I'm researching gold tracking and tracing techniques to verify origins of gold. I'd like to find out about what the current state of the art, and future techniques that are under development. I'm most interested in understanding the precision of the techniques: can trace a gold sample to individual mines, regions, countries, etc? Please note I'm a social scientist looking at economy and compliance systems in gold mining, not asking questions tp develop any new laboratory techniques. 

Specific questions:

One refinery's compliance system looks at the chemical composition of gold to try and verify whether the gold was sourced from a particular mine as reported. What kind of tests are involved, how do they work, how precise are they & how reliable are they? (keeping in mind such test types may vary and of course only the refinery itself can speak to the particular technique it uses)

Do multiple systems to test gold's origins exist? What are the tradeoffs of each?

Does anyone have experience working to trace (back to the past from a sample) or track (real-time, using techniques from tags to weighing/testing) gold samples as they move from mine to refinery or mine to shop?

If the current state of testing techniques cannot reliably verify gold origins (?), why not? Is it a matter of the state of science, the cost of testing, reliability, or other issues? Is there current research that seeks to develop new techniques that might overcome problems?