Petrochemical characteristics of leucogranite and a case study of Bengbu leucogranites  

作　　者：GUO SuShu LI ShuGuang 

机构地区：[1]CAS Key laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science andTechnology of China, Hefei, 230026, China

出　　处：《Chinese Science Bulletin》2009年第11期1923-1930,共8页

基　　金：Supported by National Natural Science Foundation of China (Grant No. 40634023)

摘　　要：Leucogranites have a relatively narrow variation in SiO2 content (70.5%―75.5%). Giving similar SiO2 content, leucogranites have relatively higher Al2O3 (>13.5%) and lower TFeO + MgO (<2.5%) contents than those of normal granites. These petrochemical characteristics suggest that leucogranites are de-rived from partial melting at relatively low temperature and are not significantly affected by fractional crystallization. In the present study, we propose that the Al2O3 vs SiO2 and TFeO + MgO vs SiO2 dia-grams can be used to distinguish leucogranites from normal granites. In addition, we report the major element compositions of the Jurassic granitic intrusions from Jingshan-Tushan-Mayishan in the Bengbu area, east-central China. Using the Al2O3 vs SiO2 and TFeO + MgO vs SiO2 diagrams and the comparison with the High Himalayan leucogranites in mineralogical and petrochemical characteristics, we suggest that the Jingshan-Tushan-Mayishan intrusions belong to a leucogranite belt. Similar to those of the High Himalayan leucogranites, the Bengbu leucogranites have low Mg# values, indicating that they resulted from low temperature dehydration partial melting of the subducted continental crust of the South China Block at the crustal depth.Leucogranites have a relatively narrow variation in SiO2 content （70.5%-75.5%）. Giving similar SiO2 content, leucogranites have relatively higher Al2O3 （〉13.5%） and lower TFeO ＋ MgO （〈2.5%） contents than those of normal granites. These petrochemical characteristics suggest that leucogranites are de- rived from partial melting at relatively low temperature and are not significantly affected by fractional crystallization. In the present study, we propose that the Al2O3 vs SiO2 and TFeO ＋ MgO vs SiO2 dia- grams can be used to distinguish leucogranites from normal granites. In addition, we report the major element compositions of the Jurassic granitic intrusions from Jingshan-Tushan-Mayishan in the Bengbu area, east-central China. Using the Al2O3 vs SiO2 and TFeO ＋ MgO vs SiO2 diagrams and the comparison with the High Himalayan leucogranites in mineralogical and petrochemical characteristics, we suggest that the Jingshan-Tushan-Mayishan intrusions belong to a leucogranite belt. Similar to those of the High Himalayan leucogranites, the Bengbu leucogranites have low Mg# values, indicating that they resulted from low temperature dehydration partial melting of the subducted continental crust of the South China Block at the crustal depth.

关 键 词：淡色花岗岩 岩石化学特征 蚌埠地区 SIO2含量 高喜马拉雅 案例 分离结晶作用 部分熔融 

分 类 号：P588.121[天文地球—岩石学] P588.14[天文地球—地质学]