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  

Geochemical Characteristic, Zircon U-Pb Ages, and Lu-Hf Isotopic Compositions of the Yongfu Pluton in Longyan, Fujian Province

作　　者：康丛轩[1,2] 周延 范飞鹏[1] 苗娜[3] 李凤春[4] 孙建东[1] 吕劲松[1] KANG Congxuan ZHOU Yan FAN Feipeng MIAO Na LI Fengchun SUN Jiandong LV Jinsong(Nanjing Center of Geological Survey, CGS, Nanjing 210016, Jiangsu, China School of Earth Sciences and Engineering, Hohai University, Nanjing 211100, Jiangsu, China Jiangsu Team of Coal Geophysical Prospecting and Surveying, Nanjing 210046, Jiangsu, China Testing Center of Shandong Bureau, China Metallurgy and Geology Bureau, Jinan 250014, Shandong, China)

机构地区：[1]中国地质调查局南京地质调查中心,江苏南京210016 [2]河海大学地球科学与工程学院,江苏南京211100 [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

出　　处：《大地构造与成矿学》2017年第5期960-973,共14页Geotectonica et Metallogenia

基　　金：中国地质调查局项目(12120113071400;D20160037)资助

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。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 （σ） 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 eHf（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.

关 键 词：锆石U-PB年龄 LU-HF同位素 岩体成因 永福岩体 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]