摘要
鄂东南地区邹清辉长闪长岩体是该区六大岩体中最基性的岩体,对约束区内晚中生代岩浆起源和构造环境具有重要意义。本文对邹清辉长闪长岩开展了全岩地球化学、锆石U-Pb年代学和Sr-Nd-Hf同位素研究。结果表明,邹清辉长闪长岩的锆石U-Pb年龄为(150.7±1.5)Ma;主量元素具有低硅(SiO_(2)含量为52.12%~55.04%)、富钾(K_(2)O含量为2.54%~3.34%)特征,属高钾钙碱性-钾玄岩系列岩石;微量元素显示富集轻稀土元素和大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,体现弧型岩浆特征;锆石ε_(Hf)(t)值为-10.7~-6.1,全岩(^(87)Sr/^(86)Sr)i值为0.707163~0.708443,εNd(t)值为-7.0~-6.4。结合野外接触关系,认为邹清辉长闪长岩是侵位早于殷祖岩体的主体石英闪长岩,可能代表了鄂东南地区晚中生代岩浆活动的开端。邹清辉长闪长岩为富钾的玄武-安山质岩浆产物,起源于俯冲背景下的富集岩石圈地幔部分熔融。结合长江中下游成矿带三阶段岩浆岩的地球化学特征和时空分布规律,认为晚中生代古太平洋板块的西向俯冲和逐步后撤机制,可以合理解释区域上该时期内岩浆岩的形成和分布。
The Zouqing gabbrodiorite is the most basic one among the six major plutons in the southeastern Hubei and is therefore of great significance to constrain the late Mesozoic magma origin and the regional tectonic environment in the area.In this paper,whole-rock geochemistry,zircon U-Pb geochronology and Sr-Nd-Hf isotopic compositions of the Zouqing gabbro diorite have been studied.The results show that the LA-ICP-MS zircon U-Pb age of the Zouqing gabbrodiorite is(150.7±1.5)Ma.Compositions of the major elements of the gabbrodiorite samples are characterized with relatively low contents of SiO_(2)(52.12%~55.04%)and relatively high contents of K_(2)O(2.54%~3.34%),indicating that the Zouqing gabbrodiorite belongs to the high-K calc-alkaline to shoshonite series.The compositions of trace elements of gabbrodiorite samples show that the samples are enriched in light rare earth elements and large ion lithophile elements,but depleted in high field strength elements of Nb,Ta,and Ti,with characteristics of arc type magmatic rocks.Their zirconε_(Hf)(t)values vary from-10.7 to-6.1 and their whole rock(^(87)Sr/^(86)Sr)ivalues andεNd(t)values vary from 0.707163 to 0.708443 and from-7.0 to-6.4,respectively.Combined with the field contact relationship,it is believed that the Zouqing gabbrodiorite was emplaced earlier than the quartz diorite of the Yinzu pluton,and it could represent the beginning of the Late Mesozoic magmatic activity in the southeastern Hubei.The Zouqing gabbrodiorite was product of the potassium-rich basaltic-andesitic magma,which was originated from the partial melting of the enriched lithospheric mantle in a subduction environment.Combined with geochemical characteristics and temporal and spatial distribution regularities of magmatic rocks of three stages in the Middle and Lower Yangtze River Metallogenic Belt,it is believed that the mechanism of the westward subduction and then gradual rollback of the paleo-Pacific plate in the late Mesozoic could be used to reasonably explain the formation and distribution of the late Mesozoic igneous rocks in the region.
作者
罗华
郭盼
吴波
蔡恒安
李欢
龚志愚
LUO Hua;GUO Pan;WU Bo;CAI Heng-an;LI Huan;GONG Zhi-yu(Hubei Geological Survey,Wuhan 430034,China;Hubei Provincial Key Laboratory of Resource and Ecological Environment Geology,Wuhan 430074,China;No.1 Geological Brigade of Hubei Geological Bureau,Daye,Hubei 435000,China)
出处
《矿物岩石地球化学通报》
CAS
CSCD
北大核心
2022年第6期1207-1223,共17页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
湖北省地质局矿产地质调查项目(KCDZ2022-14)
湖北省地质局科技项目(KJ2021-9-1)。
关键词
辉长闪长岩
殷祖岩体
鄂东南地区
古太平洋板块
长江中下游
gabbrodiorite
Yinzu pluton
southeastern Hubei
paleo-Pacific plate
Middle and Lower Yangtze River
