Interaction of rock and atmosphere: patinas on Mediterranean monuments |
| |
Authors: | M Garcia-Vallès M Vendrell-Saz J Molera F Blazquez |
| |
Institution: | (1) Dept. Cristal.lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona. c/Martí Franquès s/n, E-08028 Barcelona, Spain Tel.: +34 93 402 1342 · Fax: +34 93 402 1340, ES |
| |
Abstract: | This paper analyzes – chemically, mineralogically, and petrolographically – the patinas developed on several Mediterranean
monuments made with different stones (siliceous and carbonatic) in order to establish their origin and their evolution under
the present environmental conditions, and to evaluate the environmental parameters controling their development. Most of the
patinas show a common sequence of layers, which, from the outer to the inner zone, are: (1) present bioactivity and/or biological
remains, (2) gypsum-rich patina, and (3) calcitic brown to orange patina. Each one may exhibit different fabrics (from micritic
to stromatolitic) and may be more or less continuous and homogeneous. The main mineral components are calcite and gypsum,
but Ca-oxalates and Ca-phosphates have also been found associated to biological structures, as well as quartz and clays. The
different fabrics and textures have been interpreted as consequence of changes in the environmental conditions which seem
to be related to the biological activity, facilitating the growth of different organisms and leading to the development of
a deposit with distinct characteristics (fabric, texture, porosity, etc.). The gypsum-rich patina has been interpreted as
a sulphation of the underlying calcitic layer by the action of atmospheric pollutants or as dry or wet deposition from the
atmospheric dust. The mineralogy and texture of the patina is independent of the nature of the underlying rock and only in
few cases a micritization process has been observed as interaction between patina and rock. Recently, the penetration of endolithic
microflora produced drillings and the development of a fissuration system parallel to the surface, and thus the detachment
of the crust from the rock and even flackening of the rock itself has been observed. Consequently, under the present climatic
conditions in the Mediterranean basin, erosion is a more active process than deposition, and the crusts and patinas show a
tendency to disappear from the surface of the monuments.
Received: 3 November 1996 · Accepted: 10 September 1997 |
| |
Keywords: | Patina Gypsum Calcite Oxalate Marble Granite Limestone Mediterranean Environment Climatic change |
本文献已被 SpringerLink 等数据库收录! |
|