This paper highlights published and new field and petrographic observations for late-stage (crustal 16 level) deformation associated with the emplacement of kimberlites and other mantle-derived 29 17 magmas. Thus, radial and tangential joint sets in the competent 183 Ma Karoo basalt wall rocks to 32 18 the 5 ha. Lemphane kimberlite blow in northern Lesotho have been ascribed to stresses linked to 34 19 eruption of the kimberlite magma. Further examples of emplacement-related stresses in 35 36 20 kimberlites are brittle fractures and close-spaced parallel shears which disrupt olivine macrocrysts. 37 21 In each of these examples, there is no evidence of post-kimberlite regional tectonism which might 38 39 22 explain these features, indicating that they reflect auto-deformation in the kimberlite during or 40 41 23 immediately post-emplacement. On a microscopic scale, these inferred late-stage stresses are 42 43 24 reflected by fractures and domains of undulose extinction which traverse core and margins of some 44 25 euhedral and anhedral olivines in kimberlites and olivine melilitites. Undulose extinction and kink 45 46 26 bands have also been documented in olivines in cumulates from layered igneous intrusions. Our 47 48 27 observations thus indicate that these deformation features can form at shallow levels (crustal 49 50 28 pressures), which is supported by experimental evidence. Undulose extinction and kink bands have 51 52 29 previously been presented as conclusive evidence for a mantle provenance of the olivines -i.e. that 53 30 they are xenocrysts. The observation that these deformation textures can form in both mantle and 54 31 crustal environments implies that they do not provide reliable constraints on the provenance of the 32 olivines. An understanding of the processes responsible for crustal deformation of kimberlites could 33 potentially refine our understanding of kimberlite emplacement processes. 34 35 31 50 2017) argued that the majority of kimberlitic olivines are cognate phenocrysts. Skinner (1989) took 51 an intermediate view, concluding that the euhedral olivine phenocrysts and microphenocrysts are 52 cognate to the kimberlite, but that the majority of macrocrysts are xenocrysts. 37 53 54 These contrasting interpretations have important implications for the composition and generation of 40 41 55 kimberlite magmas. If a majority of olivines are cognate, this would point to a highly Mg-rich 43 56 primitive kimberlitic liquid, whereas the xenocrystal model implies a carbonatitic, relatively Mg-poor 57 primary magma. It is therefore clearly critical to determine the origin of kimberlite olivines in order 10 346 Frieder Reichardt for providing the Murowa dyke sample illustrated in Fig. 3a&b. The core sample 12 13 347 illustrated in Fig. 3d was kindly provided by Petra Diamonds Ltd. Tsodilo Resources (a Canadian-14 348 listed diamond exploration company), kindly facilitated a field visit to the company's BK16 15 16 349 kimberlite, located in the mid-Cretaceous (~90 Ma) Orapa pipe cluster in central Bots...