Towards a paleogeography and tectonic evolution of Iran: Discussion

Although Berberian and King must be complimented extensively in Iran and subtly casts doubts on the abil on their attempt to synthesize the geology and tectonic of other geologists, I must point out that many evolution of Iran, I must point out several errors in their Berberian's publications are in the form of unpublish paper concerning the Neyriz-Sirjan region. This area is internal reports, which are unavailable. Thus his fit critical to the tectonic history of Iran as it encompasses work cannot be evaluated. Also, Berberian and Ki the Zagros ophiolite belts, a paired metamorphic zone have completely ignored the extensive field work and a Mesozoic-Cenozoic volcanic/plutonic belt. Adib (1978) on the metamorphism of the Neyriz-Sirj They state (p. 241) that ophiolite emplacement took area, even though it was referenced many times in place only during the Late Cretaceous, because it seems Haynes and Reynolds (1980). In particular, they conthat there is no disruption in the sedimentation process of sider the metamorphic rocks west of Sirjan to be the Zagros and Central Iran during Middle Jurassic time, Abukuma type (p. 247). This is not true as south of t' and discount the idea proposed by Haynes and Reynolds Cheshmeh Anjir fault the metamorphic rocks are clea (1980) that ophiolites were emplaced during both Barrovian type with kyanite being locally abundz Middle Jurassic and Late Cretaceous times. Their first (Haynes and McQuillan 1974; Adib 1978; Haynes a error is that they claim our age of 170 Ma for initial Reynolds 1980). North of the Cheshmeh Anjir fault t ophiolite obduction is only based on one sample. This is metamorphism is indeed Abukuma type (Adib 19; untrue as we clearly stated (Haynes and Reynolds 1980) Haynes and Reynolds 1980). that our hornblende age, from the Makran, agreed The last error is Berberian and King's division of the remarkably with a previous WAr age of 170 + 8 Ma Quaternary volcanic rocks of the Aj-Bazman zone intc from the Neyriz area (Adib 1978). Berberian and King calc-alkaline and alkaline series. They claim the Aj(p. 241) discount our 170 + 5 Ma 40Ar-39~r hornblende Bidkhan zone (Fig. 18) is alkaline. The reference age because "It is possible that the radiometric age has (Dimitrijevic 1973) quoted by Berberian and King f o ~ been disturbed by later retrograde recrystallization and "Mosahim" and "Dehaj" volcanics actually states the] argon loss. " Frankly, this is ridiculous because argon are calc-alkaline not alkaline (Dimitrijevic 1973, Table loss would mean that our 170Ma age is too young; 1). Also, the rocks of this belt are predominantly therefore, the real age of ophiolite emplacement would andesite to dacite. Admittedly, alkalic types are present, have to be older than Middle Jurassic and not younger as is common in most calc-alkaline belts, but the rocks (Late Cretaceous) as required by Berberian and King. are silica saturated, not unsaturated as would be required Moreover, the remarkably flat plateau of our sample for the true alkaline series. Petrochemical analysis indicates that little or no argon movement has occurred. (Ghorashi-Zadeh 1978) of the 2.8 + 0.2 Ma Late Dacite Berberian and King are guilty of "selecting" data as they dome at Sar Cheshmeh (situated between Bidkhan and do not dispute our Late Cretaceous ages for biotite and Mosahim) indicates that these dacites lie within t' muscovite (Haynes andReynolds 1980). As hornblende calc-alkaline field as defined by Irvine and Barag has a higher argon blocking temperature than micas, (1971). why did they not query the mica ages? Also, their paper It is not the intent of this discussion to comment on t contains references to dates obtained by other workers; tectonic significance of the above, rather to point out t why were these not disputed, particularly as several of significant errors in Berberian and King's data in ord these are K/Ar ages? that the interested reader can draw his own conclusion Berberian (P. 256) 'laims have worked his, D. 1978. Geology of the metamorphic a( t south-westem margin of the central-eastem Iranian mic~ 'paper by M. Berberian and G. C. P. King, 1981. Canadian plate (Neyriz area). Neues Jahrbuch fuer Geologie UI Journal of Earth Sciences, 18, pp. 210-265. Palaeontologie Abhandlungen, 156, pp. 393-409.