高級礦床學(xué)8找礦案例斑巖礦床課件

高級礦床學(xué)-斑巖型礦床斑巖銅礦1高級礦床學(xué)-斑巖型礦床斑巖銅礦1斑巖銅礦(Porphyrycopperdeposits)為世界提供了50%以上的銅金屬(over100producingmines)。Theircloserelativestheporphyrymolydepositsproduce70%oftheworld'smoly.Bothdeposittypeswillbediscussedseparately,buttheysharemanycharacteristicsandareformedinsomewhatsimilarmanners.2斑巖銅礦(Porphyrycopperdeposits)全球斑巖銅礦分布圖絕大多數(shù)斑巖銅礦形成于中新生代，與離散板塊邊緣上及附近的火山鏈有關(guān)（環(huán)太平洋、古地中海和古亞洲洋）。極少數(shù)為古生代，分布在古生代板塊邊緣上，如U.S.S.R、UnitedStates。3全球斑巖銅礦分布圖3全球已知最大的88個斑巖銅礦產(chǎn)于美國西南部，成礦時代為58-72Ma。巖體形態(tài)典型斑巖銅礦床呈圓筒狀，產(chǎn)于巖株?duì)顜r體中，出露面積為1.5x2km（橢圓狀），核部為斑巖質(zhì)，向外到邊部為中—粗粒等粒的成分相似的巖石。主巖巖石學(xué)一般地，容礦主巖為長英質(zhì)侵入體，成分為石英正長巖、石英二長巖、花崗閃長巖系列；閃長巖—正長巖系列4全球已知最大的88個斑巖銅礦產(chǎn)于美國西南部，成礦時代為58-熱液蝕變LowellandGuilbert總結(jié)的斑巖銅礦蝕變模式，圍繞斑巖株依次出現(xiàn)4個蝕變暈鉀化帶-都存在。特征：次生的鉀長石、黑云母和/或綠泥石交代原生的鉀長石、斜長石和鎂鐵質(zhì)，及微量的絹云母。絹英巖化帶

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可存在。特征：脈石英、絹云母、黃鐵礦和微量綠泥石、伊利石和金紅石，交代鉀長石和黑云母。泥化帶（Argillic）-可存在。特征：高嶺石、蒙脫石等粘土礦物及微量浸染黃鐵礦。斜長石強(qiáng)烈蝕變、鉀長石不受影響，黑云母綠泥石化。青盤巖化帶（Propylitic）

-都存在。特征：綠泥石、方解石、微量綠簾石。鎂鐵質(zhì)礦物強(qiáng)烈蝕變，斜長石消失。在深部，上述各帶融為一體，構(gòu)成石英-鉀長石-絹云母-綠泥石組合。5熱液蝕變566HypogeneMineralization礦體產(chǎn)出環(huán)境:1）整個巖株內(nèi)；2）部分巖株部分圍巖；3）僅在圍巖內(nèi)礦體通常為陡壁圓筒狀，也有板狀、扁圓錐狀（tabulartoflatconical）礦化為浸染狀或細(xì)網(wǎng)脈狀，銅品位0.4-1%Cu，含微量Mo和gold。礦化呈帶狀：InnerZone

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與鉀化帶吻合，一般直徑數(shù)百米，相對地硫低，但鉬最高。黃鐵礦2-5%，py/cp比約3:1。礦化為浸染狀而非細(xì)網(wǎng)脈狀。OreZone

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大致分布在potassic-phyllic帶邊界上，黃鐵礦5-10%，py/cp比約2.5:1。主要礦物為黃銅礦，呈細(xì)網(wǎng)脈狀。其他礦物有斑銅礦、硫砷銅礦和輝銅礦。PyriteZone

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包括phyllicandargillic(若存在)的大部。黃鐵礦相當(dāng)高，可達(dá)10-15，py/cp比約15:1。礦化即有浸染狀又有脈狀。許多附加的外來硫化物相開始出現(xiàn)在上部。OuterZone

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與propyliticzone吻合。黃鐵礦微量，銅礦物稀有。閃鋅礦和方鉛礦常見，但常為邊界品位級。

礦化為脈狀。7HypogeneMineralization788BrecciaZones-Oftenmajororecarriersintheporphyrysystem.Haveveryhighgrades(2-5%Cu)andcanoccurbothintheporphyryorthecountryrock.Maybeformedbyhydrothermalactivity,gravitationalcollapseorlaterexplosivevolcanism.9BrecciaZones-Oftenmajoror在成礦區(qū)帶上，斑巖銅礦、鉬礦和錫礦明顯呈帶狀分布，與距板塊俯沖帶的距離有關(guān)，銅礦離海溝最近，而鉬錫依次分布在海溝內(nèi)側(cè)。10在成礦區(qū)帶上，斑巖銅礦、鉬礦和錫礦明顯呈帶狀分布，與距板塊俯VerticalExtentofPorphyryBodies斑巖銅礦與小高位小巖株和陸相鈣堿性火山作用有關(guān)。因而侵入體為層火山所覆蓋，青盤巖化延展到火山巖中，其它蝕變于其界面處。一般地，此模式說明斑巖銅礦是更大的成礦體系的一部分，包括高位淺成低溫貴金屬礦床。11VerticalExtentofPorphyryBo閃長巖模式斑巖礦床有兩個不同的體系：其一為“LowellandGuilberttype”，以美國西南部以石英二長巖-花崗閃長巖為特征。其二為AndesandPacificIslands.主巖為閃長巖，偶為正長巖。兩者的特征對比見表。閃長巖體系的特征為：低硫逸度，存在磁鐵礦，蝕變僅有鉀化帶和青盤巖化帶，金為重要組分，而鉬稀有或缺失。12閃長巖模式12ComparisonoftheLowell-GuilbertandDioriteTypesofPorphyryCopperDepositsFEATURELOWELL-GUILBERTDIORITEHostPlutonQuartzMonzonitetoGranodiorite(S)Qtz.DioritetoDiorite(I)AlterationPotassic

Phyllic

Argillic

PropyliticPotassic

PropyliticMineralizationQuartzinfracturesCommonCommonErraticOrthoclaseinfracturesCommonErraticMagnetiteMinorCommonPyriteinfracturesCommonLessCommonMolybdeniteCommonRareChalcopyrite/bornite>3:1<3:1GoldRareImportantStructureBrecciaMayOccurRareStockworkImportantImportant這些差異可以理解為：日本島弧侵入體沒有斑巖銅礦，在巖相學(xué)上他們屬于兩類花崗巖（“S”and“I”type）。前者為陸殼深熔作用形成的，后者為板塊俯沖期間部分熔融的最后階段的分異產(chǎn)物。13ComparisonoftheLowell-GuilbCharacteristicsofS&ITypeGranitesFEATURESTYPEITYPEGabbro:diorite:granite2:18:8015:50:35Na2O(felsic)<3.2%>3.2%Al2O3/Alkalis+CaO>1:1<1:1Ironoxideilmenitemagnetite87Sr/86Sr>.706.704-.706NormativecorundumdiopsideAssoc.metalsSn,WAuGenesisCrustalanatexisofsedimentsPartialmeltofmantleSandItypegranites的特征對比，與LowellandGuilbertandDiorite斑巖礦床所揭示的特征相似。閃長巖模式的礦床形成于大洋巖石圈俯沖所致的部分熔融作用，而LowellandGuilbert模式礦床代表遠(yuǎn)離板塊邊界陸殼的熔融作用。14CharacteristicsofS&IType成因典型斑巖體系的最明顯特征是其大小。熱液不僅滲透到母侵入體中，而且滲透至圍巖中。認(rèn)為容礦巖體侵入至淺部（0.5-2km深)。侵入體結(jié)晶開始時，巖漿房的蒸汽壓隨不相容元素進(jìn)入蒸汽相而增大，當(dāng)蒸汽壓超過上覆巖石的圍壓時發(fā)生退化沸騰。快速沸騰的液體最終克服巖石的拉伸強(qiáng)度從硅酸鹽熔體中分離出來，導(dǎo)致強(qiáng)烈的網(wǎng)脈狀角礫化(如:waterat2Kb壓力和5000C的水由于沸騰體積增加至少10%)。此外，沸騰是吸熱反應(yīng)，正在逸出的蒸汽膨脹時需要巖漿中的熱，因而，快速降低了巖漿房中的溫度,，形成侵入體中心的斑狀結(jié)構(gòu)。15成因151616流體包裹體證據(jù)氧同位素研究表明鉀化帶黑云母的值與巖漿水相當(dāng)，而絹英巖化帶的絹云母虧損18O，表明為天水。泥化帶也是如此。1）侵入體上升至地殼開始結(jié)晶；2）巖漿熱液對流在侵入體內(nèi)和附近形成鉀化帶；3）圍巖中的天水對流形成青盤巖化，對流由侵入體熱所驅(qū)動；4）隨著侵入體的冷卻，天水體系疊加至巖漿體系之上，形成phyllic-argillicalterationzones。17流體包裹體證據(jù)1）侵入體上升至地殼開始結(jié)晶；17問題：1）為什么閃長巖模式礦床僅有potassic-propyliticalteration?2）為什么閃長巖模式巖漿水-天水系統(tǒng)從不互相侵入？18問題：1）為什么閃長巖模式礦床僅有potassic-propBinghamCanyon,UtahLocationLiesabout30kmsouthwestofSaltLakeCity,Utahatanaltitudeof2000meters.FromahistoricperspectiveoneofthemostfamousminesintheUnitedStates.19BinghamCanyon,Utah19RegionalGeologyBinghamissituatedintheBasinandRangetectonicprovince.TheOquirrahMountainsformahorstblockoffoldedPaleozoicrocksboundedbynorthtrendingfaults.TheprincipalcountryrocksarePennsylvanianquartzitesandlimestonesfoldedandintrudedduringtheMesozoic.TheorebodyitselfoccursinoneofaseriesofsmallerhorstsboundedbythenorthwesttrendingBearandOccidentalFaultswhichupliftthenortheasttrendingCoppertonAnticline.MineralizationisinoradjacenttotheBinghamstock,aporphyriticgranodiorite.Theslightlyyounger(?)LastChancestocktothesouthisbarren.BothhavebeenagedatedatEocene.TherearethreetypesofmineralizationintheOquirrahMountainsalluvialgoldAg-richgalenaandsphaleriteveinsinlimestonesporphyrycoppermineralization20RegionalGeology20GeologyoftheBinghamCanyonPorphyryCopperDepositThedepositoccursinatriangularzoneofdisseminatedandveinletcoppersulfidemineralization1.5x2.5kminplanandatleast500metersinthickness.Themajorityoftheoreisinthegranodiorite,butsubstantialreservesarepresentinthemetamorphosedPaleozoics.Theoriginalhostintrusivewasagranodiorite,butsubsequenthydrothermalalterationhasresultedinarockmorecloselyapproximatingagranite.Thestockhasawelldefinedpotassicalterationzonecharacterizedbysecondarybiotite,poorlydefinedphyllicalterationandaspottyandirregularpropyliticalterationzone.Argillicalterationisabsent.Extensivebrecciationofboththeintrusiveandcountryrockiscommon.Theprimarymineralizationaverages1-4%oftherock.Thecoreoftheintrusiveismolyrichwithpyriteabundantonlyinthephylliczone.Chalcopyriteandminorbornitearetheonlyprimarycoppersulfidesrecovered.Peripheralskarndepositsconsistingofenargite,galena,sphaleriteandtetrahedriteareimportantinthesurroundingmetasediments.TypicalofmostAmericandeposits,earlyminingwasfromasupergeneenrichmentzoneofchalcocite,malachiteandnativecopperlyingbeneathabarrenlimonitecap10-100metersthick.Muchofthissupergeneorehasbeenminedout.21GeologyoftheBinghamCanyonGenesisNospecificgeneticmodelhasbeenproposedfortheBinghamCanyondeposit.Ratherit'sgenesisisthoughttobesimilartothatofallthesouthwesternporphyrycopperdeposits.22Genesis22PorphyryMolyandTinDepositsInadditiontocopperthereareotherporphylyrelatedtypesofmineralization,mostnotablymolybdenumandtin.Whileeachofthethreetypesofporphyrydepositscontainappreciablequantitiesoftheotherelements,theyarenonethelessgeologicallydistinctenoughtoconstituteendmembersoftheporphyryspectrum.Originallyitwasthoughtthatallmolydepositsbelongtoasinglegroup.Itisnowacceptedthattherearetwosubtypes.ThenomenclatureisconfusingsinceonetypeistermedsimplyporphyrymolywhilethesecondtypeistheClimaxtype.23PorphyryMolyandTinDepositsPorphyryMolySubtype1）與花崗閃長巖—石英二長巖類I型花崗巖有關(guān)。與I型斑巖銅礦（閃長質(zhì)）相比，略顯酸性。礦物只有輝鉬礦，脈狀和浸染狀，品位低(0.1-0.2%MoS2)。2）蝕變不易識別，但鉀蝕變普遍。由于巖石富鉀，難以識別鉀化。有些硅化僅出現(xiàn)在鉬礦脈周圍。Orebodiesaresheet-liketotabular.Depositsrangeinagefrom30-80MYandoccurinassociationwithMesozoictorecentsubductionzones,particularlythosewithsteepangles.Nosimplegeneticmodelseemstofitallofthedepositsinthissubgroup.Clearlytheyarerelatedtosubductionandevidencefromfluidinclusionsandisotopesfavorsagenesissimilarifnotidenticaltothedioritetypeporphyrycopperdeposits.Anunansweredquestionistherelationshipofthemolydepositstothecopperdeposits.QuartzHillinAlaskalieslessthan50kmfromanactivetrenchleadingsomegeologiststosuggestthatporphyrymolydepositsformatshallowerdepthsnearerthetrenchthandoporphyrycopperdeposits.However,intheAndeswherebothmolyandcopperdepositshavebeenextensivelymappedthemolydepositslieinabelttotheeastofthecopperdepositsandfartherfromthetrench.Unfortunately,agedifferencesbetweenthecopperandmolybeltsaswellaschangesintheangleofsubductioncomplicatethepictureintheAndes.24PorphyryMolySubtype242525ClimaxTypeMolyDepositsClimaxtype鉬礦與A型(S型亞類)花崗巖有關(guān)。其與S型不同點(diǎn)是富K2O和F。礦體均在巖體中，輝鉬礦為主礦物，但可回收錫鎢。品位高于斑巖鉬礦，平均約0.35%

MoS2,某些礦床高達(dá)0.7%。蝕變?yōu)閺浬⑿?，?qiáng)烈的硅化及鉀化、青盤巖化、磁鐵礦-黃玉化，偶見弱的絹英巖化/泥化。礦體為傘形。成礦年齡約30Ma。已知的Climaxtypemolydeposits位于西Cordillera,大致從中Montana至北NewMexico。若與中生代俯沖帶有關(guān)（尚有爭議），礦床則分布于板緣1000km內(nèi)。A-type或非造山花崗巖認(rèn)為是大陸裂谷的產(chǎn)物（尚有爭議）。

另一可能性是與俯沖有關(guān),礦床形成在俯沖淺角度的地區(qū)。鍶同位素比大于0.706，常超過0.740。高氟說明陸殼混染。俯沖帶深部的熱使加厚的陸殼基底發(fā)生熔融。這些巖漿慢慢混染陸殼物質(zhì)而富集K和Mo。26ClimaxTypeMolyDeposits26Climax,Colorado位置位于Denver西部約100km，海拔4000m的陸地分界線。概述位于ColoradoFrontRange，由元古代片巖和片麻巖(IdahoSpringsGroup)所組成，被元古代SliverPlumeGranite所侵入。FrontRange構(gòu)造復(fù)雜，但褶皺卻以北東向?yàn)橹?。古生代沉積巖不整合于元古代基底之上。MosquitoFault切割Climax巖株，為區(qū)內(nèi)主要斷裂，它從古生代活動至今。早第三世淺侵入體和流紋質(zhì)火山作用是本區(qū)最后的地質(zhì)事件。GeologyoftheClimaxDeposit主要礦化帶直徑約1.5km，成為了侵入于IdahoSpringsGroup中的巖株和巖脈的頂帽。MosquitoFault切過礦帶的西部。4個巖體控制了礦化，時代為Oligocene世。巖株西南部最老，次為中央巖株，共同構(gòu)成了Climax花崗閃長巖體。最后它們被AplitePhaseandthePorphyriticGranite所侵入。

27Climax,Colorado2728282929Alterationconsistsofearlypotassicalteration,weaksericiticalterationandlate,intensesilicification.Fourphasesofmineralizationarerecognized,eachcorrelatedwithanintrusion.Thefirstthreeformthethickumbrella-likeorebodies(Figure).Theearliest,anduppermost,Cerescoorebodyhasbeenalmostcompletelyremovedbyerosion.BeneaththeCerescolietheUpperandLower(younger)orebodies,correlatingwiththesecondandthirdintrusions.Thefourthintrusionproducedsilicification,butnomineralization.Mineralizationconsistsofazoneofirregularveinletscontainingquartz,K-sparandfine-grainedmolybdenite.Someoreoccursinlargerveinlets(pseudo-pegmatites)andalongjointsurfaces.Fluoriteandtopazarecommonaccessoryminerals,asarewolframite,pyriteandcassiterite.GenesisThoughttobesimilarinmanyrespectstoporphyrycopperdeposits,howevertherocksaremoresilicicsuggestingeithersignificantcrustalcontaminationoranentirelycrustaloriginfortheintrusives.Whilesomecopperdepositsoccurinsettingssuggestiveofmultipleintrusivephasesthereappearstobeonlyasingleorebody,inmarkedcontrasttomolydepositswhereeachintrusivehasanassociatedorezone.30AlterationconsistsofearlypTinDepositsPorphyrytindepositsarerestrictedtoalinearbeltintheAndesMountainseastofthecopper-molybelts.Hostintrusivesaregenerallylatiteporphyrystockstotruegranites.Thereisacloseassociationwithstratovolcanoesindicatingveryshallowlevelsofemplacement.Ratherthanthetypicalflaringstock,intrusionsassociatedwithtindepositsappeartobenarrowfinger-likeprojections.Themainoremineraliscassiterite,oregradesaveraging0.1-0.2%SnO2.Theoreoccursasanearlydisseminatedphasethatissub-oregradefollowedlaterveins.Alterationconsistsofsilicification,sericitization,propylitizationanddeeplevelquartz-tourmaline.Thereisanabsenceofpotassicalteration.Insomeinstances,thereareassociatedperipheralbasemetalvein-typedeposits.31TinDeposits31GenesisThoughttobeatwostagemodel(Figure).Emplacementofshallowplug-likestockintheventofafelsicstratovolcano.Magmatic-meteoricwatersystemdevelopsasigneousactivitywanescausingpervasivealterationandthedisseminatedtinmineralization.Astemperaturedeclinescoolingcausesfracturingoftherocks.Thesefractureswidenanddeepeneventuallytappingthedeepermagmachamberfeedingthevolcano.Thisallowsvolatilestoescapethechamberandstreamupward.Coolingcausesdepositiononfracturewallsgeneratingthevein-typetinmineralization.32Genesis323333CharacteristicsofPorphyryCu-Mo-SnDeposits1RestrictedtothePhanerozoic(mostlyMesozoic-Tertiary).Closelyassociatedwithfelsicintrusivesofqtzdioritetoqtzmonzonitecomposition.2Accompaniedbycharacteristicalterationenvelope.potassic-->phyllic-->argillic-->propylitic.3Strongzoninginrelationshiptoplateboundaries.Cu>Mo>Snmovinginlandfromtheplatemargin.4Closelyassociatedwithislandarcdevelopmentandsubductionzonesatconvergentocean-continentplateboundaries.5Oreoccursinalarge,low-gradeshelladjacenttothepotassiczone.Chalcopyriteandbornitemostcommonmineralswithlessermolybdeniteandcassiterite.6Isotopicevidencesuggestsshallowdepthsofmagmagenerationandsignificantgroundwaterinteraction.34CharacteristicsofPorphyryCuVein-typeDepositsThesewereonceoneofthemostsoughtafterandheavilyminedtypesoforedeposits.ThefamousminingdistrictsoftheWestaremainlyvein-typedeposits.Vein-typedepositsrepresentaprogressioninto"true"hydrothermaldepositsthatlieatsomedistancefromthe"igneous"source.Todaythisgrouphasdeclinedmarkedlyinimportance,butstillproducesmuchoftheworld’ssilverandtungstenandsomegoldandbasemetals.Thesearchforthistypeofdeposithasbeenabandonedlargelybecausetheytendtobesmallanddifficulttofind.LindgrenClassification-Stillmuchinvogueforthedescriptionofvein-typedeposits(SeeHandoutsforHypothermal,MesothermalandEpithermaldeposits).Thesehandoutsdatefromthe1930’s,butwiththeexceptionoftemperaturedata,theinformationhaschangedverylittle.35Vein-typeDeposits35GeneralCharacteristicsAlthoughasagroupthedepositsvaryconsiderablyinsize,mineralogyandgeologicenvironments,allhavecertainunifyingfeatures:associationinspaceandtimewithcalc-alkalineigneousactivity;clearlyepigeneticwithoreshavingvein-likeformandclosespatialrelationshiptofaulting;oremineralsaredepositedasopenspacefillingalongdilatantzonesorasreplacementsofcarbonatehostrocks;zonationischaracteristicandalwayspresent(Figure);depositionisfromhydrothermalfluidsatdepthsoflessthan3km;sulfurisusuallyofmagmaticorigin(34S=0);districtsarestructurallycomplex;someformofalterationisalwayspresent,oftensericiticataminimum;oftenseeaprogressionfrommagmaticwatertometeoricwaterlaterintheparageneticsequence.36GeneralCharacteristics36Variousmorerecentclassificationsofvein-typedepositshavebeenproposed,butnonehavebeenadopteduniformly.Mostgeologistshaveswitchedto"type"groupsofdeposits(e.g.Carlin-type,Creede-type).Thisoftenleadstoacertaindegreeofconfusion.37VariousmorerecentclassificaHypothermalDeposits300-

500°C(highpressure;greatdepth)CharacterofVeins-Markeddevelopmentofreplacementtextures.Gradationaltopegmatiticoredeposits.DiagnosticOreMineralscassiteriteSnO2hematiteFe2O3graphiteCilmeniteFeTiO3magnetiteFe3O4molybdeniteMoS2marmatite(Zn,Fe)SpyrrhotiteFe1-xSrutileTiO2scheeliteCaWO4topazAl2SiO4(OH,F)woiframite(FeMn)WO4OtherCommonMetallicMineralsarsenopyriteFeAsSbismuthBibismuthiniteBi2S3chalcopyriteCuFeS2galenaPbSgoldAupyriteFeS2

CharacteristicGangueMineralsfeldsparpyroxeneamphibolegarnetmicasspineltourmaline

WallRockAlterationIron-magnesiumMetasomatism–以富鐵黑云母、電氣石、鈣鐵榴石（石榴石）、角閃石和輝石為特征。Sericitic–

存在但不廣泛。Propylitization-Hasbeendescribed,butisveryrare38HypothermalDeposits300-500MesothermalDeposits

200-300°C(moderatepressure;moderatedepth)脈體特征

–

均勻板狀脈，脈壁較平直。交代常見，以碳酸鹽為盛。少見張性充填，分帶良好，脈系長而大。skutterrudite(Co,Ni)As3smaltite(Co,Ni)As3chloanthite(Ni,Co)As3

arsenopyriteFeAsSbismuthiniteBi2S3bournonitePbAuSbS3borniteCu5FeS4chalcociteCu2SchalcopyriteCuFeS2covelliteCuScobaltiteCoAsSenargiteCu3AsS4galenaPbSgoldAumolybdeniteMoS2pyriteFeS2niccoliteNiAstetrahedriteCu12Sb4S4tennantiteCu12As4S4sphaleriteZnSQuartzSiO2ankeriteCa(MgFe)(CO3)2CalciteCaCO3dolomiteCaMg(CO3)2FluoriteCaF2sideriteFeCO3WallRockAlteration-DependentonthetypeofhostrockSericitic-DevelopsinfeldspathicrocksFeldsparsaltertosericiteandmaficmineralstopyrite.Dolomitization-Developsincarbonaterocks.Characterizedbyankeriteandsecondarycalciteanddolomite.Silicification-Alsomostcommonlydevelopedincarbonates,butnone-the-lessalsocommoninfeldspathicrocks.Jasperization-Characterizedbytheappearanceofjasper,aniron-richvarietyofamorphoussilica.39MesothermalDeposits200-300EpithermalDeposits

50-200°C(

lowpressure;shallowdepth)CharacterofVeins–

受主巖構(gòu)造控制張性充填，脈常呈皮殼狀、條帶狀、梳狀。DiagnosticOreMineralscinnabarHgSacanthiteAg2SstibniteSb2S3argentiteAg2SchalcociteCu2SproustiteAg3AsS3pyargyriteAg3SbS3

arsenopyriteFeAsSborniteCu4FeS5bismuthiniteBi2S3chalcopyriteCuFeS2copperCuelectrumAuAggalenaPbSgoldAumarcasiteFeS2polybasite9Ag2S-Sb2S3orpimentAs2S3silverAgpyriteFeS2realgarAsStetrahedriteCu12Sb4S13tennantiteCu12As4S13adulariaKAlSi3O8aragoniteCaCO3aluniteKAl(OH)12(S04)bariteBaSO4calciteCaCO3chalcedonySi02dolomiteCaMg(CO3)2fluoriteCaF2rhodochrositeMnCO3quartzSi02Silicification–

不一定直接與成礦流體有關(guān)，早階段蝕可緊隨礦化之后。Propylitization–

發(fā)育綠泥石、綠簾石、方解石，似與礦化有關(guān)，巖石呈特征的綠色。Sericitic-Formationoftheassemblagesericitepluspyrite.Notalwayspresentandusuallyoflimitedaerialextent.Alunitization-Nearsurfacealterationassociatedwithdescendingmeteoricwaters.Characterizedbytheformationofalunite.40EpithermalDeposits50-200°MesothermalBase-MetalVeinsOccurinrocksofallages,butmostimportantdistrictsareofPaleozoic/Mesozoicage.Seemtoberestrictedtoorogenicbelts,inparticulartheRockyMountains.Assuch,thewesternCordilleraisfamousfortheconcentrationofthistypeofdeposit.FormMostofthelargedepositsarereplacement-typeassociatedwithmajorfaultsystems.Overalltheshapeofmostdistrictsislinearreflectingthestrongcontrolfaultinghasonoredeposition.Setting礦床與鈣堿性火山作用及其侵入體密切相關(guān)，盡管大部分地區(qū)地質(zhì)情況復(fù)雜，但成礦時代卻集中在侵入事件的峰期后不久。典型巖株為淺成相石英閃長巖至花崗巖。斷裂作用是區(qū)內(nèi)主要特征，可填出至少一條區(qū)域斷裂。一般地礦體與主斷裂無關(guān)，但與其平行的次級斷層或年輕的交切斷層有關(guān)。41MesothermalBase-MetalVeins41Alteration變化大，決定于主巖性質(zhì)。砂巖中蝕變限于礦脈兩側(cè)數(shù)厘米，而碳酸鹽內(nèi)可達(dá)數(shù)千米。

碎屑巖內(nèi)為簡單的硅化，而碳酸鹽和變質(zhì)巖內(nèi)有絹英巖化+泥化+青盤巖化。蝕變通常是復(fù)雜的，難以區(qū)分，特別是脈體之間的蝕變相互疊加。MineralogyCu,Fe,Pb,Zn硫化物為主，次為硫鹽礦物。常見礦物為黃鐵礦、黃銅礦、斑銅礦、方鉛礦、閃鋅礦、砷黝銅礦tennantite

、黝銅礦tetrahedrite、硫砷銅礦enargite、輝銅礦chalcocite和藍(lán)輝銅礦digenite。磁黃鐵礦缺失，由此限定了其上限。

所列礦物大多是銀的重要載體，為世界銀資源的主體。共生序列極其復(fù)雜，顯示其形成歷史長。在中溫區(qū)沿走向礦物分帶，從而呈現(xiàn)出亞帶來。Gangue脈石礦物種類少，主要為方解石、石英、菱鐵礦、白云石、鐵白云石42Alteration42Geochemistry流體包裹體表明成礦溫度為250-4000C，鹽度較低(1-4wt%)。穩(wěn)定同位素?cái)?shù)據(jù)支持巖漿硫的觀點(diǎn)

，說明至少早期礦物與巖漿水有關(guān)。GenesisEarlygeneticmodelssuggestedthatthemajorfaultswithinthedistrictsservedasconduitsformagmaticwaterswhichflowedalongthefaultsinsearchofeasilyreplaceablerocks(carbonates)wheredepositionoccurred.Thismodelisnotwithoutitsproblems.Firststableisotopesindicatethatinmanydistrictsmeteoricwaterhasplayedasubstantialrole.Secondthereistheproblemofcarryingsulfurandoremineralsinthesamefluid.Despitetheseproblemsthemodelhasbeenlittlechangedormodified.Thelackofemphasisonthesedepositsinrecentyearsisprobablyamajorreasonfortheratherincompletemodel.Forinstance,comparethemtoepithermaldepositsthatwillbediscussedinaseparatelecture.Modelsforepithermaldepositsarecomplexandleavefewunansweredquestions.43Geochemistry43Coeurd‘AleneDistrict,IdahoTheCoeurd‘AlenedistrictisoneofthemostfamousintheUnitedStates.Ithasproducedalmostcontinuouslysinceitwasdiscoveredin1857.Thedistrictproducesmainlysilverwithbyproductlead,zincandcopper.LocationTheCoeurd‘Alenedistrictextendseast-westabout50

kmandnorth-southabout25kmalongthewestflankofthenorthernRockyMountains.44Coeurd‘AleneDistrict,Idaho4RegionalGeologyThebasalrocksintheregionareapartoftheweaklymetamorphosedsandstonesandshalesoftheProterozoicBeltSupergroup.TheseareunconformablyoverlainbyCambrianrocks.Allrocksarehighlyfoldedandfaulted.Thefoldstrendgenerallynorth-south,althoughimmediatelysouthoftheOsborneFaultthefoldsstrikemorenearlyeast-west.Thelargestfaultintheregionistheeast-westtrendingOsborneFault(Figure)whichhasbeentracedfor800kmalongstrikeandisknowntohaveadisplacementof15,000meters.Manyothersmallersubparallelfaultshavebeenmappedmanyofwhichseemtocontrolthemajorveinsystems.45RegionalGeology45IntrusivesarenotconspicuousintheCoeurd‘Alenedistrict,butseveralsmallCretaceousagestocksofgranodioriteandmoazonitearepresenttothenorthoftheOsborneFault.ThesearethoughttobeoffshootsofthemuchlargerIdahobatholithtothesouth.46IntrusivesarenotconspicuousOreDepositsHundredsofveinandlodedepositsoccurwithinthedistrict,mostalongdilatantfaultzonesandasreplacements

alongbeddingplanesofthehostrocks.VeinstrendsubparalleltotheOsborneFault.Quartzitestendtobebetterorehoststhanargillitessincetheformerhasagreaterdensityofbrittlefractures.Thesefracturesarethoughttohaveformedasaconsequenceofoblique-slipalongtheOsborneFault.SomedepositsappeartobeclearlyassociatedwiththeCretaceousageintrusives,butforothersthatassociationismoretenuous.Silveristhemostsignificantmineralization,butthereisalsorecoverablelead,zinc,copperandgold.Associatedganguemineralsarepyrite,arsenopyrite,quartz,siderite,andcalcite.Thereisastrongmineralzoningwithinthedistricts:silver-zincwithpyritenearthestockssilver-copperwithsideritealongthesouthandsoutheastedgeofthedistrictsilver-leadeastandwestsidesofthedistrictAlterationislargelyrestrictedtosericitization.Otheralterationincludeslocalsilicificationandweakbleaching.47OreDeposits47GenesisTheCoeurd’AleneveinswerelongthoughttoberelatedtointrusionoftheMesozoicIdahobatholith,howeverU/PbisotopesindicatedagesthatwereProterozoic.Thispresentedamajorproblem.DiscoveryofundeformedstratiformoresintheBeltSupergrouptotheeastinMontanathatareclearlyunrelatedtoigneousactivityhavecausedsomegeologiststoproposeamodifiedgeneticmodel.TheybelievethattheCoeurd扐leneoreswereoriginallydepositedasstratiformsediment-hostedsulfidesduringthePrecambrianandremobiizedtotheircurrentlocationsduringtheMesozoicbyheatfromtheintrusives.48Genesis48放映結(jié)束！無悔無愧于昨天，豐碩殷實(shí)的今天，充滿希望的明天。49放映結(jié)束！無悔無愧于昨天，豐碩殷實(shí)的今天，充滿希望的明天。4高級礦床學(xué)-斑巖型礦床斑巖銅礦50高級礦床學(xué)-斑巖型礦床斑巖銅礦1斑巖銅礦(Porphyrycopperdeposits)為世界提供了50%以上的銅金屬(over100producingmines)。Theircloserelativestheporphyrymolydepositsproduce70%oftheworld'smoly.Bothdeposittypeswillbediscussedseparately,buttheysharemanycharacteristicsandareformedinsomewhatsimilarmanners.51斑巖銅礦(Porphyrycopperdeposits)全球斑巖銅礦分布圖絕大多數(shù)斑巖銅礦形成于中新生代，與離散板塊邊緣上及附近的火山鏈有關(guān)（環(huán)太平洋、古地中海和古亞洲洋）。極少數(shù)為古生代，分布在古生代板塊邊緣上，如U.S.S.R、UnitedStates。52全球斑巖銅礦分布圖3全球已知最大的88個斑巖銅礦產(chǎn)于美國西南部，成礦時代為58-72Ma。巖體形態(tài)典型斑巖銅礦床呈圓筒狀，產(chǎn)于巖株?duì)顜r體中，出露面積為1.5x2km（橢圓狀），核部為斑巖質(zhì)，向外到邊部為中—粗粒等粒的成分相似的巖石。主巖巖石學(xué)一般地，容礦主巖為長英質(zhì)侵入體，成分為石英正長巖、石英二長巖、花崗閃長巖系列；閃長巖—正長巖系列53全球已知最大的88個斑巖銅礦產(chǎn)于美國西南部，成礦時代為58-熱液蝕變LowellandGuilbert總結(jié)的斑巖銅礦蝕變模式，圍繞斑巖株依次出現(xiàn)4個蝕變暈鉀化帶-都存在。特征：次生的鉀長石、黑云母和/或綠泥石交代原生的鉀長石、斜長石和鎂鐵質(zhì)，及微量的絹云母。絹英巖化帶

–

可存在。特征：脈石英、絹云母、黃鐵礦和微量綠泥石、伊利石和金紅石，交代鉀長石和黑云母。泥化帶（Argillic）-可存在。特征：高嶺石、蒙脫石等粘土礦物及微量浸染黃鐵礦。斜長石強(qiáng)烈蝕變、鉀長石不受影響，黑云母綠泥石化。青盤巖化帶（Propylitic）

-都存在。特征：綠泥石、方解石、微量綠簾石。鎂鐵質(zhì)礦物強(qiáng)烈蝕變，斜長石消失。在深部，上述各帶融為一體，構(gòu)成石英-鉀長石-絹云母-綠泥石組合。54熱液蝕變5556HypogeneMineralization礦體產(chǎn)出環(huán)境:1）整個巖株內(nèi)；2）部分巖株部分圍巖；3）僅在圍巖內(nèi)礦體通常為陡壁圓筒狀，也有板狀、扁圓錐狀（tabulartoflatconical）礦化為浸染狀或細(xì)網(wǎng)脈狀，銅品位0.4-1%Cu，含微量Mo和gold。礦化呈帶狀：InnerZone

–

與鉀化帶吻合，一般直徑數(shù)百米，相對地硫低，但鉬最高。黃鐵礦2-5%，py/cp比約3:1。礦化為浸染狀而非細(xì)網(wǎng)脈狀。OreZone

–

大致分布在potassic-phyllic帶邊界上，黃鐵礦5-10%，py/cp比約2.5:1。主要礦物為黃銅礦，呈細(xì)網(wǎng)脈狀。其他礦物有斑銅礦、硫砷銅礦和輝銅礦。PyriteZone

–

包括phyllicandargillic(若存在)的大部。黃鐵礦相當(dāng)高，可達(dá)10-15，py/cp比約15:1。礦化即有浸染狀又有脈狀。許多附加的外來硫化物相開始出現(xiàn)在上部。OuterZone

–

與propyliticzone吻合。黃鐵礦微量，銅礦物稀有。閃鋅礦和方鉛礦常見，但常為邊界品位級。

礦化為脈狀。56HypogeneMineralization7578BrecciaZones-Oftenmajororecarriersintheporphyrysystem.Haveveryhighgrades(2-5%Cu)andcanoccurbothintheporphyryorthecountryrock.Maybeformedbyhydrothermalactivity,gravitationalcollapseorlaterexplosivevolcanism.58BrecciaZones-Oftenmajoror在成礦區(qū)帶上，斑巖銅礦、鉬礦和錫礦明顯呈帶狀分布，與距板塊俯沖帶的距離有關(guān)，銅礦離海溝最近，而鉬錫依次分布在海溝內(nèi)側(cè)。59在成礦區(qū)帶上，斑巖銅礦、鉬礦和錫礦明顯呈帶狀分布，與距板塊俯VerticalExtentofPorphyryBodies斑巖銅礦與小高位小巖株和陸相鈣堿性火山作用有關(guān)。因而侵入體為層火山所覆蓋，青盤巖化延展到火山巖中，其它蝕變于其界面處。一般地，此模式說明斑巖銅礦是更大的成礦體系的一部分，包括高位淺成低溫貴金屬礦床。60VerticalExtentofPorphyryBo閃長巖模式斑巖礦床有兩個不同的體系：其一為“LowellandGuilberttype”，以美國西南部以石英二長巖-花崗閃長巖為特征。其二為AndesandPacificIslands.主巖為閃長巖，偶為正長巖。兩者的特征對比見表。閃長巖體系的特征為：低硫逸度，存在磁鐵礦，蝕變僅有鉀化帶和青盤巖化帶，金為重要組分，而鉬稀有或缺失。61閃長巖模式12ComparisonoftheLowell-GuilbertandDioriteTypesofPorphyryCopperDepositsFEATURELOWELL-GUILBERTDIORITEHostPlutonQuartzMonzonitetoGranodiorite(S)Qtz.DioritetoDiorite(I)AlterationPotassic

Phyllic

Argillic

PropyliticPotassic

PropyliticMineralizationQuartzinfracturesCommonCommonErraticOrthoclaseinfracturesCommonErraticMagnetiteMinorCommonPyriteinfracturesCommonLessCommonMolybdeniteCommonRareChalcopyrite/bornite>3:1<3:1GoldRareImportantStructureBrecciaMayOccurRareStockworkImportantImportant這些差異可以理解為：日本島弧侵入體沒有斑巖銅礦，在巖相學(xué)上他們屬于兩類花崗巖（“S”and“I”type）。前者為陸殼深熔作用形成的，后者為板塊俯沖期間部分熔融的最后階段的分異產(chǎn)物。62ComparisonoftheLowell-GuilbCharacteristicsofS&ITypeGranitesFEATURESTYPEITYPEGabbro:diorite:granite2:18:8015:50:35Na2O(felsic)<3.2%>3.2%Al2O3/Alkalis+CaO>1:1<1:1Ironoxideilmenitemagnetite87Sr