试论陆相火山岩区火山地层单位与划分──关于火山岩区填图单元划分的讨论

火山活动具多旋回性，一个火山活动旋回的岩浆作用产物及其形成的火山构造形迹具时空分布协调性，同一旋回的火山构造在空间上呈串珠状或并列式展布，不同旋回的火山构造在空间上呈叠置式展布；火山喷发类型与火山岩相具一致性，岩相及相序是推演古火山演化历史、恢复古火山机构的主要依据，亦是组成火山地层并且成因意义的单元；不同旋回火山机构内的火山地层层序的综合、叠置是建立区域火山地层层序的基础；火山构造是火山岩区地质构造的主要内容，以区域构造、火山构造、火山岩浆作用产物的岩相为内容的火山岩相构造图是揭示火山岩区地质构造特征的综合性图件；环形火山构造叠置与区域线形构造交织分布组成线─环形境构造格局．是火山岩区所特有的构造面貌，在火山地质图上应得到充分的体现；。根据上述认识，对陆相火山岩区作为火山地层填图单元的岩石地层单位群─组─段─层划分提出了方案，建议用旋回─组─岩相─层（即火山构造─组─岩相─层）四级作为火山地层划分单位和填图单元，其中旋回火山构造一致，组与火山机构演化阶段一致，岩相与火山喷发类型一致，层为岩相内容的补充。据此填制的火山地质图才能真正成为反映火山岩浆作用及其产物的特色和具普遍意义的图件。

APPROACH TO VOLCANIC STRATIGRAPHIC UNITE AND ITS DIVISION IN CONTINENTAL VOLCANIC TERRAIN

The reslults of many years' study show that Mesozoic volcanic belt in Southeastern Coast of China is charactered of muticycles. Product of magmatism by a volcanic cycle is consistent with its tectonic trace spaciously, tempararily and genetically. Volcaoic tectonism during the same cycle is marked by overlapping distribution in space but volcanic ectonisom during different cycles shows a coordinate distribufion in space. All of these formed the special ring structure cut overlap and with line structrue intercalated composed of line-ring structure, which is showed in the geological map in volcanic area.In the development and evolution of volcanic apparatus though the troes of volcanic eruption are different, troes of volcanic eruption are consistent with volcanic facies.It can be inferred that volcanic facies and sequence in volcanic apparatus are the important base for reappearing evolutional history of palaeovolcanic apparatus and resuming the palaevolcanic landscape as well as the formation of volcanic stratisraphy and the volcanic stratigraphic unite with genetic hoportance.Combined with volcanic statigraphies in volcanic apparatus of various cycles, overlap is a foundation for establishing regionally volcanic stratigraphyies. Volcamc structure is the important framework in volcanic terrain. Structural map showing volcanic facies charactered by facies producted by volcanic mapmatism reveals geotectonic featues in volcanic terrain.Based on the above mentioned views, we propose that stratigraphic sequence of continental volcanic terrain consists of cycle (volcanic apparatus) -group (evolution period uf volcanic apparatus ) - facies (type of volcanic eruption) -stratigraphy. We regard these as mapping unites and drawing up geological maps.