Back-transformation processes in high-pressure minerals: implications for planetary collisions and diamond transportation from the deep Earth

Progress in Earth and Planetary Science

Table 2 P–T–t conditions and estimated values of kinetic parameters for the back-transformation in bridgmanite

Run No.	Pressure (GPa)	Temperature (°C)	Duration (s)	Phase¹	n	ln k	ln k for the averaged n value²
OEn formation from amorphous bridgmanite
M2718	1.0	330	410	Brg
	1.1	615	620	Complete amo
	1.1	765	1655	OEn	2.02	− 13.9	− 13.1 (0.07)
M2619	1.3	310	290	Brg
	1.2	410	410	Partial amo
	1.2	510	700	Partial amo
	1.2	615	1560	Complete amo
M2621	1.4	310	265	Brg
	1.3	410	425	Partial amo
	1.4	510	375	Partial amo
	1.3	615	450	Complete amo
	1.2	820	485	OEn	1.89	− 5.90	− 5.76 (0.22)
backtra11	1.5	310	560	Brg
	1.5	510	2050	Partial amo
	1.5	715	1620	Complete amo			− 18.4^#
backtra12	1.8	310	510	Brg
	1.6	410	460	Brg
	1.7	510	470	Partial amo
	1.6	615	1250	Partial amo
	1.6	715	1400	Complete amo
	1.6	820	720	OEn	No kinetic data obtained
	1.4	920	840	OEn
M2618	4.2	410	130	Brg
	4.1	510	460	Brg
	4.0	615	305	Brg
	4.2	720	465	Partial amo
	3.9	820	30	Complete amo
	4.0	820	690	OEn	1.79	− 9.10	− 9.61 (0.08)
Bridgmanite to HP-CEn transformation
M2613	7.7	410	440	Brg
	7.8	514	485	Brg
	8.0	617	420	Brg
	7.9	720	265	Brg
M2715	7.8	515	1165	Brg
	8.1	620	1560	Brg
	7.9	820	2515	HP CEn	0.40	− 2.18

¹Brg, bridgmanite; amo, amorphization; OEn, orthoenstatite; HP CEn, high-P clinoenstatite
²The uncertainties in rate constant are listed in parentheses
^#The maximum k value was estimated (see text)