%0 Map %D 2002 %T Fulton Chain-of-Lakes Area: West Central Adirondack Mountains, New York %A P. R. Whitney %A R. H. Fakundiny %A Y. W. Isachsen %K geology %B New York State Museum Map and Chart Series %I The University of the State of New York %C Albany, New York %G eng %0 Journal Article %J Northeastern Geology and Environmental Sciences %D 2002 %T Geology, geochemistry, and mineralogy of the Iron Mountain skarn, Adirondack Highlands, New York %A P. R. Whitney %K geology %B Northeastern Geology and Environmental Sciences %V 24 %P 245-260 %G eng %0 Journal Article %J Northeastern Geology and Environmental Sciences %D 2002 %T Skarns in the Adirondack Highlands, New York: Distribution, geochemistry, origin, and tectonic implications %A P. R. Whitney %K geology %B Northeastern Geology and Environmental Sciences %V 24 %P 261-275 %G eng %0 Journal Article %J Geochimica et Cosmochimica Acta %D 1998 %T Rare Earth Element Metasomatism in Hydrothermal Systems; the Willsboro-Lewis Wollastonite Ores, New York, USA %A P. R. Whitney %A J. F. Olmsted %K garnet-pyroxene skarns %K New York %K rare earth elements %K Willsboro-Lewis district %K wollastonite ores %X

Wollastonite ores and garnet-pyroxene skarns in the Willsboro-Lewis district, New York, USA were formed in a complex hydrothermal system associated with the emplacement of a large anorthosite pluton. Contact-metamorphic marbles were replaced by wollastonite, garnet, and clinopyroxene during infiltration metasomatism involving large volumes of water of chiefly meteoric origin. Rare earth elements (REE) in these rocks show large departures from the protolith REE distribution, indicative of substantial REE mobility. Three types of chondrite-normalized REE distribution patterns are present. The most common, found in ores and skarns containing andradite-rich garnet, is convex-up in the light REE (LREE) with a maximum at Pr and a positive Eu anomaly. Europium anomalies and Pr/Yb ratios are correlated with XAd in garnet. This pattern (type C) results from uptake of REE from hydrothermal fluids by growing crystals of calcsilicate minerals, principally andradite, with amounts of LREE controlled by the difference in ionic radius between Ca++ and REE3+ in garnet X sites. The Eu anomaly results either from prior interaction of the fluids with plagioclase-rich, Eu-positive anorthositic rocks in and near the ore zone, or by enrichment of divalent Eu on growth surfaces of garnet followed by entrapment, or both.

Relative enrichment in heavy REE (type H) occurs in ores and skarn where calcsilicates, including grossularitic garnet, in contact-metamorphic marble have been concentrated by dissolution of calcite. In most cases a negative Eu anomaly is inherited from the marble protolith. Skarns containing titanite and apatite exhibit high total REE, relative light REE enrichment, and negative Eu anomalies (type L). These appear to be intrusive igneous rocks (ferrodiorites or anorthositic gabbros) that have been converted to skarn by Ca metasomatism. REE, sequestered in titanite, apatite, and garnet, preserve the approximate REE distribution pattern of the igneous protolith.

Post-ore granulite facies metamorphism homogenized zoned mineral grains without causing complete intergranular reequilibration and does not appear to have significantly affected the whole-rock REE distributions. These results demonstrate that extensive REE metasomatism can occur in hydrothermal systems at shallow to intermediate depths and that REE geochemistry may be useful in discerning the origin of skarns and skarn-related ore deposits.

%B Geochimica et Cosmochimica Acta %V 62 %P 2965-2977 %G eng %U http://dx.doi.org/10.1016/S0016-7037(98)00230-0 %R 10.1016/S0016-7037(98)00230-0 %0 Journal Article %J Geology %D 1996 %T Proterozoic Low-Ti Iron-oxide Deposits in New York and New Jersey; Relation to Fe-oxide (Cu-U-Au-rare earth element) Deposits and Tectonic Implications; Discussion and Reply %A P. R. Whitney %A McLelland, J. M. %A Foose, M. P. %K geology %B Geology %V 24 %P 382-384 %G eng %0 Report %D 1995 %T Wollastonite Deposits of the Northeastern Adirondacks %A P. R. Whitney %A J. F. Olmsted %E Garver, J. I. %E Smith, J. A. %K geology %B Field Trip Guidebook %C Schenectady, New York %P 25-38 %G eng %0 Report %D 1995 %T Wollastonite Deposits of the Northeastern Adirondacks %A P. R. Whitney %A J. F. Olmsted %E Garver, J. I. %E Smith, J. A. %K geology %B Field Trip Guidebook %I 67th annual meeting of the New York State Geological Association %C Schenectady, New York %P 25-38 %G eng %0 Journal Article %J Precambrian Research %D 1992 %T Charnockites and Granites of Western Adirondacks, New York, USA; A Differentiated A-type Suite %A P. R. Whitney %K geology %X

Granitic rocks in the west-central Adirondack Highlands of New York State include both relatively homogeneous charnockitic and hornblende granitic gneisses (CG), that occur in thick stratiform bodies and elliptical domes, and heterogeneous leucogneisses (LG), that commonly are interlayered with metasedimentary rocks. Major- and trace-element geochemical analyses were obtained for 115 samples, including both types of granitoids. Data for CG fail to show the presence of more than one distinct group based on composition. Most of the variance within the CG sample population is consistent with magmatic differentiation combined with incomplete separation of early crystals of alkali feldspar, plagioclase, and pyroxenes or amphibole from the residual liquid. Ti, Fe, Mg, Ca, P, Sr, Ba, and Zr decrease with increasing silica, while Rb and K increase. Within CG, the distinction between charnockitic (orthopyroxene-bearing) and granitic gneisses is correlated with bulk chemistry. The charnockites are consistently more mafic than the hornblende granitic gneisses, although forming a continuum with them. The leucogneisses, while generally more felsic than the charnockites and granitic gneisses, are otherwise geochemically similar to them. The data are consistent with the LG suite being an evolved extrusive equivalent of the intrusive CG suite.

Both CG and LG suites are metaluminous to mildly peraluminous and display an A-type geochemical signature, enriched in Fe, K, Ce, Y, Nb, Zr, and Ga and depleted in Ca, Mg, and Sr relative to I- and S-type granites. Rare earth element patterns show moderate LREE enrichment and a negative Eu anomaly throughout the suite. The geochemical data suggest an origin by partial melting of biotite- and plagioclase-rich crustal rocks. Emplacement occurred in an anorogenic or post-collisional tectonic setting, probably at relatively shallow depths. Deformation and granulite-facies metamorphism with some partial melting followed during the Ottawan phase of the Grenville Orogeny, yielding the present migmatitic granitic and charnockitic gneisses.

%B Precambrian Research %V 57 %P 1-2 %G eng %U http://www.sciencedirect.com/science/article/pii/0301926892900923 %R 10.1016/0301-9268(92)90092-3 %0 Report %D 1985 %T Rocks and Problems of the Southeastern Adirondacks %A P. R. Whitney %E Lindemann, R. H. %K geology %B Field Trip Guidebook %I New York State Geological Association, 57th annual meeting %C Saratoga, New York %P 47-67 %G eng %0 Report %D 1985 %T Rocks and Problems of the Southeastern Adirondacks %A P. R. Whitney %E Lindemann, R. H. %K geology %B Field Trip Guidebook %C Saratoga, New York %P 47-67 %G eng %0 Journal Article %J Northeastern Geology %D 1983 %T A Three-stage Model for the Tectonic History of the Adirondack Region, New York %A P. R. Whitney %K geology %B Northeastern Geology %V 5 %P 61-72 %G eng %0 Journal Article %J Economic Geology and the Bulletin of the Society of Economic Geologists %D 1975 %T Use of Oxide-coated Stream Gravels in Geochemical Surveys; A Test Case %A P. R. Whitney %K geology %B Economic Geology and the Bulletin of the Society of Economic Geologists %V 70 %P 252 %G eng %0 Journal Article %J Contributions to Mineralogy and Petrology %D 1973 %T Origin of Coronas in Metagabbros of the Adirondack Mts., New York %A P. R. Whitney %A McLelland, J. M. %K geology %X

Metagabbros from two widely separated areas in the Adirondacks show development of coronas. In the Southern Adirondacks, these are cored by olivine which is enclosed in a shell of orthopyroxene that is partially, or completely, rimmed by symplectites consisting of clinopyroxene and spinel. Compositions of the corona phases have been determined by electron probe and are consistent with a mechanism involving three partial reactions, thus:

(a) Olivine=Orthopyroxene+(Mg, Fe)++.

(b) Plagioclase+(Mg, Fe)+++Ca++=Clinopyroxene+Spinel+Na+.
 
(c) Plagioclase+(Mg, Fe)+++Na+=Spinel+more sodic plagioclase+Ca++.
 
Reaction (a) occurs in the inner shell of the corona adjacent to olivine; reaction (b) in the outer shell; and (c) in the surrounding plagioclase, giving rise to the spinel clouding which is characteristic of the plagioclase in these rocks. Alumina and silica remain relatively immobile. These reactions, when balanced, can be generalized to account for the aluminous nature of the pyroxenes and for changing plagioclase composition. Summed together, the partial reactions are equivalent to:

(d) Olivine + Anorthite = Aluminous orthopyroxene + Aluminous Clinopyroxene + Spinel (Kushiro and Yoder, 1966).

In the Adirondack Highlands, coronas between olivine and plagioclase commonly have an outer shell of garnet replacing the clinopyroxene/spinel shell. The origin of the garnet can also be explained in terms of three partial reactions:

(e) Orthopyroxene+Ca++=Clinopyroxene+(Mg, Fe)++.

(f) Clinopyroxene+Spinel+Plagioclase+(Mg, Fe)++=Garnet+Ca+++Na+.
 
(g) Plagioclase+(Mg, Fe)+++Na+=Spinel + more sodic plagioclase+Ca++.
 

These occur in the inner and outer corona shell and the surrounding plagioclase, respectively, and involve the products of reactions (a)-(d). Alumina and silica are again relatively immobile. Balanced, and generalized to account for aluminous pyroxenes and variable An content of plagioclase, they are equivalent to:

(h) Orthopyroxene+Anorthite+Spinel=Garnet (Green and Ringwood, 1967).

Amphibole coronas about opaque oxides in rocks of both areas are the result of oxide/plagioclase reactions with addition of magnesium from coexisting olivine.

Based on published experimental data, pressure and temperature at the time of corona formation were on the order of 8 kb and 800° C for the garnet bearing coronas, with somewhat lower pressures indicated for the clinopyroxene/spinel coronas.

%B Contributions to Mineralogy and Petrology %V 39 %P 81-98 %G eng %U http://link.springer.com/article/10.1007/BF00374247 %R 10.1007/BF00374247 %0 Journal Article %J Geochimica et Cosmochimica Acta %D 1969 %T Variations of the K/Rb Ratio in Migmatitic Paragneisses of the Northwest Adirondacks %A P. R. Whitney %K geology %X

Data for the migmatitic paragneisses of the Northwest Adirondacks indicate fractionation of potassium and rubidium during metamorphism and migmatization; total rock KRb ratios are controlled to a significant degree by modal composition. Biotite-poor granitic veins and lenses show KRb ratios averaging 431 in contrast to the host gneisses which have an average KRb ratio of 271. Paragneisses from the zone of granulite facies metamorphism show significantly higher (mean 307) KRb ratios than those from the amphibolite facies (231), indicating the possibility of regional depletion in Rb relative to K under intensive metamorphic conditions.

%B Geochimica et Cosmochimica Acta %V 33 %P 1203-1211 %G eng %U http://www.sciencedirect.com/science/article/pii/0016703769900428 %R 10.1016/0016-7037(69)90042-8