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Mantle sources and magma genesis of Quaternary volcanic rocks in the Halaha River and Chaoer River area,Great Xing’an Range
Author(s): ZHAO YongWei and FAN QiCheng Key Laboratory of Active Tectonics and Volcano, Institute of Geology, CEA, Beijing 100029, China
Pages: 1119-
1129
Year: 2012
Issue:
4
Journal: Acta Petrologica Sinica
Keyword: 大兴安岭; 哈拉哈河-绰尔河; 第四纪火山岩; 地球化学; 地幔源区; 岩浆成因;
Abstract: 哈拉哈河-绰尔河第四纪火山地处重力梯度带上的大兴安岭中段。火山岩主要类型为钠质系列碱性橄榄玄武岩。火山岩大离子亲石元素和轻稀土元素相对富集,轻重稀土分异程度弱((La/Yb)N=8~12),稀土元素和微量元素配分曲线与大同碱性玄武岩平行,总体上表现出与OIB相似的特征。在Sr-Nd-Pb同位素组成特征上表现出亏损地幔的特点(εNd=4.8~5.9),接近MORB的源区范围。哈拉哈河-绰尔河第四纪火山岩岩浆由轻稀土富集的石榴子石二辉橄榄岩低程度(8%~15%)部分熔融产生,火山岩高MgO(>9%)、Ni(>200×10-6)和Mg#(60~70),表明它们是较原始的岩浆,岩浆上升过程经历了橄榄石和辉石为主的弱分离结晶作用,没有受到地壳物质明显混染。区域伸展作用引发软流圈地幔上涌是哈拉哈河-绰尔河第四纪火山的岩浆成因。
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