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Orbitally forced sphalerite growth in the Upper Mississippi Valley District

M. Li1,

1Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA

H.L. Barnes1

1Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Li, M., Barnes, H.L. (2019) Orbitally forced sphalerite growth in the Upper Mississippi Valley District. Geochem. Persp. Let. 12, 18–22.

n/a

Geochemical Perspectives Letters v12  |  doi: 10.7185/geochemlet.1929
Received 19 June 2019  |  Accepted 5 October 2019  |  Published 12 November 2019
Copyright © The Authors

Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0




Figure 1 Sphalerite samples from West Hayden, Hendrickson, and Edgerton orebodies. Coloured photographs are shown with three growth stages of A (early), B (middle), and C (late) following McLimans et al. (1980)

McLimans, R.K., Barnes, H.L., Ohmoto, H. (1980) Sphalerite stratigraphy of the upper Mississippi Valley zinc-lead district, southwest Wisconsin. Economic Geology 75, 351-361.

. The rock colour grayscale profile was measured along the traverse (green) in grayscale images. Length of the black bar is 2 cm. Samples from Hendrickson and Edgerton orebodies share the same scale.
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Figure 2 Grayscale trace of a cross section of sphalerite (black) and its linear trend (purple). De-trended data (gray) are shown with its 32 mm (dashed red) and 9 mm (solid blue) Gauss bandpass filtered cycles (passband: 0.031 ± 0.008 and 0.11 ± 0.02 cycles/mm, respectively).
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Figure 3 2π MTM power spectrum (thin black) and periodogram (gray) of the grayscale series shown with robust red-noise models. The red-noise fit to the spectrum is based on the best fit to the log power of the 20 % median smoothed spectrum (dashed pink). The 90 % (solid red), 95 % (dashed red), 99 % (blue dashed line), and 99.9 % (dot green) confidence limits are shown. Cycle wavelengths are also marked.
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Figure 4 Sphalerite deposition rate. (a) The COCO analysis shows optimal deposition rate at 0.27 μm/a. (b) Null hypothesis testing of the data series indicates that 0.08 μm/a and 0.27 μm/a deposition rates have significance levels less than 1 %. (c) Number of contributing astronomical parameters. (d) Squared correlation coefficient for the amplitude envelope fit (r2envelope) and (e) the spectral power fit (r2power). (f) Combined envelope and spectral power fit (r2opt) at test deposition rate.
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