Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by Gifkins, C. C. Articles by Allen, R. L. Search for Related Content GeoRef GeoRef Citation

Textural and Chemical Characteristics of Diagenetic and Hydrothermal Alteration in Glassy Volcanic Rocks: Examples from the Mount Read Volcanics, Tasmania

Cathryn C. Gifkins

Centre for Ore Deposit Research, University of Tasmania, GPO Box 252-79, Hobart, Tasmania, Australia 7001

Rodney L. Allen

Volcanic Resources Ltd., Guldgatan 11, 93632, Boliden, Sweden

Corresponding author: email,cgifkins{at}utas.edu.au

The Mount Black and Sterling Valley Volcanics comprise a complex Cambrian succession of originally glassy, felsic to mafic, submarine volcanic facies in western Tasmania. The Mount Black and Sterling Valley Volcanics have been modified by the combined effects of diagenesis, hydrothermal alteration, and regional metamorphism. Metamorphosed diagenetic and hydrothermal alteration facies have been distinguished, using a combination of alteration mineralogy, overprinting relationships, texture, distribution, intensity, and whole-rock geochemistry.

Alteration facies that are interpreted to be the regionally metamorphosed equivalents of diagenetic clays and zeolites are regionally extensive and overprinted by the regional cleavage. Although widespread, their distribution is patchy and their intensities are highly variable, reflecting the complexity of the original textures in glassy volcanic rocks. Thin films of sericite, carbonate, and chlorite-sericite-hematite replace clays that coated original glassy surfaces at the onset of diagenesis, prior to compaction. Feldspar-quartz-sericite, chlorite-sericite, and chlorite-sericite-hematite alteration facies replace zeolites and clays that filled pore space and altered glass, prior to and synchronous with compaction. The final diagenetic alteration facies, chlorite-epidote, began after compaction and continued during metamorphism. Diagenetic alteration involved significant mineralogical and textural changes but only minor changes in chemistry. The chemical changes associated with diagenetic alteration facies are consistent with the interaction of rhyolitic and basaltic glass with seawater during burial.

Alteration facies that are interpreted to be hydrothermal are local in distribution, crosscut stratigraphic boundaries, and involve significant changes in texture, mineralogy, and composition. Early hydrothermal alteration facies (quartz-sericite and calcite-quartz-hematite) predated compaction and were synchronous with diagenesis. Chlorite-calcite-magnetite and chlorite-pyrite alteration facies were synchronous with regional deformation and are associated with tectonic breccias, faults, and shear zones. Chlorite-quartz-calcite alteration facies postdated regional deformation.

This article has been cited by other articles:

				P. Mercier-Langevin, B. Dube, M. D. Hannington, D. W. Davis, B. Lafrance, and G. Gosselin The LaRonde Penna Au-Rich Volcanogenic Massive Sulfide Deposit, Abitibi Greenstone Belt, Quebec: Part I. Geology and Geochronology Economic Geology, June 1, 2007; 102(4): 585 - 609. [Abstract] [Full Text] [PDF]

				G. Giorgetti, T. Monecke, R. Kleeberg, and M. D. Hannington LOW-TEMPERATURE HYDROTHERMAL ALTERATION OF SILICIC GLASS AT THE PACMANUS HYDROTHERMAL VENT FIELD, MANUS BASIN: AN XRD, SEM AND AEM-TEM STUDY Clays and Clay Minerals, April 1, 2006; 54(2): 240 - 251. [Abstract] [Full Text] [PDF]

				R. R. Large, R. R. Large, J. McPhie, J. B. Gemmell, W. Herrmann, and G. J. Davidson The Spectrum of Ore Deposit Types, Volcanic Environments, Alteration Halos, and Related Exploration Vectors in Submarine Volcanic Successions: Some Examples from Australia Economic Geology, August 1, 2001; 96(5): 913 - 938. [Abstract] [Full Text] [PDF]

				W. Herrmann, W. Herrmann, M. Blake, M. Doyle, D. Huston, J. Kamprad, N. Merry, and S. Pontual Short Wavelength Infrared (SWIR) Spectral Analysis of Hydrothermal Alteration Zones Associated with Base Metal Sulfide Deposits at Rosebery and Western Tharsis, Tasmania, and Highway-Reward, Queensland Economic Geology, August 1, 2001; 96(5): 939 - 955. [Abstract] [Full Text] [PDF]

				R. R. Large, R. R. Large, J. B. Gemmell, H. Paulick, and D. L. Huston The Alteration Box Plot: A Simple Approach to Understanding the Relationship between Alteration Mineralogy and Lithogeochemistry Associated with Volcanic-Hosted Massive Sulfide Deposits Economic Geology, August 1, 2001; 96(5): 957 - 971. [Abstract] [Full Text] [PDF]

				R. R. Large, R. R. Large, R. L. Allen, M. D. Blake, and W. Herrmann Hydrothermal Alteration and Volatile Element Halos for the Rosebery K Lens Volcanic-Hosted Massive Sulfide Deposit, Western Tasmania Economic Geology, August 1, 2001; 96(5): 1055 - 1072. [Abstract] [Full Text] [PDF]

				M. G. Doyle and M. G. Doyle Volcanic Influences on Hydrothermal and Diagenetic Alteration: Evidence from Highway-Reward, Mount Windsor Subprovince, Australia Economic Geology, August 1, 2001; 96(5): 1133 - 1148. [Abstract] [Full Text] [PDF]