摘要
华北陆块南缘外方山店房金矿区内出露后沟、水漉塘和店房钾长花岗斑岩体(脉),其与隐爆角砾岩筒及金矿化有密切的空间关系。为查明钾长花岗斑岩体的侵位时代、岩石成因和源区性质,本次开展了锆石U-Pb定年、锆石Hf同位素及岩石地球化学分析等研究。结果表明岩体具有高硅、高钾、富铝、低镁的特征,属钾玄岩系列Ⅰ型花岗岩,轻重稀土元素分馏明显,具有弱的Eu负异常,岩石富集Rb、K、Ba等,亏损Nb、Ta、Sr、P、Ti等元素。锆石具有核—边结构,其中锆石边SHRIMP U-Pb年龄142.6±2.1Ma(MSWD=1.4),_(εHf)(t)=-23.0^-13.8,两阶段模式年龄主要集中于2075~2652 Ma;锆石核LA-ICPMS U-Pb年龄可分为两组,即2169~2336Ma和1732~1881Ma,Hf同位素组成可分为两组,_(εHf)(t)分别集中于-13.1^-4.8和-4.5~3.7,模式年龄主要集中于2376~2805Ma。表明钾长花岗斑岩体形成于142.6±2.1Ma的早白垩世早期,岩浆可能由2169~2336Ma的古老下地壳新太古代太华群部分熔融而成,并有地幔组分参与,岩浆在上升或定位过程中捕获了1732~1881Ma熊耳群火山岩的锆石。结合区域构造背景认为,该岩体是早白垩世古太平洋板块向欧亚大陆俯冲致使华北陆块岩石圈减薄伸展而引起的岩浆活动的产物。
The Hougou,Shuilutang and Dianfang K-feldspar granite porphyry bodies,outcropping within Dianfang gold deposit,Waifangshan region,south margin of the North China Craton,is spatially related to the Cryptoexplosivebreccia pipe and the gold mineralization.In order to confirm the intrusive age,lithogenesis and magma source characteristics of the K-feldspar granite porphyriey,this study adopt zircon U-Pb dating,Hf isotopic and petrogeochemical analysis.These granites are shoshonite series I type granites with high SiO2,K2O,Al2O3 and low MgO contents,and are characterized by enrichments in Rb,K,Ba and LREE but depletions in Nb,Ta,Sr,P,Ti and HREE,as well as weakly negative Eu anomalies.Zircon grains of the K-feldspar granite porphyriey are characterized by core-rim structure.Zircon rim SHRIMP U-Pb dating yields weighted mean 206Pb/238U age of 142.6±2.1Ma,withεHf(t)values of-23.0~-13.8 and tDM2 ages of 2652~2075 Ma;Zircon core LA-ICPMS U-Pb dating show that the 207Pb/235U ages are clustered in 2169~2336Ma and 1732~1881Ma,withεHf(t)values of-13.1~-4.8 and-4.5~3.7 respectively and corresponding tDM1 ages of 2376~2805Ma,indicating that the emplacement ages for K-feldspar granite porphyriey are at 142.6±2.1Ma of the early Cretaceous.Its magma source is probably derived from partial melting of the ancient continental crust of 2169~2336Ma of the Neoarchean Taihua Group,with mantle component contributed to its formation,and the zircon grains of 1732~1881Ma of Xionger Group volcanic captured by the ascending magma during the diagenetic process.In combination with the regional geological features and geodynamic settings,the K-feldspar granite porphyriey are the product of magmatic activity caused by North China Craton lithospheric thinning due to the subduction of the Pacific plate toward the Eurasian continent.
作者
田永飞
叶会寿
李正远
毕珉烽
王鹏
原瑞杰
刘艺博
TIAN Yongfei;YE Huishou;LI Zhengyuan;BI Minfeng;WANG Peng;YUAN Ruijie;LIU Yibo(MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing,100037,China;China Geo-Engineering Corporation Overseas construction Group,Beijing 100101;China University of Geosciences,Beijing 100083,China;Songxian Jinniu Limited Liability Company,China National Gold Group Corporation,Henan Luoyang 471400,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2016年第8期1755-1777,共23页
Acta Geologica Sinica
基金
地质调查项目(12120114035401
1212011220869)
国家自然科学基金(41272104)联合资助
关键词
锆石U—Pb年龄
HF同位素
岩石地球化学
早白垩世钾长花岗斑岩
店房金矿
Zircon U-Pb ages
Hf isotopic composition
Petrogeochemstry
Early Cretaceous K-feldspar granite porphyry
Dianfang gold deposit
