Artesian water is no guarantee that it is perfect for mash chemistry. That water may be right for one beer and poor for another style or it may not be good for anything. You just can't tell by stating that the water is 'Spring Water' or 'Artesian Water'.
Hopefully you have a water report or have had it lab tested. You should visit the Bru'n Water site and download Bru'n Water to help with your mash water chemistry. There is a large section on Water Knowledge included with the program.
Regarding the use of ionized water, it might be OK for sparging if the pH is within the desired range of 5.5 to 6.0. You mention Ionized Water. That is somewhat of a meaningless term. Now if you meant Deionized Water, then it might be a good starting point for sparging. The problem with using un-mineralized water like this is that the overall ion content in the wort may not be sufficient for several important processes in the ferment. The most important would be to have the Ca content at a minimum of 40 ppm (preferably 50 ppm) and the Mg content at a minimum of 5 ppm. Using deionized water may not be a problem if that artesian water already had high Ca and Mg and this dilution just brings it down to reasonable levels.
Visit the Bru'n Water site here: