Impact-generated hydrothermal circulation and metasomatism of the rochechouart astrobleme: mineralogy and major and trace element distribution

The energy released during a hypervelocity impact on Earth can generate high temperatures in the target rock. There are currently 170 known impact structures worldwide, of which over one-third contain fossil hydrothermal systems [1]. Results from the analysis of these hydrothermal systems have many implications for the study of the origin of life on Earth and potential thereof on Mars. Hypervelocity impacts are also of particular economic interest as they may produce, expose or concentrate high commodity resources such as hydrocarbons, precious metals and ore minerals

Impact fracturing and aqueous alteration of the CM carbonaceous chondrites

Aqueous alteration of the CM carbonaceous chondrites has produced a suite of secondary minerals, and differences between meteorites in their abundance defines a progressive alteration sequence [e.g. 1, 2]. The means by which this water gained access to the original anhydrous constituents of the meteorites is the subject of considerable debate. Studies of rock texture, mineralogy and bulk chemical composition have concluded that solutions were generated by the melting of water ice in situ, and remained essentially static as a consequence very low intergranular permeabilities [e.g. 3, 4]. By contrast, results of oxygen isotope work and modelling have suggested that the fluids moved considerable distances within the parent body [5, 6]. Given the intergranular permeability of the CMs, an extensive fracture network would be required to support such flow. Clues to how the two very different models for aqueous alteration of the CMs can be reconciled have been recently provided by Rubin [7]. He recognised a good correlation between the magnitude of impact-induced compaction of CM meteorites and their degree of aqueous processing, with the more highly deformed meteorites being more altered. Here we have asked whether compaction was accompanied by the development of fracture networks that could have provided the conduits for aqueous solutions that mediated all or some of the alteration

Impact-generated hydrothermal circulation and metasomatism of the rochechouart astrobleme: mineralogy and major and trace element distribution

The energy released during a hypervelocity impact on Earth can generate high temperatures in the target rock. There are currently 170 known impact structures worldwide, of which over one-third contain fossil hydrothermal systems [1]. Results from the analysis of these hydrothermal systems have many implications for the study of the origin of life on Earth and potential thereof on Mars. Hypervelocity impacts are also of particular economic interest as they may produce, expose or concentrate high commodity resources such as hydrocarbons, precious metals and ore minerals

Impact fracturing and aqueous alteration of the CM carbonaceous chondrites

Aqueous alteration of the CM carbonaceous chondrites has produced a suite of secondary minerals, and differences between meteorites in their abundance defines a progressive alteration sequence [e.g. 1, 2]. The means by which this water gained access to the original anhydrous constituents of the meteorites is the subject of considerable debate. Studies of rock texture, mineralogy and bulk chemical composition have concluded that solutions were generated by the melting of water ice in situ, and remained essentially static as a consequence very low intergranular permeabilities [e.g. 3, 4]. By contrast, results of oxygen isotope work and modelling have suggested that the fluids moved considerable distances within the parent body [5, 6]. Given the intergranular permeability of the CMs, an extensive fracture network would be required to support such flow. Clues to how the two very different models for aqueous alteration of the CMs can be reconciled have been recently provided by Rubin [7]. He recognised a good correlation between the magnitude of impact-induced compaction of CM meteorites and their degree of aqueous processing, with the more highly deformed meteorites being more altered. Here we have asked whether compaction was accompanied by the development of fracture networks that could have provided the conduits for aqueous solutions that mediated all or some of the alteration