安徽黄梅尖地区基性脉岩年代学和地球化学特征  

Chronology and geochemical characteristics of basic dykes in the Huangmeijian area, Anhui Province, China

作　　者：邓一潇 王正其[1] 匚李丽荣 曹达旺 肖金根 杨彪[2] DENG Yi-xiao;WANG Zheng-qi;LI Li-rong;CAO Da-wang;XIAO Jin-gen;YANG Biao(Fundamental Science on Radioactive Geology and Exploration Technology Laboratory,East China University of Technology,Nanchang 330013,China;Anhui Nuclear Exploration Technology Centre Institute,Wuhu 241000,China)

机构地区：[1]放射性地质与勘探技术国防重点学科实验室(东华理工大学),江西南昌330013 [2]安徽省核工业勘查技术总院,安徽芜湖241000

出　　处：《矿物学报》2019年第6期617-626,共10页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目(批准号：41040019);安徽省地质勘查科学研究基金项目(编号：2012-K-2)

摘　　要：对庐枞盆地黄梅尖岩体内发育的辉绿玢岩开展了K-Ar法定年和系统的岩石地球化学特征研究。研究表明,辉绿玢岩形成年龄为107Ma±,属于晚白垩世产物。岩石出现2种辉石(单斜辉石和斜方辉石),w(SiO2)介于51.93%~58.87%之间,具有富碱、高钾、贫钛等特征,岩石富集LREE、大离子亲石元素和强不相容元素,无Eu亏损现象,显示出洋岛玄武岩(OIB)相似的稀土元素和微量元素配分曲线。锶同位素初始值(ISr)介于0.70575~0.70588,DSr值介于57.46~58.80,(143Nd/144Nd)i介于0.512124~0.512188,εNd(t)值范围为-6.1^-7.3。我们认为黄梅尖辉绿玢岩属钾玄岩,其源区性质表现出富集地幔(EMI型)特征,庐枞盆地岩浆作用形成和演化与扬子陆块-华北陆块间陆陆碰撞后的伸展环境及软流圈物质上涌导致富集地幔部分熔融有关。黄梅尖钾玄岩限定了岩石圈减薄的时限,推测岩石圈减薄动力学演化过程可能对热液型铀成矿有重要的制约作用。The K-Ar dating and detailed study on petrogeochemical characteristics of diabase-porphyrite in the Huangmeijian pluton in the Luzong basin were carried out in this paper.The results indicate that the diabase-porphyrite was formed in Late-Cretaceous with an age of 107 Ma.It is characterized with containing two kind of pyroxenes(clinopyroxene and orthopyroxene),SiO2 contents of 51.93%-58.87%,alkaline rich,high K content,poor in Ti,enriched in LREE,LILE,and incompatible elements,no Eu depletion,and has similar REE and trace element distribution patterns to those of the oceanic basalt(OIB).It has(87Sr/86Sr)i values of 0.70575-0.70588,DSr values of 57.46-58.80,(143Nd/144Nd)i values of 0.512124-0.512188,andεNd(t)values varying from-6.1 to-7.3.It is concluded that the diabase-porphyrite in the Huangmeijian area belongs to shoshonite which was originated from enriched mantle(EMI);The formation and evolution of magmatism in the Luzong basin were related to the extensional environment after the continental collision between the Yangzi and North China blocks and the partial melting of the enriched mantle which was caused by the upwelling of asthenospheric materials.As the age of Huangmeijian shoshonite has fundamentally constrained a time limit for the lithospheric thinning in the Luzong area,it is speculated that the dynamic evolution process of the lithospheric thinning could be played an important constraint on the hydrothermal uranium mineralization.

关 键 词：钾玄岩 K-Ar法定年 岩石地球化学 黄梅尖岩体 庐枞盆地 

分 类 号：P588.13[天文地球—岩石学] P597[天文地球—地质学]