氣液交代變質(zhì)巖

氣-液變質(zhì)作用及其巖石（氣液變質(zhì)巖）1、概述1）.氣-液變質(zhì)作用——熱的氣體和溶液作用于已形成的巖石，使其產(chǎn)生礦物成分、化學成分及結(jié)構(gòu)構(gòu)造的變化，此過程稱為氣-液變質(zhì)作用.2）.氣-液變質(zhì)作用常沿構(gòu)造破碎帶及礦脈邊緣發(fā)育，是一種找礦標志，又被稱為近礦蝕變或圍巖蝕變。3）.熱的氣體和溶液大部分來自于巖漿、部分來自于圍巖及地下熱水。4）.形成的巖石種類多，主要取決于圍巖成分、結(jié)構(gòu)構(gòu)造，以及氣液的性質(zhì)、交代作用方式、過程和外部條件。氣液變質(zhì)巖類型矽卡巖云英巖絹英巖及黃鐵絹英巖青盤巖類蛇紋石化巖硅化巖綠泥石化巖葉臘石化巖硫酸鹽化巖（明礬石化、石膏化、硬石膏化、重晶石化和黃鉀鐵礬化）鉀化巖（包括白云母化巖和黑云母化巖）鈉化巖碳酸鹽化巖（包括方解石化、白云石化、菱鐵礦化和菱鎂礦化）

1）矽卡巖熱接觸變質(zhì)作用——形成熱接觸變質(zhì)巖接觸交代變質(zhì)作用——形成接觸交代巖Here,quartzmonzoniteintrudedanMg-richlimestone.Metamorphismandmetasomatismproducedfourzonesnearthecontactthreeranginginsizefrom3cmto15minwidth.Theouterzoneconsistsofcalcitemarbleorcalcite-brucite[MgOH2]marble,showinglittlemetasomatism.Closertothecontactisthemontecellitezone.

Thiszoneconsistsofcalcite,montecellite[Ca(Mg,Fe)SiO4]andoneormoreofthemineralsclinohumite[Mg(OH,F)2.4Mg2SiO4],forsterite,mellilite,spurrite[2Ca2SiO4.CaCO3],tilleyite[Ca3Si2O7.2CaCO3],andmerwinite[Ca3MgSi2O8]主要巖石類型(1)矽卡巖是石榴石+輝石(透輝石)及其它Ca、Fe硅酸鹽礦物組成的巖石。(2)它是在深度不大或中等深度下由碳酸鹽巖（石灰?guī)r、白云巖等）與中酸性侵入巖接觸時，發(fā)生接觸交代作用而形成。(3)矽卡巖分2類：

鈣質(zhì)矽卡巖——石榴石+透輝石+符山石方柱石硅灰石

鎂質(zhì)矽卡巖——鎂橄欖石+透輝石+金云母+硅鎂石(4)矽卡巖形成的晚期，常有金屬礦物大量聚集而形成礦床，即矽卡巖型礦床。如我國長江中下游地區(qū)的Fe、Cu礦 如：湖北大冶Fe礦，安徽銅官山Cu礦Chapter30:MetamorphicFluids&MetasomatismFigure30.23.

Thethreeprincipaltypesofskarns.FromKerrick(1977)J.Petrol.,18,144-181.Winter(2010)AnIntroductiontoIgneousandMetamorphicPetrology.PrenticeHall.Chapter30:MetamorphicFluids&MetasomatismFigure30.28.

a.

Metasomaticzonesseparatingquartzdiorite(bottom)frommarble(top).ZonationcorrespondstothirdrowfrombottominTable30.1.b.

Symmetricmetasomaticveinindolomite.ZonationcorrespondstolastrowinTable30.1.AdamelloAlps.AfterFrischandHelgeson(1984)Amer.J.Sci.,284,121-185.PhotoscourtesyofHalHelgeson.Winter(2010)AnIntroductiontoIgneousandMetamorphicPetrology.PrenticeHall.ba1cm1cmChapter30:MetamorphicFluids&MetasomatismFigure30.31.

Zonationinanexperimentalskarnformedatthecontactbetweengranodioriteandlimestoneat600oC,Pfluid=0.1GPa(XCO2=0.07).AfterZharikov,V.A.andG.P.Zaraisky(1991)Experimentalmodelingofwall-rockmetasomatism.InL.LPerchuck(ed.),ProgressinMetamorphicandMagmaticPetrology.AMemorialVolumeinHonorofD.S.Korzhinskii.CambridgeUniversityPress.Cambridge,pp.197-245.PhotocourtesyG.Zaraisky.Winter(2010)AnIntroductiontoIgneousandMetamorphicPetrology.PrenticeHall.矽卡巖的分帶ZonationinskarnsystemsTransferofheatandmassfromintrusionsorfluidconduits熱和物質(zhì)的轉(zhuǎn)移；自巖漿源或流體通道Intrusion侵入巖Calcareouswallrock石灰質(zhì)圍巖Endoskarn內(nèi)矽卡巖Massive/metasomaticskarn致密塊狀/交代矽卡巖Reactionskarn反應矽卡巖Bleachedmarble漂白的大理巖Marble大理巖Limestone灰?guī)rHornfels角巖Fluidescapestructures流體逃逸構(gòu)造Garnet/pyroxeneratiodecrease石榴石/輝石比例變小Garnetcolourlighter石榴石顏色變淺Pyroxenecolourdarker輝石顏色變深CuZn-Pb38.3mEndoskarn.Darkredgarnet內(nèi)矽卡巖。深紅色石榴石45.2mRedgarnet紅色石榴石46.3mBrowngarnet棕色石榴石48.2mYellow

garnet黃色石榴石54.2mLightyellow

garnet淺黃色石榴石某含銅矽卡巖自侵入體而遠的分帶

ZoningawayfromintrusioninaCuskarn2）.云英巖，黃鐵絹英巖、次生石英巖由中酸性巖類交代而成.CaAl2Si2O8+F-+OH-

CaF2+電氣石NaAlSi3O8+F-+OH-

KAlSi3O8+F-+OH-

白云母+SiO23）黃鐵絹英巖CaAl2Si2O8+F-+OH-

CaF2+電氣石NaAlSi3O8+F-