北大别木子店地区早白垩世辉长岩地球化学特征及其对构造环境的指示  

Geochemical characteristics of Early Cretaceous gabbro inMuzidian area,North Dabie and its indicative significance for tectonic environment

作　　者：万俊 孔令耀 刘成新 杜小锋 廖明芳 郭盼 邓新[2] WAN Jun;KONG Lingyao;LIU Chengxin;DU Xiaofeng;LIAO Mingfang;GUO Pan;DENG Xin(Hubei Geological Survey,Wuhan 430034,Hubei,China;Wuhan Center,China Geological Survey,Wuhan 430205,Hubei,China)

机构地区：[1]湖北省地质调查院,湖北武汉430034 [2]中国地质调查局武汉地质调查中心,湖北武汉430205

出　　处：《地质通报》2024年第8期1446-1458,共13页Geological Bulletin of China

基　　金：中国地质调查局项目《长江经济带中段红安-咸宁地区区域地质调查》(编号:DD20190050);湖北省地质局项目《湖北省东大别中生代岩浆岩时空演化序列与成矿规律调查研究》(编号:KCDZ2023-05)。

摘　　要：为揭示大别造山带基性岩的成因及构造背景,应用LA-ICP-MS锆石定年和地球化学分析,探讨了北大别木子店地区雷家湾辉长岩的成岩年龄、地球化学特征,并通过与安徽段基性—超基性岩对比,揭示了大别造山带基性—超基性岩成因和构造环境。结果显示,北大别木子店地区雷家湾辉长岩成岩年龄为122.3±1.0 Ma。雷家湾辉长岩的SiO2含量介于45.00%~50.69%之间,平均值为48.02%;Mg#值变化范围在45.62~53.49之间,平均值为47.86;K2O+Na2O含量变化于4.68%~7.03%之间,平均值为6.31%,属于碱性系列;富集Rb、Ba、K、Sr等大离子亲石元素(LILE)和轻稀土元素,亏损Ta、Nb、Zr、Ti等高场强元素(HFSE)和重稀土元素;与安徽段基性—超基性岩具有相似的野外特征和岩石地球化学性质。岩石成因研究显示,雷家湾辉长岩的幔源母岩浆有地壳物质的加入,作用方式应该为源区的混合,地壳物质的加入可能与三叠纪以来扬子板块向华北板块俯冲后加厚岩石圈的拆沉作用有关。大别造山带130 Ma左右基性—超基性岩的出现可能暗示构造体制由挤压向伸展转换。In order to reveal the genesis and tectonic background of basic rocks in Dabie orogenic belt,LA−ICP−MS zircon dating andgeochemical analysis were carried out to discuss the diagenetic age and geochemical characteristics of Leijiawan gabbro in Muzidianarea,North Dabie,and by comparing with the basic−ultrabasic rocks in Anhui section,the genesis and tectonic environment of Dabieorogenic basic−ultrabasic rocks are revealed.The results show that the diagenetic age of the Leijiawan gabbro in the Muzidian area ofNorth Dabie is 122.3±1.0 Ma.The SiO2 content of the Leijiawan gabbro is between 45.00%and 50.69%,with an average of 48.02%.The Mg#value ranged from 45.62 to 53.49,with an average of 47.86.The content of K2O+Na2O varied from 4.68%to 7.03%,with anaverage of 6.31%,belonging to the alkaline series.It is enriched in light rare earth elements and large ion lithophile elements(LILE)such as Rb,Ba,K and Sr,and depleted in heavy elements and high field strength elements(HFSE)such as Ta,Nb,Zr and Ti.It hassimilar field and geochemical characteristics to the mafic−ultramafic rocks of Anhui.The petrogenesis study shows that themantle−derived magma of Leijiawan gabbro was added with crustal materials,and the mode of action is the mixing in magma source.The addition of crustal material may be related to the delamination of thickened lithosphere after subduction of Yangtze plate to North China plate since Triassic.The occurrence of mafic−ultramafic rocks at ca.130 Ma in Dabie orogenic belt may imply the structuralsystem transforms from compression to extension.

关 键 词：锆石U-PB定年 岩石地球化学 辉长岩 木子店 北大别 地质调查工程 

分 类 号：P534.53[天文地球—古生物学与地层学] P588.124[天文地球—地质学]