Adirondack Highlands, New York Western Minerals Supplementary Materials
OCR PDF of supplemental information for the Anorthosite-Charnockite Metamorphic Suite-Adirondack Mountains, New York collection.
Western Minerals Inc.
Western Minerals Inc.
1980
AD suite
Anorthosite
The specimen was collected from the Oregon Dome Massif. The Oregon Dome is similar in all respects to the anorthosites described and analyzed by Buddington (1939) for the Adirondack High Peaks region (Marcy Massif). Texturally, the present specimens are partly granulated and are fairly typical of Adirondack anorthosites situated near the margins of the massifs. Of particular interest in this specimen is the occurrence of garnet. In general, this rims both oxides, usually ilmenite and clinopyroxene (and sometimes cored by orthopyroxene). The assemblage is typical of garnet-clinopyroxene subfacies of the granulite (deWaard, 1965).
The following information is from the original OCR document: The reactions producing this assemblage have been discussed by McLelland and Whitney, "Origin of Garnet in the Anorthosite-Charnockite Suite of the Adirondacks" 1977, Contributions to Mineralogy and Petrology, v. 60, p.161-181.
Thin section shows plagioclase and orthopyroxene.
1980
Western Minerals Inc.
AD-17
Calcsilicate rock
Minerals found in the calcsilicate facies contain quartz, diopside, enstatitic pyroxene, tremolite, calcite, and phlogopite. However, only a few thin sections have been found to contain all phases. In some specimens, the pyroxene is close to 100% enstatite. The assemblage may be due to the reaction tremolite=diopside+ enstatite + quartz +fluid. This reaction discussed by Boyd, "Hydrothermal Investigations of Amphiboles," in Abelson, p.377-396.
Thin section shows calcite, diopside and phlogopite.
Western Minerals Inc.
AD-8
Charnockite
This charnockite is similiar to most of the Adirondack charnockites that occur interlayered with other metastratified units. Like its analogues, the Canada Lake charnockite shows conformable realationships with enveloping units. Mineralogically, these charnockites consist of 50-60% gray-green mesoperthite, 20-30% quartz, 5-10% sodic plagioclase, and minor amounts of biotite, hornblende and orthopyroxene. The latter mineral is only sporadically in any outcrop. It is not known whether these rocks represent metasediments, metaplutonics, or metavolcanics. The latter possibility is favored by field relationships and homogeneity.
Thin section shows K-feldspar, quartz and plagioclase.
Western Minerals Inc.
AD-2
Charnockite
This particular charnockite has been described, with analyses by deWaard and Romey, "Petrogenetic Relationships in the Anorthosite-Charnockite Series of the Snowy Mountain Dome," in Anorthosite Volume, New York State Museum Memoir 18, p.307-315. In this article, the authors show that a gradational contact exists between the anorthosite and surrounding charnockitic rocks. This is interpreted as the result of a comagmatic history for the rocks in question. The charnockites contain occasional xenocrysts of andesine which are believed to have been plucked off of the already solidified anorthosite by the still molten charnockite. Hills and Isachsen (1975) have dated these rocks at 1173±14 Ma.
Thin section shows K-feldspar, quartz and clinopyroxene.
1980
Western Minerals Inc.
AD-22
Coarse anorthosite
This coarse-grained specimen is typical of the massive, homogeneous anorthosite that occurs within the Marcy Massif and underlies the High Peaks region of the Adirondacks. The anorthosite from Route 3 is best represented by analyses 5-L and 8, Table 3, Buddington (1939). Also by analyses A, 16, and 17, Table 4, p. 3 , and by Table 5, p. 32, Buddington (1939).
Thin section shows plagioclase, clinopyroxene and ilmenite.
1980
Western Minerals Inc.
AD-18
Diopsidite
Pods and lenses of green diopsidite commonly occur along with the marbles. They are often composed of over 90% diopside.
Thin section contains diopside.
1980
Western Minerals Inc.
AD-9
Fayalite-ferrohedenbergite-mesoperthite granite
This granite post-dates deformation and metamorphism. Silver got a U/Pb zircon age of 1125 Ma. This is a most unusual rock type. This rock has small quantities of fayalitic olivine and ferrohedenbergite that occur with mesoperthite and quartz. It also contains iron-rich orthopyroxene (Fe~90%).
Thin section shows feldspar with perthitic texture, quartz and olivine.
1980
Western Minerals Inc.
AD-21
Garnetiferous amphibolite
This specimen is similar to the famous garnet deposits at Barton Mines at Gore Mountain. The garnets at Gore Mountain can attain diameters of 3 feet. At the Speculator road cut, garnet of 8-10 inches in diameter have been found, but smaller examples were considered to be best suited for the purposes of this suite. Both at Gore Mountain and Speculator, the original rock can be shown to have been an olivine metagabbro. The present mineralogy consists of garnet, hornblende, and plagioclase with the development of narrow rims of very anorthitic plagioclase (An₈₀) surrounding many of the garnets. In addition, orthopyroxene locally replaces hornblende near the plagioclase rims.<br /><br />The following information is from the original OCR document: The origin of the garnetiferous amphibolites has been discussed by Bartholome, "Genesis of the Gore Mountain Garnet Deposit", 1960, Economic Geology, v. 55, p. 255-277. The rims of calcic plagioclase and associated orthopyroxene has been discussed by deWaard, "The Occurrence of Garnet in the Granulite Facies of the Adirondack Highlands, " 1965, Journal of Petrology, v.6, p. 165-191. DeWaard shows convincingly that these rims are formed during the reaction hornblende + garnet + quartz = orthopyroxene + plagioclase + H₂O.<br /><br />Thin section shows plagioclase, hornblende and garnet.<br /><br /><br /><br />
1980
Western Minerals Inc.
AD-10
Garnetiferous leucogneiss
This rock type is characteristic of the light colored layers in the Sacandaga Formation. The mineralogy consists of garnet, feldspar, and quartz. Occasionally, sillimanite and skeletal oxides occur. Both plagioclase and microcline are present. Quartz modes occur as high as 40-50%.
Thin section shows quartz, plagioclase and garnet.
1980
Western Minerals Inc.
AD-13
Garnetiferous olivine metagabbro
This specimen is typical of the olivine metagabbros that occur throughout the Adirondacks. These rocks are of great petrologic interest for they contain classic examples of garnet coronas and spinel-clouded plagioclase. Note the preservation of ophitic and sub-ophitic igneous textures even though these rocks have experienced granulite facies conditions. A magnificent example of transition to eclogite facies.
The following information is from the original OCR document: Detailed reactions accounting for both metamorphic assemblages and textures are developed in McLelland and Whitney, "A Generalized Garnet-Forming Reaction for Metamorphic Rocks in the Adirondacks," 1980, Contributions to Mineralogy and Petrology, v.72, p. 111-122. Explanations for a number of metamorphic textures in these rocks can be found in McLelland and Whitney, "Compositional Controls On Spinel and Garnet Formation in Plagioclase of Olivine Metagabbros," 1980, Contributions to Mineralogy and Petrology.
The first 2 thin sections show a plagioclase lath and a garnet with plagioclase and olivine surrounding it. The second 2 thin sections show a garnet with plagioclase corona and olivine crystals surrounding the garnet.
1980
Western Minerals Inc.
AD-16
Mangerite-charnockite
This specimen is typical of the metaigneous charnockitic rocks associated with the massif anorthosites in the Adirondacks. With variation in the quantity of modal quartz, the rock qualifies as either a charnockite or a mangerite. Quartz content is sufficiently variable to result in both rock types in a single outcrop. These rocks are part of the Mt. Arab complex (earlier referred to as the Tupper Lake Complex (Buddington 1939 p. 116)). The average modes of the mangerite (pyroxene syenite gneiss) and the associated charnockites are:<br /><table style="height:240px;"><tbody><tr><td>
<p>Â </p>
</td>
<td>
<p>Pyroxene syenite gneiss (1)</p>
</td>
<td>
<p>Charnockite (2)</p>
</td>
</tr><tr><td>
<p>Microperthite</p>
</td>
<td>
<p>46</p>
</td>
<td>
<p>46</p>
</td>
</tr><tr><td>
<p>Oligoclase</p>
</td>
<td>
<p>42</p>
</td>
<td>
<p>24</p>
</td>
</tr><tr><td>
<p>Quartz</p>
</td>
<td>
<p>3.3</p>
</td>
<td>
<p>16</p>
</td>
</tr><tr><td>
<p>Ferrohypersthene</p>
</td>
<td>
<p>2.0</p>
</td>
<td>
<p>6</p>
</td>
</tr><tr><td>
<p>Ferroaugite</p>
</td>
<td>
<p>3.6</p>
</td>
<td>
<p>1.4</p>
</td>
</tr><tr><td>
<p>Hornblende</p>
</td>
<td>
<p>1.8</p>
</td>
<td>
<p>2.8</p>
</td>
</tr><tr><td>
<p>Garnet</p>
</td>
<td>
<p>-</p>
</td>
<td>
<p>0.5</p>
</td>
</tr><tr><td>
<p>Â </p>
</td>
<td>
<p>Â </p>
</td>
<td>
<p>Â </p>
</td>
</tr><tr><td>
<p>(1)Â Â Â McLelland average of 5</p>
<p>(2)Â Â Â Analysis 112, Table 32, Buddington, 1939<br /><br /></p>
</td>
</tr></tbody></table>
Thin section shows K-feldspar, plagioclase and hypersthene.
1980
Western Minerals Inc.
AD-20
Marble
This calcite marble is typical of most Adirondack metacarbonates. In the majority of instances, original dolomite has reacted to yield calcsilicates. Also present in these specimens are small, serpentinized droplets which may originally have been diopside or forsterite. Remnant grains of each of these minerals have been found in the marble. Accessory minerals are graphite, tourmaline, sphene, and sulfides. Adirondack marbles rarely occur by themselves. Rather, they tend to be interlayered with garnetiferous amphibolites similar to AD-10 (but not necessarily of igneous origin) and calcsilicates such as specimens AD-8 and AD-9. Quartzites and metapelitic layers occur with the marbles.
Thin section shows dolomite and serpentinized diospide
1980
Western Minerals Inc.
AD-7
Megacrystic potassium feldspar gneiss
This lithology is characterized by 1-4 inch long megacrysts of microperthite in a groundmass of quartz, oligoclase, hornblende, orthopyroxene, garnet, and oxide. Although the contacts of this unit are everywhere conformable, the rock is believed to represent a metamorphosed igneous plutonic rock. Similar lithologies are present at other stratigraphic horizons in the Adirondacks. In the Northwest Adirondack Lowlands, Buddington referred to a similar lithology as the Hermon Granite Gneiss. The present samples would be more appropriately referred to as metamorphosed quartz-monzonites. Sporadic occurrences of orthopyroxene indicate that, locally at least, the lithologies are charnockitic.
Thin section shows plagioclase, quartz, hornblende and orthopyroxene.
1980
Western Minerals Inc.
AD-5
Orthopyroxene gabbro
This specimen is typical of the saturated gabbros of the Adirondacks. The plagioclases are generally in the range of An₄₀ and the orthopyroxenes average close to En₆₀. Antiperthite is locally developed. Scattered grains of ilmenite and garnet occur. These gabbros may be genetically related to the anorthosites of the region.
Thin section shows plagioclase, orthopyroxene and hornblende.
1980
Western Minerals Inc.
AD-6
Pyroxene-quartz-plagioclase gneiss
This specimen consists of 50-60% andesine, 20-30% quartz, and minor pyroxene and hornblende. Associated with this lithology are 2-6 inch layers of pyroxene-plagioclase granulite and amphibolite. It is believed that the Royal Mountain Member gneiss represents a metamorphosed layered instrusion of overall tonalitic composition. Numerous internal features, such as xenoliths and possible slump structures, support this hypothesis.
Thin section shows plagioclase, quartz and hornblende.
1980
Western Minerals Inc.
AD-3
Quartz-microcline-diopsite gneiss
This specimen displays an unusual and distinctive lithology that occurs primarily in lower, marble-rich units (for example, the Cedar River Formation).
Thin section shows quartz, K-feldspar and clinopyroxene.
1980
Western Minerals Inc.
AD-15
Quartzite
This specimen is typical of the 5-10 foot thick coarse grained layers of glassy quartzites that comprise this formation. In most instances the quartzites are about 90% quartz. Feldspar and garnet are encountered locally. This is presumed to be the uppermost stratigraphic unit in the Adirondacks and typical of Adirondack quartzite generally.
Thin section shows primarily quartz with a minor amount of feldspar.
1980
Western Minerals Inc.
AD-1
Sillimanite-garnet-biotite-quartz-plagioclase gneiss
The predominant lithology of the Peck Lake Formation is a sillimanite-garnet-biotite-quartz-oligoclase gneiss with pods and lenses consisting of two feldspars and quartz (anatectic?). The lithology is widespread throughout the Adirondacks and may represent a metapelite or metagraywacke. European geologists have referred to similiar lithologies as "kinzigites" (deWaard, 1962).
Thin section shows sillimanite, quartz, biotite and plagioclase.
1980
Western Minerals Inc.
AD-4
Sillimanite-garnet-quartz-feldspar gneiss
This specimen is extremely rich in sillimanite. European geologists refer to such lithologies as "khondolites." This locality is very near some of the old graphite production sites west of Hague.
Thin section shows sillimanite, garnet, k-feldspar.
1980
Western Minerals Inc.
AD-11