华北克拉通大青山地区古元古代晚期钾长伟晶岩脉SHRIMP锆石U-Pb定年和Hf同位素组成.pdf

第31卷第6期
地质通报
Vo1.31.No6
2012年6月
GEOLOGICAL BULLETIN OF CHINA
「un.,2012
基础地质
华北克拉通大青山地区古元古代晚期钾长伟晶岩脉
SHIRMIP锆石U-Pb定年和Hf同位素组成
马铭株',万渝生1,徐伸元2,刘守偈,颉颃强,董春艳1,刘敦
MA Ming-zhu, WAN Yu-sheng, XU Zhong-yuan, LIU Shou-jie
Xie Hang-qiang, DONG Chun-yan, LIU Dun-yi
1.中国地质科学院地质研究所北京离子探针中心,北京100037;2.吉林大学地球科学学院,吉林长春130061
1. Bejing SHRTP Cener, Institute of Geology, Chinese Academy of Geological Sciences, Bejjing 100037, China
2. College of Earth Sciences, lin University, Changchun 130061, Jilin, China
摘要:报道了华北克拉通大青山地区哈德门沟钾长伟晶岩脉的锆石 SHRIMP UーPb年龄和Hf同位康组成。钾长伟晶岩脉广泛
分布,不定向切割早期地质体。部分钾长石具出溶结构,利用三元长石温度计获得其形成温度为750~800℃。锆石粒度粗大,大
多異等轴状,锆石的阴极发图像中部具板状环带或扇形结构,边部出现振荡环带。 SHIRIMP石UーPb定年,数据点位于谐和
线上,Pb/2Pb年龄加权平均值为1841Mat9Ma(MSWD=1.5)。错石的siり和twa(Hf分别为-10.4~-6.6和2498~2648Ma。结
合其它资料,可得出如下结论:①大青山地区至少在1.84Ga巳进入伸展体制;②钾长伟晶岩脉形成于高温条件;③钾长伟晶岩
脉的物质来自该区早前寒武纪变质甚底。
关键词:钾长伟晶岩脉; SHRIMP错石U-Pb定年;Hf同位素;古元古代;大青山地区
中图分类号:P534.3;P58.131;P597.3文献标志码:A文章编号:1671-2552(2012)06-0825-09
Ma M Z, an Y S, Xu Z Y, Liu S J Xie E Q, Dong C Y, Liu D Y. Late Paleoproterozoic K-feldspar pegmatite veins in
Dagin shan area, North China Craton: SHRIMP age and Hf composition of zircons. Geological Bulletin of China, 2012, 31
(6):825-833
Abstract: This paper reports SHRLMP age and Hf isotope composition of zircons from a K-feldspar pegmatite vein in the Wulanbu-
lang Hademengou area of southern Daqing Mountain, North China Craton. Pegmatite veins widespread in this area cut early Precambri
an geological bodies. Some K-feldspar grains show exsolution structures with formation temperatures from 750 to 800C in terms of
ternary feldspar geothermometry. The zircons are large and mostly equant. In cathodoluminescence images, they show banded or sector
zoning in the center of the crystal and oscillatory zoning in the outer domain. Data are distributed on concordia with a weighted mean
Pb age of 1841+9 Ma(/ W1=1. 5). They have g ft)and tmw(Hf values ranging from-10.4to-66 and 2498 Ma to 2648 Ma,
respectively. Combined with data available, some conclusions can be drawn as follows: O the tectonic environment changed from com-
pression to extension at least before 1.84 Ga in the Daqing Mountain area; ) the K-feldspar pegmatite veins were formed under the con-
dition of high temperature; ) the K-feldspar pegmatite veins were derived from the early Precambrian basement.
Key words: K-feldspar pegmatite vein; SHRIMP zircon U-pb dating; Hf isotope; Palaeoproterozoic; Daqing Mountain area
收稿日期:2011-11-15;修订日期:2012-04
资助项目:中地质调查局重点项目《华北克拉通西部孔兹岩带古元古代构造热事件及意义》(编号:12120111062)、《华北克拉通太古
宙早期古老陆壳物质的寻找、鉴别和研究(编号:1212011120151)、《中国地质构造区划与区域地质调査综合集成》(编号
1212010811033)和国家自然科学基金项日《华北克拉通西部孔兹岩带大青山地区早前寒武纪某些关键地质问题: SAIRIMIP
年代学和地球化学研究》(批准号:41002062)
作者简介:马铭株(1986-),女,在读博士,地球化学专业。Eーmai:mingzhu_1015@163.com
通讯作者:万渝生(1958-),男,研究员,从事年代学和前寒武纪地质研究。E-mai:wansheng@bjshrimp.cn