库鲁克塔格基性岩墙群K-Ar等时年龄测定及其有关问题讨论  

K Ar ISOCHRON DATING OF KULUKTAG MAFIC DYKES, XINJIANG AUTONOMOUS REGION, AND DISCUSSION ON SOME RELATED QUESTIONS

作　　者：刘玉琳[1] 张志诚[1] 郭召杰[1] 黄宝玲[1] 穆志国 

机构地区：[1]北京大学地质学系

出　　处：《高校地质学报》1999年第1期54-58,共5页Geological Journal of China Universities

基　　金：国家"九五"重点科技攻关资助

摘　　要：新疆库鲁克塔格基性岩墙群的四个样品的ＫＡｒ表观年龄为４５５６７３Ｍａ，等时年龄为２８７±１３Ｍａ。这一年龄与近几年报道的沿天山构造带的早二叠世火山岩年龄一致。氩初始值为５０８，在Ｐ型岩浆范围内，结合稀土、微量元素特征。There has been increasing interest in the study of dyke swarms which are related to rifting and continental break up Kuluktag dyke swarms are located in the northeast part of Tarim Basin, Xinjiang, China The dykes, parallel to each other, intruded into the Archaean and early Proterozoic rocks Four samples collected from the dykes are dated with K Ar method The apparent ages are discordant, ranging from 455 to 673 Ma Using the Ludwing's ISOPLOT, an isochron age of 287±13 Ma was obtained with a correlation cotfficicent of 0 9850, This age is concordant with the ages of volcanic rocks along the Tianshan Mt structure zone dated around 280 Ma The K Ar isochron method has some advantage for dating mafic dykes: (1) These rocks are often fresh and slightly affected by alteration; (2) The closure temperature of mafic rocks for argon is high; (3) The measurement precision of mass spectrometer is much higher than it was before, so that low K samples can be well measured; The potassium abundance of mafic dykes is about 0 5 1 5% and suitable for K Ar dating; (4) The whole rock method is used, so that the tough work of selecting monomineral fraction is not necessary Moreover, the initial argon can be eliminated by this method, but the atmospheric argon must be removed in the experimental process Igneous rocks originated from different sources have different initial argon ratios The initial argon ratio for Kuluktag dykes is 508, belonging to mantle plume type according to Kaneoka and Takaoka (1985) We infer that the magma of the dykes originated from “enriched mantle” The REE and trace elements features of the dykes are also typical of “enriched mantle” and are in good agreement with those of basalts related to plume

关 键 词：库鲁克塔格 基性岩墙群 等时年龄 钾-氩 

分 类 号：P588.124[天文地球—岩石学]