大兴安岭东北部霍龙门地区早二叠世花岗岩的锆石U-Pb年龄、地球化学特征及构造意义  

ZIRCON U-Pb AGES,GEOCHEMICAL CHARACTERISTICS AND TECTONIC IMPLICATIONS OF THE EARLY PERMIAN GRANITES IN HUOLONGMEN AREA,NORTHEAST DA HINGGAN MOUNTAINS

作　　者：李成禄[1,2] 徐文喜 李胜荣 宋志超[3] 王卓 曲晖 赵忠海 徐国战 LI Chenglu XU Wenxi LI Shengrong SONG Zhichao WANG Zhuo QU Hui ZHAO Zhonghai XU Guozhan(School of Earth Sciences and Resources,China University of Geosciences ,Beijing 100083,China Heilongjiang Institute of Geological Survey,Harbin 150036,China No. 5 Institute of Geological Survey of Heilongjiang Province, Harbin 150090,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]黑龙江省地质调查研究总院,黑龙江哈尔滨150036 [3]黑龙江省第五地质勘察院,黑龙江哈尔滨150090

出　　处：《矿物岩石》2017年第3期46-54,共9页Mineralogy and Petrology

基　　金：中国地质调查局项目(1212010781024);黑龙江国土资源科研项目(201603)

摘　　要：黑龙江霍龙门地区位于兴蒙造山带东部的兴安地块和松嫩地块接触带上,区内花岗岩类以晚古生代花岗岩为主,岩性主要为正长花岗岩、二长花岗岩、碱长花岗岩和二长闪长岩等。研究区的正长花岗岩的SHRIMP锆石U-Pb定年结果为294.8 Ma±1.8Ma,表明其形成于早二叠世,且在早三叠世(244.6 Ma±4.1 Ma)遭受了较弱的岩浆侵位事件的叠加影响。该时代岩石的主量元素具有高钾(K_2O质量分数平均为4.52%)、富钠(Na_2O质量分数平均为3.85%)、略富铝(Al_2O_3质量分数平均为13.73%)、低镁(MgO质量分数平均为0.21%)和贫磷(P_2O_5质量分数平均为0.06%)贫钙(CaO质量分数平均为0.61%)的特征;微量元素表现出Th,Zr,Nd,Rb明显富集,而Ba,Sr,P,Ti明显亏损;稀土元素具有轻稀土元素富集、重稀土元素相对亏损的特征,有较明显的负Eu异常(δEu平均为0.49),轻重稀土元素分馏程度较强。岩石总体上属于高钾钙碱性系列花岗岩。花岗岩的R_1-R_2构造环境判别图解与微量元素Rb-Yb+Nb,Rb-Yb+Ta构造环境判别图解显示,该期发育的早二叠世花岗岩处于碰撞造山晚期向造山期后伸展的构造环境,结合区域北东向大量分布晚石炭世-早二叠世期间反映造山期后伸展环境的A型花岗岩的特征及本区所处的构造环境推测,研究区内早二叠世花岗岩应为兴安地块与松嫩地块北东向碰撞造山晚期向造山期后伸展拉张环境下岩浆侵位的产物。The Huolongmen area in Heilongjiang Province is tectonically located at the junction between the Songnen Block and the Xing＇an Block in the east of the Xingmeng oregenic belt. Large volumes of Neopaleozoic granitic rocks of syenogranite, monzogranite, alkali-feldspar and monzodiorite distribute in the area. Zircon U-Pb SHRIMP dating of syenogranite yields a con- cordant age of 294.8 Ma±1.8 Ma,and the syenogranite experienced superposition of early Trias- sic（244. 6 Ma±4.1 Ma）magma intrusion. Major element analysis shows that the rock is of high K20（mean value 4.52%）and alkali contents（mean value 8. 37%）,slightly high in Al2O3 （mean value 13.73%）content and low MgO（mean value 0.21%, P2O5 （mean value 0.06%）and CaO （mean value 0. 61%） contents. Trace element studies reveal the enrichment of Th, Zr, Nd, Rb and depletion of Ba, Sr, P and Ti. Meanwhile, the samples are enriched in LREE and depleted in HREE with pronounced Eu anomalies（mean value 0.49）, suggesting a high degree of fractionation（La/ Sm） N = 3. 61- 5.34, （Gd/Yb） N = 0.81- 1.41）. The granites generally belong to the high-K calc- alkaline series and produced by the magma that experienced a relatively higher degree of crystalli- zation differentiation. Most Neopaleozoic granite samples fall in the post-orogenic zone and vol- canic arc granite zone in the R1-R2 structural setting discrimination diagram. （Yb＋Nb）-Rb versus （Yb＋Ta）-Rb discrimination diagram suggests that the Xing＇an Block and Songnen Block experi- enced a tectonic setting from late orogenic collision to post orogenic extension during late Paleozo- ic.

关 键 词：花岗岩 锆石U-PB年龄 地球化学 霍龙门地区 大兴安岭 

分 类 号：P588.12[天文地球—岩石学] P597.2[天文地球—地质学]