| 青藏高原新生代火山岩矿物化学及其岩石学意义 |
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| 作者单位： | ：赖绍聪 西北大学地质系 西安 710069 |
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| 摘 要： | This paper deals with the features of mineral
chemistry about olivine, pyroxene, feldspar, sanidine megacryst and garnet megacryst from
Cenozoic volcanic rocks, Qinghai-Tibet plateau. The forming condition including
temperature and pressure of the volcanic rock series is also studied. The results show
that olivine belongs to forsterite (Fo=81—85) and clinopyroxene is rich in TiO2
(1.06%—1.74%). Especially the sanidine megacryst is optical homogeneous. There are not
zonal texture, exsolution texture and twin crystal. It is low in ordering degree and
belongs to K-sanidine. The garnet megacryst mainly consists of Alm and Pyr, which
crystallization depth resembles the depth of middle crust. The mineral chemistry, major
element and isotopic features indicate that of the Cenozoic volcanic rocks in the north
part of the Qinghai-Tibet plateau mainly consists of shoshonite series formed in the
intracontinental orogenic belt, which primary magma originated from a particular
enrichment upmantle and accreted crust-mantle mixed belt.
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