安徽铜陵凤凰山岩体LA-ICP-MS锆石U-Pb年龄和地球化学特征  

LA-ICP-MS Zircon U-Pb Ages and Geochemical Characteristics of the Fenghuangshan Pluton in Tongling,Anhui

作　　者：王次松[1] 吴才来[2] 郑坤 吴迪 单士锋 李翔[1] 古全德 WANG Cisong;WU Cailai;ZHENG Kun;WU Di;SHAN Shifeng;LI Xiang;GU Quande(The 321 Geology Party,Bureau of Geology and Mineral Exploration of Anhui Province,Tongling,Anhui,244033;Key Laboratory of Deep-Earth Dyamics of MNR,Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing,100081)

机构地区：[1]安徽省地质矿产勘查局321地质队,安徽铜陵244033 [2]自然资源部深地动力学重点实验室、中国地质科学院地质研究所,北京100037 [3]中国地质科学院地质力学研究所,北京100081

出　　处：《地质论评》2018年第5期1237-1250,共14页Geological Review

基　　金：国家自然科学基金资助项目(批准号：41472063)的成果

摘　　要：安徽铜陵是我国著名的铜—金多金属矿集区,区内广泛出露与成矿作用有着密切关系的中酸性侵入岩,其中,凤凰山岩体是区内出露面积最大的岩体,岩体周围分布着许多重要的铜、金、钼等金属矿床。为了探讨凤凰山岩体的成因及构造意义,本文对该岩体开展了岩石学、锆石U-Pb年代学、岩石地球化学等方面的研究。研究结果表明,该岩体主要由花岗闪长岩和石英二长闪长岩组成,锆石LA-ICP-MS U-Pb年龄分别为140.6～144.7 Ma和142.2～143.4 Ma,反映岩体侵位时代为140.6～144.7 Ma。岩石主要由斜长石、石英、碱性长石组成,其次含角闪石、黑云母,副矿物为磷灰石、锆石等,岩体内部常见闪长质微粒包体。岩石的铝饱和指数A/CNK<1.1,Na_2O>K_2O,具Ⅰ型花岗岩特征。岩石的轻稀土元素富集而重稀土元素亏损,Eu呈较弱的负异常,富集Rb、Ba、Th、U、K等大离子亲石元素,相对亏损Nb、Ta、P、Ti等高场强元素,反映其源岩可能主要为壳幔混合源,形成岩体的岩浆是由古老地壳部分熔融形成的长英质岩浆与起源于富集地幔的富碱玄武质岩浆混合后形成。Objectives： Tongling area of Anhui province is a famous copper—gold polymetallic ore concentration area in the middle and lower reaches of Yangtze River of eastern China.The intermediate—acid intrusions related to largescale mineralization are widely exposed in the area.Fenghuangshan pluton is the largest one with 10 km^2 exposed area in all intermediate—acid plutons from Tongling.Some copper,gold and molybdenum deposits are distributed around the body.Thus,it is of great significance to study petrology,zircon U-Pb chronology and geochemistry of the pluton.This paper is aimed to discuss the petrogenesis and tectonic implications of the Fenghuangshan pluton.Methods： Based on the field work,through the microscope observation,the whole rock chemical analysis and zircon U-Pb LA-ICP-MS dating of the pluton,we determine the emplacement time and geochemical affinity of the pluton.Results： Petrologically, the Fenghuangshan pluton is mainly composed of granodiorite and quartz monzodiorite.The zircon U-Pb LA-ICP-MS dating yielded ages of 140.6～144.7 Ma for the granodiorite,and 142.2～143.3 Ma for the quartz monzodiorite,indicating that the emplacement time of the pluton is from 144.7 Ma to 140.6 Ma.Mineralogically,both kinds of rocks in the pluton are mainly composed of plagioclase,quartz,alkaline feldspar,amphibole and biotite with different contents,and the common accessory minerals are apatite,zircon.In addition, the pluton contains a large amount of microgranular diorite enclaves, showing a magma mixing.Geochemically,the rocks show significant features of Ⅰ-type granite with aluminum saturation index（ A/CNK〈 1.1）,and Na2O 〉K2O.It is also enriched in light rare earth elements（ LREE） and large ion lithophile elements（ LILE）（ such as Rb,Ba,Th,U,K）,depleted in heavy rare earth element（ HREE） and part of high field strength elements（ HFSE）（ such as Nb,Ta,P,Ti）,and has LREE differentiation to be obvious but HREE,with slightly negative Eu anomaly in REE patterns.Conclusions：

关 键 词：锆石U-PB年代学 岩石地球化学 岩石成因 构造意义 凤凰山岩体 铜陵 

分 类 号：P618.2[天文地球—矿床学]