Balmat, Hyatt, Edwards, Pierrepont, Empire State

New York, USA

Main commodities: Zn Pb Ag
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The Balmat, Hyatt, Edwards and Pierrepont zinc-lead deposits are hosted by Mesoproterozoic Grenville Series (1120 Ma) marbles, located is located ~2 km SW of Fowler, in St. Lawrence County in north-western New York State, USA (#Location: 44° 15' 51"N, 75° 24' 33"W).

The Adirondack Mountains and the Balmat District are located within an outlier of the Grenville Province on the margin of the Canadian Shield. This orogenic province comprises a series of intense accretionary events that occurred during the Mesoproterozoic in the final stages of assembly of the supercontinent Rodinia, interpreted to have resulted from a continent-continent collision between Laurentia and Amazonia (e.g. Rivers et al., 1989, 2012). Following the Grenville accretionary events, a phase of tectonic relaxation occurred and the Canadian Shield margin underwent rifting, erosion and eventually was overlain by a cover sequence of Palaeozoic sedimentary rocks. Paleozoic deposition began with the late Cambrian to early Ordovician Potsdam Sandstone, followed by a limestone-dolostone sequence (Derby et al., 2013). Magmatism accompanied both orogenesis and rifting and is represented by numerous igneous intrusions of a range of ages, which have been metamorphosed to varying degrees (Makarenko et al., 2018).
  Following the Neoproterozoic to early Cambrian passive regime, and the late Cambrian to early Ordovician period of deposition, tectonic events intensified and began the process of building the Appalachian Mountains during the Mid Ordovician Taconic; Mid to Late Devonian Acadian; and late Carboniferous to Permian Alleghenian orogenies. The Adirondack Mountains however, were not formed until the Mesozoic, when vertical uplift and erosion between 250 and 60 Ma exhumed the slightly elliptical, ~180 x 150 km Adirondack dome of ~1350 to 1040 Ma Mesoproterozoic metamorphic and igneous rocks surrounded by flat-lying Palaeozoic sedimentary rocks. This dome is a structural inlier, but an outlier in that it is an isolated uplifted basement exposure, connected only by a narrow neck, known as the the Frontenac Axis, to the main NE-SW Grenville Province which is to the NW. However, other narrower elongated cores of the same basement rocks continue to the south and SW within the Appalachians, through New York, New Jersey, Pennsylvania and Virginia to as far south as Georgia (McLelland, Selleck and Bickford, 2013; Makarenko et al., 2018).
  The Adirondacks are lithologically and topographically divided into two main terranes, the Highlands and Lowlands, separated by a steep, NE-SW trending, NW dipping, oblique normal fault zone known as the Carthage-Colton shear/mylonite zone. The Adirondack Lowlands comprise the relatively small northwestern 70 x 100 km triangular portion of the Adirondacks, and the Highlands make up the main body of the dome. The Mesoproterozoic rocks have undergone pronounced high temperature ductile deformation that resulted in large, upright to flat-lying folds formed during two major orogenic events: the composite 1210 to 1140 Ma Shawinigan Orogeny (comprising the 1240 to 1220 Ma Elzevirian and 1190 to 1140 Ma Shawinigan Orogenies) and the 1090 to 980 Ma two pulse Grenville Orogeny (the 1190 to 1120 Ma Ottawan and 1005 to 980 Ma Rigolet orogenies). Orogenesis was accompanied by high grade regional metamorphism ranging from upper amphibolite (~6 to 7 kbar, ~600 to 750°C) to granulite facies (~7 to 8 kbar, ~800 to 830°C) conditions producing strong, widespread, penetrative deformation resulted in mylonite and ribbon gneiss. The Lowlands have been metamorphosed to amphibolite grade, the Highlands to higher granulite grade (McLelland, et al., 2010). This is interpreted to imply the Lowlands were initially at a shallower depth compared to the Highlands, but have been down-dropped across the Carthage-Colton shear/mylonite zone more recently. Both the Shawinigan and Grenvilles orogenic events were followed by post-orogenic igneous activity, i.e., a voluminous ~1155 Ma anorthosite-mangerite-charnockite-granite suite and a distinctive ~1050 Ma Lyon Mt. Granite that rims much of the Adirondack Highlands (McLelland et al., 2013; Makarenko et al., 2018).
  Balmat lies within the Adirondack Lowlands where the principal rock suites belong to the ~1.3 to 1.25 Ga Grenville Supergroup, a 5 to 6 km succession of metamorphosed sedimentary terranes that are composed of marbles and paragneisses with minor amphibolites and quartzites that constitute a section of the Grenville Province known as the 'Central Metasedimentary Belt' (Davidson, 1998). Other zinc deposits are also hosted by this same metasedimentary belt within the main Grenville Province to the north in Canada. The Adirondack Lowlands rocks were deposited in an extensional (back-arc?) basin prior to the final accretion of the Grenville Province (Chiarenzelli et al., 2015), specifically, before the termination of widespread extension by the Elzevirian Orogeny. The supergroup has been divided into three stratigraphic units: the Upper Marble Formation, the Popple Hill Gneiss and the Lower Marble Formation (Makarenko et al., 2018).
  The central, and widespread Popple Hill Gneiss between the two marble units mainly comprises fine-grained grey mesosomes of plagioclase, mainly oligoclase, and black biotite, with lesser pink leucosomes and megacrysts of K feldspar and quartz. Black amphibolite interlayers within this unit probably represent oceanic basalt sills, and contain plagioclase-rich leucosomes (USGS). Geochemical compositions of the predominant rock type is consistent with dacite volcanics rather than clastic sediments. The gneissic unit and leucogneisses lower in the section are interpreted to be of probable ash-flow tuff, as massive volcanic outpourings within a platformal-type sedimentary sequence (Carl, 1988). The zinc mineralisation at Balmat is hosted within the Upper Marble Formation (Makarenko et al., 2018).
  The Upper Marble Formation is an ~1 km thick succession of shallow water carbonates (including stromatolitic units) composed of multiple dolomitised marbles, siliceous dolomitic marble, quartz-diopsidic marble and periodic beds of anhydrite up to 25 m thick, with occasional talc-tremolite-anthophyllite schists, serpentine-talc beds, pyritic schist, sillimanite-garnet schist and quartz-graphitic schist, locally capped by quartz-biotite-diopside-scapolite gneiss. This formation has been subdivided into 16 units, including distinct marker horizons within the marble that indicate favourable locations for zinc mineralisation. The latter include a pyritic schist, a dark grey dolomitic marble and periodic anhydrite bands. The anhydrites are of particular significance as zinc deposition appears to be closely associated with anhydrite bands. Marker units 6, 11 and 14 contain massive stratabound sphalerite bodies occurring soon after anhydrite beds in the lithologic sequence. Units 6 to 10 locally host semi-massive crosscutting sphalerite bodies where structures intersect the massive sphalerite bearing units listed above (Makarenko et al., 2018).
  Massive, generally conformable, orebodies, of which there are up to 15, are distributed at up to 7 'stratigraphic' levels within the ~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 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 (Whelan et al., 1984).
  Intense tectonism has extensively deformed the Upper Marble and obliterated virtually all primary structures and textures. The dominant structure in the district is the Sylvia Lake Syncline, a major SW-NE trending, tight to isoclinal recumbent sheath fold with a shallowly dipping axial plane exposed between the Balmat and the Edwards mines. Exposure of the Upper Marble Formation is limited, generally occurring along the axis of the syncline. Sphalerite tends to occur within axial zones and on the limbs of local scale folds and faults associated with the syncline. Contrasting ductility and competence characterises the Upper Marble Formation, ranging from very ductile anhydrite and sulphide bands to moderately ductile dolomitic marble to moderately brittle calcitic and serpentinous dolomitic marble to brittle silicious interlayered quartzite and diopside. Anhydrite and sulphide bands are relatively thin, and sulphide beds are spatially restricted, but tend to occur together in consolidated ductile zones. When exposed to stress, the brittle rocks fractured, and the structures evolved into thrust faults in the ductile rocks. The thrust faults served to propagate folds. The tendency of folds to form in the most ductile regions is interpreted to have caused the sphalerite to be concentrated in the noses of folds (Makarenko et al., 2018).
  Four phases of deformation are recognised from early large scale recumbent nappes, NE striking isoclinal folding, open to tight steep NNE folds and a NNW trending folding stage (Whelan et al., 1984).

Occurrences of zinc and lead were reported on the Balmat farm as early as 1838, but it was not until 1927 that a drilling program by what was then St. Joseph Lead Company (later to become the Zinc Corporation of America - ZCA) outlined a major deposit of high-grade zinc mineralisation which later developed into the No.2 Mine. Subsequent drilling in 1946 and 1965 led to the development of the No.3 and No. 4 Mines respectively. In 1979 further drilling outlined high-grade zinc mineralisation leading to the development of the Pierrepont mine. At the northeast end of the district, St. Joe and predecessors and subsequently ZCA, have operated the Edwards mine from 1915 to 1980 and the Hyatt mine sporadically since 1918, but neither deposit has approached the size of the Balmat deposits. Mining at Balmat has taken place between 1930 and 2001, before reopening from 2006 to 2008.

Some 30 individual orebodies in 4 main mines have been exploited in the district:
Balmat Mine with a total production of 30.7 Mt @ 8.6% Zn (Knight, 2017), included the:
    - Balmat No. 2 Mine with production from 1952 to 2001 - 5.7 Mt @ 9% Zn (USGS mrdata database) from the Main, Streeter, Hanging Wall, Number One and American orebodies. Mineralisation is hosted by banded quartz-diopside, calcitic-siliceous marble and sepentinous diopsidic marble. The structure of these orebodies is dominated by the Sylvia Lake syncline which plunges at 25°NNW. Sulphides have flowed across stratigraphy along shears and into dilatent fold hinges and fractures, resulting in complex geology (DeLorriane et al., 1993)
    - Balmat No. 3 Mine with production from 1930 to 2001 - 17.8 Mt @ 9% Zn (USGS mrdata database) from the Upper Gleason, Lower Gleason, West Gleason, Loomis, Loomis C and part of the Sylvia Lake orebodies. Host rocks are dolomitic marbles, quartzite, and siliceous diopside (locally) (DeLorriane et al., 1993);
    - Balmat No. 4 Mine with production from 1965 to 2001 - 9.4 Mt @ 8% Zn (USGS mrdata database) from the Fowler, Upper Fowler and Mud Pond orebodies. Host rocks are a quartz-diopside-dolomitic-calcitic marble (DeLorriane et al., 1993). Hudbay Minerals Inc purchased the idle Balmat assets in September 2003. The Balmat No. 4 Mine re-opened in 2006 and operated into 2008 before being placed on care and maintenance in August 2008. Between 2006 and 2008, 0.855 Mt @ 7% Zn was mined from the Davis, Mud Pond, Mahler, Fowler, Upper Fowler and New Fold orebodies.
Hyatt Mine, which is ~6 km NE of the Balmat deposits, had a total production of 6.0 Mt @ 10.8% Zn, from 6 orebodies between 1918 and 1998 (Knight, 2017).
Edwards Mine, which is ~5.5 km NE of the Hyatt mine, had a total production of 1.0 Mt @ 8.3% Zn, from 6 orebodies between 1909 and 1980 (Knight, 2017).
Pierrepont Mine, which is ~24 km NE of the Edwards mine, had a total production of 2.4 Mt @ 16.3% Zn, from 2 orebodies between 1982 and 2001 (Knight, 2017).
Total Balmat production to 1993 was of the order of 37 Mt @ 9.4% Zn, 0.5% Pb (Delorraine, Dill, Knight and Johnson, 1994);
TOTAL district production between 1909 and 2008 was - 40.1 Mt @ 9.4% Zn (Knight, 2017).

The Balmat No. 4 mine was recommissioned as the Empire State Mine by Titan Mining Corporation in January 2018 and recommenced production in March of the same year. The mine exploits the Mud Pond, Mahler, New Fold, NE Fowler, Davis, Sylvia Lake and Cal Marble orebodies. These orebodies are scattered, although all but NE Fowler and Cal Marble are connected by existing development to the shaft. The orebodies are up to 15 m thick, but average 2.4 m, and dip at between 20 and 35°, with local variations of from 10 to 90°. The individual mineralised zones are up to 150 m wide and of the order of 1800 m. long. While generally continuous, these mineralised zones have considerable geometrical variability.

  Mineral Resources as at 1 October, 2020 (Titan Mining Corporation website) were:
    Measured + Indicated Resource - 1.555 Mt @ 11.72% Zn;
    Inferred Resource - 5.943 Mt @ 11.11% Zn;
  Open pit
    Measured + Indicated Resource - 0.636 Mt @ 3.13% Zn;
    Inferred Resource - 0.197 Mt @ 3.37% Zn.

Sections of this description are drawn from "Makarenko, M., Gopinathan, I., Reeves, A. and Raponi, R., 2018 - Preliminary economic assessment, updated technical report, Empire State Mines, Gouverneur, New York, USA; an NI 43-101 Technical Report prepared by JDS Energy and Mining Inc., for Titan Mining Corp., 267p." and "Knight, R., 2017 - Zinc Exploration and Discovery in the Balmat‐Edwards‐Pierrepont District, NY, USA; Québec Mines, 2017, November 20 to 23, 2017, Québec City Convention Center. 62p."

The most recent source geological information used to prepare this summary was dated: 2018.     Record last updated: 25/6/2021
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:
Delorraine, W.F., Dill, D.B., Knight, R.H. and Johnson, J.T.,  1993 - Geology of the Balmat Zinc Mines, St. Lawrence County, New York: in Thompson, T.B., (Ed.), 1993 Selected Mineral Deposits of Vermont and the Adirondack Mountains, New York, Society of Economic Geologists Guidebook Series,   v.17, pp. 26-48.
Knight, R.H.,  2005 - Recent zinc ore discoveries in the Balmat-Edwards district, northwest Adirondacks, New York state: a case history: in Paper No. 20-6,    Geological Society of America Abstracts with Programs,   Vol. 37, No. 1, p. 64.
Lea, E.R. and Dill, D.B., Jr.,   1968 - Zinc deposits of the Balmat-Edwards District, New York: in Ridge, J.D., (Ed.), 1968 Ore Deposits of the United States 1933-1967, Graton-Sales Volume, American Institute of Mining, Metallurgical and Petroleum Engineers   v.1, pp. 20-48.
Matt, P., Powell, W., deLorraine, W.F. and Chiarenzelli, J.,  2019 - Sulfide and silicate anatexis in the Balmat zinc deposit (New York, USA) and its implications for ore remobilization: in    Ore Geology Reviews   v.107, pp. 392-401.
Matt, P., Powell, W., Mathur, R. and deLorraine, W.F.,  2019 - Zn-isotopic evidence for fluid-assisted ore remobilization at the Balmat Zinc Mine, NY: in    Ore Geology Reviews   v.116, 20p. doi.org/10.1016/j.oregeorev.2019.103227
Matt, P.D.,  2019 - The Role of Fluids in Ore Remobilization at the Balmat Zinc Deposit, NY: in    City University of New York (CUNY), Graduate Faculty in Earth and Environmental Sciences,   Thesis, submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, 67p.
McLelland, J., Selleck, B. and Bickford, M.E.,  2013 - Tectonic evolution of the Adirondack Mountains and Grenville inliers within the USA,: in    Geoscience Canada, Geological Association of Canada,   v.40, pp. 318-333.
Whelan, J.F., Rye, R.O. and deLorraine, W.,  1984 - The Balmat-Edwards Zinc-Lead deposits - sedimentary ore from Mississippi Valley-type fluids: in    Econ. Geol.   v.79, 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, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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