捷克波西米亚盆地斯特拉砂岩型铀矿床成矿特征及成矿模式

Metallogenic characteristics and model of sandstone-type uranium deposits in Straz area, Bohemia Basin, Czech Republic

【研究目的 】捷克波西米亚盆地斯特拉地区是著名的铀成矿区,区内砂岩型铀矿床的成矿作用复杂,厘定其成矿特征和成矿模式对于完善砂岩型铀矿成矿理论研究、对中国同类型矿床找矿勘查具有重要借鉴意义。【研究方法 】本文在总结前人对斯特拉地区砂岩铀矿床地质特征和成矿条件的基础上,对其铀源、成矿阶段以及矿床成因进行综合研究并对中国松辽盆地同类砂岩型铀矿进行了对比研究。【研究结果 】斯特拉矿床根据其矿物组合特征可划分为6个成矿阶段,分别是炭质-伊利石阶段、赤铁矿-高岭土阶段、铀富集阶段、多金属成矿阶段、褐铁矿化阶段以及赤铁矿-石英阶段。通过研究认为,出露于盆地东北部的元古代和古生代的黑云母花岗闪长岩和斑状黑云母花岗岩较低的Th/U值表明,这两类岩石中部分铀以活性铀形式存在,是成矿潜在的铀源。斯特拉矿床是以白垩系富铀沉积层位为基础,在其上叠加了早阿尔卑斯期岩浆热液作用,后因地壳缓慢上升,导致铀重新活化,进一步在盆地内层间氧化带局部叠加铀成矿作用,形成板状、脉状、卷状3种铀矿体共存的砂岩型铀矿床。【结论 】本文提出了成矿模式:斯特拉地区砂岩型铀矿床属于多铀源—以盆地基底原始铀源为主、多阶段大地构造控矿—以早阿尔卑斯期(~70 Ma)造山运动为主、多成因复合成矿—以早阿尔卑斯期岩浆热液叠加成矿为主的“三多三主”复合成因砂岩型铀矿床。

This paper is the result of mineral exploration engineering.[Objective]Straz area(Bohemia Basin,Czech Republic)is a well-known uranium metallogenic area.The mineralization of sandstone-type uranium deposits is complex.Determining its metallogenic characteristics and metallogenic model is of great significance to perfect the metallogenic theory of sandstone-type uranium deposits and know the prospecting and exploration of the similar uranium deposits in China.[Methods]On the basis of summarizing the geological characteristics and metallogenic conditions of sandstone-type uranium deposits in the Straz area,this study focus on the uranium source,metallogenic stage and genesis of the deposits,and comparative studies are conducted by the similar sandstone-type uranium deposits in Songliao Basin.[Results]The Straz deposit can be divided into six metallogenic stages according to its mineral assemblage characteristics,i.e.,carbon-hydromica,hematite-kaolinite,uranium,polymetallic,limonite and hematite-quartz stage.Proterozoic and Paleozoic igneous,metasedimentary,and sedimentary rocks outcropping to the northeast of the Bohemia Basin are considered potential sources for uranium.The Lusatian Massif contains biotite granodiorite and porphyritic biotite granite with.The low Th/U ratios suggest that part of the uranium is probably present in leachable form and these rocks constitute viable uranium sources.[Conclusions]The metallogenic model of the Straz area belongs to the“three factors and three majors”:Multi uranium source-basin basement primary uranium source,multi stage tectonic ore controlling-early Alps(about 70 Ma)orogenic movement,multi genetic composite mineralization-early Alps magmatic hydrothermal superimposed mineralization.