U-Pb systematics of pre-Cambrian carbonates: The Riphean Sukhaya Tunguska Formation in the Turukhansk Uplift, Siberia
- Institute of Pre-Cambrian Geology and Geochronology, St. Petersburg (Russian Federation); and others
A brief review of the geochemistry of U, Th, and Pb in oceanic water and marine carbonates is given, and the U-Th-Pb systematics in limestones and dolomites of the Sukhaya Tunguska Formation in the Turukhansk Uplift is studied. The analysis of phases with different solubilities in ammonium acetate and hydrochloric acid and the plotting of available results along the {sup 207}Pb/{sup 204}Pb-{sup 206}Pb/{sup 204}Pb coordinates yield an age of 1035{plus_minus}60 Ma. This value matches the stratigraphic position of the Sukhaya Tunguska Formation rocks at the Middle-Late Riphean boundary and may be interpreted as the age of an early diagenesis of sediments. Evidence for the temporal compatibility of the processes of sedimentation, dolomitization, and early diagenesis is provided. Isotope-geochemical data, which indicate a recent uranium loss by carbonate rocks, are in good agreement with results of the study of Cenozoic evolution in the Turukhansk Uplift. The average {sup 238}U/{sup 204}Pb value (8.22) calculated for the source of the Sukhaya Tunguska carbonate deposits suggests that Pb from mantle sources or a relatively young crust was abundant in the near-contact fluid phase that governed the composition of carbonate rocks 1035{plus_minus}60 Ma ago.
- OSTI ID:
- 192045
- Journal Information:
- Lithology and Mineral Resources, Vol. 30, Issue 5; Other Information: PBD: Sep-Oct 1995; TN: Translated from Litologiya; No. 5, 525-536(1995)
- Country of Publication:
- United States
- Language:
- English
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