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Lookup NU author(s): Professor David ManningORCiD
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A new genetic model is proposed for the formation of the St Austell kaolin deposits, incorporating geological, isotopic, paragenetic and microthermometric evidence from kaolin-quartz veins combined with a reconstruction of the thermal evolution of the Cornubian pluton during the Mesozoic. Fluid inclusions in quartz, paragenetically associated with kaolin, document that the kaolinization took place at temperatures between 50°C and 100°C, indicating that the kaolinization is a low-temperature hydrothermal event coincident with the oil generation window. Kaolinization occurred prior to the unroofing of the pluton, during the Late Jurassic to Early Cretaceous. The kaolinization is thus contemporary with the major Early Cretaceous uplift that affected the Cornubian massif as a consequence of rifting in the offshore Western Approaches. Geological, isotopic and geochemical considerations argue strongly against the involvement of unmodified meteoric waters in the kaolinization process. The most plausible fluid types for the kaolinization are either basinal brines expelled from Permo-Triassic sediments of the adjacent offshore Plymouth Basin, or highly evolved meteoric waters that circulated through the sediments enclosing the pluton. The kaolinization process converted large volumes of fractured granite to a porous quartz-kaolin rock matrix.
Author(s): Psyrillos A, Burley S, Manning DAC, Fallick A
Publication type: Article
Publication status: Published
Journal: Geological Society Special Publication
Year: 2003
Issue: 214
Pages: 175-195
Print publication date: 01/01/2003
ISSN (print): 0305-8719
ISSN (electronic):
Publisher: Geological Society Publishing House
URL: http://dx.doi.org/10.1144/GSL.SP.2003.214.01.11
DOI: 10.1144/GSL.SP.2003.214.01.11
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