西藏措麦地区新生代火山岩相初步研究

西藏措麦地区处于冈底斯火山—岩浆弧的中段,新生代火山活动强烈,火山岩相发育齐全。根据火山喷发类型、火山物质搬运方式和定位环境,可划分为爆发相、爆溢相、喷溢相、侵出相、潜火山岩相、火山通道相、喷发—沉积相等7大类型。再依据区内火山活动特点,火山相序及相组合特征,结合火山沉积地层及其接触关系,可将其火山活动划分四个喷发—沉积旋回,依序对应于典中组、年波组、帕那组、鱼鳞山组四个岩石地层单位。文章阐述了各类型火山岩相的基本特征,对各火山岩相序、相组合及火山活动旋回作了初步分析和归纳,对提高整个冈底斯地区火山岩研究程度,具有一定的实际意义。

Study on Cenozoic volcanic rock facies in the Cuomai area,Tibet

The Cuomai area of Tibet is situated in the middle part of the Gandise volcano-magma arc,in which there were strong volcanic activities in Cenozoic Ear and developed complete facies of volcanic rocks.The volcanic rocks can be divided into such seven main facies as explosive facies,explosion-efflusion facies,eruption-efflusion facies,extrusive facies,cryptovolcanic facies,volcanic vent facies,and eruption-sedimentary facies.Further,by its volcanic activities characteristics,the volcanic facies sequence,the facies assemblage features,and in combination with the volcanic-sedimentary strata and their contact relationship,the volcanic activity can also be classified into four eruption-sedimentation cycles in turn corresponding with such four stratigraphic units as Dianzhong Formation,Nianbo Formation,Pana Formation,Yulinshan Formation.The paper fully elaborates the basic characteristics of every type level of volcanic rock facies,preliminarily analyzes and concludes the facies sequences and facies assemblages of every type of volcanic rock,and cycles of volcanic activities,which is of actual significances in improving the study level of the volcanic rocks in the whole Gandis area.