羌塘雀莫错一带基性超基性岩群基本特征及构造环境

The ultrabasic and basic rocks and their tectonic settings in the Qoimaco region, Qiangtang on the Qinghai-Xizang Plateau

关键词:  雀莫错  基性超基性岩带  青藏高原

Key words:  Qoimaco  ultrabasic and basic rocks  Qinghai-Xizang Plateau

摘要:

雀莫错一带的基性超基性岩群为单辉橄榄岩-橄榄辉长岩-辉长岩-辉绿岩组合,橄榄辉长岩表现为低SiO₂、K₂O、Na₂O、TiO₂、P₂O₅,辉长岩、辉绿岩表现为较高的Na₂O、TiO₂。总体具较高的MgO和较低的ΣREE、Sr、Ta,且Na₂O大于K₂O,副矿物富含磁铁矿,时代属喜马拉雅期。橄榄辉长岩为大洋拉斑玄武岩系列,辉长岩、辉绿岩为碱性岩系列。构造环境为大洋中脊。

Abstract:

The ultrabasic and basic rocks widespread in the Qoimaco region, Qiangtang on the Qinghai-Xizang Plateau are dominated by the clinopyroxene peridotite-olivine gabbro-gabbro-diabase associations. Petrochemically, the olivine gabbro is characterized by lower SiO₂, K₂O, Na₂O, TiO₂ and P₂O₅, while the gabbro and diabase by higher Na₂O and TiO₂. On the whole, these associations of Himalayan in age display the features of higher MgO, Na₂O>K₂O, lower ΣREE, Sr and Ta. Moreover the accessory minerals are rich in magnetite. The (olivine) gabbro may be assigned to the oceanic tholeiite series, while the gabbro and diabase to the alkaline series. The tectonic settings of the ultrabasic and basic rocks in the Qoimaco region are the same as the mid-oceanic ridge basalts.