![]() ![]() Here we report lingunite and amorphous labradorite (maskelynite) formed probably due to concentration of shock induced T in shocked doleritic basement rocks at the Lockne impact structure, Sweden. To our knowledge, transformation of plagioclase into high pressure polymorphs, due to reverberations of shock-wave at heterogeneous mineral interfaces has not been reported so far. It is noteworthy that, even though there are 188 confirmed impact structures on Earth 18, many with feldspar bearing target rocks, there is only one short report on silicate-hollandite in a target rock of the Manicougan impact structure 19. Transformation of plagioclase into lingunite is accompanied by amorphization of the plagioclase 17. In particular, lingunite, a high P-T polymorphs of sodic plagioclase has been observed in stony meteorites 9, 10, 11, 12, 13 or synthesized in anvil cells by compressing sub-millimeter sized material 14, 15, 16. The high pressure-temperature (P-T) phase transitions in plagioclase are especially sensitive to monitor shock-induced phase transitions in stony meteorites, which resemble in their composition to terrestrial mafic rocks. Theoretical studies suggest that the propagation of shock waves across heterogeneous interfaces, such as the interface of different minerals with impedance contrast, may lead to longer duration of the same pressure and higher magnitude of temperature, thus, promoting the kinetics of nucleation of the high-pressure polymorph 6, 7, 8. For instance, extreme shock deformations conserved in meteorite impacts can be uncovered through identification of high-pressure polymorph transformations and microstructures such as, the shock-induced graphite-diamond phase transition in gneiss from the Ries Crater, Germany 6. In situ shock localization can be determined, on a large scale by seismic investigations 1, 2, 3, and at the micrometer scale by using petrological imprints in minerals and rocks 4, 5, 6. Shock localization is an important issue in many geoscientific fields.
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