Geophysiology of mineral deposits - a model for a biological driving force of global changes through Earth history |
| |
| Authors: | WE Krumbein H-J Schellnhuber |
| |
| Institution: | Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky Universität, PO Box 2503, D-2900 Oldenburg, Germany |
| |
| Abstract: | The upper mantle, crust, hydrosphere and atmosphere of Earth are kept in a geophysical, geochemical and thermodynamical state far from astrophysical and planetary equilibrium. The system oscillates around a quasi-stable centre following laws governing dissipative or dynamic systems. The energy and materials necessary for such global pseudo-equilibria are fed in, stored and released on a geological time-scale by (a) the energy and electron channelling processes of photosynthesis, respiration and fermentation, (b) biologically controlled accumulation of energy and matter into crustal reservoirs and much later (c) release of the latter from crust and upper mantle into surface-related geotectonical and geochemical cycles. Phototrophic and chemorganotrophic bacterial microorganisms of microbial mats, potential stromatolites or microbialites are capable of anoxygenic and oxygenic photosynthesis, of aerobic and anaerobic respiration and of organic and inorganic fermentation, i.e. disproportioning of energy-rich molecules. In this way large amounts of photosynthate are transformed on a global scale into hydrocarbons and sulphides (sulphate serving as electron acceptor for anaerobic respiration or fermentation). Inorganic reduced compounds produced by the same processes of photosynthesis followed by respiration and fermentation are stored as sulphides of iron, lead, zinc, silver, gold etc. All the aforementioned microbial processes can transfer energies and matter at a global scale. Thus disparities of the Earth's crust and mantle from the geochemical equilibrium may not be caused solely by internal temperature, radioactivity and gravity gradients, but increasingly by life processes. The biogenic formation of energy-rich compounds on a global scale delivers huge amounts of energy and electrons to the crust, which are recycled through geological time. The quantities of energy involved appear in themselves to be sufficient to provide the driving force for geotectonic processes. Thus, a model of geophysiological equilibration of geochemical cycles and geotectonics is proposed in which the biota play the role of energy and matter transmitters for geodynamic processes. Living matter controls and transfers more than 10% of the Earth's mass in this system with turnover times of up to 500 million years. The transfer speed of each individual atom according to the model must have gradually decreased since the Precambrian, while the amounts of energy and matter stored and cycled have in turn increased, as also witnessed by the increase in the thickness of the crust. Earth as a bioplanet has come of age. |
| |
| Keywords: | |
|
|
