摘要
本文主要报道内蒙古中部白乃庙地区侵入古生界徐尼乌苏组沉积地层中的石英二长闪长岩脉的锆石LA-ICP-MS法U-Pb定年结果。测试结果显示大量锆石为捕获锆石并获得了从古元古代1.9Ga到中元古代1.26Ga左右的谐和年龄。其中中元古代年龄可划分为1.7Ga,1.6～1.47Ga和1.26Ga等三个不同阶段;前两阶段年龄分别与华北克拉通化之后初始裂谷和非造山岩浆作用以及白云鄂博裂谷中火成碳酸盐的侵位时代相对应;而1.26Ga的年龄则与全球格林威尔构造-岩浆热事件时代相吻合。结果表明华北北缘存在中元古1.26Ga左右岩浆热事件。该结果为进一步认识华北北缘地壳演化及华北板块是否参与过罗迪尼亚超大陆演化提供了重要线索。
For LA-ICP-MS U-Pb dating, zircons are separated from a quartz monzodiorite dike that intruded in the Paleozoic sedimentary strata of the Xuniwusu Formation in the Bainaimiao area, Inner Mongolia. All zircon grains show clear internal structure of magmatic rhythmical zones by CL imagines, implying their magmatic genesis. As a result, zircon grains with various concordant U-Pb ages scattering between 1.9 and 1.26Ga, are suggest to be captured. The Meso-Proterozoic U-Pb ages recorded by the captured zircon grains can be grouped into three stages of 1.7, 1.6～1.47, and 1.26Ga, respectively. The former two stages are consistent with the time of initial rifting event taken place after the assemblagment of the North China craton ( NCC) and an anorogenic magmatism of igneous carbonate in Bayan Obo rift, respectively. 7 out of 12 captured zircons yield U-Pb ages clot around 1. 26Ga with ^(207)Pb/^(206)Pb weighted mean age of 1263±8Ma which is equivalent to the time of the globle Grenvill tectono-thermal event. The results of zircon U-Pb dating show that the 1. 26Ga tectono-thermal event took place in northern margin of the NCC, which is significant for further study on crustal evolution of the NCC and provide an important clue for whether the NCC has been participated in the amalgmation of Rodinia.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第6期1512-1518,共7页
Acta Petrologica Sinica
基金
国家自然基金项目(40772122)
国土资源部地调局华北地区基础地质调查及数据更新项目(1212010811001)资助.
