福建永安湍石楼前组地层特征及年代依据  

Stratigraphic Characteristics and Dating Basis of Tuanshi Louqian Formation in Yongan City,Fujian Province

作　　者：赵关健[1] Zhao Guanjian(The Western Geological Party of Fujian,Sanming,365001)

机构地区：[1]福建省闽西地质大队,三明365001

出　　处：《福建地质》2024年第2期100-106,共7页Geology of Fujian

摘　　要：在永安南部湍石一带发现一套变质火山碎屑岩,岩石总体变形较弱、变质较浅,原岩结构、构造多有保留。主要岩石类型为变质英安质晶屑凝灰岩。火山喷发作用表现为空落相,呈现较强的火山活动特征。研究区楼前组与长汀张地楼前组剖面对比,区内层位仅相当于张地楼前组下段。LA-ICP-MS锆石U-Pb同位素测年样中的锆石CL图像晶形发育好,韵律环带清晰,且Th/U比值大,为0.58~4.85,均为岩浆锆石的特点。锆石U-Pb谐和年龄为(754.8±3.3)Ma,代表了变质火山岩的成岩年龄,说明了楼前组形成地质时代为南华纪。A set of metamorphic pyroclastic rocks has been found in the Tuanshi area in the south of Yongan.The deformation of the rocks is weak and the metamorphism is shallow.The original rock structure and structure are mostly preserved.The main rock type is metamorphic crystalline tuff.Volcanic eruption is empty phase,showing strong volcanic activity characteristics.The profile comparison between the Louqian Formation of the study area and the Changting Zhangdi Louqian Formation shows that the stratification in the area is only equivalent to the lower part of the Zhangdi Louqian Formation.The LA-ICP-MS zircon U-Pb isotope dating sample shows that the crystal shape of the zircon CL image is well developed and the rhythm zone is clear.The Th/U ratio is high,ranging from 0.58 to 4.85,which is characteristic of magmatic zircons.The U-Pb age of the zircon is(754.8±3.3)Ma,which represents the diagenetic age of the metamorphic volcanic rocks,indicating that the geological age of the Louqian formation is Nanhua Period.

关 键 词：年代依据 地层特征 湍石楼前组 福建永安 

分 类 号：P588.14[天文地球—岩石学]