班公湖-怒江板块缝合带发现侏罗纪洋岛型岩石组合
The discovery of the Jurassic OIB-type rocks in the Bangong Lake-Nujiang River suture zone
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摘要: 那东洋岛大地构造位置位于班公湖-怒江板块缝合带西段，洋岛型岩石组合平行于蛇绿混杂岩带南侧展布，夹持于侏罗系木嘎岗日群之中。那东洋岛玄武岩与木嘎岗日群复理石砂板岩呈过渡接触关系。那东洋岛岩石组合主要由3种岩石组成：玄武岩、玄武质砾岩、灰岩或礁灰岩，那东洋岛的岩石组合具有多旋回性。对那东洋岛中的玄武岩进行地球化学分析，玄武岩为OIB型玄武岩。以往研究认为班公湖-怒江洋盆在侏罗纪处于大洋演化阶段，那东洋岛的发现对揭示班公湖-怒江洋在侏罗纪的演化历史具有重要意义。Abstract: Nadong oceanic island is located in the western part of the Bangong Lake-Nujiang River suture zone. It occurs as an EW-trending belt in parallel with ophiolite and is associated with the Jurassic Muga Kangri Group. There exists transitional contact relationship between the OIB-type basalts and the flysch of the Muga Kangri Group. The OIB-type rocks are composed of basalt, basaltic conglomerate, limestone and/or reef limestone. Furthermore, these rocks display several volcanic eruption cycles. Geochemical data show that all the basalts have typical OIB features. Studies have also shown that a Jurassic ocean basin existed in the Bangong Lake-Nujiang River suture zone. Thus the discovery of the Nadong oceanic island plays a key role in revealing the evolutionary history of the Bangong-Nujiang Ocean during the Jurassic.
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