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碱性玄武质岩浆起源于上地幔或者更深处,是了解地幔物质组成的重要窗户.熔体包裹体是主矿物在结晶过程中被捕获的,不易受到后期地质作用的影响,最早结晶的矿物橄榄石所捕获的熔体可以有效地记录原始岩浆的物理化学信息.在此次研究中,利用激光拉曼光谱(LA-Raman)对华北克拉通东部山东杨庄新生代碱性玄武岩橄榄石中,73个熔体包裹体内的气体组分进行了原位分析,并利用激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)对寄主橄榄石的主微量元素进行了测试.结果显示,熔体包裹体中含有高含量的CH4等烃类,而且含有石墨和碳酸盐等矿物,这为CH4在上地幔高温高压条件下能够稳定存在提供了直接证据,也表明中国东部地幔存在低氧逸度的区域.橄榄石斑晶具有高Ni,高Fe/Mn比值的特点,指示源区可能存在辉石岩组分.结合其他地球化学和地球物理资料,西太平洋板块对中国东部岩石圈地幔的俯冲效应可以很好地解释玄武岩源区存在辉石岩组分和CH4富集特征的现象.CH4是深部碳的重要存在形式之一,太平洋板块俯冲作用可能是中国东部深部碳循环重要的动力学机制.
Basic basaltic magma originates in the upper mantle or deeper and is an important window for understanding mantle material composition. Melt inclusions are the main minerals that are captured during the crystallization and are not susceptible to post-geological effects. The earliest crystallized mineral olives The melt captured by the stone can effectively record the physicochemical information of the original magma.In this study, we used laser Raman spectroscopy (LA-Raman) to study the Cenozoic alkaline basaltic olivine in Yangzhuang, eastern Shandong Craton, The gas components in 73 melt inclusions were analyzed in situ and the major and trace elements of the host olivine were tested by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results showed that the melt inclusions The body contains high levels of CH4 and other hydrocarbons, and contains minerals such as graphite and carbonate, which provide direct evidence that CH4 can stably exist under the conditions of high temperature and high pressure in the upper mantle. It also shows that there is low oxygen fugacity in the eastern mantle of China Region.The peridotite phenocrysts are characterized by high Ni and high Fe / Mn ratios, indicating that pyroxene components may be present in the source regions.Combining with other geochemical and geophysical data, the western Pacific plate alignment The subduction effect of the eastern lithospheric mantle can well explain the pyroxenite component and CH4 enrichment characteristics in the basalt source area.CH4 is one of the important forms of deep carbon and the subduction of the Pacific plate may be the deep carbon in the eastern part of China Cycle important kinetic mechanisms.