南极Bolingen岛屿高级变质地块地壳演化的地球化学及锆石U-Pb、Hf-O同位素制约

Granulite-facies rocks in the Bolingen Islands, Antarctica, represent important suites of rocks exposures for investigating the development of high-grade metamorphic terrains in East Antarctica. Zircon grains from various rocks covering the Bolingen Islands will be analysed for U-Pb ages, Hf and O isotopes, and trace elements, using in situ SHRIMP and LAM-ICPMS techniques, to evaluate the terrane-scale crustal evolution, and for the correlation of terranes. U-Pb age are used to estimate the timing of terrane-scale events, primarily magmatic and metamorphic episodes; Hf and O isotopes provide information on the relative contributions of juvenlie material and reworked older crust at each stage of crustal evolution; trace-element patterns of zircons are used to characterise original magma types. Felsic gneiss, mafic gneiss, metasediments, granite, the analysis of such populations sampled in these rocks generates U-Pb ages that can be used to date fundamental terrane-scale events-magmatic episodes, metamorphism and activity and to constrain metasedimentary provenance. Such as the degree of crustal recycling or the importantance and timing of juvenile( mantle-derived) contributions to the crust. The study will provide an important temporal framework for the correlation of other parts of a complex mosaic of metamorphic terraness from East Antarctica. The new data are to be encourage revised models for Gondwana assembly.

东南极Bolingen岛屿的变质岩系经历了麻粒岩相变质作用，是探索下地壳地质过程的窗口。以Bolingen岛屿高级区为主要研究对象，开展深入的地质、锆石微区U-Pb定年和Hf-O同位素分析及与全岩元素和Nd同位素研究。建立该区域早古生代至元古代构造热事件精细年代学框架，确定该区域各岩系的地球化学性质、地壳增生规律及形成构造背景。重点确定研究区原岩为岩浆岩的空间分布、地球化学特征及形成演化，示踪研究区原岩物质组成、（岩浆）源区性质，成因及构造背景，结合区域地质资料，探讨南极Bolingen岛屿高级变质地体形成演化及其地球动力学背景。联系东南极其他陆块的地质特征，探讨区域地壳组成、形成和演化以及源区性质，进而为研究东南极各镶嵌块体拼合的构造关系提供地球化学制约。

南极Bolingen岛屿变质杂岩的锆石年龄记录了该区地壳演化的历史。研究发现Bolingen岛屿长英质片麻岩的锆石揭示存在三期重要的地质事件，第一期的1091±25 Ma岩浆活动事件，第二期的1031±8 Ma的变质事件，第三期的523±5 Ma的地质热事件。依据锆石Hf的模式年龄识别出普里滋湾地区存在1.8-2.4 Ga重要的地壳形成期，该区域大陆地壳从地幔中抽取主要在1.8-2.4 Ga这个时期。该期地壳生长与已经在冈瓦纳大陆识别出的时期一致, 显示它们是区域大陆生长的主要时期。区域格林维尔期岩石的锆石U-Pb和Hf同位素的研究反映其岩浆来自古老的地壳和新生的幔源物质的贡献，区域泛非期岩石则主要是地壳重熔的结果。这些新成果对理解东南极地质演化具有重要科学意义。