摘要
汾渭地堑系是华北克拉通中部新生代一条重要的张性断陷带,以往研究成果主要集中在其形成过程及动力学机制方面,但对其开启时限的研究由于缺乏定量的测年对象,一直悬而未解。此次研究在汾渭地堑系相邻的中条山奇峰一带发现了一系列不规则状的花岗斑岩岩脉。对该套花岗斑岩岩脉的测年结果表明,其年龄序列主要集中在1769.8±8.7 Ma和69.14±0.85 Ma两个阶段,前者与熊耳群火山岩的主体年龄一致,代表了继承性锆石的特点,后者代表了花岗斑岩岩脉的形成年龄。奇峰花岗斑岩岩脉样品的Ga/Al均大于2.6,表现富硅、碱、钾,贫钙,高镁的特点,稀土元素中轻稀土富集、重稀土亏损,具有A型花岗岩的特点,形成于拉张的构造背景下。结合区域地质背景认为,该套花岗斑岩岩脉指示了汾渭地堑系南段开启的时限,研究成果为汾渭地堑系的开启时限提供了新的证据。
The Fen-Wei graben system is an essential Cenozoic extensional fault-depression belt in the central part of the North China craton.Previous research achievements mainly focused on its formation process and dynamic mechanism,but the initial time has been unresolved due to the lack of quantitative dating objects.This paper first reports the granite porphyry dikes in the andesite of the Majiahe formation in the Xionger group of the Zhongtiaoshan orogenic belt adjacent to the Fen-Wei graben system.The dating results of the granite porphyry dikes indicate that the age sequence concentrates mainly in two stages,1769.8±8.7 Ma and 69.14±0.85 Ma.The former is consistent with the primary age of the volcanic rocks of the Xionger group,representing the characteristics of inherited zircons,and the latter represents the formation age of the granite porphyry dikes.The Ga/Al value ratios of granite porphyry dikes of the Qifeng samples are all greater than 2.6,characterized by enriched silicon,alkali,potassium,depleted calcium,and high magnesium.The rare earth elements are enriched in light and depleted in heavy rare earth elements.The Qifeng granite porphyrite dikes are I-type granites,indicating that the tectonic setting is extensional.The research provides new evidence for the initial time of the southern part of Fenwei graben in the Cenozoic.
作者
崔加伟
李振宏
井向辉
寇琳琳
CUI Jiawei;LI Zhenhong;JING Xianghui;KOU Linlin(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081,China;Key Laboratory of Active Tectonics and Geological Safety,Ministry of Natural Resources,Beijing 100081,China;Exploration and Development Institute of PetroChina Changqing Oil field Company,Xi’an 710018,Shanxi,China;National Engineering Laboratory of Low Permeability Oil and Gas Field Exploration and Development,Xi’an 710018,Shanxi,China)
出处
《地质力学学报》
CSCD
北大核心
2023年第4期485-496,共12页
Journal of Geomechanics
基金
中国地质调查局地质调查项目(DD20221644,DD20190018)
国家自然科学基金项目(41702216,41972119)。
关键词
锆石U-PB年代学
地球化学特征
花岗斑岩岩脉
中条山
汾渭地堑系
zircon U–Pb geochronology
geochemistry
granite porphyry dikes
Zhongtiaoshan Mountains
Fen-Wei graben system
