北大巴山早古生代地幔交代作用与煌斑岩浆的起源和演化
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本文为国家自然科学基金资助项目(编号 49402035)的成果。


The Early Paleozoic Mantle Metasomatism and the Origin and Evolution of Lamprophyric Magma from North Daba Mts.
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  • 中国地质科学院西安地质矿产研究所,710054;西北大学地质系,西安,710069    
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  • Xian Institute of Geology and Mineral Resources, CAGS, Xian,710054;Northwest University, Xian, 710069    
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    摘要:

    产于陕西岚皋境内、赋存于碱质煌斑杂岩中的金云角 闪 辉石岩捕虏体是交 代地幔捕虏体。微量元素和SrNd同位素的对比研究表明,金云角闪辉石岩型交代地幔是寄 主煌斑岩的源区。金云角闪辉石岩捕虏体富含高Na、Ti的角闪石是本区寄主煌斑岩富Ti, 具 低K/Na值的根本原因。煌斑杂岩的同位素地球化学研究表明,早古生代地幔交代作用相对 于煌斑岩的侵位是一个相对近的时间间隔,大约发生于距今600~700 Ma。寄主煌斑岩 的 原生岩浆是金云角闪辉石岩型地幔经较大程度部分熔融而形成,原生岩浆为相似于橄榄金伯 利岩和橄辉玢岩的碱质超基性煌斑岩浆,其经初步分离结晶后形成两个不同的母岩浆,分别 相当于橄榄金伯利岩浆和橄辉玢岩岩浆,两个母岩浆各自具有不同的分离结晶系列,形成不 同的岩石类型。

    Abstract:

    The phlogopiteamphibolepyroxenite xenoliths contained in alkali lam pr ophyre i n Langao County, Shaanxi Province are metasomatized mantle xenoliths.Studies of the characteristics of trace elements and SmNd isotopes indicate that t he phlogopiteamphibolepyroxenitetype mantle is the source of lamprophyre a nd the rich content of highTi and highNa amphibole is the major reason for the form ation of lamprophyre magma with highTi content and lowK/Na ratio. Studies of isotope d ata of lamprophyre indicate that the time when enrichment of mantle metasomatism occurred in the source was close to the emplacement time of the lamprophyre mag ma, which possibly took place in 600~700 Ma BP.. The primary magma of the lamprop hyr e was derived by great degree of partial melting of the mantle represented by ph logop iteamphibolepyroxenite xenoliths, which was similar to the compositions of o liv ine kimberlite or olivine pyroxene porphyrite and generated two parental magmas a fter initial fractional crystallization, one corresponding to olivine kimberlite magma and the other to olivine pyroxene porphyrite magma. The two parental magm as have different trends of fractional crystallization and form different rock t ypes.

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徐学义,夏林圻,夏祖春,黄月华.1999.北大巴山早古生代地幔交代作用与煌斑岩浆的起源和演化[J].地质论评,45(7):689-697,[DOI].
Xu Xueyi, Xia Linqi, Xia Zuchun, Huang Yuehua.1999. The Early Paleozoic Mantle Metasomatism and the Origin and Evolution of Lamprophyric Magma from North Daba Mts.[J]. Geological Review,45(7):689-697.

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