The authors introduce the recognized Cretaceous basic volcanic rocks( basalts) in the originally called Huashan Group in Dahongshan area,Hubei. The LA-ICP-MS U-Pb zircon dating data shows that the basic volcanic rocks formed at 128. 3 ± 1. 4 Ma. There has been an intraplate volcanic eruption during Early Cretaceous according to the testing results of major,rare earth element( REE) and trace elements of the basalts. This kind of volcanic rock has low content of Nb,Ta and Sr,and high content of Ti/Y,slightly enriched in light rare earth element( LREE) ,and which is similar to within-plate ba-salt(WPB)or oceanic-island basalt(OIB). It is corroborative for some previous researchers' view,whose evidences were from the Late Mesozoic(130 Ma)granites in Qinling-Dabie Orogenic Belt(QDOB). This preliminary study may infer that there is an extensional period at the Early Cretaceous in the southern boundary of QDOB after the Triassic-Middle Jurassic subduction and collision of Yangtze Block to North China Block.%介绍湖北大洪山地区花山群中的白垩纪基性火山岩(玄武岩).LA-ICP-MS U-Pb锆石测年表明,该基性火山岩形成于(128.3±1.4)Ma.根据主量元素、 稀土元素和微量元素的测试结果,该地区在早白垩世存在板内火山喷发.该火山岩具有低Nb、Ta和Sr、 高Ti/Y的特征,略微富集轻稀土元素,类似于大陆板内玄武岩型或者洋岛玄武岩型.与前人在秦岭大别造山带(QDOB)中发现的中生代晚期(130 Ma左右)的花岗岩证据相互印证.该初步研究可能揭示,扬子地块在三叠纪—中侏罗世向华北地块俯冲碰撞造山后,于早白垩世(128 Ma左右)处于伸展环境.
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