Exploration for Soapstone Occurrences: Use of Bulk Chemical Analyses to Select Potential Formation Areas

Abstract:

Soapstone is a talc and carbonate containing metamorphic ultramafic rock commonly found in greenschist-amphibolite facies greenstone belts. The regional metamorphism and shear zones as pathways for CO2 containing water fluids are interpreted to have been essential to the formation of soapstone. In spite of the supposed uniform metamorphic conditions favourable to talc-carbonate soapstone, also unaltered serpentinites are usually found in the same location areas and deposits. The objective of this study is to define the bulk chemical response of ultramafic rocks to form soapstone in hydration-carbonation metamorphic processes. Thermodynamic calculations and pseudosection modelling indicate that soapstone is most likely to occur in high silica low magnesium ultramafic sequences, because they turn to talc-carbonate even with very low CO2 content of metamorphic fluids. This is a new approach to classify and locate potential deposit areas in soapstone exploration.

• Periodical: Key Engineering Materials (Volume 548)
• Pages: 10-19
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.548.10
• Online since: April 2013
• Authors: Seppo Leinonen
• Keywords: Exploration, Metamorphism, Soapstone, Thermodynamic Modelling, Ultramafic Rocks

References

[1] A. Kärki, S. Leinonen and J. Uusitalo: Soapstones - how should they be defined, Abstract presented at 33rd International Geological Congress, Oslo (2008).

[2] C. de Capitani: THERIAK-DOMINO User's Guide, Version 1402005; http://titan. minpet. unibas.ch/minpet/theriak/theruser.html (04/2007).

[3] C. de Capitani and K. Petrakakis: The computation of equilibrium assemblage diagrams with Theriak/Domino software, American Mineralogist 95 (2010) pp.1006-1016.

DOI: 10.2138/am.2010.3354

[4] H. Papunen, T. Halkoaho and E. Luukkonen: Archaean evolution of the Tipasjärvi - Kuhmo - Suomussalmi Greenstone Complex, Finland, Geological Survey of Finland, Bulletin 403 (2009) p.68.

DOI: 10.1016/j.precamres.2012.12.004

[5] A. Kontinen: An Early Proterozoic Ophiolite - The Jormua Mafic - Ultramafic Complex, Northeastern Finland, Precambrian Research 35 (1987) pp.313-341.

DOI: 10.1016/0301-9268(87)90061-1

[6] J. Säntti, A. Kontinen, P. Sorjonen-Ward, B. Johanson and L. Pakkanen: Metamorphism and Chromite in Serpentinized and Carbonate - Silica - Altered Peridotites of the Paleoproterozoic Outokumpu - Jormua Ophiolite Belt, eastern Finland, International Geology Review, Volume 48, Issue 6 (2006) pp.494-546.

DOI: 10.2747/0020-6814.48.6.494