Pre-historic Bolivia - Puma Punku site - what is it and who built it?

It's dead simple to summarise, Puma Punku is a pre-historic site in Bolivia, close by the modern city of La Paz, at an elevation of 12,000 feet in the Andes mountains. Dating of the Puma Punku stones is all over the place; some place them as late as 600 AD, some as early as 12,000 BC. I mean, come on.

The precision of the stone work is like Stonehenge on acid. Mirror flat surfaces. Right angles everywhere. Hundreds of tonnes per carved/pressed andecite block. Intricate engineering, grooving and drilling of stone as hard as granite - even by today's technological standards this stuff is insane!

What was Puma Punku's purpose? What was used to carve/press these andecite blocks? And when did it all (really) happen?

COSMOGENIC DATING OF THE PUMA PUNKU STONES: well, it turns out that a researcher called David Swenson's had an indiegogo startup project to fund Cosmogenic Dating via beryllium-10 has been fully funded, as of January 29th 2014.

When are the dating results to be published? If they're out already, what are the results? Best I can find on this on-going subject is it's a scam. I hope not.

MARCH 15TH UPDATE: Daniel Pik, director of CRPG (the French lab doing the tests) officially refuses to release the (implied or suggested) 2000+BC dates his lab has calculate via Cosmogenic Dating for the Puma Punku stones to David Swenson. The lab have offered to refund the money, but (as seen in Swenson's online response) he has declined, demanding that he has no more samples and he wants his date. CRPG has yet to issue a public statement on this matter.