内蒙古三七林场一带中生代火山岩地球化学特征与构造环境研究

三七林场一带中生代火山岩中,满克头鄂博期岩石组合为粗面岩、粗面英安岩-流纹岩组合,玛尼吐期岩石组合为玄武安山岩-粗面岩、粗面英安岩组合,白音高老期岩石组合为流纹质岩石组合。岩石地球化学研究表明,火山岩应属亚碱性系列之钙碱性亚系普通型火山岩,并有向碱性系列演化之趋势。稀土配分形式均为轻稀土富集型,具明显的负Eu异常、弱负Eu异常均存在,稀土总含量随时代的变新有增加的趋势。根据主微量元素和稀土元素特征,并结合前人研究成果,该区火山岩继承了古生代基底和洋壳俯冲的一些地球化学特征,火山岩源区为受早期俯冲流体交代了的岩石圈地幔;在岩石圈伸展减薄背景下,源区发生减压融熔形成了岩浆,岩浆具有同源岩浆演化特征,形成原因应为古亚洲洋或蒙古-鄂霍茨克洋闭合造山后的伸展环境有关。

Discuss On Geochemical Characteristics and Tectonic Environment of the Sanqi Forest Farm Mesozoic Volcanic Rocks in Heilongjiang Pronvince

In the Mesozoic volcanic rocks of the Sanqi forest farm, The Manketouebo rocks is a combination of coarse-facies and coarse dacite-rhyolite, The Manitu rocks are composed of basaltic andesite-coarse facies, The Baiyingaolao rocks is rhyolitic rock assemblage.Rock geochemical study shows that the volcanic rocks should be sub-alkaline series of calc-alkaline sub-series of ordinary volcanic rocks, and to the evolution of the trend of alkaline series.The rare earth enrichment patterns are all light rare earth enrichment type, with obvious negative Eu anomaly, weak negative Eu anomaly are the same, the total content of rare earth with the times change has increased.The volcanic rocks inherited some geochemical characteristics of the Paleozoic basement and oceanic subduction, and the volcanic source area is the lithosphere mantle that is confronted by the early subduction fluid.On the background of extensional thinning of the lithosphere.magmatic magmas occur in the source zone, and magmatic magmas have homogenized magmatic evolution, which should be related to the extensional environment after the ancient Asian ocean or Mongolia-Okhotsk orogenic orogeny.