Petrochemical characteristics of leucogranite and a case study of Bengbu leucogranites.

Leucogranites have a relatively narrow variation in SiO[sub2] content (70.5%-75.5%). Giving similar SiO[sub2] content, leucogranites have relatively higher Al[sub2]O[sub3] (>13.5%) and lower TFeO + MgO (<2.5%) contents than those of normal granites. These petrochemical characteristics suggest that leucogranites are derived from partial melting at relatively low temperature and are not significantly affected by fractional crystallization. In the present study, we propose that the Al[sub2]O[sub3] vs SiO[sub2] and TFeO + MgO vs SiO[sub2] diagrams 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 Al[sub2]O[sub3] vs SiO[sub2] and TFeO + MgO vs SiO[sub2] 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[sup#] 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. [ABSTRACT FROM AUTHOR]