黑龙江多宝山地区晚泥盆世A型花岗斑岩年代学、地球化学特征及其地质意义  

Geochronology,Geochemistry and Geological Significance of the Late Devonian A-Type Granite Porphyry in the Duobaoshan Area,Heilongjiang Province

作　　者：符安宗 李成禄 石国明 杨文鹏 杨元江 郑博 李金明 Fu Anzong;Li Chenglu;Shi Guoming;Yang Wenpeng;Yang Yuanjiang;Zheng Bo;Li Jinming(Heilongjiang Institute of Natural Resources Survey,Harbin 150036,China)

机构地区：[1]黑龙江省自然资源调查院,哈尔滨150036

出　　处：《吉林大学学报（地球科学版）》2024年第3期811-827,共17页Journal of Jilin University：Earth Science Edition

基　　金：黑龙江省重点研发计划项目(GA21A204);黑龙江省地质矿产局科研项目(HKY202302);中国地质调查局项目(DD20160047-07)。

摘　　要：黑龙江多宝山地区位于兴蒙造山带东段,为兴安地块与松嫩地块的拼合部位,是研究嫩江—黑河洋(古亚洲洋分支)构造演化的关键地段。对嫩江市多宝山地区西侧出露的花岗斑岩开展岩石学、年代学和元素地球化学等方面的研究,以期限定其形成时代,探讨岩石成因及构造背景,为嫩江—黑河洋构造岩浆演化提供依据。花岗斑岩呈肉红色,具多斑状结构,块状构造,斑晶由钾长石、石英和少量的斜长石组成,基质主要由微晶结构的长英质矿物和少量黑云母组成。LA-ICP-MS锆石U-Pb加权平均年龄为(365.1±2.6)Ma,形成于晚泥盆世晚期。岩石地球化学具有高质量分数的SiO_(2)、K_(2)O,低质量分数的CaO、MgO和Al_(2)O_(3),高TFeO/MgO和Rb/Sr值,富集Rb、Th、Zr和Hf元素,贫Sr、Ba、Eu、Ti和P元素,REE配分曲线呈燕式分布,负铕异常明显,表现出A型花岗岩的特征。以高的Zr/Hf值,Na_(2)O、TFeO质量分数和相对低的P_(2)O_(5)、Rb质量分数区别于高分异I型、S型花岗岩。特征微量元素比值与大陆地壳相应值相近,且岩石具有较低的MgO、Cr质量分数和Mg#值,指示其源区主要来自地壳。综合分析表明,该期花岗斑岩为非典型A1亚类花岗岩,兼具火山弧和板内花岗岩的元素地球化学特征,形成于嫩江—黑河洋北向俯冲挤压体系下派生的局部拉张环境。The Duobaoshan area,situated within the contact zone between the Xing’an and Songnen blocks in the eastern part of Xing’an-Mongolia orogenic belt,holds significant importance in the study the tectonic evolution of Nenjiang-Heihe Ocean,which is the north branch of Paleo-Asian Ocean.In this paper,we present a detailed investigation of petrology,geochronology and geochemistry of the granite porphyries exposed in the western Duobaoshan area with the aims to identify their geochronology and petrogenesis,and further to reveal the tectonic-magmatic evolution associated with the Nenjiang-Heihe Ocean.The investigated granite porphyries are flesh red,with multi porphyry structure and massive structure.Their phenocrysts predominantly comprise potassium feldspar,quartz and a small amount of plagioclase.The matrix is mainly composed of felsic minerals with microcrystalline structure and minor biotites.The LA-ICP-MS U-Pb zircon age suggest the granite porphyry formed at Late Devonian(365.1±2.6 Ma).Moreover,the granite porphyries are geochemically characterized by high SiO_(2)and K_(2)O contents,along with low CaO,MgO and Al_(2)O_(3)compositions,and high TFeO/MgO and Rb/Sr ratios.They are enriched in Rb,Th,Zr and Hf,and depleted in Sr,Ba,Eu,Ti,P,with swallow-like REE patterns and negative Eu anomalies,showing the characteristics of A-type granite.Distinguished from highly differentiated I-type and S-type granites,they display a high Zr/Hf ratio,Na_(2)O,TFeO content and relatively low P_(2)O_(5),Rb content.The low MgO,and Cr contents and Mg#values,together with their characteristic trace element ratios,indicated the predominant crustal source contribution.Based on the regional geology and the geochemical characteristics of the studied rocks,we concluded that the granite porphyry is an A1 subtype granite,which has the geochemical characteristics of both volcanic arc and intraplate granite.Furthermore,we infer that the granite porphyry should be formed in the local extensional environment during the northward subduction of Ne

关 键 词：晚泥盆世 锆石U-PB年龄 地球化学 A型花岗岩 花岗斑岩 黑龙江多宝山地区 

分 类 号：P59[天文地球—地球化学] P588.12[天文地球—地质学]