摘要
锆石成因研究是判断锆石年龄意义的基础。本文以鲁西隆起区莱芜辉绿岩岩墙的锆石U_PbSHRIMP年代学研究为例,从锆石成因入手探讨基性岩墙群的锆石地质年代学分析中出现的一些问题。本区基性岩墙内存在两类锆石,一种是从围岩捕获的残余锆石,其谐和年龄为2 5 37±16Ma ;另一种为岩墙原生的岩浆锆石,谐和年龄为1139±2 5Ma和115 7±18Ma ,说明岩墙侵位时代约为中元古代。基性岩墙内原生岩浆锆石很少,因此,要谨慎分析锆石的成因类型和年龄谱系,不能简单地以大多数数据的平均年龄为准,而应该以地层接触关系和岩浆岩交切关系为基本证据,结合各种同位素绝对年龄的分析来确定基性岩墙的侵位时代。
Based on a study of SHRIMP U-Pb chronology of zircons from diabase dykes in Laiwu area of western Shandong, this paper deals with zircon chronology of mafic dyke swarms. Two types of zircons are distinguished: zircons entrapped from the host rock with the concordia age of 2?537±16 Ma, and original igneous zircons with the concordia ages of 1?139±25 Ma and 1?157±18 Ma. The data suggest that the mafic dyke swarms in Laiwu area were emplaced during Mesoproterozoic. Few original zircons are developed in mafic dykes, so the origin and age populations of zircons should be analyzed with care. It is not proper to regard the average of most values as the real age of dyke emplacement. The field relationship between overlying strata and dyke swarms and the intersecting relations of the intrusions should be studied in detail.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2005年第3期179-185,共7页
Acta Petrologica et Mineralogica
基金
国家自然科学基金资助项目 (4 0 172 0 66
40 3 14 14 )
