Sphalerite-bearing detrital ‘sand’ bodies in Mississippi Valley-type zinc deposits Mascot-Jefferson City district,Tennessee |
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| Authors: | J F Matlock K C Misra |
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| Institution: | (1) Halliburton NUS Environmental Corporation, 800 Oak Ridge Turnpike, 37830 Oak Ridge, Tennessee, USA;(2) Department of Geological Sciences, University of Tennessee, 37996-1410 Knoxville, Tennessee, USA |
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| Abstract: | The Mississippi Valley-type sphalerite mineralization in the Mascot-Jefferson City zinc district of East Tennessee occurs
as open-space fillings in breccia bodies within the upper part of the Knox Group (Lower Ordovician) which is truncated by
a regional unconformity. A lower age limit of mineralization is constrained by the formation of solution-collapse breccia
bodies, which are believed to be related to the post-Knox unconformity. The breccias contain irregularly distributed “sand”
bodies that represent cavities filled with well-laminated and size-graded, sphalerite-bearing, detrital, internal sediments.
The texture, composition, and fluid inclusion characteristics of the sphalerite, are consistent with its local derivation
from the wallrocks as detrital grains. The conformability between the laminations in the sediments and the bedding planes
of the host carbonate rocks suggests that the sand bodies formed prior to the regional deformation event (Alleghenian orogeny).
The stylolitization of carbonate and sphalerite clasts in the internal sediments as well as the deformation of the sphalerite
are also consistent with a pre-Alleghenian age for the emplacement of the main-stage sphalerite mineralization in the Mascot-Jefferson
City district and, by analogy, in other Lower Ordovician-hosted Mississippi Valley-type districts of the southern Appalachians. |
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