松辽盆地北部晚中生代中酸性火山岩地球化学特征及成因探讨  

STUDY OF GEOCHEMICAL CHARACTERISTICS AND GENESIS OF MID-ACIDIC VOLCANIC ROCKS OF LATE MESOZOIC IN NORTHERN SONGLIAO BASIN

作　　者：王对兴[1,2] 李胜荣[1] 赵凯华[2] 王青春[2] 李伟[2] 王祥[2] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]石家庄经济学院资源学院,河北石家庄050031

出　　处：《矿物岩石》2013年第3期70-77,共8页Mineralogy and Petrology

基　　金：中国地质调查局地质调查项目(编号:1212011121068)

摘　　要：针对松辽盆地北部发育的一套以流纹岩为主的晚中生代中酸性火山岩进行的岩相分析,结合K-Ar年龄测定发现该地区至少发生过3期火山活动喷发。主、微量元素研究显示,中性火山岩为亚碱性-弱碱性系列,流纹岩属低镁、低钛流纹岩系列,且为A型流纹岩;富集REE,Rb,Th,较强烈亏损Ba,Sr,P,Eu,Ti,表明原始岩浆可能由年轻成分与古老地壳混合部分熔融产生,且在岩浆演化过程中经历了较强烈的斜长石、磷灰石、钛铁矿等矿物的分离结晶作用,并暗示其演化过程中可能经历了不同程度的地壳混染作用。构造判别图解显示该地区晚白垩世火山岩属于伸展背景下板内岩浆活动,晚侏罗世到早白垩世火山岩具有弧火山岩的特征,且多数属于非造山环境下的产物,这与该区晚中生代A型花岗岩表现一致。Through analysis of lithofacies and K-Ar age dating,it was recognized that the mid-a- cidic volcanic rocks,mainly rhyolites of Late Mesozoic in northern Songliao Basin, experienced 3 stages of volcanic eruption. Major and trace elements geochemistry studies showed that the inter- mediate volcanic rocks belonged to subalkaline-alkalescence series,and low magnesium and titani- um series of rhyolites, characteristic of A-type rhyolite. These volcanic rocks prominently enriched incompatible elements, such as REE, Rb, Th, and had obvious negative Ba, Sr, P, Eu, Ti anoma- lies,indicating that the primary magmas was derived from a mixture of juvenile component and ancient crust, produced by fractional crystallization of plagioclase, apatite and ilmenite in magmatic evolution, and contaminated by the crust in different level during evolution. Discrimination dia- grams indicated that the volcanic rocks of late Cretaceous were produced by magma activity in ex- tensional setting within plate, possessed characters of arc volcanic rocks of anorogenic environ- ment, similar to A-type granites of Late Mesozoic in the studied area.

关 键 词：松辽盆地北部 晚中生代 中酸性火山岩 地球化学 构造成因 

分 类 号：P588.121[天文地球—岩石学] P588.122[天文地球—地质学]