松辽盆地长岭断陷营城组火山岩的时代与岩石成因

对松辽盆地长岭断陷查干花次凹营城组火山岩进行了LA--ICP--MS U--Pb 年代学和岩石地球化学研究。确定研究区内火山岩形成于104 ～ 112 Ma 的早白垩世晚期。营城组火山岩主要由粗面岩、流纹岩、钠闪碱流岩、流纹质岩屑晶屑凝灰岩组成，化学成分显示均为流纹岩，属碱性系列。火山岩高硅富碱、贫铝钙镁; 铕负异常明显( δEu = 0. 16 ～ 0. 65) ，轻重稀土元素分馏较强［( La /Yb) N］ = 7. 15 ～ 10. 38; 富集大离子亲石元素K、Ｒb 和LＲEE。Ba、Sr 出现强烈的负异常，强烈亏损高场强元素P、 Ti，而Nb、Ta 并不亏损。该区中酸性火山岩由玄武质岩浆底侵导致新生地壳岩石部分熔融形成。

Chronology and petrogenesis of volcanic rocks in Yingcheng Formation from Changling depression in Songliao Basin

The volcanic rocks of Yingcheng Formation in the Chaganhua block of Changling depression， Songliao basin，formed in the Early Cretaceous，dated by zircon U-Pb ages ranging between 104 and 112 Ma． Petrologically， the Yingcheng Formation is composed dominantly of trachyte，rhyolite，comendite and rhyolitic tuff， which all belong to subalkaline series and correspond to rhyolite in chemical composition． Geochemically，the volcanic rocks are rich in silicon and alkalis，poor in aluminum，calcium and magnesium，and characterized by light rare earth elements enrichment and heavy rare earth elements depletion，e. g. the chondrite normalized ( La /Yb) N values of 7. 15 ～ 10. 38 and δEu values of 0. 16 ～ 0. 65． Primitive mantle-normalized multi-element patterns are characterized by relative enrichments in K，Ｒb，and LＲEE but depletions in Ba and Sr，as well as P and Ti． However， they exhibit little or no depletion in Nb and Ta． The rhyolites magma was originated from partial melting of juvenile crustal materials．