The nature and significance of illite associated with quartz-hematite hydrothermal veins in the St. Austell Pluton, Cornwall, England

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doi: 10.1180/0009855013640011
Authors:Psyrillos, A.; Manning, D. A. C.; Burley, S. D.
Author Affiliations:Primary:
University of Manchester, Department of Earth Sciences, Manchester, United Kingdom
Volume Title:Clay Minerals
Source:Clay Minerals, 36(4), p.585-597. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0009-8558
Publication Date:2001
Note:In English. 31 refs.; illus., incl. 2 tables
Summary:Quartz-hematite veins in the St. Austell pluton feature an assemblage of authigenic kaolin, illite, chlorite and hematite. Similar assemblages occur in altered granites adjacent to the veins. Complex textures in the veins and altered granites show that kaolin was an initial precipitate from hydrothermal fluids that was subsequently replaced by illite, hematite and chlorite. The sequence of mineral precipitation reflects a kinetic control on crystal growth, with early non-equilibrium precipitation of kaolin from fluids with compositions appropriate for the equilibrium formation of illite. Hematite formed under relatively oxidizing conditions that subsequently became more reducing to permit the late precipitation of chlorite. Illite associated with the quartz-hematite veins differs texturally, mineralogically and chemically from the coarsely crystalline hydrothermal muscovite (sericite or gilbertite) associated with quartz-tourmaline veins and greisen. Quartzhematite veins are thus considered to record a distinct mineralization event that is not related to the early greisenization or the economic kaolinization.
Sections:Clay minerals
Subsections:Petrology; weathering; soils
Subjects:Authigenic minerals; Clastic sediments; Framework silicates; Hematite; Hydrothermal alteration; Illite; Kaolin; Metasomatism; Oxides; Quartz; Sediments; Sheet silicates; Silica minerals; Silicates; Cornwall England; England; Europe; Great Britain; United Kingdom; Western Europe; Saint Austell Pluton
Abstract Numbers:02M/3786
Record ID:2002044050
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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