0．1 GPa块状榴辉岩脱水部分熔融:局部熔融体系和温度的影响

Dehydration Partial Melting Experiment on Solid Eclogite at 0.1 GPa: The Influence of Localized Melting System and Temperature

选取了湖北英山东冲河含有含水矿物黑云母和角闪石的退变质榴辉岩块状样品,在0．1 GPa的恒压下,分别进行了 750、800、850、900℃四个温阶、恒温加热4 h的开放体系的脱水部分熔融实验．熔融从含水矿物的脱水暗化开始,850℃时出现玻璃质熔体．镜下观察显示,熔体主要分布在后成合晶边界、熔融程度最高的样品顶端、石英颗粒边界及裂隙内部这3 个局部熔融体系内．受局部体系内部物质组成的控制,同一温阶、不同体系内的熔体成分变化很大,呈基性、中性和酸性．随着温度的升高,同一体系内的熔体成分均向酸性方向演化．该实验结果表明,恒压下局部熔融体系内物质组成的不同和温度的变化是影响熔体成分的2个重要因素,这为理解榴辉岩块状样品的脱水部分熔融行为及与其他基性变质岩类的熔融行为进行对比提供了实验依据．

This study presents the open and dehydration melting experiments on solid retrograde eclogite from Dongchonghe in Yingshan, Hubei Province. The sample contains hydraous hornblende and biotite. The experiments are at 0. 1 GPa and 750, 800, 850 and 900 ℃. The duration time for heating is 4 h. The initial melting commences from dehydration melting of hydrous minerals, and melts appear at 850 ℃. Melts are mainly in the three localized melting systems： they are the grain boundaries of symplectite, one side of sample on which is higher melting degree, and the grain boundaries and cracks of quartz. Because of different compositions of minerals in different localized melting systems, chemical compositions of melts range from basic to acid at the same temperature. And it runs to acid at the same localized melting system as increase of tem- perature. This study implies, at the same pressure, temperature and different compositions of minerals in different localized melting systems are the two main factors that influence compositions of melts. And it provides experimental evidences to un- derstand dehydration melting behavior of eclogite and to contrast with other basic metamorphic rocks.