Shock-Induced Incongruent Melting of Olivine in Kamargaon L6 Chondrite

In this study, we report for the first-time shock-induced incongruent melting of olivine in an ordinary chondrite. Several olivine grains (Fo(74)), entrained in the shock-melt vein of the Kamargaon L6 chondrite, were dissociated into magnesiowustite (X-Fe = 0.71) and orthoenstatite (X-Fe = 0.22). We propose that the breakdown of olivine took place as a result of incongruent melting to produce magnesiowustite and Mg-rich liquid. We suggest that bridgmanite may have crystallized as the second phase from the olivine melt which back-transformed to a low-pressure phase of orthoenstatite from subsequent high-temperature and low-pressure events. In this case, olivine grains may have experienced pressure and temperature of similar to 25 GPa and similar to 2500 degrees C, respectively. Our results suggest that the incongruent melting of olivine may possibly operate as one of the alternative mechanisms of dissociation reaction driving the phase transformation of olivine in the natural systems.