摘要
苏北连淮地区的海州群是一套元古宙的火山变质岩套。火山岩以酸性和基性为主，中性火山岩稀少。其稀土元素明显分为富轻稀土元素无明显铕异常和富轻稀土元素明显铕负异常两种分布型式，显示“双峰式”组合特征。结合海州群沉积建造、构造格局及重力异常等资料都说明该区存在一个后期闭合的陆内裂谷──海州地堑式地槽。上地幔低比例部分熔融产生的碱性玄武岩浆和基底花岗质片麻岩局部重熔等产生的碱性、偏碱性流纹岩浆喷出海底，形成了海州群双峰式火山岩组合。
Widely spread in the Lianyungang-Huaiyin area,northern Jiangsu,the Proterozoic Haizhou Group strata consist of a suite of volcanic rocks,which are principally acidic and basic,rarely intermediate.The volcanic rocks formed in marine environment,and may be divided into two series:series-A and series-C.The series-A occurs in the Jinping Formation and the middle of the Yuntai Formation,and are mainly alkaline basic volcanic rocks,while the series-C occurs in the upper and lower member of the Yuntai Formation,and are mainly alkaline and subalkalic acidic those.The REE abundance distribution pattern of the series-A is characterized by high REE content (68.47-197.62 ppm),the enrichment of LREE (LREE/HREE=4.24-9.84) and no apparent Euanomaly(δEu=0.94-1.08).It was resulted from the partial melting of the upper mantle.The REE pattern of the series-C is characterized by high REE content (109.26-683.07 ppm),the enrichment of LREE (LREE/HREE=4.25-17.59) and a significant negative Eu-anomaly (δEu=0.14-0.75).It is the result of the remelting of basal sialic crust. The Haizhou Group volcanic rocks have a typical bimodal pattern.The Haizhou Group volcanic rocks differ from those of ophiolite complexes and those from the island arc.They have geochemical affinity to volcanic rocks from the intracontinental rift,indicating that the studied area is a taphrogeosyncline in terms of tectonics,located in the austral margin of the ancient North Jiangsu-South Shandong metamorphic terrain.The taphrogeosyncline formed through intracontinental rifting.
出处
《地球化学》
CAS
CSCD
北大核心
1994年第C00期182-191,共10页
Geochimica
