北大别木子店岩体斑状黑云二长花岗岩的年龄与成因:锆石U-Pb定年、Hf同位素与稀土元素证据  

Age and Petrogenesis of the Porphyritic Biotite Monzogranite in the Muzidian Complex in Northern Dabie Mountains: Evidences from Zircon U-Pb Dating,Hf Isotopes and REE Geochemistry

作　　者：胡俊良[1,2] 刘劲松[1,2] 刘阿睢 张鲲[1] 金世超[1] 定立[1] HUJun-hang 1,2, LIU Jm-song1,2, LIU A-sui1 , ZHANG Kun1 ,JIN Shi-chao1,, DING Li1(1. Wuhan Center of China Geological Survey, Wuhan 430205, China; 2.Research Center for Petrogeaesis and Mineralization of Granitoid Rocks, China Geological Survey, Wuhan 430205, China)

机构地区：[1]中国地质调查局武汉地质调查中心,武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,武汉430205

出　　处：《矿物岩石地球化学通报》2018年第4期750-759,共10页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局地质调查项目(12120113068000,DD20160334)

摘　　要：为对大别山地区燕山期中酸性岩类的成因提供进一步证据,对北大别木子店岩体的主要岩类——斑状黑云二长花岗岩进行了LA-ICP-MS锆石U-Pb定年、原位Hf同位素及稀土元素分析。结果显示,岩石的锆石U-Pb年龄为（131.1±0.5）Ma,属早白垩世。岩石为一套高钾钙碱性,具有明显的埃达克岩特征。锆石的176Hf/177Hf值为0.282 084-0.282 297,εHf（t）为-21.83--13.98,tDM2为1826-2246 Ma,表明岩石来自碰撞造山期后俯冲板片中地壳物质的熔融;该源区主要为古元古代地壳物质,可能存在中元古代壳幔混源或富集地幔来源的物质加入,还可能有早太古代古老地壳物质的贡献。岩石形成的构造背景为大别造山带从挤压向伸展的转换阶段,该转换极有可能发生在131.1±0.5 Ma。In order to further provide evidences for exploring petrogenesis of the Yanshanian intermediate-acidic rocks in the Dabie mountains,a study on U-Pb dating,in-situ Hf isotopes and REE geochemistry of zircons from the porphyritic biotite monzogranite of the Muzidian complex which is located in the northern part of the Dabie Mountains has been carried out in this paper by using LA-ICP-MS.Results show that the zircon U-Pb age of（ 131. 1±0. 5） Ma for the porphyritic biotite monzogranite indicates that the rock was formed in Early Cretaceous. It belongs to a high-K calc-alkaline granite,with obvious characteristics of adakite. Its magmatic zircons have176 Hf/177 Hf values varying from 0. 282084 to 0. 282297 and εHf（ t） values varying from-21. 83 to-13. 98,with crustal model ages（ tDM2） varying from 1286 to 2246 Ma. This indicates that it could be mainly derived from partial melting of the Paleoproterozoic crust rocks of the subducted slab in post-collisional orogenic period,with possible minor input of the mixture of the mantle and crust or of the enriched mantle in Mesoproterozoic,and even possible contribution of the Eoarchean crustal materials. It is suggested that the rock could be formed in a process of the tectonic transition,which mostly could occur at 131. 1 ± 0. 5 Ma,from compressional to extensional setting for the Dabie Orogenic Belt.

关 键 词：北大别 木子店岩体 锆石U-PB年代学 HF同位素 成因机制 

分 类 号：P597[天文地球—地球化学]