南岭离子吸附型稀土矿床成矿规律研究新进展
发布时间：2018-11-18 12:52
【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CIA85%时,CIA与∑REE呈正相关,当85%CIA100%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-adsorbed rare earth ore is the dominant resource in China and the main source of heavy rare earths in the world. In the 1980s, China carried out a lot of research on the metallogenic regularity of such deposits, but there are still many unsolved mysteries. In order to understand the distribution characteristics and metallogenic regularity of ion adsorbed rare earth resources, 52 ion adsorbed rare earth deposits were comprehensively studied by the three dilute project group of the Institute of Mineral Resources of the Chinese Academy of Geological Sciences from 2011 to 2015. This paper introduces some new advances in the study of rare earth metallogenic regularity: (1) the ion adsorbed rare earth deposits are widely distributed in South China, the most developed in Nanling, and also found in Vietnam, Laos, Thailand and the United States in recent years. The deposit mainly occurs in weathering crust of granite and acid volcanic rock, and has also been found in weathering crust of metamorphic rock and limestone in recent years. It is still the most important type of rare earth deposit. (2) the metallogenic granite was formed in a wide range of ages, and the zircon U-Pb age was concentrated in the three intervals of 461T 384 Ma, 228T 242Ma and 189~94Ma. Compared with LREE type ore-forming granite, HREE type is more silicon-rich, rich in HREE, has strong negative Eu anomaly, generally high Rb, and low Ti,Zr,Hf,Nb,Ta,Ba,Sr and other trace elements, suggesting that HREE type metallogenic granite magma experienced a high degree of differentiation. It is worth noting that some LREE metallogenic granites are relatively rich in HREE, especially in Y. the ratio of light and heavy rare earth elements (LREE/HREE) is mostly between 1 and 3, and weathering is easy to form HREE weathering crust. This is probably one of the important sources of heavy rare earth resources in the future. (3) the genesis of rare earth minerals in ore-forming granites is diverse, including magmatic genesis (such as sphene, cinnamonite, monazite, yttrium phosphate ore, etc.), fluid metasomatism (rare earth fluorocarbonates) and epigenesis (water phosphate cerium ore, water phosphate lanthanum ore, etc.). The endogenous mineralization of rare earth elements is largely affected by fluid metasomatism. (4) the content of rare earth elements in the vertical section of weathering crust is "bow back", that is, the content of REE in the topsoil and semi-weathered layer is low, and the content in the total weathering layer is high, but it is affected by the factors of topography, geomorphology and surface water, etc. The change curve of rare earth content shows various forms. The vertical LREE and HREE can be stratified and enriched, that is, the upper part of the weathering layer is enriched with LREE, and the lower part of the HREE, can be enriched in the lower part of the weathering layer at the same time. There is a significant correlation between chemical weathering alteration index (CIA) and total rare earth element (鈭，
本文编号：2340084
[Abstract]:Ion-adsorbed rare earth ore is the dominant resource in China and the main source of heavy rare earths in the world. In the 1980s, China carried out a lot of research on the metallogenic regularity of such deposits, but there are still many unsolved mysteries. In order to understand the distribution characteristics and metallogenic regularity of ion adsorbed rare earth resources, 52 ion adsorbed rare earth deposits were comprehensively studied by the three dilute project group of the Institute of Mineral Resources of the Chinese Academy of Geological Sciences from 2011 to 2015. This paper introduces some new advances in the study of rare earth metallogenic regularity: (1) the ion adsorbed rare earth deposits are widely distributed in South China, the most developed in Nanling, and also found in Vietnam, Laos, Thailand and the United States in recent years. The deposit mainly occurs in weathering crust of granite and acid volcanic rock, and has also been found in weathering crust of metamorphic rock and limestone in recent years. It is still the most important type of rare earth deposit. (2) the metallogenic granite was formed in a wide range of ages, and the zircon U-Pb age was concentrated in the three intervals of 461T 384 Ma, 228T 242Ma and 189~94Ma. Compared with LREE type ore-forming granite, HREE type is more silicon-rich, rich in HREE, has strong negative Eu anomaly, generally high Rb, and low Ti,Zr,Hf,Nb,Ta,Ba,Sr and other trace elements, suggesting that HREE type metallogenic granite magma experienced a high degree of differentiation. It is worth noting that some LREE metallogenic granites are relatively rich in HREE, especially in Y. the ratio of light and heavy rare earth elements (LREE/HREE) is mostly between 1 and 3, and weathering is easy to form HREE weathering crust. This is probably one of the important sources of heavy rare earth resources in the future. (3) the genesis of rare earth minerals in ore-forming granites is diverse, including magmatic genesis (such as sphene, cinnamonite, monazite, yttrium phosphate ore, etc.), fluid metasomatism (rare earth fluorocarbonates) and epigenesis (water phosphate cerium ore, water phosphate lanthanum ore, etc.). The endogenous mineralization of rare earth elements is largely affected by fluid metasomatism. (4) the content of rare earth elements in the vertical section of weathering crust is "bow back", that is, the content of REE in the topsoil and semi-weathered layer is low, and the content in the total weathering layer is high, but it is affected by the factors of topography, geomorphology and surface water, etc. The change curve of rare earth content shows various forms. The vertical LREE and HREE can be stratified and enriched, that is, the upper part of the weathering layer is enriched with LREE, and the lower part of the HREE, can be enriched in the lower part of the weathering layer at the same time. There is a significant correlation between chemical weathering alteration index (CIA) and total rare earth element (鈭，
本文编号：2340084
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