Coupled mineral-fluid evolution of a basin and high: kaolinization in the SW England granites in relation to the development of the Plymouth Basin

Abstract 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.

[1]  S. Burley,et al.  The nature and significance of illite associated with quartz- hematite hydrothermal veins in the St. Austell pluton, Cornwall, England , 2001, Clay Minerals.

[2]  F. Stuart,et al.  The origin and evolution of base metal mineralising brines and hydrothermal fluids, South Cornwall, UK , 2001 .

[3]  S. Gleeson,et al.  Post‐magmatic hydrothermal circulation and the origin of base metal mineralization, Cornwall, UK , 2000, Journal of the Geological Society.

[4]  D. Manning,et al.  Geological controls on kaolin particle shape and consequences for mineral processing , 1999, Clay Minerals.

[5]  D. Manning,et al.  Geochemical constraints on kaolinization in the St Austell Granite, Cornwall, England , 1998, Journal of the Geological Society.

[6]  D. C. Bain,et al.  Report of the Association Internationale Pour L’étude Des Argiles (Aipea) Nomenclature Committee for 1996 , 1997 .

[7]  D. Manning,et al.  Primary lithological variation in the kaolinized St Austell Granite, Cornwall, England , 1996, Journal of the Geological Society.

[8]  J. Willis-Richards,et al.  Geochronological evidence for post-Variscan cooling and uplift of the Carnmenellis granite, SW England , 1996, Journal of the Geological Society.

[9]  H. Gilg,et al.  Stable Isotope Geochemistry of Clay Minerals , 1996, Clay Minerals.

[10]  A. Psyrillos.  Low-temperature hydrothermal mineralisation in the St.Austell Pluton, Cornwall, England. , 1996 .

[11]  E. Chatzitheodoridis,et al.  Precision and reproducibility of in situ oxygen isotope ratio measurements on quartz obtained using an Isolab 54 ion microprobe , 1995 .

[12]  C. Onasch,et al.  Disequilibrium partitioning of oxygen isotopes associated with sector zoning in quartz , 1995 .

[13]  K. Magara.  North sea formation waters atlas , 1995 .

[14]  T. Gałkiewicz.  Geofluids: Origin, Migration and Evolution of Fluids in Sedimentary Basins , 1995 .

[15]  K. McClay,et al.  3D analysis of inverted extensional fault systems, southern Bristol Channel basin, UK , 1995, Geological Society, London, Special Publications.

[16]  A. Ruffell.  Evolution and hydrocarbon prospectivity of the Brittany Basin (Western Approaches Trough), offshore north-west France , 1995 .

[17]  I. Lyon,et al.  High-precision, in situ oxygen isotope ratio measurements obtained from geological and extra-terrestrial materials using an Isolab 54 ion microprobe , 1995 .

[18]  I. Lyon,et al.  Isotopic fractionation in secondary ionization mass spectrometry , 1994 .

[19]  R. Scrivener,et al.  Timing and significance of crosscourse mineralization in SW England , 1994, Journal of the Geological Society.

[20]  C. Smalley,et al.  Part 4: Compositional variations of North Sea formation waters , 1994, Geological Society, London, Memoirs.

[21]  Richard H. Sibson,et al.  Crustal stress, faulting and fluid flow , 1994, Geological Society, London, Special Publications.

[22]  C. Rochelle,et al.  Fluid-rock interactions during continental red bed diagenesis: implications for theoretical models of mineralization in sedimentary basins , 1994, Geological Society, London, Special Publications.

[23]  R. Goldstein,et al.  Systematics of fluid inclusions in diagenetic minerals , 1994 .

[24]  A. R. Fraser,et al.  Depth-Dependent Transformation of Kaolinite to Dickite In Sandstones of the Norwegian Continental Shelf , 1993, Clay Minerals.

[25]  H. Murray,et al.  Kaolin Genesis and Utilization , 1993 .

[26]  L. Snee,et al.  Thermochronology of the Cornubian batholith in southwest England: Implications for pluton emplacement and protracted hydrothermal mineralization , 1993 .

[27]  C. M. Bristow.  The Genesis of the China Clays of South-West England - A Multistage Story , 1993 .

[28]  J. Macquaker,et al.  Authigenic Clays Diagenetic Sequences and Conceptual Diagenetic Models in Contrasting Basin-Margin and Basin-Center North Sea Jurassic Sandstones and Mudstones , 1992 .

[29]  R. Gayer,et al.  THE PORTLEDGE-PEPPERCOMBE PERMIAN OUTLIER , 1992 .

[30]  S. Fortier,et al.  Volume self-diffusion of oxygen in biotite, muscovite, and phlogopite micas , 1991 .

[31]  Uk Cornwall,et al.  Hot dry rock , 1990 .

[32]  R. Hillis,et al.  The geology of the western English Channel and its western approaches , 1990 .

[33]  D. Manning,et al.  Evolution of the Cornubian ore field, Southwest England; Part II, Mineral deposits and ore-forming processes , 1989 .

[34]  S. Burley,et al.  Timing diagenesis in the Tartan Reservoir (UK North Sea): constraints from combined cathodoluminescence microscopy and fluid inclusion studies , 1989 .

[35]  N. Harris.  Diagenetic quartzarenite and destruction of secondary porosity: An example from the Middle Jurassic Brent sandstone of northwest Europe , 1989 .

[36]  P. Aagaard,et al.  Origin and evolution of formation waters from oil fields on the Norwegian shelf , 1989 .

[37]  S. Thompson,et al.  Notes and cross-sections illustrating inversion tectonics in the Wessex Basin , 1989, Geological Society, London, Special Publications.

[38]  D. Roberts,et al.  Basin inversion in and around the British Isles , 1989, Geological Society, London, Special Publications.

[39]  A. Thomas-Betts,et al.  Models of convective fluid flow and mineralization in south-west England , 1988, Journal of the Geological Society.

[40]  J. Sutter,et al.  Thermochronology of economic mineral deposits; dating the stages of mineralization at Panasqueira, Portugal, by high-precision 40 / 39 Ar age spectrum techniques on muscovite , 1988 .

[41]  A. Thomas-Betts,et al.  3-D numerical modelling of the conductive heat flow of SW England , 1988 .

[42]  R. P. Foster.  Fluid inclusion studies , 1988, Journal of the Geological Society.

[43]  R. Hillis.  The geology and tectonic evolution of the Western Approaches Trough , 1988 .

[44]  R. Scrivener,et al.  Role of basinal brines in the genesis of polymetallic vein deposits, Kit Hill-Gunnislake area, SW England , 1987 .

[45]  John G. Ramsay,et al.  The techniques of modern structural geology , 1987 .

[46]  J. Ramsay,et al.  Folds and fractures , 1987 .

[47]  H. Ohmoto,et al.  Chapter 2. KINETICS of ISOTOPIC EXCHANGE at ELEVATED TEMPERATURES and PRESSURES , 1986 .

[48]  M. Warner,et al.  Deep seismic reflection profiling between England, France and Ireland , 1986, Journal of the Geological Society.

[49]  D. Cole,et al.  Kinetics of isotopic exchange at elevated temperatures and pressures , 1986 .

[50]  T. Shepherd,et al.  A Practical Guide to Fluid Inclusion Studies , 1985 .

[51]  M. Steckler.  Uplift and extension at the Gulf of Suez: indications of induced mantle convection , 1985, Nature.

[52]  Grant Garven,et al.  The role of regional fluid flow in the genesis of the Pine Point Deposit, Western Canada sedimentary basin , 1985 .

[53]  H. Eugster.  Oil shales, evaporites and ore deposits , 1985 .

[54]  J. Andrews,et al.  The evolution of saline and thermal groundwaters in the Carnmenellis granite , 1984, Mineralogical Magazine.

[55]  T. J. Reynolds,et al.  Preparing Doubly Polished Sections of Temperature Sensitive Sedimentary Rocks: RESEARCH METHOD PAPER , 1984 .

[56]  James R. Cochran,et al.  Effects of finite rifting times on the development of sedimentary basins , 1983 .

[57]  C. J. Bray,et al.  Sheeted vein Sn-W mineralization and greisenization associated with economic kaolinization, Goonbarrow china clay pit, St. Austell, Cornwall, England; geologic relationships and geochronology , 1983 .

[58]  A. Whiteman,et al.  Geological atlas of western and central Europe , 1983 .

[59]  L. Cathles,et al.  Thermal constraints on the formation of mississippi valley-type lead-zinc deposits and their implications for episodic basin dewatering and deposit genesis , 1983 .

[60]  A. Rankin,et al.  The character and evolution of hydrothermal fluids associated with the kaolinized St. Austell granite, SW England , 1983, Journal of the Geological Society.

[61]  M. Crawford,et al.  Fluid inclusions : applications to petrology : a short course sponsored by the Mineralogical Association of Canada and held immediately prior to the 1981 annual meeting in Calgary, Alberta, May 7th-10th , 1983 .

[62]  T. Harrison,et al.  Investigations of an intrusive contact, northwest Nelson, New Zealand—I. Thermal, chronological and isotopic constraints , 1980 .

[63]  V. Guinn.  Principles of Isotope Geology , 1978 .

[64]  M. Clynne,et al.  Freezing point depression of aqueous sodium chloride solutions , 1978 .

[65]  J. M. Moore,et al.  Fluid inclusions and mineralization at Cligga Head, Cornwall, England , 1977, Journal of the Geological Society.

[66]  S. Sheppard.  The Cornubian batholith, SW England: D/H and 18O/16O studies of kaolinite and other alteration minerals , 1977, Journal of the Geological Society.

[67]  S. Epstein,et al.  Hydrogen isotope fractionation between OH-bearing minerals and water , 1976 .

[68]  C. S. Exley.  Observations on the formation of kaolinite in the St. Austell granite, Cornwall , 1976, Clay Minerals.

[69]  Y. Kharaka,et al.  Hydrogen and oxygen isotope exchange reactions between clay minerals and water , 1976 .

[70]  H. Taylor.  The Application of Oxygen and Hydrogen Isotope Studies to Problems of Hydrothermal Alteration and Ore Deposition , 1974 .

[71]  S. Epstein,et al.  The oxygen and hydrogen isotope geochemistry of clay minerals , 1970 .

[72]  P. A. Ziegler,et al.  Geological atlas of Western and Central Europe , 1969 .

[73]  R. Clayton,et al.  The use of bromine pentafluoride in the extraction of oxygen from oxides and silicates for isotopic analysis , 1963 .

[74]  H. Craig.  Isotopic Variations in Meteoric Waters , 1961, Science.

[75]  C. S. Exley.  MAGMATIC DIFFERENTIATION AND ALTERATION IN THE ST. AUSTELL GRANITE , 1958, Quarterly Journal of the Geological Society of London.

[76]  J. Bigeleisen,et al.  Conversion of Hydrogenic Materials to Hydrogen for Isotopic Analysis , 1952 .

[77]  N. Pounds.  The China Clay Industry of Southwest England , 1952 .

[78]  A. W. Groves.  The Unroofing of the Dartmoor Granite and the Distribution of its Detritus in the Sediments of Southern England , 1931, Quarterly Journal of the Geological Society of London.

[79]  J. Collins.  Note on some Geological Features observable at the Carpalla China-Clay Pit in the Parish of St. Stephen's, Cornwall , 1909, Quarterly Journal of the Geological Society of London.