TheBaimazhainickeldeposit,YunnanProvince,China,islocatedinthesouthernpartoftheSanjiang(Tri-river)alkali-richintrusiverockbelt(SanjiangARIR).Inthispaperwasconducted40Ar-39Ardatingoftwophlogopitesinlamprophyreswhichare,asdikes,widelydistributedintheorefield,andtwoplateauageswereac-quired,i.e.,32.46±0.62Maand32.01±0.60Ma,respectively(averaging32.23±0.60Ma).Theagesareobviouslyyoungerthanthoseoftheore-hostedcomplexandmineralizationoftheBaimazhainickeldeposit.Incombinationwiththecharacteristics,itisindicatedthatlamprophyresintheorefieldandthoseintheSanjiangARIRaresimilarintectonicsetting,mineralassemblageandgeochemistry.Itisconsideredthatlamprophyresintheorefieldaretheim-portantcomponentoftheSanjiangARIR,andthelamprophyresandore-hostedcomplexintheorefieldrepresenttheproductsoftwotimesofdifferentmagmaticactivityfromdifferentmantlesources.Ontheotherhand,theageoflamprophyresintheorefieldisolderthanthatofthestrike-slipshearingoftheAilaoshan-Honghefaultbelt,sug-gestingthatthestrike-slipshearingoftheAilaoshan-Honghefaultbeltisnotthefactorleadingtomagmaticactivityoflamprophyresintheorefield,whileitismorepossiblethatmagmaticactivityoftheSanjiangARIRpromotedstrike-slipshearingofthefaultbelt.
