| 福建龙岩永福岩体锆石U-Pb年龄、地球化学特征及Lu-Hf同位素组成 |
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| 引用本文： | 康丛轩,周延,范飞鹏,苗娜,李凤春,孙建东,吕劲松.福建龙岩永福岩体锆石U-Pb年龄、地球化学特征及Lu-Hf同位素组成[J].大地构造与成矿学,2017,41(5). |
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| 作者姓名： | 康丛轩 周延 范飞鹏 苗娜 李凤春 孙建东 吕劲松 |
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| 作者单位： | 1. 中国地质调查局南京地质调查中心,江苏南京210016;河海大学地球科学与工程学院,江苏南京211100;2. 中国地质调查局南京地质调查中心,江苏南京,210016;3. 江苏煤炭地质物测队,江苏南京,210046;4. 中国冶金地质总局山东局测试中心,山东济南,250014 |
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| 摘 要： | 永福岩体位于永梅晚古生代拗陷带中部。利用LA-ICP-MS锆石U-Pb定年法测得永福岩体中YF-1样品的年龄为133±1 Ma(MSWD=0.50)、YF-2样品的年龄为143±1 Ma(MSWD=0.59),说明其形成于早白垩世,与燕山期岩浆活动有关。该岩体富硅、碱,里特曼指数σ=0.96~2.43,铝饱和指数(A/CNK)=0.98~1.66,属高钾钙碱性系列,准铝质到过铝质范围。稀土元素总量较高,LREE相对富集,HREE相对亏损;具中-弱Eu负异常,弱Ce负异常到无异常,轻重稀土的分馏较微弱;微量元素表现为亏损元素Ba、Sr、K、P和Ti,富集Th、U、Zr、Hf等元素。样品YF-2~YF-7具有S型花岗岩特征,为永福岩体主体,源岩可能来自古-中元古代下地壳沉积岩;而样品YF-1具有Ⅰ型花岗岩特征,源岩可能来自古-中元古代下地壳火成岩。锆石的εHf(t)值除一颗来自残留基底为正值外,其他锆石全部为负值(-4.30~-11.82),Hf同为素二阶段模式年龄tDM2为1.45~1.92 Ga,表明永福岩体可能形成于古老地壳物质的重融。岩体形成于燕山期地壳的伸展背景下,在岩石圈伸展作用下幔源岩浆底侵促使古-中元古代下地壳沉积岩先发生部分熔融,形成永福岩体早期的S型花岗岩,岩浆作用后期,古-中元古代下地壳火成岩部分熔融,形成永福岩体晚期的I型花岗岩。
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| 关 键 词： | 锆石U-Pb年龄 Lu-Hf同位素 岩体成因 永福岩体 |
Geochemical Characteristic,Zircon U-Pb Ages,and Lu-Hf Isotopic Compositions of the Yongfu Pluton in Longyan,Fujian Province |
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| KANG Congxuan,ZHOU Yan,FAN Feipeng,MIAO Na,LI Fengchun,SUN Jiandong,LV Jinsong.Geochemical Characteristic,Zircon U-Pb Ages,and Lu-Hf Isotopic Compositions of the Yongfu Pluton in Longyan,Fujian Province[J].Geotectonica et Metallogenia,2017,41(5). |
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| Authors: | KANG Congxuan ZHOU Yan FAN Feipeng MIAO Na LI Fengchun SUN Jiandong LV Jinsong |
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| Abstract: | The Yongfu pluton is located in the central part of the late Paleozoic Yongmei Depression.LA-ICP-MS U-Pb dating of zircons from two samples of the pluton yielded ages of 133±1 Ma (sample YF-1) and 143±1 Ma (sample YF-2),respectively.The granitic rocks are characterized by high silicon and alkali,with Rittmann Index (o) of 0.96-2.43 and Aluminum Saturation Index (A/CNK) of 0.98-1.66,belonging to metaluminous to peraluminous calc-alkaline series.The granites are rich in LREE showing right-dipping REE patterns with moderate negative Eu anomalies and insignificant negative Ce anomalies.They are depleted in Ba、Sr、K、P and enriched in Th、U、Zr、Hf elements.Samples YF-2-YF-7,which are representative of the main Yongfu granite,have the characteristics of S-type granite,while sample YF-1 has the characteristics of I-type granite.Zircons from the granites have negative εHf(t) values of-4.30--11.82,and the two stage Hf model ages (tDM2) of 1.45-1.92 Ga,which suggested that the Yongfu granites were formed by remelting of the Paleo-Meso-proterozoic lower crustal.We propose that the Yongfu pluton emplaced in a crustal extension setting of Yanshanian,the S-type granites were possibly derived from Paleo-Meso-proterozoic sedimentary rocks in the lower crust,and I-type granite was probably derived from Paleo-Meso-proterozoic igneous rocks in the lower crust in late stage. |
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| Keywords: | ziron U-Pb ages Lu-Hf isotope rock genesis Yongfu pluton |
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