关键词: 珠江口盆地, 恩平凹陷, 阳江—一统断裂带, 火山岩相, 火山机构, 地球化学, 储层

Abstract:  In order to clarify the evolution model and controlling factors of distribution of volcanic rocks in the southwestern Enping sag, Pearl River Mouth basin, based on the datasets of the target area and adjacent area, the lithological and lithofacies characteristics are identified with thin section and logging firstly, then the volcanic edifice characteristics are identified with well and seismic datasets, finally, the genesis of volcanic rocks are identified with geochemical data. The results show that basalt-dominated volcanic rocks developed in southwestern Enping sag. Through drilling data, four types of volcanic rock are identified, namely hyaloclastite, massive basalt, amygdaloid basalt, and hydrothermal breccia. The Cenozoic volcanic rocks in the study area are divided into two kinds of lithofacies and four kinds of subfacies：Volcanic conduit facies （including hidden breccia subfacies）, effusive facies （including hyaloclastic rock subfacies, tabular lava flow subfacies, and braid lava flow subfacies）. At the same time, four eruption periods are identified based on sedimentary rock interfaces, and volcanic crater-near volcanic crater, proximal volcanic facies belts, middle-distance and distal volcanic facies belts are divided according to each period. Volcanic reservoirs are complex, and the physical properties of volcanic conduits-near volcanic crater and proximal volcanic facies belts are relatively good. The basaltic magma of different stages in the research area was formed by the separation and crystallization of homologous mantle derived magma. The magma chamber is located in the lower crust and has undergone strong crustal assimilation and mixing. According to the seismic data, it is identified that the fault in the study area is characterized by two phases of activity. The Pearl River Formation is NEE-NE trending in the sedimentary period, and the Hanjiang Formation is NWW-NW trending in the sedimentary period up to now. The origin of the magma is associated with deep-seated faults. The NW sinistral strike-slip component induces a weak leftward rotation in the volcanic facies, gradually transforming its shape from a straight line into an inverse S-curve.

Key words: Pearl River Mouth basin, Enping sag, Yangjiang-Yitong fault zone, volcanic facies, volcanic edifice, geochemistry, reservoirs