Discussion: Comments on -Basalt columns: Large scale constitutional supercooling by John Gilman JVGR, 2009 and presentation of some new data J. Volcanol. Geotherm. Res. 184 2009, 347–350Report as inadecuate




Discussion: Comments on -Basalt columns: Large scale constitutional supercooling by John Gilman JVGR, 2009 and presentation of some new data J. Volcanol. Geotherm. Res. 184 2009, 347–350 - Download this document for free, or read online. Document in PDF available to download.

1 GENERIC-ENSMSE - Département Géochimie, environnement, écoulement, réacteurs industriels et cristallisation 2 LMV-ENSMSE - Laboratoire Magma et Volcan 3 SPIN-ENSMSE - Centre Sciences des Processus Industriels et Naturels

Abstract : Some comments are offered on the paper by John J. Gilman J. Volc. Geoth. Res., 184, 2009, 347–350, proposing that large scale constitutional supercooling may explain the formation of basalt columns. This hypothesis was presented twenty years ago Guy, B. and Le Coze, J., C. R. Acad. Sc. Paris, 311, II, 1990, 943–949. However, in contrast to what is postulated by Gilman, I proposed that the chemical variations that may optionally show in the prisms do not relate to the major elements Al, Si,

. but rather to H2O and other volatiles. Thermal contraction, which is the more generally accepted hypothesis, also plays a role, particularly in the central -entablature- of the flows. The fingers formed by constitutional supercooling show instead in the colonnades. Original observations are presented that support the hypothesis of supercooling, in particular the existence of circular and radiating structures within the columns, that cannot be explained by meteoric weathering nor by the influence of the fractures delimiting the prisms. Various directions for research are proposed.

Keywords : basalt columnar jointing constitutional supercooling thermal contraction circular structures





Author: Bernard Guy -

Source: https://hal.archives-ouvertes.fr/



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