四川盆地简阳地区二叠系火山喷发旋回、环境与模式

四川盆地简阳地区二叠系峨眉山玄武岩发育火山碎屑岩优质储层，永探1井为该区二叠系火山碎屑岩气藏的首口工业气井，但目前对于该区火山喷发旋回、古地理环境及喷发模式的认识还不清楚，制约了对岩相、储层分布的认识和勘探区带评价。为此，从研究该区火山岩岩石组合特征入手，分析火山喷发旋回，结合区域地层、岩相古地理研究成果综合对比确定火山喷发环境，建立火山喷发模式，综合钻井、重磁力、地震等资料预测区域火山机构的分布特征。研究结果表明：①该区二叠系火山岩纵向发育5套岩性、4个喷发旋回（期次），早期两个旋回强烈爆发，以火山碎屑岩为主，晚期两个旋回能量减弱，发育浅成侵入岩；②该区火山岩为东吴运动抬升后陆相环境喷发，主喷发期与峨眉山玄武岩基本一致，为中—晚二叠世之交及其后的100万年（1 Myr）；③简阳—中江地区北东向主断裂和北西向次级断裂的交汇处为深层岩浆上涌通道，控制该区发育中心式多火山口喷发形成的复式火山机构，有利于爆发相火山碎屑岩叠置、连片规模分布。结论认为，简阳地区火山岩与峨眉山玄武岩喷发环境、喷发时代一致，但喷发模式及岩性、岩相却存在着较大的差异，为峨眉山大火成岩省的特殊组成部分。

Permian volcanic eruption cycle,environment and model in the Jianyang area of the Sichuan Basin

High-quality pyroclastic reservoirs are developed in the Permian Emeishan basalt in Jianyang area of the Sichuan Basin. Well Yongtan 1 is the first industrial gas well drilling into the Permian pyroclastic gas reservoir in this area. So far, however, volcanic eruption cycle, paleogeographic environment and eruption model in this area have not been clarified, which restricts the understanding of lithofacies and reservoir distribution and the evaluation on exploration zones. Based on the characteristics of volcanic rock assemblage in this area, this paper analyzed the volcanic eruption cycle. Then, combined with the comprehensive result comparison of regional stratigraphy and lithofacies paleogeography, volcanic eruption environment was determined and a volcanic eruption model was established. Finally, the distribution characteristics of regional volcanic mechanism were predicted on the basis of drilling, gravity and magnetism and seismic data. And the following research results were obtained. First, 4 eruption cycles (periods) with 5 sets of lithology are vertically developed in the Permian volcanic rocks of Jianyang area. In the early two cycles, eruption is strong and pyroclastic rocks are dominant. In the late two cycles, energy is weak and shallow intrusive rocks are developed. Second, volcanic rocks in this area are the eruptive products in the continental environment after the uplift of Dongwu movement. The main eruption period is the turn of Middle to Late Permian and one million years (1 Myr) after that, which is basically consistent with the eruption period of Emeishan basalt. Third, the intersection of NE main fault and NW secondary fault in Jianyang-Zhongjiang area is the upwelling channel of deep magma. It controls the development of complex volcanic mechanism formed by the central multi-crater eruption in this area, and it is conducive to the superposed and continuous distribution of pyroclastic rocks of eruptive facies in the large scale. In conclusion, volcanic rocks in Jianyang area and the Emeishan basalt are basically the same in eruption environment and age, but more different in eruption model, lithology and lithofacies. Therefore, volcanic rocks in Jianyang area are a special part of Emeishan large igneous province.