老挝甘蒙省钾镁盐矿床含矿段的矿物学和地球化学特征及成因高翔,蔡克勤,李代荣,彭强,方勤方,秦红(中国地质大学科学研究院,北京100083)摘要:老挝甘蒙省钾镁盐矿床位于呵叻盆地的东隅,本文以该矿床ZK318钻孔的含矿段———下盐层为研究对象,对其开展了系统的矿物学和地球化学特征研究。结果说明,矿石矿物以石盐、钾石盐和光卤石为主,含少量方硼石和硬石膏。根据矿物与主量元素的分布特征,将下盐层分为5个次层,由下至上顺序为:盐岩层(石盐为主)→钾盐岩层(钾石盐为主)→光卤石岩层(光卤石为主)→薄盐岩层(石盐为主)→钾盐岩层(钾石盐为主)。微量元素Br值均大于200×10-6,说明卤水来源于海水;由盐岩层→钾盐岩层→光卤石岩层,B含量呈现出逐渐升高的趋势,说明B含量与卤水盐度呈线性关系。但顶部钾盐岩层的B含量高达890×10-6,与少量方硼石的存在相吻合,指示成矿卤水除了海水外,还有深部热液的奉献。按照卤化物卤水蒸发浓缩的顺序,光卤石是该卤水浓缩的最后阶段,但在光卤石沉积之后,又晶出一薄层石盐,说明曾经历过一次短暂的淡水补给。上、下两层钾石盐具有根本相同的Br含量,分别为1790×10-6和1792×10-6,且均直接沉积在石盐之上,故为原生钾石盐,而非光卤石的次生淋滤产物。认为甘蒙省钾镁盐矿床为海源陆相沉积,海水和深部热液是成钾物质的主要来源,钻孔中出露的两层钾石盐均为原生沉积。关键词:钾镁盐矿床;矿物学;地球化学;成因;老挝甘蒙省中图分类号:P619.21+1;P578.3+2文献标识码:A文章编号:100026524(2021)0420578211Mineralogicalandgeochemicalcharacteristicsandgenesisofthepotassium2magnesiumsaltdepositinKhammouanProvince,LaosGAOXiang,CAIKe2qin,LIDai2rong,PENGQiang,FANGQin2fangandQINHong(InstituteofEarthSciences,ChinaUniversityofGeosciences,Beijing100083,China)Abstract:Thepotassium2magnesiumsaltdepositinKhammouanProvinceofLaosislocatedineasternKhoratBasinwhichbelongstoupperCretaceoussaltsedimentarybasin.Theformationofthedepositunderwentthreesedimentarycycleswhichformedthreesaltsections,i.e.,upper,middleandlowersections,andeverysaltsec2tionincludestwolayers,namelysaltlayerandclaylayer.Theoreislocatedinthelowersaltlayeroflowersaltsection.ThispapermainlystudiedthemineralogicalandgeochemicalcharacteristicsofthelowersaltlayerbasedonZK318well.Theresultsshowthathalite,sylviteandcarnallitearemainminerals,withsmallamountsofbo2raciteandanhydrite.Incombinationwiththecharacteristicsofminerals,majorelementsandtraceelements,thelowersaltlayercanbedividedintofivelayersinupwardorderofhalitelayer→sylvitelayer→carnallitelayer→thinhalitelayer→uppersylvitelayer.Bromine(Br)values(higherthan200×10-6)showthatthebrinecamefromseawater,andcarnalliteoccurredatthehigheststageofbrineconcentration,asshownbyitshighest收稿日期:2021204225;修订日期:2021205230基金工程:国家重点根底研究开展方案“973〞资助工程(2021CB403004)作者简介:高翔(19712),女,博士,副教授,从事矿物学的教学和科研工作,E2mail:xgao@cugb.edu.cn。---本文来源于网络，仅供参考，勿照抄，如有侵权请联系删除---Brvalueof2572×10-6amongfivelayers.Boroncontentshowedagradualincreasefromhalitelayerthroughsylvitelayertocarnallitelayer,suggestingthatboroncontentisinlinearcorrelationwithsalinityofthebrine.Boronvalueoftheuppersylvitelayerisupto890×10-6,whichisconsistentwiththeexistenceofboracitemin2eralrevealedbyXRD,indicatingthatorebrinecamefromseawateranddeephydrothermalsolution.Inaddi2tion,accordingtotheevaporativeorderofhalidebrine,theorderofcrystallizationwashalite→sylvite→carnal2lite,andcarnalliteseemedtobethelastsedimentaryperiodinhalidebrine.However,inZK318well,thereappearsathinlayerofhaliteabovethecarnallitelayer,whichshowsthatitunderwentashortper...