内蒙古东部晚第四纪玛珥式火山的堆积序列及喷发过程研究

Research on the accumulation sequence and eruptive process of Late Quaternary Maars in eastern Inner Mongolia

随着全球火山研究的深入,地质学家在大多数火山群中均发现了特殊成因的玛珥式火山。以低平火山口和低矮锥体著称的玛珥式火山主要由具有爬升层理、平行层理、大型低角度交错层理等结构构造的基浪堆积物组成,是火山喷发演化过程研究的重要对象。近年来,在内蒙古东部的诺敏河、阿尔山-柴河和阿巴嘎火山群中也先后发现了典型的玛珥式火山及基浪堆积物。本文从野外火山地质特征着手,以火山学与火山地质学理论为指导,结合国内外玛珥式火山的研究成果,对内蒙古东部晚第四纪玛珥式火山的分布、产物和结构构造等火山地质特征进行了归纳总结,将其大致划分为3个喷发期次,分别是以基浪堆积物为主的射汽-岩浆爆发、以降落-溅落堆积物为主的岩浆喷发和以碱性橄榄玄武岩为主的岩浆溢流期次。复合火山的活动时代总体属于晚更新世,其中玛珥式火山的形成时代为晚更新世早中期。通过分析研究区的地层、火山产物和区域断裂构造等地质特征,推断射汽-岩浆爆发的深度较浅,并进一步探讨了玛珥式火山的成因机制,模拟其喷发演化过程,认为玛珥式火山与斯通博利式、夏威夷式等类型火山具有继承性演化关系。

With the progress in the research on global volcanoes,geologists have discovered volcanoes of Maars type with special genesis in most volcanic groups. Maars,characterized by low-relief,broad volcanic crater and low flat cone,are mainly composed of base surges with climbing bedding,parallel bedding,large low-angle crossbedding and some other structures,thus being an important object for studying the evolution process of volcanic eruption. Many Maars with typical base surges have recently been discovered from Nuominhe,Arshan-Chaihe and Abaga volcanic clusters in eastern Inner Mongolia. Based on comprehensive field survey and available researches both in China and aboard,the authors summarized the geological features of the late Quaternary Maars in eastern Inner Mongolia by theories of volcanology and volcanic geology,including their distribution,products and typical structures. The activity of the volcano is divided into three stages: phreatomagmatic eruption stage dominated by base surges,magma eruption stage represented by fall-spatter deposits,and magma overflow stage with alkaline olivine basalt. These composite volcanoes were active in the late Pleistocene,whereas the Maars mainly erupted at early to middle stage stated above. The unique strata,volcanic product and regional tectonic structure all indicate that phreatomagmatic eruption was generated at the shallow depth. Based on the discussion of the genetic mechanism and evolution simulation,the authors infer that there exists an inherited relationship between Maars and other volcanoes,such as Strombolian and Hawaiian.