STABLE-ISOTOPE GEOCHEMISTRY OF KAOLINITE FROM THE WHITE SECTION, BLACK RIDGE, CLERMONT, CENTRAL QUEENSLAND - IMPLICATIONS FOR THE AGE AND ORIGIN OF THE WHITE SECTION

Kaolinite from the Black Ridge, Clermont, has relatively low deltaO-18 (12.3 parts per thousand to 14.8 parts per thousand) and very low del taD values with a large variation (- 120 parts per thousand to -85 par ts per thousand). Comparison of these data with those from the nearby Denison Trough and elsewhere in eastern Australia, together with previ ous studies of the mineralogy of the sedimentary rocks, suggests that extensive kaolinization of the ''White Section'' resulted from weather ing during the Late Triassic to Early Jurassic periods. The relatively large variation in deltaD values of kaolinite probably derives from p ost-formational isotopic exchange with other fluids. The similarity be tween deltaO-18 values of kaolinites from Black Ridge and from the Den ison Trough suggests that the small Miclere-Black Ridge basin may have been part of the Denison Trough before the Late-Triassic inversion. T he preservation of original deltaD values in kaolinite at Black Ridge indicates that unlike the Denison Trough, which was reburied at more t han 1000 m, the Miclere-Black Ridge basin was not reburied at great de pth during the Mesozoic period.