When I think about northern Canada I remember rough roads, mud, and snow. You might want to check out the Surley Pugsley + Endomorph tires for your trail & snow riding. Get it built up with disc brakes & decent components (Deore XT, etc.). This fits all of your criteria except for weight. However, it will allow you to bike comfortably in all 4 seasons over any type of surface.
I have a LHT and would recommend it except for the lack of disc brakes. Braking is improved with Koolstop Salmon pads & can be pushed further with higher end brake components (Pauls, etc.).
I would completely avoid carbon fiber, it sounds like you are going to be hitting a lot of potholes and rocks.