There is no place that you are going to find abundant gold veins, by definition. Gold is a rare spawn of iron, so anywhere that you find iron veins you can also find gold, but it will never be abundant. Your best bet if you need gold in quantity, is to pick an area high in iron veins, and mine them all repeatedly, eventually you will get a gold vein or two. I got most of mine in the Stonetalon Mts.