摘要
本文在对闽北前寒武纪基底岩石进行较详细研究的基础上,以单颗粒锆石U-Pb稀释法为主,配合角闪石^(40)Ar/^(39)Ar法和全岩Sm-Nd法,获得了麻源群和马面山群及其有关岩石的大量年代学信息。研究表明,闽浙变质基底于1850Ma左右发生了强烈的岩浆构造热事件,导致花岗质岩浆的侵位,这一年龄可做为麻源群岩石的年龄上限。马面山群的年龄为1100—1438(?)Ma,变质年龄略小于1100Ma。测年结果表明,闽北变质基底在774—870Ma和426—458Ma时曾发生过两次叠加构造热事件,表现为岩石的混合岩化作用和/或变形作用以及岩浆活动等基底岩石的改造作用,这两个时期分别相当于晋宁运动和加里东运动。火山岩中2142—2589Ma的碎屑锆石年龄表明,本区或邻近地区有更老的早元古代甚至太古宙基底岩石,这对于认识中国大陆东南缘基底具有重要意义。
This paper reports on the geochronological study of Precambrian metamorphic basement in Northern Fujian, in which the single zircon U-Pb dilution method, hornblende ^(40)Ar/^(39)Ar and whole rock Sm-Nd methods are used and many significant geochronological data are gained from the Mayuan Group and Mamianshan Group (Precambrian). It is inferred that the intensive magma tectonothermal events occurred for 1 850 Ma in the Fujian-Zhejiang metamorphic basement, which result in the emplacement of granitic magma. The age 1 850 Ma can be defined as the upper limite age of the Mayuan Group. The age of Mamianshan Group is 1100—1430 (?) Ma and its metamorphic age is less than 1100Ma. During 774—870 Ma and 426—458 Ma (equivalent to Jinning Movement and Caledonian Movement, respectively)there occurred the two superimposed tectonothermal events in the Northern Fujian metamorphic basement, which show up the reformation of basement rocks by the migatization and/or deformation and magmatic activity. The age of 2142—2589 Ma for the elastic zircon from the volcanic rocks indicates that there possibly exist an early Proterozoic or Archean basement in the surveyed area and adjacent region, which is of important significance for recognizing the basement of southeastern continental margin in China.
出处
《福建地质》
1993年第1期17-32,共16页
Geology of Fujian
基金
地质行业定向基金
部分工作为自然科学基金
关键词
地质年代学
锆石
前寒武纪
基底
dating of zircon, geochronology, Northern Fujian, Precambrian basement
