Based on drilling data,field outcrops,geochemistry analysis of rock samples and the research achievement of Sanshui basin in recent years,the volcanic rock of Huayong group,including the lithology characters and eruption cycle are discussed.The volcanic rock in Huayong group mainly consists of rhyolite,trachyte and basalt interbedded,displaying bimodal features in chemical composition.Four eruption sub-cycles were recognized according to the variation of lithology during the deposition period.Each cycle begins with rhyolite and trachyte eruption then ends up with basalt eruption.The first and second sub-cycles are mainly central eruption while the third and fourth sub-cycles are fissure overflow eruption.Besides,the volcanic activity gradually weakened.With the comparison of volcanics distribution characteristics nearby,the volcanic rocks in Huayong group,Sanshui basin are continental rift type rocks developing with a tension environment,as well as a significant record during the early cracking period of South China sea.%以区域钻井资料、野外露头勘查、岩石样品地球化学分析为依据,结合近年来三水盆地火成岩研究成果,细致刻画盆地内华涌组火山岩的岩性、时空分布以及喷发特征.华涌组火山岩以流纹岩、粗面岩与玄武岩互层为主,呈典型双峰式组合.根据岩性变化特征在华涌组沉积期内识别出四个火山喷发亚旋回,各旋回均由酸性流纹岩或粗面岩喷发开始,以基性玄武岩喷发结束.其中第一、二亚旋回以中心式喷发为主;第三、四亚旋回以裂隙溢流喷发方式为主,火山活动逐渐由强减弱.通过与周边地区区火山岩分布特征的对比研究,可以确定三水盆地华涌组火山岩是在拉张背景下发育的大陆裂谷型火山岩,是南海开裂初期的重要物质记录.
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