| 伊朗马斯杰德达吉(Masjed Daghi)始新世斑岩成因:来自光谱学与U-Pb年代学和地球化学的证据 |
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| 引用本文： | 寇冠玉,周晔,郑远川,于佳兴.伊朗马斯杰德达吉(Masjed Daghi)始新世斑岩成因:来自光谱学与U-Pb年代学和地球化学的证据[J].现代地质,2021,35(2):535-551. |
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| 作者姓名： | 寇冠玉 周晔 郑远川 于佳兴 |
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| 作者单位： | 1.中国地质大学(北京) 地球科学与资源学院,北京 1000832.中国地质调查局 昆明自然资源综合调查中心,云南 昆明 650011 |
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| 基金项目： | 国家自然科学基金项目(41803045);中央高校基本科研业务费项目(2652019119)。 |
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| 摘 要： | 伊朗马斯杰德达吉(Masjed Daghi)斑岩型矿床位于阿哈尔—乔勒法(Ahar-Julfa)/阿拉斯巴兰(Arasbaran)成矿带的西北部,目前针对该斑岩矿床的研究相对较少,许多地质问题有待解决。为了补充马斯杰德达吉斑岩型矿床成因的地球化学证据,更好地厘定斑岩形成时间,了解矿床形成过程,对矿区中钻孔采集的石英二长斑岩中的长石、石英和锆石等矿物进行了红外-拉曼光谱、同位素及U-Pb定年、主量和微量元素等测试,同时对斑岩全岩主微量元素进行了分析测试。光谱学测试结果显示斑岩样品中的长石斑晶主要为斜长石,少量为钾长石。锆石U-Pb定年结果显示其成岩年龄为(54.1±1.5) Ma (MSWD=0.48),属早始新世,为矿前斑岩。岩体内发育的斜长石具有较低的K2O(0.2%~1.8%)、较高的CaO(1.7%~8.7%)和Na2O(6.5%~9.7%)。这些斑岩中的长石具有相对过量的Al,反映了成岩岩浆具有较高的水含量。锆石Ce4+ / Ce3+比值为152~543,平均330,指示较高的氧逸度。斑岩SiO2含量高达63.4%,含有相对较高的K2O(4.9%)和Sr/Y值(120.0~121.6),显示为具有埃达克特征的钾玄质石英二长斑岩。锆石εHf(t)值为+4.5~+13.5,平均值+10.3,为正异常。另外,二阶段模型年龄(TDM=841~260 Ma)表明岩浆起源于亏损地幔物质。马斯杰德达吉始新世斑岩形成于碰撞前大洋俯冲环境,更可能来自基性岩浆,因经历了俯冲洋壳脱水和地幔楔部分熔融的过程,而具有高氧化和富水的特征。
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| 关 键 词： | 马斯杰德达吉 斑岩型矿床 长石 锆石 电子探针 U-Pb定年 |
| 收稿时间： | 2020-09-23 |
| 修稿时间： | 2020-10-15 |
Genesis of Eocene Porphyry in Masjed Daghi,Iran:Evidence from Spectrographic,U-Pb Dating and Geochemical Characteristics |
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| KOU Guanyu,ZHOU Ye,ZHENG Yuanchuan,YU Jiaxing.Genesis of Eocene Porphyry in Masjed Daghi,Iran:Evidence from Spectrographic,U-Pb Dating and Geochemical Characteristics[J].Geoscience——Journal of Graduate School,China University of Geosciences,2021,35(2):535-551. |
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| Authors: | KOU Guanyu ZHOU Ye ZHENG Yuanchuan YU Jiaxing |
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| Institution: | 1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083,China2. Center of Natural Resources of Kunming, China Geological Survey, Kunming,Yunnan 650011,China |
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| Abstract: | The Ahar-Julfa/Arasbaran metallogenic belt is located in the Urmieh-Dokhtar magmatic Arc of the central part of the Tethyan metallogenic belt.The Masjed Daghi porphyry deposit in Iran is located in the northwestern part of the Ahar-Julfa metallogenic belt,in which the porphyry deposits have not been sufficiently studied.This paper is based on the Eocene porphyry from the Masjed Daghi porphyry deposit,with the aim to deepen the understanding on the metallogenic background and magmatic environment of the Ahar-Julfa metallogenic belt.We used infrared spectroscopy,raman spectroscopy,electron probe microscopic analyzer(EPMA),whole-rock major-and trace-element analyses,and zircon trace element and U-Pb-Lu-Hf isotope analyses to clarify the formation setting,oxygen fugacity,water content and other characteristics of the ore-forming magma.Zircon U-Pb dating of the porphyry yielded Eocene(54.1±1.5 Ma)age and positiveεHf(t)ratios(+4.5 to+13.5),with TDMages of 260 to 841 Ma.The rocks have high K2O(4.9%)and Sr(120×10-6-122×10-6)but low Y(5×10-6)contents.In addition,the porphyries have high zircon Ce4+/Ce3+ratios(152-543),and their plagioclase has high Al content.Such evidence indicates that the Eocene Masjed Daghi porphyries have water-rich and high-O fugacity features,and were generated from mafic magma upwelling during subduction. |
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| Keywords: | Masjed Daghi porphyry deposit feldspar zircon EPMA U-Pb dating |
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