Thanks for the answer. Unfortunately, there is no brand or model number visible. I'm sure it is butted tubing as it is very thin at the ends. I have been riding it and not losing any sleep but was wondering if heat treated aluminum was more likely to crack along a gouge like this. The bike is a touring/hybrid used 90+% on paved roads with the remainder being well packed gravel or dirt roads. The only hard use is on the occassional hill climb or when I can't avoid a pothole or other hazard.