大兴安岭北段塔河地区晚寒武世中基性火山岩的发现及其地质意义

发布时间：2019-06-13 19:59

【摘要】：新林-喜桂图断裂北东段塔河地区发育一套中基性火山岩,岩石类型为玄武安山岩、玄武粗安岩和粗面玄武岩,前人曾将其划归为中-晚侏罗世塔木兰沟组。本次工作区在塔河北瓦拉干林场一带,采用LA-ICP-MS同位素测定方法,在玄武安山岩和粗面玄武岩中分别取得锆石~(206) Pb/~(238) U年龄平均值为(501.1±1.4)Ma(23个数据点)和(500.50±0.95)Ma(14个数据点);首次确定了大兴安岭北段塔河以北寒武系火山地层的存在。中基性火山岩,具有亚碱性岩系列钾玄岩特征,且无任何变质变形;Eu微弱负异常,(La/Yb)_N=16.63~25.91;富集Ba、Rb、Sr、K,亏损Nb、Ta、Ti。岩浆的形成可能与岛弧背景下的拉伸作用有关,同时指出额尔古纳地块塔河以北地区寒武系的存在并非是局部现象,很可能有一定的分布范围。这一研究成果为重新认识大兴安岭北段局部地区中生代火山岩、探讨新林-喜桂图构造带演化历史及西伯利亚南缘额尔古纳地块大陆地壳演化提供了新的资料。
[Abstract]:A set of medium-base volcanic rocks are developed in the Tahe area of the North East section of the fault of the new forest-Xinguo. The types of rocks are Xuanwu Anshan, Xuanwu coarse and coarse-faced basalts. In this work area, a LA-ICP-MS isotope determination method was used to determine the mean values of (501.1, 1.4) Ma (23 data points) and (500.50-0.95) Ma (14 data points) in the Basalt and the coarse-faced basalts, respectively, with the method of LA-ICP-MS. The existence of the Cambrian volcanic formation in the north of the northern section of the Daxing 'an Mountains was first determined. The medium-based volcanic rocks have the characteristics of subalkaline rock series of potassium and basalt, without any deterioration and deformation; Eu weak negative anomaly, (La/ Yb) _ N = 16.63-25.91; enrichment of Ba, Rb, Sr, K, and loss of Nb, Ta, and Ti. The formation of the magma may be related to the tensile action in the background of the island arc, and it is also pointed out that the presence of the Cambrian system in the north of the Tahe of the Erguana Block is not a local phenomenon, and it is likely to have a certain distribution range. The result of this study is to re-recognize the Mesozoic volcanic rocks in the local area of the northern part of the Daxing 'an Mountains, and to study the evolution history of the new forest-Xinguo tectonic belt and the evolution of the continental crust in the Erguana, the southern part of the Siberia.
【作者单位】：中国地质调查局沈阳地质调查中心;
【基金】：中国地质调查局地质调查项目(DD20160201-01,1212011220435,DD20160343-08,DD20160343-09,1212011085210,DD20160345-17)~~
【分类号】：P588.14

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