新疆北部基性岩脉^(40)Ar/^(39)Ar年代学研究  

^(40)Ar/^(39)Ar Geochronology of mafic dykes in north Xinjiang

作　　者：周晶[1] 季建清[1] 韩宝福[1] 马芳[1] 龚俊峰[1] 徐芹芹[1] 郭召杰[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

出　　处：《岩石学报》2008年第5期997-1010,共14页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划项目<中亚造山带大陆动力学过程与成矿作用>(编号:2007CB411300);国家重点基础研究发展计划项目<中国西部中亚型造山与成矿>(编号:2001CB409802)之研究成果

摘　　要：晚古生代以来,新疆北部地区侵入了一系列的基性岩脉,成为了解该地区地壳生长过程的重要窗口。本文采用激光^(40)Ar/^(39)Ar 年代学方法,对整个北疆地区出露的基性岩脉进行了精细年代学研究。从数据特征上分析,低本底激光^(40)Ar/^(39)Ar方法能对低钾含量、极少量样品(0.1mg～5mg)进行精细定年,所以非常适合进行基性岩脉的精细定年。本文展示的基性岩脉激光^(40)Ar/^(39)Ar 方法的高质量数据显示新疆北部基性岩脉群的活动时限跨越332～174Ma,为石炭纪—侏罗纪。由数据分析可以看出,新疆北部基性岩脉群在时间上,呈现脉动式侵位特征,在332～174Ma 之间,有多达6～7次脉动式活动,时间间隔大致为20～30Ma。从基性岩脉所揭示的大地构造含义来分析,新疆北部地区从石炭纪到侏罗纪处在一个相似的地壳演化阶段,为一个陆壳垂向生长、区域构造应力场显示拉张的构造环境,并在时间、空间上具有相对统一的特征。A series of mafic dykes, intruded since Late Paleozoic, give a good way to understand the process of crustal growth in north Xinjiang. Using laser ^40Ar/^39 dating method, we have got the accurate dating results of mafic dykes from north Xinjiang. Based on the characteristic of dating data, we draw the conclusion that laser ^40Ar/^39Ar dating is a suitable method to get precise age for a small amount of samples （0.1 mg- 5mg） with low potassium content. Therefore, the difficulty of dating mafic dykes can be solved with this method. The high quality laser ^40Ar/^39 Ar dating results demonstrate that the mafic dykes from north Xinjiang intruded from Carboniferous to Jurassic （332 - 174Ma）. The intrusive mafic dykes seems to be impulsive intrusion. There are nearly 6 -7 times impulsive events with the interval around 20 - 30Ma. It shows a similar crustal evolution process from Carboniferous to Jurassic period in north Xinjiang. During this period, the region was in a vertical growth of continental crust, and the regional tectonic stress field shows an extension tectonic setting. North Xinjiang is the coherent tectonic unit either on time or space scale.

关 键 词：基性岩脉 ^40AR/^39AR年代学 地壳生长 新疆北部 

分 类 号：P597.3[天文地球—地球化学] P588.134[天文地球—地质学]