新太古代花岗片麻岩中麻粒岩包体磷灰石U-Pb定年对燕辽裂陷槽中元古代长城群底界年龄的制约  

U-Pb dating of apatite from the granulite xenoliths in the Neoarchaean granitic gneiss:constraints on the base age of the Mesoproterozoic Changchengian Group in the Yanliao Aulacogen,northern North China Craton

作　　者：周红英[1,2,3,4] 李怀坤[1,2,3,4] 张健[1,2,3,4] 崔玉荣 李惠民[1,2,3,4] ZHOU Hong-ying;LI Huai-kun;ZHANG Jian;CUI Yu-rong;LI Hui-ming(Tianjin Center,China Geological Survey,Tianjin 300170,China;Key Laboratory of Coast Geo-environment,China Geological Survey,Ministry of Nartural Resources,Tianjin 300170,China;Key Laboratory of Uranium Geology,China Geological Survey,Tianjin 300170,China;North China Center for Geoscience Innovation,China Geological Survey,Tianjin 300170,China)

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]自然资源部中国地质调查局海岸带地质环境重点实验室,天津300170 [3]中国地质调查局铀矿地质重点实验室,天津300170 [4]中国地质调查局华北科技创新中心,天津300170

出　　处：《地质调查与研究》2020年第2期81-88,共8页Geological Survey and Research

基　　金：国家自然科学基金面上项目“铌铁矿微区原位U-Pb同位素定年标准物质的研制(41873066)”;中国地质调查局项目“中国大地构造演化和国际亚洲大地构造图编制(DD20190359)”。

摘　　要：近年来,燕辽裂陷槽中-新元古界年代学研究进展突出,最重要的进展之一是长城群底界年龄的确定,目前基本可以比较准确地将其定为1650 Ma。本文报道了支持此认识的新证据——下伏于长城群常州沟组之下的新太古代片麻岩中的麻粒岩包体的磷灰石U-Pb年龄。通过高精度ID-TIMS定年方法,对天津蓟县下营镇常州村附近长城群常州沟组不整合覆盖的新太古代遵化杂岩中的麻粒岩中磷灰石进行了U-Pb定年,获得了制约“长城群”底界的年龄:207Pb/206Pb表面年龄加权平均值为1666±16 Ma(MSWD=1.8,n=11),不一致线上交点年龄1667±23 Ma(MSWD=1.7,n=11),二者在误差范围内完全一致。该测年成果再一次有力制约了燕辽裂陷槽长城群的底界年龄为1650 Ma。In recent years,remarkable advances have been made in the chronology of the Meso-to Neoproterozoic stratigraphy in the Yanliao Aulacogen within northern North China Craton.One of the most important is the determination of the base age of the Changchengian Group at^1650 Ma.In this paper,we report a new line of evidence to support this base age,i.e.the U-Pb age of apatite from the granulite xenoliths in the Neoarchaean granitic gneisses that unconformably underlying the Changzhougou Formation of the Changhengian Group at the Changzhou village,Xiaying Town,Jixian County,Tianjin.By means of high-precision ID-TIMS dating method,the apatite was analyzed for U-Pb dating,and yielded weighted mean 207Pb/206Pb age of 1666±16 Ma(MSWD=1.8,n=11)and the upper intercept age of 1667±23 Ma respectively(MSWD=1.7,n=11).Both of the ages are completely consistent within the error range.This dating result provides another robust support for the base age of the Changchengian Group at^1650 Ma in the Yanliao Aulacogen,northern North China Craton.

关 键 词：磷灰石 ID-TIMS U-PB定年 长城群底界年龄 燕辽裂陷槽 

分 类 号：P588.3[天文地球—岩石学] P597.3[天文地球—地质学]