简介：Fromthepetrologicalstudyofore-hostingfockswhichcontainlargeanorthitscrystalsandtheoccurrenceandchemicalcompositionofanorthitesandrelatedminerals,theauthorsconsiderthatthelargeanorthitecrystalsareofauthigenicorigin.Thedistributioncharacteristicsofanorthites,i.e.,theyaredistributedalongthebeddingandstructurallyweakzonesbutnotrestrictedtosynsedimentaryslumpstructures,andtherelationshipforsomeelementsbetweenanorthitesandothermineralsindicatethatanorthiteshaveresultedfromreactionofcirculatingalkalinesolutionsrichinAlandSiwithcarbonatedduringtheIndosinianorogeny.TheresultsofthisworksuggestthattheassociationofauthigenicanorthiteswithbeddedorebodiesintheDachangorefieldmaybetheevidencethatthemineralizationisrelatedtocirculatingundergroundhotwaters.

简介：Thebehaviouroftherare-earthelements(REE)duringtheweatheringofgraniteswasstudiedinsouthernGuangxi,China.Basedonthestudyoftheweatheringprofiles,thesoil,weatheredandsub-weaterebzonesareidentifiedwithdifferentREEgeochemicalbehavioursthrougtheweatheringprofilesofgranite.TheCeanomaliesoftheweatheringprofilescoveralargerangeofvalueswithmostfallingbetween1.02and1.43inthesoilzoneand0.16and0.40intheweatheredandsub-weatheredzones.Lightrare-earthelements(LREE)andheavyrare-earthelements(HREE)areenrichedtovaryingdegreeintheweatheringprofilesascomparedtohostgranites.Inthesoilzone,moreHREEsareleachedthanLREEs,andHREEsaremoreenrichedthanLREEintheweatheredandsub-weatheredzones.ItisconsideredthatinfiltrationandadsorptiononclaysaretwoprocessescontrollingtheenrichmentandformationofREEdepositsintheweatheringprofilesofgranite.

简介：TheDachangtin-polymetallicdistrict,Guangxi,China,isoneofthelargesttinorefieldsintheworld.Bothcassiterite-sulfideandZn-CuskarnmineralizationarehostedintheMid-UpperDevoniancarbonate-richsedi-mentsadjacenttotheunderlyingCretaceousLongxianggaigranite（91-97Ma）.TheLamoZn-CudepositisatypicalskarndepositinthedistrictandoccursatthecontactzonebetweentheUpperDevonianlimestoneandthegranite.Theoremineralsmainlyconsistofsphalerite,arsenopyrite,pyrrhotite,galena,chalcopyrite,andminormolybdenite.However,theageofmineralizationandsourceofthemetalsarenotwellconstrained.Inthisstudy,weusethemolybdeniteRe-Osdatingmethodandin-situPbisotopesofsulfidesfromtheLamodepositforthefirsttimeinordertodirectlydeterminetheageofmineralizationandthetracingsourceofmetals.SixmolybdenitesamplesyieldedamoreaccurateRe-Osisochronageof90.04-1.1Ma（MSWD--0.72）,whichismuchyoungerthanthereportedgarnetSm-Ndisochronageof95±11MaandquartzfluidinclusionsRb-Srisochronageof99±6Ma.ThisageisalsointerpretedastheageofZn-Cuskarnminer-alizationintheDachangdistrict.Further,inthisstudywefoundthatin-situPbisotopesofsulfidesfromtheLamodepositandfeldsparsinthedistrict＇sbiotitegraniteandgraniticporphyrydikeshaveanarrowrangeandanoverlapofPbisotopiccompositions（206pb/204pb18.417-18.594,207pb/204pb=15.641-15.746,and208pb/204pb=38.791-39.073）,suggestingthatthemetalsweremainlysourcedfromCretaceousgraniticmagma.