【摘要】 通过野外地质调查及室内综合研究,进一步阐明浙江遂昌柘岱口地区碎斑熔岩地质特征及成因。宏观上划分了碎斑熔岩相带,查明了碎斑熔岩时空分布及与围岩的接触关系;微观上通过岩石地球化学、同位素年代学及锆石饱和温度计算等方法研究该碎斑熔岩。研究区碎斑熔岩受控于柘岱口—湖山NE向大型火山构造洼地复活型破火山,具有侵出—溢流特点,为复合穹丘状地质体。岩浆演化在时空上具有连续性,具有分异岩浆"溢流—侵出—侵入"过程。岩石具有典型的连续不等粒碎斑结构和珠边结构,富碱,K2O+Na2O为8.54%~9.25%,A/CNK为0.88~1.04,为准铝质钾玄岩系列,富集Nb、Ta、Zr、Hf等高场强元素和Rb、Sr、Ba、Th等大离子亲石元素。岩石成岩温度为803℃~884℃,具有高温浅成特点。全岩Rb-Sr等时线年龄为123 Ma,为早白垩世中期九里坪期岩浆活动的产物,是壳—幔混合I型碎斑熔岩,属于活动大陆边缘靠板内的构造环境。更多还原

【Abstract】 This study carried out a detailed analysis of porphyroclastic lavas to understand its geological characteristics and origin based on field survey and comprehensive research.Through study of microscopic lithofacies,lithogeochemistry,isotopic chronology and zircon saturation temperature,porphyroclastic lava facies belt was defined at macro level,and spatial-temporal distribution of porphyroclastic lavas and its contact relationship with the surrounding rock was ascertained.The porphyroclastic lavas in the study area are controlled by a revived caldera in the large-scale NE-trending volcanic structural depression in Zhedaikou-Hushan and characterized by extrusion and effusion,suggesting a composite dome.Magma evolution of the porphyroclastic lavas shows a certain continuation spatially and temporally,indicating a magmatic differentiation process from effusion to extrusion to intrusion.Porphyroclastic lavas with typical porphyroclastic structure and pearl-edge texture are enriched in HFSEs（Nb,Ta,Zr,Hf）and LILEs（Rb,Sr,Ba,Th）,and also rich in alkali（K₂O+Na₂O=8.54%⁹.25%）,A/CNK=0.88¹.04,suggesting the lavas belong to a metaluminous shoshonite series.The diagenetic temperatures of the lavas range from 803℃to884 ℃,indicative of high temperature hypabyssal.A Rb-Sr isochron age of 123 Ma suggests that the lavas were the result of Early Cretaceous magmatic activity.Out study shows that the porphyroclastic lavas and associated granite are co-magmatic I-type rocks derived from crust-mantle mixing source,and generated in an active continental margin close to intraplate.更多还原