Geochemistry of Miocene trachytes in Bugasi, Lhasa block, Tibetan Plateau: Mixing products between mantle- and crust-derived melts?
Geochemistry of Miocene trachytes in Bugasi, Lhasa block, Tibetan Plateau: Mixing products between mantle- and crust-derived melts?
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DOI：
10.1016/j.gr.2011.06.008
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发表时间：
2012
影响因子：
6.1
通讯作者：
Jian‐Lin Chen;Wenbin Zhao;Ji‐Feng Xu;Bao-di Wang;Z. Kang
中科院分区：
文献类型：
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作者：
Jian‐Lin Chen;Wenbin Zhao;Ji‐Feng Xu;Bao-di Wang;Z. Kang
拉萨地块西部中新世布加斯火山岩（BVR）主要由粗面山岩和粗面岩组成，均属于粗顺岩系。粗面岩在地幔源粗面山岩和孔龙乡壳源钾质岩之间具有一定的过渡性，其中Sr、Ba、Ni浓度、Nb/Ta、Rb/Sr、Th/Nb、Zr/Nb和Ba/Rb微量元素比值以及Sr、Nd同位素组成最为明显。这些特征，再加上相对较高的Cr、Ni浓度和Mg#，表明粗叶组织是幔源和下地壳源熔体混合的产物。
It is generally believed that Cenozoic potassic and ultrapotassic volcanic rocks of the Tibetan Plateau were generated by partial melting of an enriched mantle region or lower crustal materials. The Miocene Bugasi volcanic rocks (BVR) in the western part of the Lhasa block are composed mainly of trachyandesites and trachytes, both of which belong to the shoshonite series. The trachytes show somewhat transitional compositions between the mantle-derived trachyandesites of the BVR and the crust-derived potassic rocks of Konglongxiang, most evident in their Sr, Ba, and Ni concentrations, Nb/Ta, Rb/Sr, Th/Nb, Zr/Nb, and Ba/Rb trace element ratios, and Sr and Nd isotopic compositions. These features, coupled with the relatively high Cr and Ni concentrations and Mg#, suggest that the trachytes are the product of mixing between mantle-derived and lower crust-derived melts.