【摘要】 宽甸新生代碱性玄武岩、地幔包体及辉石巨晶的稀有气体同位素组成和流体含量分析表明,不同岩性稀有气体含量的差异反映了岩浆作用过程中轻、重稀有气体的分馏特性,较轻的稀有气体(He、Ne)比较重的稀有气体(Kr、Xe)具有更高的活动性和不相容性;该地区上地幔源区具有典型的MORB型源区特征,以辉石巨晶为代表;地幔包体的3He/4He值较低,可能与地幔上隆过程中富集地幔流体的交代作用或地幔塑性变形作用丢失了部分原始He有关;大陆碱性玄武岩具有与大洋玄武岩截然不同的He同位素组成,反映了大陆区地幔岩浆上升过程中受到了陆壳物质混染。地幔源区40Ar/36Ar值为350左右,二辉橄榄岩和碱性火山岩的40Ar/36Ar值比大气略高,可能有大气组分的混入。部分样品中有21Ne、22Ne、129Xe、134Xe和136Xe相对于大气的过剩现象。更多还原

【Abstract】 The noble gas isotopic composition a nd content data of 2alkali basalts,3lherzolite xenoliths and 1megacryst clinopyroxene from Kuandian region confirm that a fractionation of the noble gases exists during t he magmatism,lighter noble gases,such as He and Ne,have much higher mobility and appear to be more incompatible compared with heavier ones(such as Kr and Xe ).Therefore,lighter noble gases are enriched in volcanics,especially in the volcan ics with bubbles;lherzolite xenoli ths have relatively high heavier nob le gases.Megacryst clinopyroxene has the low est abundance of noble gases,probab ly due to its high p-t generation.Noble gas isotopic compositions reveal th at the mantle source beneath Kuandia n area has a MORB-like reservoir with 3 He / 4 He value of ～10Ra (Ra:atmospheric 3 He / 4 He value)and 40 Ar / 36 Ar value of 345.6.The lherzolite xen oliths possess moderate 3 He / 4 He values of 2.59～4.53Ra,reflectin g the loss of primary helium during th e rock deformation or the metasomatism with enriched mantle fluids during the u p-lifting.The alkali volcanics have very low 3 He / 4 He values(0.47～0.61Ra ),indicating the contribution of rad iogenic 4 He,probably being resulted from crust contamination.Most samples r eveal excesses of 21 Ne and 22 Ne compared with atmospheric neon,b ut Kr and Xe isotopic compositions are indistin guishable from atmospheric values within uncertainties with only indiv idual samples having excesses of 129 Xe,134 Xe and 136 Xe.更多还原