大别造山带主簿岩体的成岩年代学、地球化学特征及成因研究  

Geochronology,geochemical characteristics and genesis of the Zhubu intrusion in the Dabie Orogenic Belt

作　　者：陈思聪 邓宇峰 袁峰 沈欢喜[3] 罗红波[3] 孟德园 朱传海 CHEN Si-cong;DENG Yu-feng;YUAN Feng;SHEN Huan-xi;LUO Hong-bo;MENG De-yuan;ZHU Chuan-hai(Ore Deposit and Exploration Centre,School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,China;Anhui Research Center for Mineral Resources and Mine Environment Engineering Technology,Hefei 230009,China;No.311 Unit,Bureau of Geology and Mineral Exploration of Anhui Province,Anqing,Anhui 246003,China)

机构地区：[1]合肥工业大学资源与环境工程学院矿床成因与勘查技术研究中心,合肥230009 [2]安徽省矿产资源与矿山环境工程技术研究中心,合肥230009 [3]安徽省地质矿产勘查局311地质队,安徽安庆246003

出　　处：《矿物岩石地球化学通报》2023年第4期830-844,共15页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：自然资源部科技项目(2020-K-14);安徽省国土资源科技项目(2021-g-2-9)。

摘　　要：大别造山带东段主簿地区广泛分布有不同期次的中酸性侵入岩,其岩浆源区的演化特征及其动力学机制的研究相对薄弱。本文通过对主簿岩体的岩石学、年代学和主、微量元素及Hf同位素分析,以期查明其源区特征及岩石成因。结果表明,主簿岩体主要由正长花岗岩及二长花岗岩构成。2件二长花岗岩和1件正长花岗岩锆石U-Pb年龄分别为(129.3±1.1)、(131.4±1.2)和(124.7±0.5)Ma。主簿岩体具有较高的10000Ga/Al值(2.4~2.8)、TFe_(2)O_(3)/(TFe_(2)O_(3)+MgO)值(0.74~0.90)和TiO_(2)/MgO值(0.4~1.2),二长花岗岩与正长花岗岩氧逸度均值分别为ΔFMQ+2.46和ΔFMQ+2.64,Ti含量地质温度计指示岩体的结晶温度为806.5℃与822.0℃,为高温、高氧逸度,与典型A型花岗岩特征相符。二长花岗岩与正长花岗岩的形成可能与伸展背景下岩石圈地幔拆沉,基性岩浆底侵引起下地壳部分熔融有关。二长花岗岩和正长花岗岩的锆石εHf(t)分别为-15.5~-22.4和-14.68~-18.85,显示其岩浆源区为古老地壳物质,并随着拆沉作用的进行,岩浆源区中幔源岩浆加入越来越多。Various intermediate-acid intrusive rocks of different periods are widely distributed in the Zhubu area in the eastern section of Dabie orogenic belt. Studies on the evolution of magma sources and dynamic mechanisms of those intrusive rocks are relatively limited. In this paper, a study on the petrology, chronology, petrogeochemistry and Hf isotope of the Zhubu intrusion has been undertaken in order to explore its feature of magma source and petrogenesis. The Zhubu intrusion, located in the eastern section of the North Dabie ultrahigh-pressure metamorphic belt, mainly consists of syenite granite and monzogranite. The weighted-mean zircon U-Pb ages of two monzogranites and one syenite granite are(129.3±1.1) Ma,(131.4±1.2) Ma, and(124.7±0.5) Ma, respectively. The Zhubu intrusion samples are characterized with relatively high 10000Ga/Al values(2.4~2.8), TFe_(2)O_(3)/(TFe_(2)O_(3)+MgO) ratios(0.74~0.90), and TiO_(2)/MgO ratios(0.4~1.2). The mean values of oxygen fugacities of the monzogranite and syenite granite are ΔFMQ+2.46 and ΔFMQ+2.64, respectively. The crystallization temperatures calculated by using the titanium-in-zircon geothermometer are 806.5 ℃ and 822.0 ℃. The high crystallization temperatures and high oxygen fugacities of samples show that the Zhubu intrusion has typical characteristics of the A-type granite. It is considered that the formation of monzogranite and syenite granite could be associated with the partial melting of the lower crust resulted from the underplating of basic magma caused by the lithospheric delamination in the extensional setting. The ε_(Hf(t)) values of zircons from the monzogranite range from-15.5 to-22.4, while those of zircons from the syenite granite range from-14.68 to-18.85, indicating that their magmas were sourced from ancient crustal materials. With the process of lithospheric delamination, more and more mantle-derived magma had been added into the magma source of the Zhubu intrusion granites.

关 键 词：A型花岗岩 锆石U-PB年龄 HF同位素 地球化学 大别造山带 拆沉作用 

分 类 号：P597[天文地球—地球化学]