metabasalt) to alkaline rock(clinkstone) and carbonatite. Carbonatites were formed at low temperature and low pressure, and its lithofacies was from the volcanic facies to hypabyssal facies. Buru area in Kenya is located between the east and the west branch of East African Great Rift Valley, by stress of the earth's crust, carbonatite intruded upward from the earth's mantle. Carbonatites were formed after the late magmatic differentiation stage, through metasomatism, rare earth elements and other microelements accumulated in further. Rare earth elements and othermicroelements are richer in carbonatites such as igneous calcite carbonatite and dolomite etc., which point the prospecting direction for ore deposit of rare earth elements and other microelements. Carbonatites surrounding the Lake Victoria has very good exploration potential.
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Key words:
- carbonatite /
- earth's mantle /
- magma intrusion /
- element enrichment /
- Buru area
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