Balmat - Edwards, Pierrepont

New York, USA

Main commodities: Zn Pb Ag
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The Balmat-Edwards-Pierrepont zinc-lead deposits are hosted by Mesoproterozoic Grenville Series (1120 Ma) marbles in north-western New York State, USA.   The Grenville Series is composed of 5 to 6 km of marbles and paragneisses with minor amphibolites and quartzites.   Four phases of deformation are recognised from early large scale recumbent nappes, north-east striking isoclinal folding, open to tight steep NNE folds and a NNW trending folding stage.

The host unit comprises relatively pure dolomitic and layered silicate (quartz-diopside) rich marbles. Massive, generally conformable, orebodies (up to 15) are distributed at various (up to 7) levels within the approximately 1 km thick marble sequence.   They are generally tabular to podiform in shape and range from 5 to 15 m in thickness with strike lengths of 15 to 240 m, and are frequently localised in fold hinges, extending down plunge for up to 1 km.   The approximately 1 Ga Grenvile event obliterated virtually all primary structures and textures.

The orebodies are composed of pyrite and sphalerite with lesser galena (pyrite:sphalerite+galena ratios of from 0 to 10) and rare pyrhotite and chalcopyrite.   These sulphides are coarsely recrystallised and intergrown with porphyroblasts of from 1 to 15 mm.   The gangue is composed of wall rock fragments, massive grey quartz and brownish calcite as well as rare barite.

For detail see the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 1996.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Whelan J F, Rye R O, Delorraine W  1984 - The Balmat-Edwards Zinc-Lead deposits - sedimentary ore from Mississippi Valley-type fluids: in    Econ. Geol.   v79 pp 239-265

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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