内蒙古达里诺尔晚新生代火山群喷发特征研究

Volcanic eruption characteristics of the Late Cenozoic Dalinor volcanic field,Inner Mongolia

达里诺尔火山群有近百座晚新生代单成因火山,其地质地貌形态各异,喷发形式多样。这些火山既有爆破式喷发,如:夏威夷式喷发,斯通博利式喷发,强斯通博利式喷发和射汽岩浆喷发;也有溢流式喷发,如盾状火山;还有岩浆缓慢侵出,如大黑山。火山群内典型火山机构表明,不同的喷发方式穿插于火山喷发过程:早期火山活动多以侵出和溢流为主,逐渐转变为岩浆爆破式喷发(强斯通博利式,斯通博利式),晚期又过渡为溢流式喷发,喷发过程大体经历一个爆破强度弱-强-弱的转变。射汽岩浆型的火山则是以剧烈的射汽岩浆爆炸开始,后期逐渐转弱为岩浆爆破喷发和溢流喷发。火山喷发过程中火山产物出现牛顿流体,宾汉流体,层流,颗粒流,涌流,空降等不同类型的运动形式,自火口向远源运动,形成差异化的火山产物。岩浆的输送速率、上升速度,以及围岩的类型,可能是造成达里诺尔火山群多样化喷发的主要因素。

Dalinor volcanic field, which contains more than one hundred late Cenozoic volcanoes, is one of the largest monogenetic volcanic fields in China. In this field, four explosive eruption types are identified：Hawaiian eruption, Strombolian eruption, violent Strombolian eruption and phreatomagmatic eruption. Effusive eruption and slow extrusion are found in the field as well. The represented volcanic edifices indicates that the eruption episode generally endured a transition from effusive or extrusive eruption （with low VEI）, through explosive eruption （with high VEI）, to effusive eruption. The phreatomagmatic eruption starts with a violent magma-water explosion, and gradually changes to magmatic explosive eruption and effusive eruption. The volcanic products are emplaced through different styles：Newton fluids, Bingham fluids, grain flows, laminar flow, surge and airfall, which help to generate varying volcanic features. The magma input rate and ascending speed, as well as wallrock nature, may be the main influence factors on the diversity of eruption styles.