大兴安岭北段早白垩世光华期火山地层格架控制因素及意义——以根河市库西火山构造洼地为例

CONTROLLING FACTORS AND SIGNIFICANCE OF EARLY CRETACEOUS VOLCANOSTRATIGRAPHIC FRAMEWORK IN NORTHERN DAXINGANLING REGION:A case study of Kuxi volcanotectonic depression

大兴安岭中生代火山岩带北段大面积分布有中酸性火山岩,形成时代主要是早白垩世光华期.区内覆盖严重,给岩石地层的划分带来很多困难.文中以中生代早白垩世光华期库西火山构造洼地为例,从火山构造洼地的形成演化及岩浆演化双重角度讨论了其对火山地层层序的控制作用.岩浆作用及火山构造洼地的演化均具有连续性和不可逆性,对火山地层的控制作用表现在岩石化学及地球化学特征的有规律的变化.利用岩石化学反演方法定量模拟了岩浆形成演化过程,以此为依据讨论了火山地层的时空演化.结合火山构造洼地不同演化阶段对特殊火山岩相的控制作用及横向的可对比性,确定了火山地层的层间叠置规律.探索性地建立了大兴安岭北段早白垩世光华期区域性火山地层格架,为大兴安岭地区早白垩世地层对比及岩浆动力学分析提供了新思路.

Huge area of acid-intermediate volcanic rocks, most of which belong to Early Cretaceous Guanghua age, are distributed in Northern Daxinganling region. Because of heavy coverage, the division of strata is difficult. This paper, taking Kuxi volcanoteetonic depression as example, discusses the forming and evolution of the volcanotectonic depression, the magmatic evolution and its control to the voicanostratigraphic sequence. The magmatism and the evolution of volcanotectonic depression are both continuous and irreversible. The lithochemistry and geochemistry vary with the volcanostratigraphy, which is controlled by the magmatism and the evolution of volcanotectonic depression. The forming and evolving process of magma is quantitatively simulated using lithochemical inverse method. Based on such result, combining with the control of the volcanotectonie depression to volcanic facies in different forming stages and correlation of different areas, the superimposition regularity of the volcanostratigraphy is determined. The regional volcanostratigraphic framework of Northern Daxinganling region in Early Cretaceous Guanghua age is established.