摘要
对福建永泰地区的辉石闪长岩开展了岩石学、锆石U-Pb年代学和岩石地球化学分析结果表明,该岩体中的SiO_(2)含量为55.29%~57.38%;Al_(2)O_(3)含量为15.84%~16.17%;Na_2O含量为3.39%~3.54%,K_2O含量为1.92%~2.18%;K_2O/Na_2O比值为0.56~0.62,总体显示富钠特征;总碱含量为5.33%~5.72%;TFe_(2)O_(3)含量为8.77%~9.09%,MgO含量为3.29%~3.72%;CaO含量为6.52%~7.06%,铁镁钙含量较高,里特曼指数(σ)为2.16~2.32,小于3.3,为高钾钙碱性岩。岩石相对富集Rb、Ba等大离子亲石元素,亏损Nb、Ta等高场强元素。锆石U-Pb测年结果显示,岩体形成时代为(97.4±1.4) Ma,为晚白垩世早期侵入体;锆石记录了(305.5±5.9)Ma(晚石炭世)年龄信息,很可能代表了源岩的结晶年龄。综合分析认为岩浆来源于晚石炭世岩浆物质的循环再造,具有I型或同熔型特征。辉石闪长岩与A型花岗岩-流纹岩形成时代相同,指示是俯冲板块后撤后伸展体制减压熔融的结果。
Petrology,zircon U-Pb chronology and lithogeochemical analysis of pyroxene diorite in Yongtai area of Fujian Province showed that the SiO_(2) content of the rock mass ranged from 55.29%~57.38%.The content of Al_(2)O_(3) was between 15.84%~16.17%;the Na_(2)O content was between 3.39%~3.54%,and the K_(2)O content was 1.92%~2.18%;K_(2)O/Na_(2)O was 0.56~0.62,which showed the characteristics of sodium richness.The total alkali content was between 5.33%~5.72%;the TFe2O3 content was 8.77%~9.09%,and the MgO content was 3.29%~3.72%;the CaO content was 6.52%~7.06%,the iron-magnesium-calcium content was high,and the Rittman index(σ)was 2.16~2.32,less than 3.3,which was calcium-alkaline rock.These rocks were relatively enriched with large ionic lipophilic elements such as Rb and Ba,and loses high field strength elements such as Nb and Ta.Zircon U-Pb dating results showed that the formation age of rock was(97.4±1.4)Ma,which was an early Late Cretaceous intrusive.Zircon also recorded(305.5±5.9)Ma age information,which was likely to represent the crystallization age of the source rock.Comprehensive analysis showed that magma comes from the recycling of late Carboniferous magma material and has the characteristics of I-type or same melting.Pyroxene diorite and A-type granite-rhyolite formed at the same time,indicating that it is the result of decompression and melting of the extensional system after the subduction plate retreated.
作者
李玉娟
Li Yujuan(Fujian Institute of Geological Survey,Fuzhou,350013)
出处
《福建地质》
2023年第4期251-260,共10页
Geology of Fujian
基金
福建省地勘专项基金“福建1∶5万嵩口、埔埕、济川幅区域地质调查”。
关键词
辉石闪长岩
锆石U-PB年龄
同熔型
晚白垩世
福建永泰
pyroxene diorite
zircon U-Pb age
syntectic type
Late Cretaceous
Yongtai County of Fujian Province
