济南辉长岩岩浆演化过程:来自熔体包裹体的证据

发布时间：2018-07-26 18:18

【摘要】：本研究首次报道了早白垩世济南辉长岩中橄榄石斑晶捕获的熔体包裹体的研究结果。济南辉长岩中橄榄石的Fo(60.3~74.6),Mn(2500~3500μg/g),Ni(70~1349μg/g),Fe/Mn比值(61.2~83.5),与源区母岩为纯的橄榄岩形成的熔体结晶出的橄榄石性质不同,可能与源区存在辉石岩的贡献有关。橄榄石中熔体包裹体主量元素具有较大的变化范围。熔体包裹体成分的标准矿物计算(CIPW)表明,MgO10%的熔体包裹体为含有霞石和橄榄石标准矿物分子的硅不饱和熔体,Mg O10%时为含石英标准矿物分子的硅饱和熔体。橄榄石中包裹有辉石和斜长石,说明岩浆演化过程应该处于开放环境。熔体包裹体的(~208Pb/~206Pb)i和(~207Pb/~206Pb)i与MgO具有良好的负相关关系,与SiO_2具有良好的正相关关系,以及熔体包裹体具有较高的SiO_2特征表明岩浆演化过程中可能有下地壳长英质组分的加入。熔体包裹体的Pb同位素落在EMI附近并向EMII延伸,其源区可能有EMI和EMII的贡献,熔体包裹体的主量元素成分说明其源区母岩可能有橄榄岩和辉石岩的贡献。
[Abstract]:This paper reports for the first time the results of the study of olivine porphyry trapped melt inclusions in the early Cretaceous Jinan gabbro. The F _ o (60.3 ~ 74.6) mn (2500 ~ 3500 渭 g / g) and Ni (70 ~ 1349 渭 g / g) Fe / mn ratio (61.2 ~ 83.5) of olivine in Jinan gabbro are different from the peridotite formed from pure peridotite in the source area, which may be related to the contribution of pyroxenite in the source area. The main elements of melt inclusions in olivine have a wide range of variations. The standard mineral calculation of melt inclusions (CIPW) shows that the melt inclusions with MgO10% are silicon-saturated melts containing standard mineral molecules of nepheline and olivine, and MgO10% are silicon-saturated melts containing quartz standard mineral molecules. The olivine contains pyroxene and plagioclase, indicating that the magmatic evolution should be in an open environment. There is a good negative correlation between (208Pb / t 206Pb) I and (207Pb / L 206Pb) I of melt inclusions and a good positive correlation with SiO_2. The higher SiO_2 characteristics of melt inclusions indicate that there may be the addition of lower crust felsic components in magmatic evolution. The Pb isotopes of melt inclusions fall near EMI and extend to EMII, and their source regions may have the contributions of EMI and EMII. The main element compositions of melt inclusions indicate that the parent rocks of the melt inclusions may have the contribution of peridotite and pyroxenite.
【作者单位】：中国科学院广州地球化学研究所同位素地球化学国家重点实验室;中国科学院大学;中国科学院青藏高原研究所;
【基金】：NSFC重大研究计划(91214202,90714001) “百人计划”择优项目联合资助
【分类号】：P588.1

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