摘要
Solubility experiments of manganocolumbite (MnNb2O6) and manganotantalite (MnTa2O6) in the haplogranite-P2O5 system were conducted under H2O-saturated condition at 800℃ and 100 MPa.The results show:1) solubilities of MnNb2O6 and MnTa2O6 in peralkaline melts are significantly higher than those in subaluminous and peraluminous melts,furthermore,solubilities of MnNb2O6 and MnTa2O6 are almost identical in hydrous peralkaline melt,but solubilities of MnNb2O6 are much less than those of MnTa2O6 in H2O-saturated subaluminous and peraluminous melts;2)solubilities of MnNb2Og and MnTa2O6 in peralkaline melts are functions of P2O5 content,which is given as:lgKsp=-0.29×P2O5-2.05 (R2=0.96) and lgKsp=-0.29×P2O5-1.79 (R2=0.98),that is,solubilities of MnNb2O6 and MnTa2O6 decrease with increasing P2O5 contents.For subaluminous melt,solubilities of MnNb2O6 and MnTa2O6 increase with increasing P2O5 contents As P2O5 contents increases in peraluminous system,solubilities of MnNb2O6 and MnTa2O6 decrease at first in relatively low P2O5 system (<3 wt% P2O5),and then keep constantly in relatively high P2O5 system (>3 wt% P2O5).The main causes of the above experiment results may be related to the mechanism of Nb,and Ta dissolved in the granitic melt and phosphorus show different structural effect in different chemical composition of silicate melts.
