摘要:
达考序列岩体由查肖叉得英云闪长岩、杂乃玛下黑云母二长花岗岩、抗涌正长花岗岩组成。单颗粒锆石U-Pb同位素年龄值为169±4 Ma,形成于中侏罗世,岩石化学成分表现为岩浆向富硅、富碱、富铝方向演化。稀土元素特征表现为轻稀土元素富集,重稀土元素平坦型。微量元素特征表现为富集大离子亲石元素Rb、K、Ba、Th,而Sr、Nb、Ta略显亏损,εNd(t)变化在-7.6~-8.1之间,(87Sr/86Sr)i值较高,变化于0.70969~0.71104之间。地球化学特征表明达考序列岩体形成构造背景为火山弧花岗岩,为壳幔混合产物。
Abstract:
The Dakao sequence of intrusion rocks is composing of Chaxiaochade tonalite,Zanaima biotite adamellite and Kangyong syenogranite.The Single zircon U-Pb ages of Dakao intrusion is 169 ±4 Ma,indicated formed in the Jurassic.The magma is evolved to be rich in silicon,alkali and aluminum.Rare earth elements are characterized by LREE enrichment,heavy REE flat.Trace elements characterized for enrichment in large ion lithophile elements of Rb,K,Ba and Th,but of Sr,Nb and Ta slightly loss;with εNd(t) changes in the range of-7.6 ~-8.1,and with(87Sr/86Sr)i values of 0.70969 ~ 0.71104.Geochemical characteristics of Dakao sequence intrusion indicated it formed in volcanic arc setting,and product of crustmantle mixing.
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