A Study on Petrological Geochemistry of the Early Cretaceous Volcanic Rocks from Changling Rift,Songliao Basin,China
A Study on Petrological Geochemistry of the Early Cretaceous Volcanic Rocks from Changling Rift,Songliao Basin,China
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发表时间：
2012
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通讯作者：
Zhang Yan-xia
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作者：
Zhang Yan-xia
松辽盆地长岭裂谷早白垩世火山岩岩石化学特征为富硅、富碱，可分为亚碱性系列和碱性系列。亚碱性系列包括高钾钙碱性系列和钙碱性系列。碱性系列为钾玄武岩系列。研究区所有火山岩样品均亏损二氧化钛和锶，相对于高场强元素，富含大离子亲石元素，除重稀土元素外，还富含轻稀土元素。这些火山岩与造山带火山岩具有相似的地球化学特征。研究区火山岩处于造山带崩塌引起的陆壳板块内广泛的构造环境中。镁铁质火山岩是地幔部分熔融的产物。但在岩浆演化过程中存在单斜辉石、橄榄石、钛铁氧化物等矿物的分离结晶。中间火山岩的形成是玄武岩岩浆差异演化的结果。酸性流纹岩的形成与断裂的大规模走滑运动有关，可形成承压应力，如使上地壳重新融化。
Early Cretaceous volcanic rocks from Changling rift in Songliao basin are characterized by petrochemically rich silicon and alkali.These samples could be divided into two series as sub alkaline series and alkaline series.The sub alkaline series include high-K calc-alkali series and calc-alkali series.The alkaline series are shoshonitic series.All samples of volcanic rocks in study area were depleted in TiO2 and Sr,enriched in large ion lithophile elements compared to high field strength elements,enriched in light rare earth element other than heavy rare earth element,and enriched in Rb and K.These geochemical features are similar to those volcanic rocks in orogenic belts.These volcanic rocks in the study area are located in the extensive structure setting within the plate of the continental crust,that it caused by orogenic belt collapse.The mafic volcanic rocks are production of partial melting of the mantle.However,there existed fractional crystallization of clinopyroxene,olivine,Ti-Fe oxide and other minerals during magmatic evolution.The forming of intermediate volcanic rocks is a result of differential evolutions of basaltic magma.The formation of acid rhyolite are related to large-scale strike-slip movement of the fault,which can form bearing stress,such as,made upper crustal to re-melt.