现代地质2012，Vol.26Issue(5)：1019-1027,9.
锡林浩特杂岩中斜长角闪岩锆石U-Pb年代学及Hf同位素研究
U-Pb Dating and Hf Isotopic Composition of Zircons in Amphibolite from the Xilinhot Complex
摘要
Abstract
The Xilinhot complex is mainly composed of biotite-plagioclase gneiss, hornblende-plagioclase gneiss, amphibolitic gneiss and granulite with lenticular or vein amphibolite rocks, whose formation and metamorphosed age and petrogenesis have been debating. Accurate determination of its formation and metamorphosed age is of great significance to understanding the formation and evolution of the Hinggan-Mongolia Orogenic Belt. Through zircon SHRIMP U-Pb dating and LA-MC-ICP-MS Hf isotopic analysis on zircons in plagioclase amphibolite from the Xilinhot complex, weighted average value of 206Pb/238U-Pb ages is (316 ±4) Ma, which indicates the Xilinhot complex should not be Precambrian. According to the field observations and petrography, the complex may be a suite of Late Paleozoic volcanic-sedimentary formation which had been subjected to strong deformation and metamorphism. According to the zircon Hf isotopic compositions of plagioclase amphibolite in the Xilinhot complex, εHι(t) value is positive ( + 4. 1 to + 17. 0) , it should have originated from the depleted mantle or crust-mantle mixing source. A mixing calculating of depleted mantle and ancient crustal end-members based on zircon Hf isotopic compositions shows that depleted mantle-derived accretion component was dominant in the plagioclase amphibolite ( after calculation, the crust to mantle mixing ratio is about 1:2). Part of the zircons model ages between 1. 8 Ga and 2. 5 Ga suggests that Paleoproterozoic crustal materials mixed with depleted mantle-derived component during the formation process of the protolith of the plagioclase amphibolite. Comparison of the Hf model age of the plagioclase amphibolite to those in the Hinggan-Mongolia Orogenic Belt shows that crustal component in the plagioclase amphibolite originated from the Hinggan-Mongolia Orogenic Belt. Almost consistent Hf model ages with those of zircon U-Pb dating suggest that the crustal accretion event took place in Late Palaeozoic.关键词
锡林浩特杂岩/SHRIMP U-Pb定年/Hf同位素/兴蒙造山带Key words
Xilinhot complex/ SHRIMP U-Pb dating/ Hf isotopic composition/ Hinggan-Mongolia Orogenic Belt分类
天文与地球科学引用本文复制引用
王善辉,陈岳龙,李大鹏..锡林浩特杂岩中斜长角闪岩锆石U-Pb年代学及Hf同位素研究[J].现代地质,2012,26(5):1019-1027,9.基金项目
国家自然科学基金项目(40973010) （40973010）
国土资源部公益性行业科研专项(201011057-3) （201011057-3）
内蒙古国土资源厅项目(05-6-YS2). （05-6-YS2）
