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.
基金
Supported by National Natural Science Foundation of China (Grant No. 40634023)
