【摘要】：興蒙造山帶北緣斷續(xù)分布的早古生代巖漿巖帶,對古生代構(gòu)造格局恢復及造山帶演化研究具有重要意義。阿巴嘎旗北部吉爾嘎郎圖巖體位于該巖漿巖帶中段,為帶內(nèi)最大的早古生代復式侵入體。LA-ICP-MS鋯石U-Pb定年表明,吉爾嘎郎圖巖體早期花崗閃長巖單元成巖年齡為455.0~495.6Ma。在主量元素組成上,巖體SiO_2含量中等(59.49%~68.22%),貧鐵、鎂,K_2O/Na_2O值(0.64~0.85)小于1,A/CNK=0.96~1.09,整體具有亞堿、弱過鋁特征。稀土及微量元素方面,巖體富Cs、Rb、Th、U、Pb,虧損Ba、Sr、P及高場強元素Nb、Ta等,稀土元素總量中等,具有弱負Eu異常(δEu=0.52~0.82)。Sr-Nd-Hf同位素分析結(jié)果顯示,巖體具有虧損的同位素組成,(~(87)Sr/~(86)Sr)i=0.7053~0.7034,ε_(Nd)(t)=0.39~4.29,2件Hf同位素樣品ε_(Hf)(t)均為正值,分別為ε_(Hf)(t)=7.6~10.8和ε_(Hf)(t)=3.7~7.9。巖石地球化學、年代學及Sr-Nd-Hf同位素綜合分析表明,吉爾嘎郎圖巖體是早古生代古亞洲洋沿蘇左旗—錫林浩特一線向北俯沖背景下,遭受了俯沖板片析出流體交代作用影響的新生下地殼部分熔融的產(chǎn)物,后期由于弧后拉張、賀根山洋盆打開與主體島弧帶分離,最終隨著古亞洲洋的整體閉合,形成了與俯沖帶彼此分隔的格局。
[Abstract]:The intermittent distribution of early Paleozoic magmatic belt in the northern margin of Xingmeng orogenic belt is of great significance to the restoration of Paleozoic tectonic pattern and the evolution of orogenic belt. The Gilgarotu rock mass in the north of Abagaqi is located in the middle part of the magmatic belt, which is the largest early Paleozoic compound intrusive body in the belt. La-ICP-MS zircon U-Pb dating shows that, The diagenetic age of the early granodiorite unit in the Gilgerangtu rock mass is 455.0 鹵495.6 Ma. In the composition of principal elements, the SiO_2 content of rock mass is medium (59.49% 68.22%), the iron, magnesium, K _ 2O and Na _ 2O values (0.64 鹵0.85) are less than 1, A 鈮，

本文編號：2493447