As a supplementary question Did an impact crater cause the formation of the gas fields in north eastern South Australia . South Australia is a well documented uranium province. Could an impact crater, as announced in early 2015 have created conditions that would have allowed South Australia to be the uranium province that it is?
Sort answer: from what we already know, NO. A comet (or asteroid) impact can influence mineral composition near the crater (high pressure and temperature) but this impact is small and diminishes quickly in respect of the radius. There is no documented quantitative difference of a mineral deposit versus its radius from an impact crater (not in cm and meters scale, but in km scale). Thus, we cannot assume that there is correlation between uranium deposits of Australia (or any other country) and impact craters. Uranium deposits can be formed in many ways: As you can see from the list, 7 out of 15 ways of uranium formation, occur in Australia. None of them due to comet impact.
1. Intrusive deposits In South Australia, Radium Hill was mined 1954-62, and large bodies of low-grade mineralisation occur in the Olary Province.
2. Granite-related deposits The dimensions of the openings have a wide range, from the massive veins of pitchblende at Jachymov deposit (Czech Republic), to the narrow pitchblende-filled cracks, faults and fissures in some of the ore bodies in Europe, Canada and Australia.
3. Polymetallic iron-oxide breccia complex deposits
4. Volcanic-related deposits In Australia, they are minor – Ben Lomond and Maureen in Qld are the most significant.
5. Metasomatite deposits Valhalla and Skal (Australia)
6. Metamorphite deposits
7. Proterozoic unconformity deposits Australia (the Alligator Rivers region in the Pine Creek Geosyncline, NT and Rudall River area, WA).
8. Collapse breccia pipe deposits
9. Sandstone deposits Basal channel deposits – wide channels filled with permeable sediments. Examples are Dalur and Khiagda (Russia) and Beverley and Honeymoon (South Australia). Mafic dykes or sills in Proterozoic sandstones – Examples at Matoush (Canada) and Westmoreland (Australia).
10. Palaeo-quartz-pebble conglomerate deposits
11. Surficial deposits
12. Lignite-coal Mulga Rock (Western Australia).
13. Carbonate deposits
14. Phosphate deposits
15. Black shale deposits