Experimental Petrology of Lunar Material: the Nature of Mascons, Seas, and the Lunar Interior

Abstract

One-atmosphere melting data show that Apollo 11 samples are near cotectic. Melting relations at pressures up to 35 kilobars show that clinopyroxenite or amphibole peridotite are possible lunar interiors. Mascons cannot be eclogite; they may be ilmenite accumulate. Hot lunar surface material will boil off alkalis.

The composition and origin of the moon

“…Similarly, it should be depleted in Fe, K, Na, Rb, S and H-O. A Ca-Al rich interior has been dismissed by Wetherhill [16], Ringwood and Essene [9] and O'Hara et_al_ [53] because it was believed that the high pressure phases of Ca-Al rich compounds would lead to densities which would violate the lunar mean density and moment of inertia. Although this is true for some assemblages, such as the Apollo 11 basalts, it is not a general characteristic of all Ca-Al rich assemblages.…”

Obvious problems in lunar petrogenesis and new perspectives

“…On the basis of experimental petrology of the lunar samples, the senior author stressed the likely importance of volatilization during lunar lava emplacement (O'Hara et al, 1970a(O'Hara et al, , 1970bO'Hara, 1972) and suggested that the Moon may have been a volatile (including water)-rich planet body at least in its early history, but this likely probability has been disregarded because it is incompatible with the "dry Moon" assumption and the LMO hypothesis, which are widely accepted by the lunar community (e.g., Wood et al, 1970). B. Io, the innermost satellite of Jupiter, is similar in size and mass to the Moon.…”

“…Volatilization during lunar lava emplacement was proposed over 40 years ago (O'Hara et al, 1970a(O'Hara et al, , 1970bO'Hara, 1972O'Hara, , 2000, but the "dry moon" assumption accepted as a fact has led to the neglect of the significance of lunar magma volatilization until recently when water in lunar glasses and mineral crystals was actually measured (Saal et al, 2008;Liu et al, 2012;Hui et al, 2013).…”

“…It should be noted that the NVOTM compilation fails to address the issue of selective volatilization during eruption, despite being published: (1) 34 years after the proposal and experimental demonstration (O'Hara et al, 1970a(O'Hara et al, , 1970bO'Hara, 1972); (2) after vesicles were reported in abundance in mare basalts (e.g., Keszthelyi, 2008); (3) after glass beads in the soils were identifi ed as fi re-fountain (pyroclastic) deposits driven by gas of lunar internal origin; (4) 14 years after the glasses were demonstrated to display varying S, Na, and K abundances as a result of variable volatilization during eruption (Delano and McGuire ,1992); and (5) three years after thermodynamic calculations on the importance of selective volatilization during eruption (Schaeffer and Fegley, 2004).…”

“…Despite this, NVOTM indexes no references to water in the Moon. The effect of water on the melting relationships of lunar materials was explored in the early lunar program (O'Hara et al, 1970a(O'Hara et al, , 1970b in order to explain the phase equilibria. Neglect of the presence and effect of volatiles means that the "established" lunar petrogenesis model needs reconsideration.…”