辽东连山关地区古元古代基性岩特征及与铀矿关系探讨  

Characteristics of Paleoproterozoic Mafic Rocks and Their Relationship with Uranium Mineralization in Lianshanguan Area,Eastern Liaoning Province

作　　者：吴迪 刘永江 王庆喜 李伟民[1] WU Di;LIU Yongjiang;WANG Qingxi;LI Weimin(Earth Science Institute,Jilin University,Changchun 130061,Jilin,China;North Uranium Co.,Ltd CNNC,Hu Ludao 125000,Liaoning,China;MOE Key Lab of Submarine Geoscience and Prospecting Techniques,Frontiers Science Center for Deep Ocean Multispheres and Earth System,College of Marine Geosciences,Ocean University of China,Qingdao 266100,Shandong,China;Research Institute No.240 CNNC,Shenyang 110032,Liaoning,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]中核北方铀业有限公司,辽宁葫芦岛125000 [3]深海圈层与地球系统前沿科学中心海底科学与探测技术重点实验室,中国海洋大学海洋地球科学学院,山东青岛266100 [4]核工业二四〇研究所,辽宁沈阳110032

出　　处：《大地构造与成矿学》2021年第4期727-744,共18页Geotectonica et Metallogenia

基　　金：国家重点研发计划(2016YFC0600108-02);国家自然科学基金(41672185);青岛市创新领军人才计划(19-3-2-19-zhc);泰山学者计划(ts20190918)联合资助。

摘　　要：连山关地区位于华北克拉通北缘铀成矿省辽东铀成矿带,以往的勘探发现铀矿周围大量基性岩发育,为进一步了解基性岩构造环境及其与铀成矿的关系,本文以钻孔深部基性岩为研究对象,通过岩石学、地球化学及年代学等研究,探讨基性岩的地质地球化学特征、形成时代、岩石成因及与铀成矿的关系。研究表明:钻孔深部基性岩以变辉绿岩和辉绿玢岩为主,具有钾、钠含量相当,过铝质等特征,属于碱性‒过碱性系列岩石;稀土元素含量偏高,轻稀土元素相对富集,重稀土元素相对亏损,轻重稀土元素分异作用不明显,Eu呈现中等程度负异常,Ce呈微弱负异常;微量元素Ba、La、Zr、Hf相对富集而U、K、P、Ti相对亏损。地球化学特点表明,研究区基性岩属于板内碱性玄武岩,源区为过渡型地幔,形成于大陆碰撞后伸展裂解的构造环境,并在上侵过程中存在地壳混染作用。连山关岩体南缘发育的韧性剪切带及相伴生的张性破裂为基性岩的就位提供空间。基性岩同时也为铀成矿提供热源、矿化剂及部分成矿流体。综合分析认为,造山期后伸展张裂阶段形成的基性岩与铀成矿关系密切,连山关岩体南部辽河群覆盖区可作为下一步重点找矿地段。The Lianshanguan area is located in the eastern Liaoning uranium metallogenic belt and belongs to the uranium metallogenetic province of the North China Craton.Previous exploration has found a large number of basic intrusions around the uranium deposits.To delineate the tectonic environment of the mafic rocks and the relationship between the mafic rocks and uranium mineralization,the mafic rocks in the deep borehole are investigated.The results show that the mafic rocks are mainly peraluminous metadiabase and sillite,which have equivalent contents of Na2O and K2O,and belong to alkaline peralkaline series.The mafic rocks are characterized by enriched LREE(light rare earth elements)and depleted HREE(heavy rare earth elements),with negative Eu anomalies and weak negative Ce anomalies,and enrichment of Ba,La,Zr,Hf and depletion of U,K,P,Ti.According to the geochemical characters,the mafic rocks are likely derived from transitional mantle and experienced crustal contamination during magma ascend,which belongs to intraplate alkaline basalts formed in extensional tectonic environment after continental collision.The ductile shear zone developed in the southern margin of the Lianshanguan granitic pluton and the associated tensile fracture might have provided space for the emplacement of the mafic rocks.Moreover,the mafic rocks provided heat,mineralizer and some ore-forming fluids for the uranium mineralization.According to the comprehensive analysis,we propose that the mafic rocks,which formed in the post orogenic extension and tensional stage,are closely related to the uranium mineralization,while the covering area of the Liaohe Group in the south of Lianshanguan granitic pluton can be considered as the key prospecting area for the uranium mineralization.

关 键 词：古元古代 基性岩 铀成矿 幔源 韧性剪切带 连山关 

分 类 号：P595[天文地球—地球化学]