黑龙江伊春地区早侏罗世A型花岗岩地球化学特征及构造环境探讨  

GEOCHEMICAL CHARACTERISTICS AND TECTONIC ENVIRONMENT OF THE EARLY JURASSIC A-TYPE GRANITES IN YICHUN AREA,HEILONGJIANG PROVINCE

作　　者：张洪文 平先权[2] 黄伟 刘金业 高博 艾磊 王刚[1] 孙艳秋 ZHANG Hong-wen;PING Xian-quan;HUANG Wei;LIU Jin-ye;GAO Bo;AI Lei;WANG Gang;SUN Yan-qiu(Mudanjiang Natural Resources Comprehensive Survey Center,CGS,Mudanjiang 157021,Heilongjiang Province,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;Mudanjiang No.2 Senior High School,Mudanjiang 157021,Heilongjiang Province,China)

机构地区：[1]中国地质调查局牡丹江自然资源综合调查中心,黑龙江牡丹江157021 [2]中国地质大学地球科学学院,湖北武汉430074 [3]牡丹江市第二高级中学,黑龙江牡丹江157021

出　　处：《地质与资源》2024年第3期280-290,共11页Geology and Resources

基　　金：中国地质调查局地调专项“黑龙江1∶5万三兴山、白桦林场、友谊经营所、鸡爪河林场(M52E021011、M52E022011、M52E023011、M52E024010)幅区域地质矿产调查”(项目编号12120113072600)。

摘　　要：黑龙江省伊春地区大地构造位于兴蒙造山带东段的小兴安岭-张广才岭弧盆系内,中生代发育多期次岩浆活动,记录了弧盆系的构造演化过程.通过对伊春北部白桦青年队地区的中生代花岗岩进行详细的岩石学及地球化学特征和年代学研究,结果显示,区内出露的中生代花岗岩主要包括中细粒正长花岗岩、似斑状二长花岗岩.中细粒正长花岗岩LA-ICP-MS锆石U-Pb测年结果为190.6±1.7 Ma,为早侏罗世.岩石地球化学特征显示具有高硅(SiO_(2)=72.8%~77.43%),富碱(Na_(2)O+K_(2)O=7.43%~8.61%),贫镁(MgO=0.11%~0.54%)、钙(CaO=0.24%~1.77%)、磷(P_(2)O_(5)=0.02%~0.08%)、钛(TiO_(2)=0.05%~0.31%)的特点,A/CNK值为1.05~1.15,为过铝质、高钾钙碱性花岗岩.微量元素方面,亏损高场强元素Nb、Ti、P和大离子亲石元素Ba、Sr,富集Rb、K、Th、Hf等元素.稀土配分曲线总体上呈不对称右倾型,且Eu负异常(δEu=0.08~0.72)明显.这些地球化学特征显示研究区早侏罗世花岗岩具A2型花岗岩的特点,形成于造山后的伸展构造背景.结合小兴安岭地区的岩浆活动和构造事件记录,认为黑龙江伊春地区早侏罗世岩浆侵位活动可能发生在古太平洋板块西向俯冲所造成的造山后伸展构造背景下.The Yichun area of Heilongjiang Province is tectonically located in the Xiaoxinganling-Zhangguangcailing arc-basin system in the eastern Xingan-Mongolian orogenic belt,with multiple-stage magmatic activities occurred in Mesozoic,which has recorded the tectonic evolution of arc-basin system.The paper studies in detail the petrology,geochemistry and chronology of the Mesozoic granites in Baihuaqingniandui area of northern Yichun.The results show that the Mesozoic granites exposed in the area mainly include fine-medium-grained syenogranite and porphyritic monzogranite.The LA-ICP-MS zircon U-Pb dating yields the age of 190.6±1.7 Ma,indicating the fine-medium-grained syenogranite was formed in the Early Jurassic.Lithogeochemically,the granites are characterized by high Si,rich in alkali,poor in Mg,Ca,P and Ti,with the A/CNK value of 1.05-1.15,belonging to peraluminous,high potassium calc-alkaline series,and depletion of HFSEs(Nb,Ti and P)and LILEs(Ba and Sr),and enrichment of elements such as Rb,K,Th and Hf.The REE patterns show asymmetrically right-dipping type,with obvious negative Eu anomaly.These geochemical characteristics reveal that the Early Jurassic granites in the area are typically of A_(2)-type,formed in the post-orogenic extensional tectonic setting.Combined with the magmatic activities and tectonic events in Xiaoxinganling Mountains,it is believed that the Early Jurassic magmatic emplacement in Yichun area may have occurred under the post-orogenic extensional tectonic background caused by the westward subduction of paleo-Pacific Plate.

关 键 词：早侏罗世 A型花岗岩 地球化学 构造环境 黑龙江省 

分 类 号：P597[天文地球—地球化学]