【摘要】 锆石U-Pb定年结果显示,松辽盆地长岭断陷松南180井中基性火山岩形成于101~116 Ma的早白垩世晚期,属于营城组,非火石岭组火山岩。岩相学观察主要由安山岩和橄榄玄武岩组成,化学成分显示为玄武岩、粗面玄武岩和玄武质粗面安山岩,属碱性系列,镁质量分数较低,镁值较小(Mg#=0.27~0.53)。稀土元素总量较高(w(∑REE)=(164.98~257.27)×10-6),轻重稀土分馏明显((La/Yb)N=6.60~10.96),铕异常微弱(δEu=0.85~1.02)。富集大离子亲石元素和轻稀土元素,Rb,K相对亏损,相容元素(Cr、Co、Ni)质量分数低,高场强元素Nb、Ta弱富集,整体表现出与OIB(洋岛玄武岩)一致的稀土图谱和微量元素特征。岩浆源区为软流圈地幔,经历了深部地幔流体的交代富集作用,岩浆未遭受地壳物质的混染。更多还原

【Abstract】 Zircon U-Pb dating results show that the intermediate-basic volcanic rocks from Changling depression in the Songliao basin formed at Early Cretaceous,rangingd from 101Ma to 116 Ma,which belong to Yingcheng Formation rather than Huoshiling Formation.Petrologically,the volcanic rocks are composed dominantly of olivine basalt and andesite,but geochemical data show that the volcanic rocks belong to alkaline series and are composed mainly of basalt,trachybasalt and basaltic trachyandesite.The intermediate-basic volcanic rocks have low contents of MgO and small Mg#(0.27-0.53);The chondrite-normalized rare earth element(REE)patterns indicate that the volcanic rocks show significant fractionation of HREE and LREE[(La/Yb)N=6.60-10.96]and weak Eu anoalies(δEu=0.85-1.02);The trace element geochemistry are characterized by enrichment in large ionic lithophile elements and LREEs,weak positive anomalies in Nb,Ta,depletion in compatible elements(Cr,Co,Ni)and Rb,K.All of the samples display highly consistent REE patterns and trace elements spider diagrams with OIB.The magma source is situated in the asthenospheric mantle,and experienced deep mantle fluid metasomatism enrichment.These rocks were not accompanied by contamination of continent crustal materials during their magmatic evolution.更多还原