| 林 坤.粤北河口岩体次英安斑岩锆石U-Pb年代学和Hf同位素特征
及其地质意义[J].地质与勘探,2021,57(2):392-401 |
| 粤北河口岩体次英安斑岩锆石U-Pb年代学和Hf同位素特征
及其地质意义 |
| Zircon U-Pb chronology and Hf isotope composition of porphyritic dacite in Hekou rock mass of northern Guangdong and their geological implications |
| 投稿时间：2020-04-22 修订日期：2021-02-18 |
| DOI：10.12134/j.dzykt.2021.02.014 |
| 中文关键词: 锆石U-Pb年代学 Hf同位素 源区分析 次英安斑岩 河口岩体 粤北 |
| 英文关键词: U-Pb chronology,Hf isotope composition,provenance analysis, porphyritic dacite,Hekou
rock mass,northern Guangdong |
| 基金项目:中国核工业地质局地质勘查项目（编号：201924、202036-1）资助 |
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| 中文摘要: |
| 河口岩体位于贵东复式花岗岩体外围北东侧，也是粤北地区代表性火山岩-次火山岩，前人对其源区特征、成岩时代、构造背景研究程度相对较低。本文在野外地质调查基础上，选取次英安斑岩进行LA-ICP-MS锆石U-Pb年代学及Hf同位素组成特征研究。结果表明，次英安斑岩的锆石U-Pb年龄为428.6±2.2 Ma、429.6±2.4 Ma，属晚加里东期火山岩系，进一步证实粤北-赣南地区存在较大范围的加里东期火山岩-次火山岩。次英安斑岩的εHf（t）变化范围较小，呈明显负值，且集中在上下地壳的演化线之间，指示其形成于陆壳物质的部分熔融，并无明显地幔物质的加入。锆石Hf模式年龄(tDM2)平均值分别为1756 Ma、1802 Ma，指示河口地区可能存在过早元古代的古老基底，次英安斑岩可能是早元古代的变质岩部分熔融的产物,形成于加厚地壳背景下的后碰撞拉张构造环境。 |
| 英文摘要: |
| The Hekou rock mass is located in the northeast periphery of Guidong compound granite mass, a representative volcanic rock-subvolcanic rock in northern Guangdong. Previous studies on its source characteristics, diagenetic age and tectonic setting remain poor. Based on field geological surveys, this paper selects porphyritic dacite from this rock mass to analyze the zircon U-Pb chronology and Hf isotope composition by LA-ICP-MS. The results indicate that zircon U-Pb ages of the porphyritic dacite are 428.6±2.2 Ma and 429.6±2.4 Ma, attributed to the late Caledonian volcanic rock series. It is further confirmed that Caledonian volcanic rocks-subvolcanic rock are widely distributed in northern Guangdong - southern Jiangxi. The variation range of the porphyritic dacite εHf(t) is small with obvious negative values, confined between the lines of evolution of the upper and lower crust, implying that it resulted from partial melting of continental crust material without obvious addition of mantle material. The mean values of zircon Hf model age (tDM2) are 1756 Ma and 1802 Ma, indicating that there may be an ancient basement of Early Proterozoic in the Hekou area. The porphyritic dacite may be the product of partial melting of metamorphic rocks from Early Proterozoic, which formed in a post-collision extensional tectonic environment with thickened crust. |
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