Ann: Pilbara Appoints New Chairman-PLS.AX, page-4

Without knowing whats going on behind the scenes it can be positive, negative or neutral.

Some of the reasons I've seen before for changing Chairman/CEO/COO/CFO at this point in the lifecycle of a project are:

1. Development focussed team, often explorer based teams do not have the expertise with government relations, permitting, engineering etc to really bring the project forward
2. Poaching - in successful explorers which lead to projects often they get sweet deals with bigger companies to takeover key positions
3. conflicts - often this occurs when one of the directors has a majority shareholding and thus wants to direct his own team, he can change key members.
4. This one is rare, but I have seen CEO/COO leave due to the fact they know their current studies are very 'optimistic' which will probably be reviewed during design and they want to get out prior. This is often blamed on the new person, which is unfair.

Overall its probably not a huge concern, but it might be prudent if you have a decent shareholding to follow the previous directors and see where they end up, and it may give you an idea why they left.