松辽盆地营城组火山机构地层结构定量模型

Quantitative models of strata texture within volcanic edifices of Yingcheng Formation in Songliao Basin,NE China

松辽盆地营城组火山岩地层主要由火山机构侧向迁移和垂向叠置而形成。目前对火山机构的内部结构认识还不清晰,制约了火山岩勘探开发进程。通过对典型酸性熔岩、酸性复合、酸性碎屑岩和中基性熔岩火山机构的综合解剖,建立其地层结构模型。酸性火山机构中多数为似层状结构,中基性火山机构中除发育似层状结构外,还常见层状结构。具有似层状结构的酸性火山机构的岩层倾角要大于具有层状结构的中基性熔岩火山机构;现今岩层倾角可为正态分布,也可呈现出偏正态或双峰态。火山岩地层结构与火山机构类型、喷发古环境(同生断层和古斜坡)密切相关;后期的挤压和掀斜作用对岩层产状变化起到显著的改造作用;后期单期次、断距小的正断层或逆断层的改造,对岩层产状的变化影响较小。此研究为火山岩地层结构内部精细解剖提供了理论依据。

The volcanostratigraphy of Yingcheng Formation was built up by volcanic edifices which migrated in lateral direction and o- verlapped in vertical succession. In present, internal structures of volcanic edifices are not clear. So development process of volcanic gas pools in Songliao Basin was decelerated. The models of strata texture within volcanic edifices were created by integrated analysis of acid lava, acid compound, and acid pyroclastic volcanic edifices as well as intermediate-basic lava ones. The strata texture of most- ly acid volcanic edifices is pseudostratified texture. The intermediate-basic lava volcanic edifices has stratified texture besides the pseudostratified texture. The dip angle of acid volcanic edifices （with the pseudostratified texture） is bigger than that of the interme- diate-basic volcanic edifices （with the stratified texture）. The dip angles show normal distribution, skewed normal distribution or hi- modal shape. The primary stratified occurrence of volcanic rocks is controlled by types of volcanic edifices, eruptive paleogeomor- phology （such as contemporaneous fault and paleoslope）, and reformed by later compressional and tilting activities. Purly later low relief normal faults or reverse faults can impact the occurrence slightly. This study offers a theoretical basis for meticulous depiction of internal structure of volcanostratigraphy.