Abstract
Lingunite nanocrystals and amorphous plagioclase (maskelynite) are identified at the contacts between augite and labradorite wedge-shaped interfaces in the doleritic rocks of the Lockne impact structure in Sweden. The occurrence of lingunite suggests that the local pressure was above 19 GPa and the local temperature overwhelmed 1000 °C. These values are up to 10 times higher than previous values estimated numerically for bulk pressure and temperature. High shock-induced temperatures are manifested by maskelynite injections into microfractures in augite located next to the wedges. We discuss a possible model of shock heterogeneity at mineral interfaces, which may lead to longer duration of the same shock pressure and a concentration of high temperature thus triggering the kinetics of labradorite transformation into lingunite and maskelynite.
Highlights
Lingunite nanocrystals and amorphous plagioclase are identified at the contacts between augite and labradorite wedge-shaped interfaces in the doleritic rocks of the Lockne impact structure in Sweden
We discuss a possible model of shock heterogeneity at mineral interfaces, which may lead to longer duration of the same shock pressure and a concentration of high temperature triggering the kinetics of labradorite transformation into lingunite and maskelynite
Previous workers have studied this dolerite in extensive detail[46,47,48,49,50], and few reports have suggested that the dolerite experienced thrust related very low grade metamorphism[26,51]
Summary
Lingunite nanocrystals and amorphous plagioclase (maskelynite) are identified at the contacts between augite and labradorite wedge-shaped interfaces in the doleritic rocks of the Lockne impact structure in Sweden. We discuss a possible model of shock heterogeneity at mineral interfaces, which may lead to longer duration of the same shock pressure and a concentration of high temperature triggering the kinetics of labradorite transformation into lingunite and maskelynite. 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. This is one of the rare reports on high P-T phase transitions of plagioclase into lingunite at heterogeneous mineral interfaces in impactites. Fragments of this global event enhanced the meteorite flux on Earth for several orders of magnitude in the late solar system history[24,25]
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