Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报

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第29卷    第7期    总第244期    2019年7月

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文章编号:1004-0609(2019)-07-1551-16
豫西蒿坪沟岩体岩石地球化学、锆石U-Pb年龄及Hf同位素组成
刘文毅1, 2, 3,刘继顺1, 2,何美香3,丁云河3,李永峰4

(1. 中南大学 有色金属成矿预测与地质环境监测教育部重点实验室,长沙 410083;
2. 中南大学 地球科学与信息物理学院,长沙 410083;
3. 河南省有色金属地质矿产局第七地质大队, 郑州 450016;
4. 河南省有色金属矿产探测工程技术研究中心,郑州 450016
)

摘 要: 蒿坪沟岩体位于华北陆块南缘沙沟-蒿坪沟银铅矿区内,主要岩性为黑云母花岗斑岩和花岗斑岩。LA-ICP-MS锆石U-Pb定年结果显示,黑云母花岗斑岩加权平均年龄为(128±1) Ma,花岗斑岩加权平均年龄为(110±1)~(112±1) Ma,表明岩体为燕山期多期次岩浆作用的产物。岩石地球化学研究表明,两期岩体为钾玄岩-高钾钙碱性系列,A/CNK值为1.03~1.09,属弱过铝质花岗岩类;轻重稀土元素分馏显著,具中等-弱的负Eu异常,均为I型花岗岩。锆石Hf同位素研究表明,εHf(t)变化范围为-22.9~-2.1,均为负值,tDM2为2617~1304 Ma。锆石Hf同位素组成以及蒿坪沟岩体中出现的继承锆石,表明其源区物质主要来源于前寒武纪变质基底岩石,在侵位过程中可能受到了上地壳的混染。结合区域地质背景,蒿坪沟岩体形成于扬子陆块与华北陆块碰撞造山后的陆内伸展环境。

 

关键词: 蒿坪沟岩体;豫西;岩石地球化学;锆石U-Pb年龄;Hf同位素

Petrogeochemistry, zircon U-Pb ages and Hf isotopic composition of Haopinggou pluton, Western Henan
LIU Wen-yi1, 2, 3, LIU Ji-shun1, 2, HE Mei-xiang3, DING Yun-he3, LI Yong-feng4

1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitor Ministry of Education, Central South University, Changsha 410083, China?
2. School of Geosciences and Info physics, Central South University, Changsha 410083, China?
3. No. 7 Geological Team, Bureau of Nonferrous Metals Geology and Mineral Resources of Henan Province, Zhengzhou 450016, China;
4. Non-Ferrous Mineral Exploration Engineering Research Center of Henan Province, Zhengzhou 450016, China

Abstract:The Haopinggou pluton occurred in the southern margin of the North China Craton, Shagou-Haopinggou Ag-Pb deposits, which includes biotite granite porphyry and granite porphyry. LA-ICP-MS zircon dating yields U-Pb age shows that the weighted average ages of biotite granite porphyry and granite porphyry are (128±1) Ma, (110±1)-(112±1) Ma, indicating that the Haopinggou pluton which formed in Yanshanian is the product of two cycles of magmatic activities at least. The compositions of these two period pluton fall into shoshonite and High-K calc-alkaline series, with an A/CNK ratio of 1.03-1.09. They have significant fractionation between LREE and HREE, with medium-weak negative Eu anomalies, which are all belonging to I-type granite. Zircon eHf(t) values of the pluton are negative(-22.9--2.1), and two-stage Hf model ages (tDM2) range from 1304 Ma to 2617 Ma. Zircon Hf isotope data, along with the presence of the inherited zircons, indicating that the Haopinggou pluton might be generated by partial melting of Precambrian metamorphic basement rocks of coupled with assimilation of the wall rocks of the upper crust. The Haopinggou pluton was emplaced after the major collisional period of the North China block and Yangtze block, in the post-collisional tectonic setting under the regional extension mechanism.

 

Key words: Haopinggou pluton; Western Henan province; petrogeochemistry; zircon U-Pb ages; Hf isotope

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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