Lunar sample 78235,100.
This rock is a norite that was strongly affected by shock metamorphism. The sample was collected by the Apollo 17 mission from the Taurus-Littrow Valley area, in a range of mountains between Mare Serenetatis and Mare Tranquillitatis. This rock has been dated at ~4.3 Ga.
Magnification key 20x = 8 mm image width 40x = 4 mm image width 100x = 1.6 mm image width 200x = 0.8 mm image width 400x = 0.4 mm image width 500x = 0.32 mm image width |
40X, plane polarized light.
This sample is of a coarse-grained norite, probably a cumulate, of the highland plutonic suite. It has undergone heavy shock metamorphism that has resulted in several shock features: impact melt veins quenched to glass, polygonized orthopyroxene, and plagioclase that has been partially converted to Maskelynite and, in some places, flow deformed. Here, highly fractured orthopyroxene is visible, as is plagioclase that has abundant exsolved oxide dust.
40X, cross polarized light.
The same field as above, but in cross polarized light much of the plagioclase is isotropic where it has been transformed to a disordered glassy state by intense shock. The plagioclase did not melt, but the crystal lattice was destroyed by the shock. Notice how the maskelynite occurs mostly in a network of fractures.
20X, plane polarized light.
An irregular fracture filled with impact melt. Bubbles occur in the glass, so presumably the glass was still liquid at low pressure after the shock wave passed.
20X, cross polarized light.
The glass in the vein is isotropic, and so is the maskelynite that is particularly abundant near the orthopyroxene grains around the margin.
40X, plane polarized light.
Another view of highly fractured orthopyroxene, plagioclase containing exsolved oxide dust, and an impact melt vein.
40X, cross polarized light.
The polygonized orthopyroxene (shattered with different domains rotated in different directions) are clearly visible. The plagioclase has undergone flow deformation, especially visible in the region from the lower left to the top center. Elongate smears of plagioclase are bent around orthopyroxene and around one another.