Journal ArticleDOI
Hydrothermal alteration of late‐ to post‐tectonic Lyon Mountain Granitic Gneiss, Adirondack Mountains, New York: Origin of quartz–sillimanite segregations, quartz–albite lithologies, and associated Kiruna‐type low‐Ti Fe‐oxide deposits
TLDR
In this article, it was shown that quartz-sillimanite veins and nodules were most likely formed from local magmatic fluids in the crystallizing carapaces of Lyon Mountain Gneiss plutons.Abstract:
Quartz–sillimanite segregations, quartz–albite lithologies (Ab95–98), and Kiruna-type low-Ti iron-oxide deposits are associated with late- to post-tectonic (c. 1055 Ma) leucogranites of Lyon Mountain Gneiss (LMG) in the Adirondack Mountains, New York State. Most recent interpretations of these controversial features, which are global in occurrence, favour hydrothermal origins in agreement with results presented here.
Field relations document that quartz–sillimanite veins and nodules cut, and therefore post-date, emplacement of host LMG leucogranites. Veins occur in oriented fracture networks, and aligned trains of nodules are interpreted as disrupted early veins. Late dykes of leucogranite cut veins and nodules demonstrating formation prior to terminal magmatism. Veins and nodules consist of sillimanite surrounded by quartz that commonly embays wall-rock feldspar indicating leaching of Na and K from LMG feldspar by acidic hydrothermal fluids. Subsequent, and repeated, ductile flow disrupted earlier veins into nodular fragments but produced little grain shape fabric.
Geochemical and petrographic studies of quartz–albite rock indicate that it formed through metasomatic replacement (albitization) of LMG microperthite by sodic hydrothermal fluids that resulted in diagnostic checkerboard albite. Low-Ti iron-oxide ores are commonly associated with the quartz–albite sub-unit, and it is proposed that hydrothermal fluids related to albitization transported Fe as well. The regional extent of sodic alteration suggests large quantities of surface-derived hydrothermal fluids. Fluid inclusion and oxygen isotope data are consistent with high temperature, regionally extensive fluids consisting primarily of evolved surface-derived brines enriched in Na and Cl. Quartz–sillimanite veins and nodules, which are significantly more localised phenomena and require acidic fluids, were most likely formed from local magmatic fluids in the crystallizing carapaces of LMG plutons.read more
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References
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Book ChapterDOI
ORIGIN OF GRANITE IN THE LIGHT OF EXPERIMENTAL STUDIES IN THE SYSTEM NaAlSi3O8–KAlSi3O8–SiO2–H2O
O. F. Tuttle,N. L. Bowen +1 more
Journal ArticleDOI
A laser-based microanalytical method for the in situ determination of oxygen isotope ratios of silicates and oxides
TL;DR: In this paper, a new laser-based microanalytical method for oxygen isotope determinations of silicates and oxides has been developed whereby analyses are made on <100 μg samples or of in situ spot determinations.
Journal ArticleDOI
Oxygen isotopic fractionation in the system quartz-albite-anorthite-water
TL;DR: Oxygen isotopic fractionations have been determined between quartz and water, albite and water and anorthite and water at temperatures from 300 to 825°C, and pressures from 15 to 25 kbar as mentioned in this paper.
Journal ArticleDOI
Multiple zircon growth and recrystallization during polyphase Late Carboniferous to Triassic metamorphism in granulites of the Ivrea Zone (Southern Alps): an ion microprobe (SHRIMP) study
TL;DR: In this paper, a metasedimentary and a meta-igneous quartz-feldspar granulite from the Val Sesia and Val Mastallone area of the Ivrea Zone (Southern Alps) are compared with respect to crystal morphology and U/Pb ages.
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