Browsing by Author "Siegfried, P"
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- ItemOpen AccessNew Pb-Pb single zircon age constraints on the timing of neoproterozoic glaciation and continental break-up in Namibia.(University of Chicago Press, 1996) Frimmel, H; Klötzli, U; Siegfried, PDating of single zircons from low-grade metamorphosed rhyolites in the Rosh Pinah Formation of the Gariep Belt in southwestern Namibia, using the Pb evaporation technique, yielded a primary crystallization age of 741 ± 6 Ma. Both the stratigraphic position and the geochemistry of the volcanic rocks indicate an early continental rift environ- ment. The new data not only provide an age for the massive Zn-Pb-Cu sulfide mineralization associated with these volcanic rocks, but they also set a maximum age limit for Neoproterozoic continental break-up in southern Namibia. This age is statistically indistinguishable from a recently reported age of 748 + 3 Ma for stratigraphically equivalent volcanic rocks in the northern rift of the Damara Belt, suggesting that the onset of the formation of the N-S-trending Adamastor ocean and of the NE-trending Khomas ocean in central and northern Namibia occurred at the same time. The volcanic unit directly overlies, in both rift grabens, a diamictite horizon with glaciogenic features. Our new results further constrain the age of this glacial epoch, which may be correlated with the Sturtian glaciation, to around 750 Ma