地质通报2013，Vol.32Issue(2)：327-340,14.
内蒙古锡林浩特地块中元古代花岗片麻岩的锆石U-Pb年龄和Hf同位素特征
Zircon U-Pb dating and Hf isotopic compositions of the Mesoporterozoic granitic gneiss in Xilinhot Block, Inner Mongolia
摘要
Abstract
The Xilinhaote block is distributed in the middle of the Hinggan-Mongolian orogenk belt in Inner Mongolia. Its meta-morphic basement was previously referred as part of "Baoyintu Rock Group", which is mainly composed of banded gneissic granites. This study shows that these banded gneissic granites are actually deformed granites. Two samples of banded gneissic granites were dated by LA-MC-ICP-MS zircon U～Pb technique. The zircons from these samples display clear oscillatory growth zoning in CL images, suggesting that they are of magmatic origin. The meta-granite (10TW53) from Sunitezuoqi area has a weighted mean 207Pb/206Pb age of 1516Ma±31Ma from the zircon cores and a weighted mean 206Pb/238U age of 451Ma±16Ma from the overgrown metamor-phic zircon rims. The zircon cores yielded εHf(t)values ranging from +2.8 to +8.5, with tDM model ages of 1.70～1.84Ga, suggesting their depleted mande origin; the zircon rims have εHf(t) vakies ranging from -6.5 to -12.7, with tDM model ages of 1.33～1.59Ga and t2DM model ages of 1.87～2.26Ga, which are similar to values of zircon nms. Another banded gneissic granite sample (10TW54) from this area displays a weighted mean 207Pb/206Pb age of 1390Ma±17Ma from the zircon cores. They have positive εHf(t) values ranging from +0.4 to +11.9, suggesting a depleted mantle source and a juvenile crustal forming event. It is suggested that the Xilinhot block is a microcontinent with Precambrian basement and it underwent crustal growth in the Mesoporterozoic period and metamorphic reformation in the Caledonian period.关键词
花岗片麻岩/锆石Hf同位素/LA-MC-ICP-MS锆石U-Pb定年/中元古代/锡林浩特地块Key words
granitic gneiss/ zircon Hf isotope/ LA-MC-ICP-MS zircon U-Pb dating/ Mesoporterozoic/ Xilinhot block/ Inner Mongolia分类
天文与地球科学引用本文复制引用
孙立新,任邦方,赵凤清,谷永昌,李艳峰,刘卉..内蒙古锡林浩特地块中元古代花岗片麻岩的锆石U-Pb年龄和Hf同位素特征[J].地质通报,2013,32(2):327-340,14.基金项目
中国地质调查局项目《兴蒙造山带中古老陆块性质与成矿背景研究》(编号:1212011085478)、《兴蒙造山带基本构造格局综合调查和研究》(编号:1212011085476) （编号:1212011085478）
