内蒙古狼人人南地区枕状玄武岩LA—ICP—MS锆石U—Pb年龄及意义.pdf

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1、第32卷第2-3期地质通报Vo1．32，Nos．2~32013年3月GEOLOGICALBULLETINoFCHINAMar．，2013内蒙古狼山西南地区枕状玄武岩LA—ICP—MS锆石U—Pb年龄及意义张进，李锦轶，刘建峰，李岩峰2，曲军峰，张义平1ZHANGJin，LIJin—yi，LIUJian—Feng，LIYan—feng，QUJun—Feng，ZHANGYi—ping1．中国地质科学院地质研究所，北京100037：2．中国地震搜救中心．北京1000491．InstituteofGeology，ChineseAcademyofGeologicalSciences，Beijing，10

2、0037，China；2．ChinaCenterforEarthquakeDisasterEmergency，Beijing，100049，China摘要：报道了新近在华北北缘西段狼山地区发现的枕状玄武岩的初步定年工作。前人将其时代定为早古生代。对选自玄武岩的32颗锆石进行了LA—IcP—MSU—Pb定年结果表明，玄武岩的锆石大量为捕获基底的锆石，其年龄和锆石内部结构复杂多样。根据锆石内部特征将其划分为4类，其中的板状锆石被定为玄武岩的自生锆石，年龄为晚古生代末期一早三叠世早期。其余均为来自阿拉善地块基底的锆石，主要为古元古代一新太古代和古生代锆石。狼山晚古生代末期的玄武岩可能产自古亚洲洋封闭

3、后由于岩石圈拆沉导致的伸展环境，该期伸展贯穿华北北缘直至阿拉善地块，暗示华北板块与阿拉善地块至少在晚古生代之前就已经拼合在一起了。关键词：狼山：枕状熔岩；古亚洲洋；锆石；LA-ICP—MS中图分类号：P588．145文献标志码：A文章编号：1671-2552(2013)02／03—0287—10ZhangJ，LiJY，LinJF，LiuJF，QuJF，ZhangYP．2013．LA-ICP-MSU-Pbagesofpillowlavabasal~insouthwesternLangshan，InnerMongoliaandtheirimplication．GeologicalBulletino

4、fChina,2013，32(2／3)：287-296Abstract：RecentfoundpillowlavabasaltsinthesouthwesternLangshananditspreliminarydatinghasbeenreportedhere．PrevioussurveyhadassigneditsageattheEarlyPaleozoic．32zirconsfrompillowlavabas~tshavebeendatedusingLA—ICP—MS．Mostzirconsfrombasaltsarecapturedfromthebasement，thedistribu

5、tionofagesandinternalstructuresofwhicharecomplicated．Fourgroupsofzirconshavebeendistinguishedbytheirinternalstructures．Amongthemthetabularzirconshavebeenbelievedastheautogeneficzir-consofpillowlavabasalts，theagesofthesezirconsrangefromtheendofPermiantotheEarlyTriassic．TherestzircoDsinthesamplesareal

6、lfromtheAlashanbasement，amongwhichPaleoprocerozoicandNewarchaeozoiczirconsandPaleozoiczirconsaremost．ThelatestLatePermianLangshanbasaksmaydevelopedintheextensionaltectonicsresultingfromthedelaminafionofthelithosphereaftertheclosureofthePaleoasianOcean，theextensionofthisperiodoccurredalongthewholenor

7、thmarginoftheNorthChinaHatein—cludingtheAlashanblock，whichmeansthattheMashanblockjointedwiththeNorthChinaPlateatleastbeforetheLatePaleozoic．Keywords：Langshan；pillowlava；PaleoasianOcean；zircon；LA——ICP—