摘要
攀枝花铁矿区内发育有浅色辉长岩墙(主要由浅色辉长岩组成),对其开展研究对进一步厘清攀西地区超大型铁矿床的形成机理具有重要意义。通过对浅色辉长岩系统的矿物学、岩石学和地球化学研究,探讨了其成因、与层状辉长岩体的关系,并约束了攀枝花铁矿床成矿作用的结束时限。野外地质调查表明,浅色辉长岩墙穿插切割层状辉长岩体、脉状铁矿体,表明其侵位时代晚于后两者,浅色辉长岩墙的侵位可能代表了该地区成矿作用的结束。电子探针分析表明,浅色辉长岩中的单斜辉石为普通辉石,斜长石为拉长石(An值52.45~52.66)。浅色辉长岩[Th/Ta]_(N)值(0.38~1.09,平均值为0.69)和[La/Nb]_(N)值(1.37~3.28,平均值为2.38)小于或略大于1,Zr/Y比值(1.44~5.08)和Zr/Nb值(3.9~8.4)均小于18。在Th/Hf-Ta/Hf图解上,浅色辉长岩样品大部分投在了地幔热柱玄武岩区。以上特征表明,形成浅色辉长岩的岩浆来源于富集地幔源区,其上侵过程中经历了低程度地壳混染,为峨眉山地幔柱的产物。在MgO对其他氧化物图解上,从层状辉长岩到浅色辉长岩,随着MgO含量的增加,主要氧化物含量线性变化,表明两者为同源岩浆演化的产物,浅色辉长岩墙可能为深部岩浆房内玄武质岩浆经液态不混熔形成的富硅、贫铁钛熔体侵位形成的。
The leucocratic gabbro dikes,mainly composed of leucocratic gabbro,are generally developed in Panzhihua iron mining area.It is important to study them in order to clarify the forming mechanism of super-large iron deposits in Panxi area.Based on the systematic mineralogical,petrological and geochemical research of the leucocratic gabbro,the genesis and its relationship with the layered gabbro body are discussed,and the end time limit of mineralization in Panzhihua iron deposit is restricted.The geological field survey shows that the leucocratic gabbro dikes cut through the layered gabbro and vein iron orebodies,indicating that the emplacement age of the dikes is later than that of the latter two,which may represent the end of the mineralization in this area.Electron microprobe analysis result indicates that the clinopyroxene in the leucocratic gabbro is common augite and the plagioclase is elongated feldspar(An value of 52.45-52.66).The[Th/Ta]_(N) value(0.38-1.09,mean 0.69)and[La/Nb]_(N) value(1.37-3.28,mean 2.38)of leucocratic gabbro are less than and slightly greater than 1,respectively,and their Zr/Y ratios(1.44-5.08)and Zr/Nb ratios(3.9-8.4)are all less than 18.Most of the leucocratic gabbro samples are plotted in the mantle plume basalt on the Th/Hf-Ta/Hf diagram.The above features indicate that the magma that formed the leucocratic gabbro is derived from the enriched mantle,and it has experienced a low degree of crust contamination during the uplifting process,which is the product of the Emeishan mantle plume.On MgO vs other oxides diagram,from layered gabbro to leucocratic gabbro,with the increase of MgO content,the main oxide content changes linearly,indicating that they are the products of same source magma evolution.The gabbro dikes might be formed by the emplacement of silicon-rich and iron-titanium-poor melting body of basaltic magma in the deep magma chamber through liquid immiscible melting.
作者
罗伟
金廷福
李佑国
彭静
刘纯波
邱春
LUO Wei;JIN Tingfu;LI Youguo;PENG Jing;LIU Chunbo1;QIU Chun(College of Engineering and Technology,Zunyi Normal University,Zunyi 563006,Guizhou,China;College of Mining Engineering,Guizhou University of Engineering Science,Bijie 551700,Guizhou,China;College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,Sichuan,China;Changzhou Vocational Institute of Mechatronic Technology,Changzhou 213164,Jiangsu,China)
出处
《矿产与地质》
2022年第1期102-110,共9页
Mineral Resources and Geology
基金
贵州省省级科技计划项目(黔科合基础-ZK〔2021〕一般204)
遵义师范学院项目(遵师BS〔2020〕5号、遵师XM〔2020〕1号-01)
贵州省教育厅青年人才项目(黔教合KY字〔2020〕146)
毕节市科学技术联合基金项目(毕科合字〔2019〕22号)共同资助。
关键词
浅色辉长岩墙
岩石成因
攀枝花岩体
峨眉山大火成岩省
leucocratic gabbro dike
petrogenesis
Panzhihua pluton
Emeishan large igneous province
