Abstract

Age and duration of Mississippi Valley–type ore-mineralizing events: Correction

Geology, v. 23, p. 233–236 (March 1995)

An error has been discovered in the calculation of the estimate for the duration of a Mississippi Valley–type (MVT) mineralization event. In the original paper, the rate of apparent polar wander (APW) for North America was expressed in degrees of drift per million years (8/m.y.) rather than in million years per degree of drift (m.y./8). This inversion resulted in an incorrect estimate for the time required to form a typical MVT ore deposit. The correct value for the rate of APW is 2.7 6 0.7 m.y./8 from the Lower Devonian to the Upper Triassic, based on locations of the eight reference paleopoles of Van der Voo (1993). The original equation is correct and is repeated as follows:  
\[2(a_{1{\mbox{--}}2}\ {-}\ a_{1{\mbox{--}}3})\ {\times}\ rate\ of\ APW\ 5\ duration\ of\ mineralization.\]

The revised estimate for the average length of time it takes to form an MVT ore deposit is 25.2 6 6.5 m.y. using the correct value for the an MVT ore deposit is 25.2 6 6.5 m.y. using the correct value for the rate of APW (Table 1). Note that the paleopole statistics for Central Tennessee have changed slightly from the original paper, incorpo-rating additional data. The updated pole position is at 111.98E, 50.58N (a1–2 = 4.08, a1–3 = 2.18, azimuth = 698) (Lewchuk and Symons, 1996).

REFERENCES CITED

Van der Voo, R., 1993, Paleomagnetism of the Atlantic, Tethys, and Iapetus Oceans: Cambridge, Cambridge University Press, 411 p.

Lewchuk, M. T., and Symons, D. T. A., 1996, Paleomagnetism and genesis of the Central Tennessee Zinc Mississippi Valley–type ore district, in Sangster, D. F., ed., Sediment hosted Pb-Zn ore deposits: Economic Geology Special Volume (in press).

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