Relationships Between Shock and Fluid Processes

Steer, Elisabeth; Schwenzer, Susanne; Wright, Ian and Grady, Monica (2015). Relationships Between Shock and Fluid Processes. In: National Astronomical Meeting 2015, 5-9 Jul 2015, Llandudno, Wales.



High shock pressure in rocks occurs across the solar system, with impacts into planetary bodies having been frequent features of the past and still occurring today, e.g., as seen in meteorite falls on Earth. The shock pressures that rocks undergo create unique physical characteristics in the targets and in the impactors. Creation of shock melt pockets, destruction of original porosity and restructuring of minerals can occur. The change of physical properties in the rocks affects later processes like fluid alteration. This study looks at shock created features in L6 chondrites and relates the features to fluid driven alteration processes in Antarctica.

Several shock features in samples in this study have been found to be directly altering weathering patterns. The shock feature with the most pronounced effect on alteration processes is the creation of polymineralic melt veins, which are more weatherable and so make pathways for alteration fluids. Also seen is a reconstruction of sulphides to create polycrystalline structures with many planes of weakness, more easily exploited by fluids, which then have greater access to the minerals to alter the sulphides. A mixture of metals and sulphides is created in some of the samples where a “fizz” mixture has been formed. The addition of planes of weakness, differential behaviour in rapidly changing temperatures and differences in weatherability have created concentrated weathering centres which affect the system around.

These processes should be common in other solar system bodies with similar targets and shock features, if water was present on those bodies.

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