| 新疆阿尔泰3号伟晶岩脉中的铯沸石：内部成分不均一性与岩浆-热液作用 |
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| 引用本文：.2004.Compositional Heterogeneity and Magmatic_Hydrothermal Evolution of Pollucite in No.3 Rare Metal Pegmatite Dyke of Altay, Xinjiang[J].Mineral Deposits,23(4):411~421 |
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| 基金项目:国家自然科学基金(批准号：40025209和40221301)和教育部博士点基金(资助号：200 0028431) |
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| 中文摘要:通过运用X射线粉晶衍射技术和电子探针定量分析、面分析技术，对阿 尔泰3号伟晶岩脉各结构带中共生矿物及其化学成分进行了研究。在不同结构带中，铯沸石 有着不同的共生矿物和化学成分。在叶钠长石_锂辉石带形成早期，铯沸石常和电气石、富 铯的锂云母共生，为成分均一的原生铯沸石，其CRK和Si/Al平均值分别为74.5和2.34。到叶 钠长石_锂辉石带形成晚期及石英_锂辉石带形成阶段，原生铯沸石发生再平衡作用，在相对 封闭体系中经历出溶作用后，形成团块状的富Na铯沸石和富Cs的铯沸石脉，并与富铯的锂云 母共生。到白云母_薄片钠长石带阶段，在热液作用下，原生铯沸石被次生铯沸石所交代。 该次生端员铯沸石的CRK和Si/Al平均值分别为93.4和2.05，它的出现表明岩浆演化从岩浆_ 热液阶段进入热液阶段。总之，铯沸石作为原始伟晶岩熔体最晚期的产物，记录了3号伟晶 岩脉原始岩浆中碱金属经过了极度分异作用。 |
| 中文关键词:地质学 铯沸石 伟晶岩 岩浆_热液作用 阿尔泰 新疆 |
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| Compositional Heterogeneity and Magmatic_Hydrothermal Evolution of Pollucite in No.3 Rare Metal Pegmatite Dyke of Altay, Xinjiang |
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| Abstract:The primary homogeneous pollucite in the No.3 rare metal pegmatite dyke is typic ally associated with spodumene, elbaite, lepidolite, Cs_enriched lepidolite and albite and has an average composition of Na0.189Cs0.689K0.001Rb0.002Mg0.002Al0.905Si2.091O6. With Si/Al ratio of 2.19～2.43 and CRK〔=100×(K+Rb+Cs)/Σ(Cs+Na+K+Rb+Ca+Mg)〕 between 70.6 and 86.5, t he primary homogeneous pollucite has locally evolved into a mosaic of Na_enriche d and Cs_enriched domains. The process experienced re_equilibration of primary p ollucite, forming a two_phase product at decreasing temperature and in a relativ ely closed system. During the late hydrothermal alteration stage, pollucite extr emely close to the ideal end_member composition occurred with the albite. With a n average CRK of 93.4 and Si/Al ratio of 2.05, the end_member pollucite was form ed as a replacement product of the primary pollucite under the hydrothermal cond ition in an open system. The researches on the diversity and complexity of pollu cite in granitic pegmatities not only reveal the evolution of late pegmatite fro m the magmatic_hydrothermal stage to the hydrothermal stage but also open up a g reater predictive potential for long_term containment of nuclear wastes in analo gous storage phases. |
| keywords:geology, pollucite, pegmatite, magmatic_hydrothermal evolution, Altay, Xinjiang |
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