黑龙江平顶山金矿赋矿花岗岩锆石U-Pb年龄、Hf同位素特征及其构造意义  

U-Pb Dating and Hf Isotopic Composition of Ore-Hosting Granites from the Pingdingshan Gold Deposit,Heilongjiang Province,and Its Geological Implications

作　　者：包真艳 王建[1] 杨言辰[1] 王林 谢志鹏[1] 宋樾[1] 刘建国[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]贵州省有色地质矿产勘查院,贵阳550000

出　　处：《地质学报》2014年第3期407-420,共14页Acta Geologica Sinica

基　　金：国家自然科学基金(编号41173034);中国地质调查局项目(编号1212011120342)资助的成果

摘　　要：平顶山金矿床位于佳木斯地块与松嫩地块的衔接处北端,地处中亚造山带的东段。前人对该矿床的岩(矿)石物理化学特征及地质特征已进行了研究,但对与成矿密切相关的花岗岩缺乏系统的岩石学、地球化学和高精度年代学等方面的研究。本次研究通过锆石的LA-ICP-MS U-Pb定年、Hf同位素示踪以及全岩的主、微量元素测试,探讨了平顶山金矿区赋矿花岗岩的源区特征、形成机制和构造背景。矿区花岗岩包括早期的浅色中粒二长花岗岩和稍晚期的细粒黑云母二长花岗岩,两期花岗岩的锆石U-Pb年龄分别为271.7±2.3 Ma和249.8±3.3Ma,对应的εHf(t)为-4.17～-0.58和-4.98～-0.49,两阶段平均模式年龄tDM2分别为1432 Ma、1457Ma,原始岩浆可能来源于中元古代增生的壳源物质的重熔。两期花岗岩均以高碱(Na2O+K2O)、富Al2O3、富集LREE和LILE(Rb、Ba、Th、U和K)、低MgO、贫HREE和HFSE(Nb、Ta、P和Ti)为特征,属高钾钙碱性系列的准铝质/过铝质I型花岗岩,代表了火山弧-同碰撞环境。结合中亚造山带东段构造演化历史,我们认为平顶山金矿的花岗岩可能是古亚洲洋向北俯冲、闭合、华北克拉通与佳-蒙陆块碰撞产物。Pingdingshan gold deposit is located in the north of the convergent area of Jiamusi massif and Songnen massif,and also in the eastern part of Central Asian orogenic belt.Previous studies only focus on the phychemical and geological characteristics of the ores and rocks in this deposit,but less attention has been given on lithology,geochemistry and geochrology of the granite which is closely related to mineralization.This study discussed source character,mechanism and tectonic setting of the ore-hosting granite using LAICP-MS zircon U-Pb dating,Hf isotopic determination,and compositions of major and trace-elements for whole rocks.The granites in the Pingdingshan gold deposit consist of early light-colored medium-grained monzogranite and slightly late fine-grained biotite monzogranite.Out results show the two granites have U-Pb ages of 271.7±2.3 Ma and 249.8±3.3 Ma,respectively,with the corresponding εHf（t） values of -4.17～-0.58 and-4.98～-0.49.Average model ages for two stages are 1432 Ma and 1457 Ma,suggesting that their parent magmas might derive from the remelting of Mesoproterozoic crust material.The granites are characterized by high Al3O3,K3O＋Na3O,LREE and LILE （Rb,Ba,Th,U and K）,and low MgO,HREE and HFSE （Nb,Ta,P and Ti）.They are chemically high-K calc-alkaline rock series,and represent volcanic arc/ syn-collision I-type granites.In combination with the evolution history of the eastern segment of the Central-Asian Orogenic Belt,we consider that the Pingdingshan granites resulted from the collision between North China Craton and Jiamusi-Mongolia massif due to the north-ward subduction and closure of the Paleo-Asian Ocean.

关 键 词：黑龙江平顶山金矿 花岗岩 U-PB年代学 Hf同位素 佳木斯地块 

分 类 号：P618.51[天文地球—矿床学] P597.3[天文地球—地质学]