Figure 6

Model of lunar OPGM dike emplacement (after Wilson and Head 2017). Circled numbers 1–6 refer to following: (1) Partial melt last equilibrates with residual mantle diapir at ~550 km, and dike propagation begins at contact of melt-rich zone with overlying mantle; (2) dike reaches ~78 km vertical for a 25 km (vertical) melt zone, then separates from the source and begins to move very rapidly upward; (3) depth of CO-rich gas formation is 7 km minimum, 50 km maximum, followed by continuous degassing of CO-rich gas with ascent; gas and foam collect at dike tip as it propagates; (4) ~7–15 vol% bubbles in magma at 0.5 km for closed system degassing, for initial C contents of 4 to 50 ppm; (5) Stage 3 degassing (H2O and SO2, S2, and H2S) begins with fragmentation (bead formation) at 0.5 km depth; (6) dike tip breaches surface releasing melt beads in hot suspension of >92 vol% gas. Modified after Wilson and Head (2003).

© De Gruyter