北山造山带马鬃山泥盆纪花岗岩对古亚洲洋构造演化的制约  

Constraints of Mazongshan Devonian Granites on the Tectonic Evolution of the Paleo-Asian Ocean in Beishan Orogenic Belt,China

作　　者：余吉远 王国强[1,2] 计波 卜涛[1,2,3] 李婷 过磊[1] YU Ji-yuan;WANG Guo-qiang;JI Bo;BU Tao;LI Ting;GUO Lei(Xi'an Center of Geological Survey,China Geological Survey(Geosciences Innovation Center of Northwest China),Xi'an 710119,Shaanxi,China;Orogen Research Center of Geological Survey,China Geological Survey,Xi'an 710119,Shaanxi,China;Strata Type Section for the Bottom of Wenlock-Shaanxi Ziyang Field Scientific Observation,Xi'an 710119,Shaanxi,China)

机构地区：[1]中国地质调查局西安地质调查中心(西北地质科技创新中心),陕西西安710119 [2]中国地质调查局造山带地质研究中心,陕西西安710119 [3]陕西紫阳中志留统底界层型剖面野外科学观测研究站,陕西西安710119

出　　处：《地球科学与环境学报》2025年第1期1-15,共15页Journal of Earth Sciences and Environment

基　　金：中国地质调查局地质调查项目(DD20240029,DD20243411,DD20242292);国家自然科学基金项目(41202045,41703038);陕西省自然科学基金项目(2023-JC-YB-233)。

摘　　要：北山造山带是一个地质构造复杂的区域,其构造演化和构造单元的划分一直是地质学界研究的热点问题。前人对该地区泥盆纪大地构造背景存在不同的观点,这些分歧主要源于对地质证据的不同解读和理论模型的差异。通过对该地区马鬃山泥盆纪花岗岩的详细分析,发现这些岩石具有显著的富K、贫Na特征,属于高钾钙碱性系列,可能来源于地壳深部的熔融过程。此外,这些岩石还显示出过铝质花岗岩的特性,这通常与特定的构造环境和源区成分有关。在稀土元素分布上,轻稀土元素和重稀土元素的明显分异,以及轻微的Eu异常,进一步指示了岩浆分离结晶过程中的复杂行为。该岩体相对富含Cs、Rb、Ba、Th、U和K等元素,而相对缺乏Nb、Ta、P和Ti等元素。利用LA-ICP-MS对锆石进行U-Pb定年分析,获得(396.3±3.5)Ma的年龄数据,说明岩体形成于早泥盆世。源区岩石主要由杂砂岩组成,可能指示了岩浆源区的沉积岩成分。马鬃山二长花岗岩的成因类型被确定为S型花岗岩,这类岩石通常与陆壳的重熔作用有关,其形成与地质历史上的同碰撞—后碰撞构造环境密切相关。综上所述,北山造山带的俯冲作用在早泥盆世已经结束,区域地质构造已经从俯冲阶段过渡到后碰撞阶段。There are great differences in tectonic evolution and tectonic unit division of Beishan orogenic belt.The key is that there is no unified understanding of the tectonic background during Devonian.In order to deepen the understanding of Paleozoic tectonic evolution in Beishan area,Mazongshan Devonian granite was selected for geochronology and geochemistry research.The K-rich,Na-poor and K-rich calc-alkaline series have the characteristics of peraluminous S-type granite.The A/CNK values are all greater than 1.1,and the differentiation of light and heavy rare earth elements is obvious.(La/Yb)N is 3.61-49.69,with slight Eu anomaly(δEu is 0.18-1.20),enrichment of Cs,Rb,Ba,Th,U and K,depletion of Nb,Ta,P and Ti,LA-ICP-MS zircon U-Pb age of(396.3±3.5)Ma,showing the granite forms in Early Devonian.Judging from the nature of its source area,the source area of the granite body is dominated by greywacke.According to the discrimination diagrams of granite genetic types such as Zr+Nb+Ce+Y-(K 2O+Na 2O)/CaO and Zr+Nb+Ce+Y-FeO T/MgO,it can be seen that Mazongshan monzongranite is S-type granite,which is formed in the tectonic environment of syn-collision and post-collision.The age,geochemical characteristics and formation environment of Mazongshan monzongranite confirm that the subduction process ends during Early Devonian in Early Paleozoic tectonic evolution of Beishan orogenic belt,and the region has entered the post-collision stage.

关 键 词：构造-岩浆演化 地球化学 花岗岩 锆石U-PB年龄 成因 泥盆纪 北山造山带 

分 类 号：P581[天文地球—岩石学]