湖南郴州芙蓉锡矿田绿泥石成分温度计应用及其成矿温度

摘要绿泥石作为自然界中分布较为广泛的矿物之一，在不同的地质环境中化学成分变化很大。前人通过对其的研究，建立了运用成分变化推导其形成温度的计算公式。近年来，这些计算公式被广泛用于反演固体矿床和流体矿产的成矿条件，为固体矿床的开发和流体矿产的勘探做出了一定的贡献。本文以湖南郴州芙蓉锡矿田为例，在归纳分析地质背景、矿床地质特征、围岩蚀变、矿物共生组合、矿物生成顺序的基础上，对该区绿泥石的成矿期次及绿泥石种类进行了划分，并运用现代测试技术对绿泥石的化学成分、晶体化学特征进行了分析。通过与其共生石英中流体包裹体均一温度的对比，将选定的成分温度计标定公式应用于湖南郴州芙蓉锡矿田，并对新疆松树沟铜矿的成矿条件进行了尝试性的估算。绿泥石在该矿床中分布较广，从早期到晚期均有形成，根据矿化蚀变期次及矿物共生组合，可将绿泥石划分为三个矿化阶段。根据绿泥石的产出特征及矿物共生组合关系，将其分为交代型及充填脉型两种类型。对绿泥石的电子探针分析表明，该区绿泥石的种类为铁镁绿泥石、辉绿泥石、鳞绿泥石和鲕绿泥石。该区绿泥石表现为富铁和四次配位铝而贫镁。充填脉型的绿泥石比交代型的绿泥石更为富铁和四次配位铝而贫镁，绿泥石成分中Fe2++AlⅣ与Fe2+/(Fe2++Mg2+)成正相关关系。该区绿泥石的X射线粉晶衍射测试结果显示其晶胞参数值均小于标准值。该区绿泥石样品的红外光谱分析显示与标准的鲕绿泥石红外光谱相符，同时反映出绿泥石中Fe的含量较高。选用的三个绿泥石成分温度计的经验公式计算出该区绿泥石的形成温度相差较大，差值为30℃～60℃。共生石英中流体包裹体均一温度测试结果表明绿泥石成分温度计具有其可应用性。Cathelineau在1985年推导出的计算公式较为准确地计算了绿泥石的形成温度。计算所得结果显示芙蓉锡矿田绿泥石的形成分为早期（280℃～320℃）、中期(210℃～260℃)及晚期（100℃～180℃）。新疆松树沟铜矿的绿泥石形成于中温环境。通过本文的研究发现绿泥石成分温度计经验公式具有其局限性，在应用上应结合其他矿物温度计相互佐证以较为准确的估算绿泥石形成温度。关键词:绿泥石，成分温度计，均一温度，芙蓉锡矿田AbstractAsoneofthemineralswhichwidelydistributeinthenature,thechloritecompositionvariesgreatlyindifferentgeologicalenvironment.Byresearchingonit,pioneersestablishedalotofformulaswhichcalculatetheformationtemperatureofchloritemakinguseofthedifferencecompositionindifferentgeological.Recently,theseformulasarewidelyusedinpresumetheore-formingconditions,andmakesomecontributiononthedevelopmentofsolidmineraldepositandtheexplorationoffluidmineraldeposit.TakingtheFurongtindepositofHunanforexampleandonthebaseofgeneralizinggeologicalbackgroundofthistindeposit,geologicalcharacteristicsoforebody,surroundingrockalteration,mineralparagenesiscombinationandmineralformativesequence,thispaperhaspartitionedthemineralizationperiodsandspeciesofchlorite,andhasstudiedonchemicalcompositionandcrystal-chemicalcharacteristicsofchloriteusingmoderntestingmethods.Bycontrastingwiththehomogenizationtemperaturesoffluidinclusionsinsymbioticquartz,thispaperhasappliedthechloritecompositionthermometerformulawhichischosefromthreeformulastotheFurongtindepositofHunanandtriedtopresumethemineralizationcondition.ofSongshugoucopperdepositofXinjiang.ChloritedistributeswidelyinFurongtindepositandgeneratesformearlystagetolaterstage.Accordingtothemineralizationandalterationstagesandintergrowthcombination,thechloritecanbedividedintothreemineralizationperiods.Accordingtoproducingcharacteristicandcolacobisiscombinationrelation,chloritecanbedividedintotwotypes,oneismetasomatictype,theotherisfillingveintype.TheresultofEMAmanifeststhatthespeciesofchloriteareleptochlorite,chamoisiteandbrunsvigiteinthisdeposit.AndthecholoritecontainshighFeandAlⅣandlowMg.ThechloriteofmetasomatictypecontainshigherFeandAlⅣandlowerMgthanthechloriteoffillingveintype.TherelationshipbetweenFe2++AlⅣandFe2+/(Fe2++Mg2+)ispositivecorrelation.TheXRDtestresultmanifeststhattheunitcellvaluesofchloritearebothlowerthanstandard.Theinfraredspectrumanalysisonchloriteshowsitsatlascorrespondswithchamosite.Theformingtemperaturesofchloritecomputedbythechosenthreeformulasvarygreatly,andthevariancevalueis30℃～60℃.ThehomogenizationtemperaturesoffluidinclusionsinsymbioticquartzindicatesthechloritecompositionthermometerformulacanbyappliedwithandusingformulawhichwasderivedbyCathelineauin1985cancomputetheformingtemperaturemoreaccurately.Theresultofcalculationrevealsthechloriteintinallotmentformedinearlystage(280℃～320℃),mediumstage(210℃～260℃)andlaterstage(100℃～180℃)andthechloriteincopperdepositofXinjiangformedinmediumtemperaturecondition.Bythisresearch,thelimitationofapplicationofthechloritecompositionthermometerformulacanbeconcluded.Andthepapersuggeststhechloritecompositionthermometerformulashouldbeusedwithothermineralthermometertocomputetheformingtemperaturemoreaccurately.Keywords:chlorite,componentthermometer,homogenizationtemperatures,Furongtindeposit目录1前言............................................................................................................................11.1绿泥石成分温度计概述......................................................................................11.2绿泥石成分温度计应用现状..............................................................................21.3选题目的及意义..................................................................................................31.4研究工作概况......................................................................................................32区域地质概况............................................................................................................52.1区域地质背景......................................................................................................52.1.1地层分布......................................................................................................52.1.2地质构造......................................................................................................62.1.3岩浆活动特点..............................................................................................62.2芙蓉锡矿田地质特征..........................................................................................62.2.1地层分布.............................................................................