琼北火山岩激光^(40)Ar/^(39)Ar定年研究  

High-precision Laser ^(40)Ar/^(39)Ar dating of Qiongbei volcanic rocks

作　　者：洒骁[1,2] 季建清[1] 周晶[1] 

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [2]中国地质大学,北京100083

出　　处：《岩石学报》2013年第8期2789-2795,共7页Acta Petrologica Sinica

基　　金：中国地质调查局地质调查项目(12120113013700)资助

摘　　要：新生代以来,雷琼地区多次、大量地喷发了一系列火山岩。前人主要基于K-Ar法对此划分了期次。本文采用激光40Ar/39Ar年代学方法,对琼北火山岩区进行了精细定年研究。低本底激光40Ar/39Ar法能够对低钾含量,极少量样品(毫克级)进行精细测定,非常适合极年轻火山岩的定年工作。结果显示的火山岩激光40Ar/39Ar法高质量数据表明琼北火山喷发活动时限跨越1.3～0.052Ma。在比较了表观年龄与等时线年龄差异之后,本文给出了年龄推荐值。正如测试数据所显示,本地区新生代火山岩普遍存在40Ar和36Ar过剩的问题,此时只有等时线年龄才代表喷发的真实年龄。Since Late Cenozoic era,volcanic rocks have been frequently and massively erupted in the Leiqiong area. Those volcanic rocks,on the basis of K-Ar dating method,are divided to several volcanic phases. In this paper,laser 40Ar/39Ar dating method is used to test and calculate the accurate time of volcanic rocks in Qiongbei area. The high quality data result by laser 40Ar/39Ar dating method shows that the time spans of eruption of Qiongbei volcanoes are around 1.3～0.052Ma. Considering the differences between the apparent ages and the isochron ages,a series of ages are recommended. As shown as the data,there are widespread inherited 40Ar＊ and 36 Ar excess in the Cenozoic volcanic rocks,then the isochorn ages are more recommended to be the real ages of the eruptions.

关 键 词：40Ar 39Ar年代学 琼北火山岩 Ar丢失与过剩 

分 类 号：P597.3[天文地球—地球化学]