Journal: Tectonics Authors: Hefferan, K.P., Karson, J.A., Hurst, S., Bloomer, S., and Saquaque, A. Title: Oblique‑Collision and Duplex Development in a Pan African Suture Zone, Anti‑Atlas Mountains, Morocco: a Field Mapping and Remote Sensing Perspective.

General Comments

The views advanced in this paper are essentially the same as those already published by Saquaque, Hefferan, and Karson in the December 1989 issue of Geology, namely that the pre‑PII‑III rocks of the El Graara inlier are composed of a southerly accretionary prism (Skouraz, Menissi, Bleida), a northern fore‑arc (Ousdrat), and a central uplifted sub‑forearc basement (Bou Azzer, Oumarou ophiolite). The interpretation is opposed to that ofLeblanc and Billaud (19778) who proposed an essentially parautochthonist model with the rocks of the ophiolite and northern Ousdrat belt formed north of and marginal to the Kerdous continent. Hefferan et al. would seem to have dropped certain speculations held in their earlier paper, but in the present paper have maintained and attempted to strengthen the evidence in support of their model.
To some extent the paper could be more tightly focused to lessen the impression of committee writing and publication shingling. For example, the first paragraph of the Abstract says nothing that has not been said before, and the content of the last two sentences of the second paragraph seem out of place relative the prior comments. The short essay on Pan‑African Orogenic belts is also not really necessary, and the build up of the section 'Bou Azzer ‑ El Graara inlier geology:...' is three times longer than the actually meat of the paper concerning the duplex development. The space could be better used to address some of the more pressing issues.

Specific Comments
While I am more in agreement with the authors than I am with Leblanc concerning the sense of subduction that led to the obduction of the El Graara complex, the attempt by the authors to bolster their case against Leblanc is not entirely satisfactory. For example, although the authors continue to assert that the southern unit of the Bou Azzer complex is an accretionary prism melange similar in character to the Franciscan of California (see also the reply by Hefferan et al. to Church in Geology 1992), they still do not provide a clear explanation as to why they consider Leblanc's map of the Bleida region (Leblanc and Billaud 1978; Leblanc and Moussine‑Pouchkine, paper in press, Precambrian Research) to be incorrect. I note in this respect that in Figure 4b a prominent unit of 'Precambrian quartzites, limestones' is shown as separating the Bleida and Menissi tracts. This begs for elaboration since although local carbonate units are present in the Menissi tract, a mappable unit of the extent shown in Fig 4b does not appear on any other map that I know of. It could perhaps reflect a too great enthusiasm for and excess trust in TM interpretation (TM is great for identifying serpentinites and quartz diorites, but it has its limitations too.) The authors also seem to be reluctant to acknowledge the structural studies carried out by Leblanc and his students, and consequently, although we know that there is a marked difference of opinion between the two schools, the basis for the difference is not well explained. After all, Billaud's thesis (Leblanc and Billaud 1978) is actually entitled 'Les structures tectoniques pan‑africaines (Precambrien superieur) du ....'. Whether the reluctance to lay out the difference in the database is the result of accident or design, it contributes to a feeling that the
authors, may not have fully appreciated the complexities of the polyphase history of the El Graara inlier. What response do the authors have regarding Leblanc's Bl, B2, B3 deformation scheme, and if deformation effects are divided into buckling and flattening components, how do they prove that intrusive bodies that cross‑cut folds but are foliated (e.g. Ousdrat) are syntectonic?
The statement concerning blueschists in the Central belt, while very titillating, is also not very useful because it does not make it clear whether all the greywackes contain fragments of blueschist, or whether one blueschist fragment has been found at one greywacke locality, or whatever. Nor is the statement informative about the mineralogy of the blueschist (e.g. crossite v glaucophane; +/‑ lawsonite). By analogy with the internal zone ophiolite belt of the Appalachians, it is certainly not impossible that within the ophiolite belt there are slivers of melange material, both tectonic and olistostromal, or even of dynamothermal aureole metamorphic rocks. For this reason I would encourage the authors to be more specific in their description of these rocks.
One unit that is critical in the interpretation of the authors and of Leblanc is the 'arkose' unit of the Skoura area. It is critical to Leblanc's hypothesis (see Leblanc and Billaud, 1978, fig. 2) because his correlation of the Skoura arkoses with those of the Bleida region allows him to maintain his autochthonist hypothesis for the Bou Azzer ophiolite. On the other hand, Hefferan et al. consider the arkoses along with the nearby calcareous metasediments to be platform sediments. Given the rather strange nature of these rocks (association of carbonates, carbonaceous schists, and oligistoschists) it is not clear why one should be persuaded by the arguments of either Leblanc or Hefferan et al. One might also ask in what way the map presented in Fig 5 is in conflict or is an improvement of the Leblanc's map Fig 6 (Leblanc 1975, thesis), and in particular how do the authors rationalize the presence of oligistoschist horizons within the spilitic greywacke units mapped by Leblanc. And if this is melange, do the authors have a map illustrating its character in the detail of Leblanc's map fig. 6. Elaboration of this point would be very valuable.
On the TM photo and the TM based map Fig 4b a jade green blob identifies ultramafic rocks within the Takroumt gneisses. However, while clinopyroxenites and serpentinites appear in the Legend of Basement Rocks on map Fig. 5, such rocks are not represented on the map. I also had difficulty matching the coordinate systems on the various map figures. For example, on the TM photo the Bleida Granodiorite is located approximately at g, 7‑8, whereas on Fig. 4b its located at h,9.1 have also located my estimated position of J. Oumarou on Figs. 4b and 6; the coordinates do not seem to correspond? The authors comment that 'it is useful to reevaluate prior interpretations.' Since however the reevaluation is restricted to a criticism of the ideas of Leblanc, I have extemporized a short essay on the historical development of ideas concerning the ophiolites of the El Graara inlier and of ophiolites in general. It is not definitive but I hope it will prove useful to the authors.
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