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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
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引用本文:王次松,吴才来,郑坤,吴迪,单士锋,李翔,古全德.2018.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[J].地质论评,64(5):1237-1250
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作者单位E-mail
王次松 1) 安徽省地质矿产勘查局321地质队安徽铜陵2440331 wcisong@126.com 
吴才来 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 wucailai@ 126.com 
郑坤 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  
吴迪 3) 中国地质科学院地质力学研究所北京100081  
单士锋 1) 安徽省地质矿产勘查局321地质队安徽铜陵2440331  
李翔 1) 安徽省地质矿产勘查局321地质队安徽铜陵2440331  
古全德 1) 安徽省地质矿产勘查局321地质队安徽铜陵2440331  
基金项目:本文为国家自然科学基金资助项目(批准号:41472063)的成果。
中文摘要: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142.2~143.4Ma,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,Na2O>K2O,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。
中文关键词: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
 
LA-ICP-MS Zircon U-Pb Ages and Geochemical Characteristics of the Fenghuangshan Pluton in Tongling, Anhui
NameInstitution
WANG Cisong1) The 321 Geology Party, Bureau of Geology and Mineral Exploration of Anhui Province, Tongling, Anhui, 244033
WU Cailai2) Key Laboratory of DeepEarth Dyamics of MNR, Institute of Geology,Chinese Academy of Geological Sciences, Beijing, 100037
ZHENG Kun2) Key Laboratory of DeepEarth Dyamics of MNR, Institute of Geology,Chinese Academy of Geological Sciences, Beijing, 100037
WU Di3) Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing,100081
SHAN Shifeng1) The 321 Geology Party, Bureau of Geology and Mineral Exploration of Anhui Province, Tongling, Anhui, 244033
LI Xiang1) The 321 Geology Party, Bureau of Geology and Mineral Exploration of Anhui Province, Tongling, Anhui, 244033
GU Quande1) The 321 Geology Party, Bureau of Geology and Mineral Exploration of Anhui Province, Tongling, Anhui, 244033
Abstract: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 large scale 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 142.2~143.3Ma 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 Na2O>K2O. 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: The Fenghuangshan pluton was emplaced at 140.6~144.7 Ma. Geochemical characteristics indicate that its source rock may be the mixed source of crust and mantle. The pluton may have been formed by the mixing of acidic magma from the partial melting of the ancient crust and alkali rich basaltic magma from the enriched mantle.
keywords:zircon U-Pb geochronology  petrochemistry  petrogenesis  tectonic implication  Fenghuangshan pluton  Tongling
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