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19120053GEOSCIENCEVol119No11Mar.2005:2004-11-01;:2004-12-20;::(40472063,40272052,40232025);:,,,1963,,,,,,(,430074):,,-,,,,:;;;:P73614:A:1000-8527(2005)01-0014-07StableIsotopesofCarbonandSulfurofCapDolomiteintheThreeGorgesanditsMechanismDiscussionWANGJia2sheng,GANHua2yang,WEIQing,HUGao2wei,GEQian(FacultyofEarthSciences,ChinaUniversityofGeosciences,Wuhan,Hubei430074,China)Abstract:Capdolomite,overlyinggloballaterNeoproterozoicglacialdepositions,occursworldwidewithsigni2ficantstablecarbonisotopicnegativeexcursioncausedmostlikelybythemethane1Basedonthestudyofrocktexturesandstructures,andstableisotopesofdolomiteandSisotopeofbariteinterlayerswithinthecapdolomiteoutcroppedintheMiaoheareaintheThreeGorges,itistestifiedthatthestableisotopesshowastrongnegativeexcursion,andtheisotopesofsulfurshowasignificantpositiveexcursion,whichissimilartothereporteddataofauthigenicbaritesformedinamodernseafloorgashydrateenvironment1Therefore,itcanbeconcludedthatthecapdolomitewasmostlikelyformedinaspecialenvironmentunderwhichahugegashydratedissociatedwiththebreakupofSnowEarthinlaterNeoproterozoic1Allofaboveanalyseswouldbehelpfultoidentifytheproxiesofpaleo2gashydratedepositioninsomedistinctivestratigraphicsectionsandtoevaluatetheglobalenvi2ronmenteffectcausedbygashydrateinearthhistory1Keywords:capdolomite;stableisotopesofCandS;mechanismdiscussion;theThreeGorges0(capdolomite),,,[1-6],,,©1994-2007ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.[7]11;21;31;41;51;61;71;81;91;101;111;121;131:;;;;;1(,2002)Fig11GeologicalmapoftheThreeGorgesarea(simplifiedfromWangetal1,2002)[5,7-10],[7,10],Kennedy[11]Jiang[5](13C-411166),,(13C=-411166)[5],(),,1019g,,3000[12](13C-95-60),(DIC)13C0,,,()[13-19],(),(),[20-27],CO,,,1(1),,©1994-2007ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.();()[7],,,315m,25060,:(7),,510cm,1170m,,95%,3%,,(),(6),0155m,,,,(97%),,(5),013m(4),0110112m(3),0108m,(2),,0147m,,(95%),,,,30(1),012m244,10cm,200,3501h,100%CO2,()25,24hCO2()MAT251,91,23PDB,011%(1)1,(2),13C-21441Table1DataofstableC,OisotopesofthecapdolomiteintheMiaohearea,theThreeGorges3/m13C/18O/HYZ-092140-6196-13114HYZ-102160-6183-16118HYZ-122190-23116-30189HYZ-153112-2194-6158HYZ-163122-2186-5139HYZ-173132-2194-4154HYZ-183142-3114-4185HYZ-193152-3108-4179HYZ-203157-3100-4160HYZ-223175-6146-11152HYZ-254110-3119-5141HYZ-264120-3137-6154HYZ-274130-3160-6122HYZ-284140-3169-6105HYZ-294150-3175-5186HYZ-304160-2144-1128HYZ-314184-3193-3182HYZ-324194-3146-3182HYZ-335104-4103-5183HYZ-345114-4105-6180HYZ-355116-3161-7108HYZ-365126-3174-5106HYZ-375136-3185-5180HYZ-385146-3197-6114HYZ-395156-3186-6120HYZ-405166-3193-5169HYZ-415176-4111-5175HYZ-425186-3180-4181HYZ-435196-4117-6107HYZ-446106-4130-6144HYZ-456116-3137-5111HYZ-466126-3177-6135HYZ-476136-4102-5122HYZ-486146-4115-6144HYZ-496156-4101-6190HYZ-506166-4115-6155HYZ-516176-3198-6160HYZ-526186-4103-81343©1994-2007ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(,2003)213CFig12DiagramofCstableisotopesofcapdolomiteintheThreeGorges-6146013C0,13C,,,,[28]CO2[29][30][31],Berner[32],3CO24,5w(Mn)/w(Sr)[33,5],,Jiang[5](13C=-411166),Kennedy[11],3,2,20cm,,,,,X2,,©1994-2007ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(12mol/L),,100g/L20mL,30min12h,,3BaSO4,EA-MS(EA)(MS)BaSO4(3mg),He,SO2,,CDT+1184LTB-2,CDT,34S,015(2)234SFig12SisotopesofcapdolomiteintheThreeGorges/m34S/HYZ-133100+37113HYZ-244105+50162HYZ-536186+361352,34S-110216,(32),(2013)(932)(3)(12)(-1010)[34],34S(21103816)[17],ODP1146(47186711)(Greinert,2002;ODP1146,2003;,2003;,2000)3Fig13ComparisionofstableSisotopesfromcapdolomiteintheThreeGorgestothedatafromothers(PETM)[35],,,4,,,Kennedy[11]Jiang[5],©1994-2007ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(),(coldven2ting)[13-14,36-37],SO42-HCO-3[38-39],Ca2+Mg2+,[15-18,36,40],CCD(),[17][15-19],,,13C[41],,,,(),[20-27],,,:[1]NarbonneGM,KaufmanAJ,KnollAH1Integratedchemos2tratigraphyandbiostratigraphyoftheWindermereSupergroup,northwesternCanada:implicationsforNeoproterozoiccorrelationsandtheearlyevolutionofanimals[J].GeologicalSocietyofAmericaBulletin,1994,106:1281-12921[2]KennedyMJ1Stratigraphy,sedimentology,andisotopicgeo2chemistryofAustralianNeoproterozoicpostglacialcapdolos2tones:deglaciation,13Cexcursions,andcarbonateprecipitation[J].JournalofSedimentResearch,1996,66:1050-10641[3]KennedyMJ,RunnegarB,PraveAR,etal1TwoorfourNeo2proterozoicglaciations?[J].Geology,1998,26:1059-10631[4]HoffmanPF,SchragDP1ThesnowballEarthhypothesis:tes2tingthelimitsofglobalchange[J].TerraNova,2002,14:129-1551[5]JiangGQ,KennedyMJ,Christie2BlickN1StableisotopicevidenceformethaneseepsinNeoproterozoicpostglacialcapcar2bonates[J].Nature,2003,426:822-8261[6]PorterSM,KnollAH,AffatonP1ChemostratigraphyofNeo2proterozoiccapcarbonatesfromtheVoltaBasin,WestAfrica[J].PrecambrianResearch,2004,130:99-1121[7],,,1[M].:,200219-521[8]Lambert