Genesis of the Heihaibei gold deposit in the East Kunlun Orogenic Belt, China: Evidence from in situ trace elements of gold-bearing sulfides and stable isotopes

•Invisible gold in gold-bearing sulfides occurs dominantly as solid solution.•The ore-forming fluids were derived from a metamorphic source.•The gold mineralization may be related to the metamorphism caused by the closure of the Paleotethys Ocean during the early Mesozoic.•It is necessary to be cautious to use smoky quartz–sulfide vein as a primary guide to ore prospecting.