Field Trip Day Three: Road Log For The Balmat Zinc Mine, New York
Published:January 01, 2001
William F. Delorraine, 2001. "Field Trip Day Three: Road Log For The Balmat Zinc Mine, New York", Part I. Proterozoic Iron and Zinc Deposits of the Adirondack Mountains of New York and the New Jersey Highlands Part II. Environmental Geochemistry and Mining History of Massive Sulfide Deposits in the Vermont Copper Belt, John F. Slack, Jane M. Hammarstrom, Robert R. Seal
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The Underground tour will examine Proterozoic Zn sulfide deposits of the Balmat Zn mine, described by deLorraine and Dill (1982) and in this volume by deLorraine (2001). The evening preceding the tour will feature a talk on Balmat geology. This talk will involve a slide show presentation with maps, cross sections, and mine models made available for inspection. The latest structural interpretations will be reviewed and there will be in-depth discussions regarding the response of massive sulfides to high-grade, near granulite- facies metamorphism in a sequence of interlayered silicated dolomitic marbles and pure marble units of extremely high ductility contrast. We will demonstrate that ore was tectonically remobilized 600 m and more laterally, by over 2000 m in the down-plunge dimension. This happened in several parent-daughter pairs. The degree and extent of remobilization of massive sulfide at Balmat appears to be unique anywhere in the world.
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Part I. Proterozoic Iron and Zinc Deposits of the Adirondack Mountains of New York and the New Jersey Highlands Part II. Environmental Geochemistry and Mining History of Massive Sulfide Deposits in the Vermont Copper Belt
This First day of the field trip visits Proterozoic iron deposits at the Podunk and Skiff Mountain iron mines, in the eastern Adirondack Mountains of New York state. Included are roadcuts to see representative lithologies and structures in the region surrounding the iron deposits. The origin of these iron deposits has been controversial, but studies by Foose and McLelland (1995) and more recently by McLelland et al. (2001b, 2001c) provide strong evidence for a high-temperture, intramagmatic origin related to late stages the Lyon Mountain Granite and correlative intrusions during the latter part of the 1090 to 1030 Ma Ottawan orogeny. The great majority of the deposits consist of low Ti magnetite ore accompanied by apatite and aegerine-augite. The apatite has high concentrations of rare-earth elements (REE) indicating to Foose and McLelland (1995) that the deposits are of Kiruna (REE-Au-U-Cu) type. This is further supported by persistent sodic (i.e., albitic) alteration associated with the ores. Most of the iron ores appear to be undeformed although they may occur in strained host rocks. Deposits are intimately associated with late tectonic to post-tectonic Lyon Mountain Granitic Gneiss that was emplaced at ca. 1055 Ma, during the waning stages of the ca. 1090 to 1030 Ma Ottawan Orogeny.