内蒙古吉尔嘎郎图早古生代岩体成因——年代学、地球化学及Nd-Hf同位素制约

发布时间：2019-06-05 10:05

【摘要】：兴蒙造山带北缘断续分布的早古生代岩浆岩带,对古生代构造格局恢复及造山带演化研究具有重要意义。阿巴嘎旗北部吉尔嘎郎图岩体位于该岩浆岩带中段,为带内最大的早古生代复式侵入体。LA-ICP-MS锆石U-Pb定年表明,吉尔嘎郎图岩体早期花岗闪长岩单元成岩年龄为455.0~495.6Ma。在主量元素组成上,岩体SiO_2含量中等(59.49%~68.22%),贫铁、镁,K_2O/Na_2O值(0.64~0.85)小于1,A/CNK=0.96~1.09,整体具有亚碱、弱过铝特征。稀土及微量元素方面,岩体富Cs、Rb、Th、U、Pb,亏损Ba、Sr、P及高场强元素Nb、Ta等,稀土元素总量中等,具有弱负Eu异常(δEu=0.52~0.82)。Sr-Nd-Hf同位素分析结果显示,岩体具有亏损的同位素组成,(~(87)Sr/~(86)Sr)i=0.7053~0.7034,ε_(Nd)(t)=0.39~4.29,2件Hf同位素样品ε_(Hf)(t)均为正值,分别为ε_(Hf)(t)=7.6~10.8和ε_(Hf)(t)=3.7~7.9。岩石地球化学、年代学及Sr-Nd-Hf同位素综合分析表明,吉尔嘎郎图岩体是早古生代古亚洲洋沿苏左旗—锡林浩特一线向北俯冲背景下,遭受了俯冲板片析出流体交代作用影响的新生下地壳部分熔融的产物,后期由于弧后拉张、贺根山洋盆打开与主体岛弧带分离,最终随着古亚洲洋的整体闭合,形成了与俯冲带彼此分隔的格局。
[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 卤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 卤0.85) are less than 1, A 鈮，

本文编号：2493447