大兴安岭北段早石炭世洋岛型玄武岩的确立及成因意义

Establish and Genesis of Oceanic Island Basic Volcanic Rock Early Carboniferous in Northern of Daxing'anling

大兴安岭北段根河地区早石炭世发育一套细碎屑岩及海相中基性火山岩石组合,归属为莫尔根河组。其中基性火山岩为细碧岩、变玄武岩,岩石富Na2O、K2O、TiO2,w(Fe2O3)/w(FeO)=0.8(平均),属碱性系列。LREE富集,Eu无异常。Ti、Y、Yb略低于MORB外,其它元素高于MORB,具大洋板内玄武岩特征。w(87Sr)/w(86Sr)初始值为0.7043,εNd(t)=3.00,表明岩浆源于富集地幔。本区莫尔根河组基性火山岩石形成的构造环境为地幔柱成因的夏威夷型洋岛环境。

There occur a series of fine elastic sedimentary rock and medium-basic volcanic rocks assemblies （including the spite and meta-basie basalt） in Genhe area of North Daxing＇anling Mts. ,belong to Moergen Formation. The studies on their geochemical eharaeteristis show that basic valeanie forks high contents of Na2 O, K2 O, TiO2 , w （ Fe2 O3 ）/w （FeO） = 0.8 （average） （ belong to alkaline series）. Enrichment in LREE and with insignificant Eu anormalies ;compared with MORB,their lightly depleted in Ti, Y, Yh,hut more enriched in others elements are similar to those of ocean intraplate hasalts. Their initial w（^87Sr）/w（^86Sr） value is 0. 7043, the ENd（t） value is 3.00,indicate that their source region are related to mantle-source. Based on above data, this paper proposes that the activity of mantle plume lead to basic volcanic rocks formed,reflecting of Hawaii-type oceanic island tectonic enviroment.