Origin of Cenozoic alkaline potassic volcanic rocks at KonglongXiang, Lhasa terrane, Tibetan Plateau: Products of partial melting of a mafic lower-crustal source?
Origin of Cenozoic alkaline potassic volcanic rocks at KonglongXiang, Lhasa terrane, Tibetan Plateau: Products of partial melting of a mafic lower-crustal source?
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青藏高原拉萨地体空龙乡新生代碱性钾质火山岩成因：镁铁质下地壳物源部分熔融的产物？
DOI：
10.1016/j.chemgeo.2010.03.003
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发表时间：
2010-05-15
期刊：
影响因子：
3.9
通讯作者：
Jie, Li
中科院分区：
文献类型：
--
作者：
Chen, Jian-lin;Xu, Ji-feng;Jie, Li
一般认为青藏高原新生代钾质和超钾质火山岩是由富集型地幔部分熔融形成的。本文报道了青藏高原拉萨地体中西部孔龙巷火山岩(KVR；K2O/Na2O&Gt；2，低镁含量)的元素和同位素组成的新资料。KVR岩样的Ar-Ar同位素测年结果为21.3 Ma，表明KVR岩浆喷发于早中新世。KVR主要由粗面岩和流纹岩组成。KVR粗面岩与青藏高原新生代钾质火山岩的对比以及富K火山岩和世界各地其他富K火山岩的熔融实验结果表明，KVR粗面岩起源于含富K矿物的镁铁质下地壳，而不是地幔来源。KVR流纹岩可能来源于中上地壳。根据测年数据、成分数据和区域构造背景，我们认为KVR及其伴生的N-S地块的形成是由青藏高原南部地区早中新世东西向区域伸展所触发的。(C)2010年爱思唯尔。版权所有。
It is generally believed that Cenozoic potassic and ultrapotassic volcanic rocks of the Tibetan Plateau were generated by partial melting of enriched mantle. This paper reports new data regarding the elemental and isotopic compositions of the KonglongXiang volcanic rocks (KVR; K2O/Na2O>2 and low MgO contents) in the middle-western Lhasa terrane, Tibetan Plateau. Ar-Ar isotope dating of a sample from the KVR yields an age of 21.3 Ma, indicating that the KVR lavas erupted during the Early Miocene. The KVR consists mainly of trachyte and rhyolite. A comparison of the KVR with Cenozoic potassic volcanic rocks of the Tibetan Plateau and the results of melting experiments involving K-rich volcanic rocks, as well as other K-rich volcanic rocks from throughout the world, reveals that the KVR trachytes originated from a mafic lower crust containing K-rich minerals rather than from a mantle source. The KVR rhyolites were probably derived from the middle upper crust. Based on age data, compositional data, and the regional tectonic setting, we propose that the formation of the KVR and associated N-S grabens was triggered by Early Miocene E W regional extension in the area of the southern Tibetan Plateau. (C) 2010 Elsevier By. All rights reserved.