| 磷灰石化学组成研究进展: 成岩成矿过程示踪及对矿产勘查的指示 |
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| 引用本文： | 谭侯铭睿, 黄小文, 漆亮, 高剑峰, 孟郁苗, 谢欢. 2022. 磷灰石化学组成研究进展: 成岩成矿过程示踪及对矿产勘查的指示. 岩石学报, 38(10): 3067-3084. doi: 10.18654/1000-0569/2022.10.11 |
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| 作者姓名： | 谭侯铭睿 黄小文 漆亮 高剑峰 孟郁苗 谢欢 |
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| 作者单位： | 1. 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081; 2. 中国科学院大学, 北京 100049 |
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| 基金项目： | 本文受中国科学院百人计划项目(Y9CJ034000)和贵州省一般项目(黔科合基础【2017】1197)资助 |
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| 摘 要： | 磷灰石广泛分布于各类岩石和矿床中, 根据其F、OH以及Cl阴离子种类可分为氟磷灰石、氯磷灰石和羟基磷灰石。磷灰石对其自身结构的变形以及化学取代有良好的耐受性, 一系列元素可以替代磷灰石中的Ca、P、F、Cl和OH, 因此其化学组成复杂。磷灰石中Ca位存在两种不同的阳离子位置, 影响不同元素在这两种位置取代的因素包括离子半径、价态以及磷灰石的种类等。岩浆过程中, 稀土(REE)、Y、Sr是磷灰石中的相容元素, 而F、Cl、OH的相容性随物理化学条件不同而变化。相较于元素在磷灰石与熔体相间的分配研究, 目前对于元素在磷灰石与流体相间的分配研究较少。磷灰石化学组成可以判别母岩类型: 如F、Cl、As、V含量可以区分Ⅰ型与S型花岗岩; REE、Sr、Y、Mn、As、Th的含量、轻稀土(LREE)的富集程度和球粒陨石标准化稀土元素配分模式可以用于判别碳酸岩、二辉橄榄岩、镁铁质岩石等岩石类型。利用磷灰石的F、Cl和CO3等挥发分的含量, 并结合Sr-Nd同位素组成, 可以识别地幔源区及其流体交代作用。磷灰石Sr/Th与La/Sm的变化可用于指示岩浆来自脱水板块或熔融沉积物。磷灰石的主微量元素(Mn、Eu)含量或元素比值(F/Cl)能够反映岩浆的分异程度, 而且Ce/Pb和Th/U比值可以反映岩浆形成过程中流体参与程度。磷灰石中的变价元素如Eu、Ce、Ga和S含量及δEu和δCe可用于推断岩浆的氧化还原状态。由于磷灰石对热液交代作用非常敏感, 所以磷灰石的结构和化学组成已广泛用于成矿过程研究。在与花岗岩有关的关键金属矿床中, 磷灰石的主、微量元素含量和Sr-Nd同位素比值常常用于区分不同花岗质岩浆的源区特征, δCe、δEu也可以用于指示花岗质侵入体的氧化还原状态; 斑岩有关的多金属矿床F、Cl、S、Mn含量以及F/Cl比值能够指示成矿岩浆-热液的来源及演化, δCe、δEu可以用于指示岩浆热液的氧逸度; 铁氧化物-铜-金和铁氧化物-磷灰石矿床中磷灰石结构、共生稀土矿物结合Na、F、Cl以及REE含量能够反映与成矿有关的岩浆-流体作用以及流体性质。磷灰石中Mn、Fe、REE、Y、F、Cl、SO3的含量或比值的差异可用于判别矿化与未矿化的岩石或者蚀变类型, 并用于区分不同矿床类型等, 对矿产勘查具有一定指示意义。磷灰石化学组成结合机器学习方法, 可以更好地识别磷灰石的来源。综上所述, 磷灰石作为一种新兴的指示矿物, 除了在成岩和成矿过程示踪方面体现出独特优势, 在矿产勘查应用方面也具有重要的应用前景。
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| 关 键 词： | 磷灰石 结晶结构 分配系数 岩石成因 成矿示踪 矿产勘查 |
| 收稿时间： | 2021-07-15 |
| 修稿时间： | 2022-04-14 |
Research progress on chemical composition of apatite: Application in petrogenesis,ore genesis and mineral exploration |
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| TAN HouMingRui, HUANG XiaoWen, QI Liang, GAO JianFeng, MENG YuMiao, XIE Huan. 2022. Research progress on chemical composition of apatite: Application in petrogenesis, ore genesis and mineral exploration. Acta Petrologica Sinica, 38(10): 3067-3084. doi: 10.18654/1000-0569/2022.10.11 |
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| Authors: | TAN HouMingRui HUANG XiaoWen QI Liang GAO JianFeng MENG YuMiao XIE Huan |
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| Affiliation: | 1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; 2. University of Chinese Academy Sciences, Beijing 100049, China |
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| Abstract: | Apatite is a ubiquitous mineral in different types of rocks and mineral deposits. Apatite is classified as hydroxyapatite, chloroapatite and fluorapatite according to the species of anions. Apatite is remarkably tolerant to structural distortion and chemical substitution, and thus a series of elements can substitute Ca, P, F, Cl and OH in it, resulting in complex composition of apatite. There are two Ca sites in apatite, the factors controlling the substitution of elements for different Ca sites include ion radius, valence and the types of apatite. Rare earth elements (REE), Y and Sr are compatible in apatite formed by magmatic process, whereas the compatibility of Cl, F and OH changes with varying physical and chemical conditions. Compared to the extensive study of element partition in melt system, the similar study is rare in hydrothermal system. Apatite Sr, Th, Y, REE contents and Sr/Y ratios can be used to indicate magmatic differentiation and discriminates the types of host rocks. For example, the contents of F, Cl, As and V can distinguish I-type granite from S-type granite, the abundances of REE, Sr, Y, Mn, As and Th, the light rare earth elements (LREE) anomaly and the normalized REE pattern can distinguish the rock types such as carbonate, lherzolite and mafic rocks. The mantle source and its fluid metasomatism can be identified by using the contents of volatile components such as F, Cl and CO3 of apatite and its Sr-Nd isotopes. In addition, the variation of Sr/Th and La/Sm in apatite can be used to indicate that the magma originated from dehydrated plates or molten sediments. The content or ratio of major (Mn, F/Cl) and trace elements (Eu) in apatite can be used to indicate the degree of magma fractionation, whereas the ratios of Ce/Pb and Th/U reflect the degree of fluid involvement in magma formation. The contents of variable-valence elements such as Eu, Ce, Ga, and S, and indexes of δEu and δCe in apatite can be used to infer oxidation-reduction state of magma. Because apatite is very sensitive to hydrothermal metasomatism, the texture and chemical composition of apatite have been widely used in the study of ore-forming processes. In granitite-related critical metal deposits, the contents of major and trace elements and Sr-Nd isotope ratios of apatite are often used to distinguish the source(s) of different granitic magmas, and δCe, δEu and Mn are used to indicate the oxygen fugacity of granitic intrusions. The contents of F, Cl, S, Mn and F/Cl ratio of porphyry polymetallic deposits can indicate the source and evolution of magma and hydrothermal solution, whereas δCe and δEu can be used to indicate the oxygen fugacity of magmatic-hydrothermal fluids. The apatite texture, the assemblages of REE minerals, combined with Na, F, Cl and REE contents in iron oxide-copper-gold and iron oxide-apatite deposits can reflect the magma-fluid interaction and the nature of fluids related to mineralization. The differences in the content or ratio of Mn, Fe, REE, Y, F, Cl and SO3 can be used to distinguish the mineralization versus barren rocks, and different types of alteration and deposits, which has indicative significance for mineral exploration. Combined with machine learning methods, apatite chemistry can better identify the origin of apatite. In conclusion, apatite, as a new indicator mineral, not only has the ability to constrain petrogenesis and ore genesis, but also has important application prospects in mineral exploration. |
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| Keywords: | Apatite Crystal structure Partition coefficient Petrogenesis Mineralization indicator Mineral exploration |
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