南岭离子吸附型稀土矿床成矿规律研究新进展
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中国地质科学院矿产资源研究所,中国地质科学院矿产资源研究所,中国地质科学院矿产资源研究所,中国地质科学院矿产资源研究所

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中国地质调查项目,青年基金,所长基金共同资助


Progress of Research on Metallogenic Regularity of Ion-adsorption Type REE Deposit in the Nanling Range
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Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences,Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences,Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences,Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences

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    摘要:

    离子吸附型稀土矿是我国的优势资源,是全球重稀土的主要来源。20世纪80年代我国对此类矿床的成矿规律开展过大量研究,但仍有诸多未解之谜。为了解目前离子吸附型稀土资源的分布特征和成矿规律,2011~2015年中国地质科学院矿产资源所三稀项目组对52个离子吸附型稀土矿床进行了综合研究,本文介绍稀土成矿规律研究方面取得的一些新进展:①离子吸附型稀土矿床广泛分布在华南地区,以南岭最为发育,近些年在越南、老挝、泰国及美国也有发现。矿床主要产在花岗岩和酸性火山岩风化壳中,近几年也在变质岩和灰岩风化壳中有所发现,但花岗岩离子吸附型稀土矿床规模较大,品位较高,仍是最为重要的一类(亚类)稀土矿床;②成矿花岗岩的形成时代范围较宽,锆石UPb年龄集中在461~384Ma、228~242Ma和189~94Ma三个区间。相对于LREE型成矿花岗岩,HREE型更加富硅,富HREE,具有强烈的负Eu异常,普遍高Rb,低Ti、Zr、Hf、Nb、Ta、Ba、Sr等微量元素,暗示HREE型成矿花岗岩岩浆经历了高度分异。值得注意的是,部分LREE型成矿花岗岩相对富集HREE,特别是富集Y,轻重稀土元素比值(LREE/HREE)多介于1~3之间,风化易形成HREE型风化壳,这很可能是今后重稀土资源的重要来源之一;③成矿花岗岩中稀土矿物的成因多样,有岩浆成因(如榍石、褐帘石、独居石、磷钇矿等)、流体交代成因(稀土氟碳酸盐类)和表生成因(水磷铈矿、水磷镧矿等),稀土元素的内生矿化很大程度上受流体交代作用影响;④发育完整的风化壳垂向剖面中稀土元素含量呈“弓背式”分布,即表土层和半风化层中含量低,全风化层中含量高,但受地形、地貌及地表水等因素的影响,稀土含量变化曲线呈多种形态。垂向上LREE和HREE可分层富集,即全风化层上部富集LREE,下部富集HREE,也可以同时富集在全风化层下部。华南大量成矿母岩和风化壳样品的化学风化蚀变指数 (CIA)与稀土元素总量(∑REE)之间存在明显的相关性,当CIA<85%时,CIA与∑REE呈正相关,当85%<CIA<100%时,CIA与∑REE呈负相关;⑤表生过程中,母岩中易风化的稀土矿物不断释放出可交换性吸附态的稀土元素,酸性淋滤作用是稀土元素迁移的动力,黏土矿物是稀土元素赋存的载体,风化程度影响稀土元素的次生富集。

    Abstract:

    Ionadsorption type REE deposit, which produces the majority of the world’s heavy rare earth resources, is one of preponderant mineral resources in China. Although many significant research projects on the metallogenic regularity of this type deposits have been carried out in 1980s, a lot of fundamental problems still need to be investigated and solved. We have completed a comprehensive geology study on 52 Ionadsorption type REE deposit in southern China from 2011 to 2015. This paper reports the research progress of metallogenic regularity of the REE deposits. Ionadsorption type REE deposit are widely distributed in south China, particularly in the Nanling Mountains. They have also been identified in Vietnam, Laos, Thailand and the United States in recent years. Known the deposits of southern China occur in the weathering profiles of granitic rocks, acidic volcanic rocks, metamorphic rocks and limestone. The deposits in granite weathering showing highgrade largescale are most important. The REE mineralized granitic rocks were formed in the Paleozoic and Mesozoic with the zircon age ranges of 461~384Ma, 228~242Ma and 189~94Ma. The HREErich parent rocks are more enriched in the SiO2 and Rb, depleted in Ti, Zr, Hf, Nb,Ta, Ba and Sr, with the significant Eu anomaly, than the LREErich parent rocks, showing they formed from a highly fractionated magma. Remarkably, part of LREErich parent rocks with higher Y and low LREE/HREE ratio (1~3) tend to formed HREE orebody. REE minerals are common in the parent rocks with complex origins, which can be divided into magmatic (eg, allanite, monazite, xenotime, xenotime), hydrothermal l(eg, bastnaesite, bastnaesite(Y), synchysite (Y)),and hypergenic minerals (eg, rhabdophane(Ce), rhabdophane(La)). And the significant enrichment of REE resulted from deuteric activity. The total REE contents in a welldeveloped weathering profile that composed of the lateritic horizon (A), the weathered horizon (B) and the weathering front (C) from surface downwards are enriched in the B horizon, and are relatively low in A horizon and C horizon. Generally, LREE are enriched in upper part in B horizon while HREE are enriched in lower part in early weathering stage, HREE and LREE are all enriched in lower part in late weathering stage. The relationship of the chemical index of alteration (CIA) and the total REE content in the weathering samples shows when CIA<85%,CIA and ∑REE have a positive correlation, when 85%<CIA<100%,CIA and ∑REE have a negative correlation. Relatively soluble REE minerals are a major sources of REE in the Ionadsorption type REE deposit, acidic leaching is attributed to the migration and concentration of REE in clay minerals, and the content of ionadsorption REE is largely depend on the weathering degree during the weatheringleaching process.

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赵芝,王登红,陈郑辉,陈振宇.2017.南岭离子吸附型稀土矿床成矿规律研究新进展[J].地质学报,91(12):2814-2827.
ZHAO Zhi, WANG Denghong, CHEN Zhenghui, CHEN Zhenyu.2017. Progress of Research on Metallogenic Regularity of Ion-adsorption Type REE Deposit in the Nanling Range[J]. Acta Geologica Sinica,91(12):2814-2827.

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  • 收稿日期:2016-07-01
  • 最后修改日期:2016-10-28
  • 录用日期:2017-12-18
  • 在线发布日期: 2017-12-20
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