太行山北段王安镇杂岩体中酸性岩锆石SHRIMP U-Pb定年、Hf同位素组成及其地质意义  

SHRIMP zircon U-Pb ages and Hf isotopes of the intermediate-acidic rocks of Wanganzhen complex in northern part of Taihang Mountains and their geological implications

作　　者：申志超[1,2] 侯增谦[1] 于枫[2] 陈志宽 李秋耘[1] 马国玺 葛峰 王志敏 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学,北京100083 [3]河北省保定地质工程勘察院,保定071051

出　　处：《岩石学报》2015年第5期1409-1420,共12页Acta Petrologica Sinica

基　　金：国家重点基础发展研究计划973项目(2011CB403100)资助

摘　　要：太行山北段王安镇杂岩体花岗闪长岩、二长花岗岩、髫髻山组火山岩-安山岩精细SHRIMP U-Pb定年和Hf同位素地球化学研究表明:花岗闪长岩体形成于135.7±1.3Ma,二长花岗岩体形成于133.7±1.1Ma,安山岩形成于138.89±0.9Ma,与杂岩体内基性侵入岩(138Ma)具有相似的形成年龄。花岗闪长岩的锆石εHf(t)值为-21.81^-16.09,相应tDMC为2.2~2.6Ga;二长花岗εHf(t)值为-20.50^-16.31,相应tDMC为2.2~2.5Ga,与杂岩体内基性岩体具有极为相似的Hf同位素特征εHf(t)=-22.8^-15.3。杂岩体中酸性岩类岩石成因可解释为:富集地幔(EMI)部分熔融形成的玄武质岩浆遭受一定程度的地壳混染以及之后的分离结晶作用对形成王安镇杂岩体中酸性岩类发挥着关键作用。与华北克拉通内部其他地区相同,晚侏罗-早白垩世北太行地区处于软流圈上涌的岩石圈伸展构造背景。The geochronologucal and geochemical data of the Mesozoic intermediate-acidic rocks from the northern Taihang Mountains provide an insight into the understanding of the nature of the Mesozoic lithospheric mantle beneath the North China interior.The Tiaojishan Formation volcanic-andesite,granodiorite,and monzonitic granite,the representative for the Wanganzhen complex,yield the SHRIMP zircon U-Pb ages of 138. 89 ± 0. 9Ma,135. 7 ± 1. 3Ma,and 133. 7 ± 1. 1Ma,respectively. The ages are consistent with the mafic rocks（ 138Ma） of Wanganzhen complex. The granodiorites have εHf（ t） values of- 21. 81 ～- 16. 09,corresponding to tDMCmodel ages of 2. 2 ～ 2. 6Ga; the monzonitic granites have εHf（ t） values of- 20. 50 ～- 16. 31,corresponding to tDMCmodel ages of 2. 2 ～ 2. 5Ga,which are rather similar with those of mafic rocks with εHf（ t） values of- 22. 8 ～- 15. 3. The origin of the intermediate-acidic rocks could be summarized as follows： the basaltic melts originated from the melting of an enriched subcontinental lithospheric mantle（ EMI） beneath the North China Craton underwent lower crustal contamination and subsequent fractional crystallisation during their ascent,which is crucial for the origin of the intermediate-acidic rocks in Wanganzhen complex. Mesozoic lithospheric extension might induce the melting of the enriched lithospheric mantle in response to the asthenosphere uprising for generating these intermediate-acidic rocks in the region.

关 键 词：王安镇杂岩体 SHRIMP U-PB定年 HF同位素 太行山北段 

分 类 号：P588.12[天文地球—岩石学] P588.14[天文地球—地质学]