PERMO-CARBONIFEROUS GOLD EPOCH OF NORTHEAST QUEENSLAND

The Ar-40/Ar-39 and U-Pb methods of isotopic dating have been used to determine the age of alteration minerals and host rocks from a number of Permo-Carboniferous Au deposits in the Tasman Fold Belt system of n ortheast Queensland. There was a continuum in porphyry-style Au minera lisation from ca 330 to 290 Ma, which post-dates epithermal Au in the Eastern Basin sequence of the Drummond Basin. Porphyry-style Au at Kid ston, and the Buck Reef, Ravenswood, formed at ca 330 Ma. The Red Dome and Mungana skarns were deposited at ca 320-310 Ma and ca 310 Ma, res pectively. The Au mineralisation at Mt Wright, and in the quartz-sulfi de veins, Ravenswood, was emplaced at ca 310-305 Ma. The youngest porp hyry-style Au deposit is Mt Leyshon, which probably formed at cc 290 M a. Where high-level intrusions are associated with Au, magmatism and m ineralisation are, in general, essentially coeval. The age of the host rocks to the Permo-Carboniferous Au deposits is variable, and may be more than 150 million years older than the mineralisation. The plutoni c-style Au deposit at Charters Towers is significantly older than the porphyry systems, and formed at ca 414Ma.