安徽庐枞盆地中巴家滩岩体的岩石地球化学特征及成因  

Rock geochemistry and genesis of the Bajiatan intrusion in the Lujiang-Zongyang volcanic basin,Anhui.

作　　者：刘珺[1] 周涛发[2] 袁峰[2] 范裕[2] 吴明安[3] 陆三明 钱存超 

机构地区：[1]中国地质大学(北京),北京100083 [2]合肥工业大学,合肥230009 [3]安徽省地质调查院,合肥230001 [4]安徽省地质调查和环境监测中心,合肥230001

出　　处：《岩石学报》2007年第10期2615-2622,共8页Acta Petrologica Sinica

基　　金：国家自然科学基金资助项目(编号:40672062和40434011);高等学校博士学科点专项科研基金项目(编号:20050359013);国家重点基础研究发展规划973项目(编号:2007CB411405;2007CB411304);安徽省优秀青年科技基金和安徽省国土厅地质勘查专项费项目项目资助。

摘　　要：巴家滩岩体位于长江中下游庐枞中生代火山岩盆地的中心地带。出露面积约4km^2。岩性主要为辉石二长岩和含英辉石二长岩,发育黄铁矿化和黄铜矿化。野外及室内证据表明该岩体可分为两期,第一期表现为闪长质岩石包体;第二期主要为早阶段的辉石二长岩和晚阶段的含石英辉石二长岩。巴家滩岩体随着由早到晚的演化,其SiO_2含量、总碱含量(Na_2O +K_2O)和岩石的氧化度不断增高。稀土配分整体呈右倾趋势,轻稀土富集,重稀土分馏不明显。岩石学、稀土和微量元素地球化学特征表明巴家滩岩体成岩物质来源于富含金云母的富集地幔Ⅱ。巴家滩岩体属于橄榄玄粗岩系,形成于伸展构造环境。巴家滩岩体具有高Al_2O_3、Sr、Sr/Y、La/Yb,低Y、Yb、Sr正异常,Eu弱负异常,与沙溪岩体的特征相似,早期包体的Cu含量高达0.8402,推断在其深部可能有可能有类似沙溪岩体的矿化岩浆存在。The Bajiatan intrusion is located in the center of the Lujiang-Zongyang volcanic basin in the middle and lower Yangtze River valley, covering an area of 4 km(2). The main rock types are pyroxene monzonite and quartz-bearing pyroxene monzonite with well-developed pyritization and chalcopyritization. According to the field and indoor evidence, magmatism for the Bajiatan intrusion may be divided into two phase: the early phase was marked by the formation of dioritic enclaves, and the late phase was mainly represented by pyroxene monzonite in the early stage and quartz-bearing pyroxene monzonite in the late stage. With magmatic evolution from the early to late stages, the contents of SiO2 and total alkalis (Na2O + K2O) and degrees of oxidation of the intrusion increased progressively. The REE patterns generally show a right-inclined trend: LREE are enriched and HREE fractionation is not pronounced. The petrology and REE and trace element geochemistry show that the rock-forming materials of the Bajiatan rock body were derived from phlogolite-rich enriched mantle II. The Bajiatan intrusion belongs to a shoshonitic rock series and formed in an extensional regime. It has higher Al2O3, Sr, Sr/Y and La/Yb lower Y and Yb, a positive Sr anomaly and a weak negative Eu anomaly. These chemical characteristics are similar to those of the Shaxi intrusion. The content of Cu in early-stage enclaves is up to 0.8402, which exceeds the commercial grade of the Shaxi porphyry copper deposit. It is inferred that mineralized magma similar to that for the Shaxi intrusion might exist at depths.

关 键 词：巴家滩岩体 庐枞盆地 富集地幔 分离结晶 同化混染 

分 类 号：P588.122[天文地球—岩石学]