Stable Isotope Geochemistry of Kaolinite from the “White Section,” Black Ridge, Clermont, Central Queensland: Implications for the Age and Origin of the “White Section”

Taihe Zhou1 and Stephen K. Dobos2
1 National Key Centre in Economic Geology, Department of Geology, James Cook University, Townsville, 4811 Queensland, Australia
2 Department of Earth Sciences, University of Queensland, St. Lucia, 4072 Queensland, Australia

Abstract: Kaolinite from the Black Ridge, Clermont, has relatively low δ18O (12.3‰ to 14.8‰) and very low δD values with a large variation (−120‰ to −85‰). Comparison of these data with those from the nearby Denison Trough and elsewhere in eastern Australia, together with previous studies of the mineralogy of the sedimentary rocks, suggests that extensive kaolinization of the “White Section” resulted from weathering during the Late Triassic to Early Jurassic periods. The relatively large variation in δD values of kaolinite probably derives from post-formational isotopic exchange with other fluids.

The similarity between δ18O values of kaolinites from Black Ridge and from the Denison Trough suggests that the small Miclere-Black Ridge basin may have been part of the Denison Trough before the Late-Triassic inversion. The preservation of original δD values in kaolinite at Black Ridge indicates that unlike the Denison Trough, which was reburied at more than 1000 m, the Miclere-Black Ridge basin was not rebuffed at great depth during the Mesozoic period.

Key Words: Inversion • Isotopic exchange • Kaolinite • Late Triassic • Low δD • Weathering

Clays and Clay Minerals; June 1994 v. 42; no. 3; p. 269-275; DOI: 10.1346/CCMN.1994.0420305
© 1994, The Clay Minerals Society
Clay Minerals Society (www.clays.org)