(1. 中南大学 地球科学与信息物理学院，长沙 410083；
2. 中南大学 湖南省有色金属资源与地质灾害探查重点实验室，长沙 410083)
摘 要: 宁芜盆地位于中国东部长江中下游成矿带，盆地内主要发育4套火山岩。本研究主要通过地球化学手段探究该火山岩地球化学性质及岩浆演化特征。结果表明：火山岩主要为安山岩、粗安岩和英安岩；早期龙王山组为低钾系列，其余3组火山岩为高钾钙碱性-橄榄玄粗岩系列。4套火山岩Mg#值为66.51~40.33，轻稀土富集，Ta、Nb、Ti亏损，指示原始岩浆形成于富集地幔部分熔融。原始岩浆形成后经历了以分离结晶为主的岩浆演化过程，主要表现为Mg#降低和向富碱系列演化。结合区域地质和年代学研究，认为宁芜火山活动发生在受古太平洋俯冲和大别造山后区域引张的共同作用下的岩石圈减薄环境，郯庐断裂早白垩世走滑使得宁芜盆地拉分和富集地幔减压熔融形成岩浆。
关键字: 宁芜盆地；火山岩；地球化学；富集地幔；岩浆演化
（1. School of Geosciences and Info-physics, Central South University, Changsha 410083, China;
2. Hunan Key Laboratory of Non-ferrous Resources and Geological Hazard Detection, Central South University, Changsha 410083, China）
Abstract:The Ningwu basin is located in the Middle-Lower Yangtze River metallogenic zone, Eastern China. Four cycles of volcanic rocks were widely found in the basin. By the tool of geochemistry, the geochemical characteristics and magma evolution of these volcanic rocks were studied. The results show that volcanic rocks are mainly andesites, trachy-andesites and dacites. The volcanic rocks of the Longwangshan formation, which were formed earlier, are low K series while volcanic rocks of other formations vary from high K calc-alkaline to shoshonite. With the Mg indexes from 66.51 to 40.33, volcanic rocks show the similar LREE-enriched patterns and depletion in high field strength elements of Ta, Nb and Ti, suggesting that the primitive magma resulted from partial melting of enriched mantle. The decreasing Mg index and the increasing alkali also indicate that the magma experienced significant fractional crystallization after forming. Combined with regional geology and dating studies, it is thought that volcanic activities in the Ningwu basin happened at the regional lithospheric thinning, resulting from the subduction of Paleo-Pacific and post-orogen extension of Dabie Mountain. At that time, active Tanlu fault triggered partial melting of the enriched mantle beneath the Ningwu basin.
Key words: Ningwu basin; volcanic rocks; geochemistry; enriched mantle; magma evolution
