Mineralogy of Amphibolite Interlayers in the Gneiss Complex, Northwest Adirondack Mountains, New York

Engel, A. E. J.; Engel, Celeste G.; Havens, Raymond Gilbert

doi:10.1086/626973

Cited by 38 publications

(10 citation statements)

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“…This appears to be ruled out by the similar composition of the hornblende in the host metagabbro and in the veins, both of which are more Al-rich than hornblende found in typical quartz-bearing hornblende-granulites (e.g. Engel et al, 1964;Hansen et al, 1987).…”

Section: Evidence For Metasomatism In Diffuse and Intermediate Veinsmentioning

confidence: 97%

Infiltration‐driven dehydration and anatexis in granulite facies metagabbro, Grenville Province, Ontario, Canada

Pattison

1991

Journal Metamorphic Geology

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Dark hornblende + garnet-rich, quartz-absent rnetagabbro boudins from the Seguin subdomain, Ontario Grenville Province, are transected by anastomosing light-coloured veins rich in orthopyroxene, clinopyroxene, plagioclase and sometimes quartz. The veins vary in texture from fine-grained diffuse veins and patches that overprint the metagabbro, to coarse tonalitic leucosomes with sharp borders. The diffuse veins and patches are suggestive of channellized subsolidus dehydration of the metagabbro, while the tonalitic leucosomes are suggestive of local internally-derived anatexis. All vein types grade smoothly into each other, with the tonalitic leucosomes being the latest.Relative to the host metagabbro, the veins have higher Si, Na, Ba & Sr, lower Fe, Mg, Ca & Ti, and similar Al. The coarser veins are enriched in K. Plagioclase becomes steadily enriched in Na in the transition from host metagabbro (An,,) to the veins (An35), and in the coarsest veins it is antiperthitic. Differences in composition of the other minerals between host metagabbro and vein are minor. Pressure-temperature estimates are scattered, but indicate a minimum temperature during vein formation of 700" C at about 8 kbar.Mass balance constraints indicate that the veins formed from the metagabbro in an open system. The transecting veins are interpreted to represent pathways of Si + Na + Ba + Sr f K f Al-enriched, low aHZ0fluids that metasornatized the host metagabbro to form the anhydrous veins., An initial period of localized solid-state dehydration of the metagabbro, represented by the diffuse veins, was followed by a transition to localized anatexis, represented by the tonalitic leucosomes. The change to anatexis may have been due to the addition of K to the infiltrating fluid, The source and delivery mechanism of the fluids is unknown.

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Section: Evidence For Metasomatism In Diffuse and Intermediate Veinsmentioning

confidence: 97%

Infiltration‐driven dehydration and anatexis in granulite facies metagabbro, Grenville Province, Ontario, Canada

Pattison

1991

Journal Metamorphic Geology

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“…*) The plagioclases in the paragneiss belonging to the granulite facies from Northwest Adirondack Mountains are also of "low-temperature form" (Engel and Engel, 1960;Engel et al, 1964). Of the twinned plagioclases in charnockites from India (Naidu, 1954), the frequency percentage of the composition plane (010) is about the same with that in the metamorphic rocks now under consideration.…”

Section: Propertiesmentioning

confidence: 90%

On Plagioclases in Metamorphic Rocks from Lützow-Holmbukta Area, East Antarctica

Suwa

1966

Proceedings of the Japan Academy

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The plagioclases, which form the subject of the present paper, are from metamorphic rocks of the area around Lutzow-Holmbukta, East Antarctica.The samples of these rocks were collected by the first wintering party of Japanese Antarctic Research Expedition (J. A. R. E.) [1956][1957][1958], and were entrusted to the author for study through Dr. T. Tatsumi, a member of the party. The area around Liitzow-Holmbukta (lat. 68-70°S., long. 37-39°E.) is composed mainly of granite and metamorphic rocks of various kinds, including ultrabasic and basic granulites, pyroxene-gneiss of an intermediate composition, and garnet-gneiss of pelitic composition, accompanied by marble and quartzite in small beds. Among the metamorphic rocks, pyroxene-and garnet-gneisses are predominant; and the ultrabasic and basic granulites occur in lenticular form in the mass of gneisses.The metamorphic complex, probably derived from a formation consisting dominantly of shale and andesite, intercalating lenticular masses of ultrabasic and basic rocks, limestone, and chert, strikes generally north-south and dips eastward at 30-60°. The age of metamorphism, as determined with biotites and euxenite in the rocks of this area by the Rb/Sr and U/Pb methods, is about 500 m, yr.-Cambrian .Host Rocks of Plagioclases Examined 1. Specimen DARE-57020905.Basic granulate occurring as blackish band in granitic gneiss from Dokkene of Langhovde.A gneissose fine-to medium-grained rock, composed of andesine (to be described later), green-yellow tinge brown hastingsite (2 V1=70°, a =1.682, ,9 =1.693, 7=1.701; Al'V = 2.024, Na + K = 0.943, APT + Fe3+ + Ti =1.159 on the basis of 24 (0, OH); TiO, =1.88 wt %), bypersthene (2V1=56°, a=1.708, 9=1.721, 7=1.724, Mg : Fe2+ : Ca = 54.0:45.1: 0.9, pleochroic, X' = pale orange and Z' = pale blue), and reddish brown biotite, and accessorily of opaque minerals, pyralspite garnet, clinopyroxene, apatite, and zircon. Si02 = 44.20 wt %; normative nepheline = 5.08%.2. Specimen JARS-57012602. Pyroxene-gneiss from East Ongul.A fine-to medium-grained blue-greyish rock, composed of

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“…Of particular note are the studies on the amphibolites that are found Okrusch (1997). This geothermometer is then applied to amphibolite samples collected within the Popple interlayered within the Major Paragneiss (Engel & Engel, 1962a;Engel et al, 1964), now called the Popple Hill gneiss and analysed by both electron microprobe and quantitative X-ray diffraction methods to establish Hill gneiss. Following a traverse from the south-west to the north-east along the strike of the Lowlands how temperatures vary along strike and what, if any, correlations exist between the modal mineralogy and (Fig.…”

mentioning

confidence: 99%

“…Following a traverse from the south-west to the north-east along the strike of the Lowlands how temperatures vary along strike and what, if any, correlations exist between the modal mineralogy and (Fig. 1), Engel & Engel (1962a) and Engel et al (1964) noted the appearance and increase of both clino-and the temperatures of equilibration. orthopyroxene at the expense of hornblende, increases in the amount of ilmenite and plagioclase (and its THE HPCQ GEOTHERMOMETER anorthite content), and decreases in (and disappearance of ) titanite and quartz.…”

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confidence: 99%

“…First, there is a surprising lack of change in Si and Al content and little variation study. When the Al isopleths of hornblende are calculated for reaction (1) using the TWQ software, in the atomic ratio Mg/(Mg+Fe) (=Mg#) in the hornblende (Engel et al, 1961;Engel & Engel, 1962b; they exhibit a fairly strong temperature dependence, with a dP/dT slope of about 22 bar K−1, making Engel et al, 1964) considering the temperature range involved ( Fig. 2a).…”

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confidence: 99%

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Hornblende geothermometry of amphibolite layers of the Popple Hill gneiss, north‐west Adirondack Lowlands, New York, USA

Liogys

Jenkins

2000

Journal Metamorphic Geology

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The exchange reaction tschermakite+2 diopside+2 quartz=tremolite+2 anorthite (HPCQ), in combination with the thermodynamic database TWQ (version 1.02, Berman, 1991), has been evaluated for its usefulness as a geothermometer. This reaction, which is both water conserving (independent of water fugacity) and which does not require the presence of garnet, is well suited for studying pyroxene‐bearing amphibolites. As an application of this geothermometer, we have re‐examined the amphibolites occurring in the Popple Hill gneiss of the Adirondack Lowlands of New York, USA, to better understand the magnitude of temperature variation preserved in the amphibolites themselves in this classic locality. At an assumed constant pressure of 7 kbar, the temperatures range from 619 to 682 °C from Edwards to Pierrepont and are uncorrelated with either distance along the strike of the region or with modal mineralogical variations. Hornblende exhibits a narrow compositional range suggesting that there has been little or no thermal gradient along the strike of the Lowlands. Temperatures recorded just north of Colton are, however, distinctly higher (694–758 °C). Although it is likely that the Popple Hill gneiss amphibolites experienced some effects of progressive metamorphism, particularly in the vicinity of Colton, the variations in modal mineralogy are most likely the result of such factors as local variations in the bulk chemistry of the protolith and in the fugacity of H2O due to infiltration of diluting species (e.g. CO2, CH4), rather than a regional temperature variation. Temperatures recorded by the HPCQ geothermometer reported here are similar in magnitude and geographic trend to those reported for graphite–calcite carbon‐isotope thermometry by Kitchen & Valley (1995), suggesting that peak metamorphism in the Adirondack Lowlands involved laterally extensive and fairly uniform isotherms.

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Mineralogy of Amphibolite Interlayers in the Gneiss Complex, Northwest Adirondack Mountains, New York

Cited by 38 publications

References 19 publications

Infiltration‐driven dehydration and anatexis in granulite facies metagabbro, Grenville Province, Ontario, Canada

Infiltration‐driven dehydration and anatexis in granulite facies metagabbro, Grenville Province, Ontario, Canada

On Plagioclases in Metamorphic Rocks from Lützow-Holmbukta Area, East Antarctica

Hornblende geothermometry of amphibolite layers of the Popple Hill gneiss, north‐west Adirondack Lowlands, New York, USA

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