Roter Kamm is a relatively young 2.5-km-diameter impact crater located in the southern Namib desert. The rocks of the crater rim are fractured and cut by numerous fine-grained, clast-rich veins and dykes that closely resemble pseudotachylytes in the field. Most veins closely match their host rocks in bulk composition and have formed by localized cataclasis of the host rock followed in many cases by partial re-crystallization that has partly obliterated the cataclastic texture in the finest grain size fraction. This thermal annealing is most prominent in the very narrow veinlets, in the margins of the larger veins, and in the most quartz-rich veins. The spatial distribution of the veins and the association of veins in quartz breccias with quartz showing planar elements are consistent with an impact origin. The similarities to pseudotachylyte occurrences at other impact sites, including the type locality at Vredefort, warrants the classification of these veins as pseudotachylytes, despite the absence of evidence for melting.

Metamorphosed pillow basalt from the actively spreading basin west of the Marianas Island Arc contains albite or oligoclase of intermediate to low structural state. A feldspathic vein occupying late fractures in one metabasalt was found to contain highly disordered plagioclase ranging in composition from An 3 to An 31 . From the absence of thermal metamorphic effects in the chlorite-montmorilloniteactinolitic amphibole-epidote-sodic plagioclase assemblage of the host rock we infer formation of the vein at low temperature. Individual feldspar grains consist of lamellae or irregular domains (compositionally distinct volumes, not the crystallographers' domains) of varied compositions. Electron microprobe analyses of these domains yield a bimodal distribution of compositions. The large sizes of the domains and the inferred low temperature of formation of the vein suggest to us that the domains may have formed as primary metastable growth features. The bimodality and other features of the compositional distribution suggest that the composition adjusted, but incompletely so, in accord with the peristerite solvus.