Akali Basalt

I understand that Alkali Basalt is high in Na2O and K2O. I also thought that these 2 chemicals decrease the more the Mafic Basalt becomes, and the more Silica content decreases. Looking at the TAS diagram this appears to be the case. However samples from a particular volcano suggest that the Basalt is more Alkali when it is becoming more Mafic. Does basalt become more alkali with less Silica or is there no connection? Any thoughts are welcome.