SIGNATURE OF CENOZOIC OROGENIC MOVEMENTS IN COMBUSTION METAMORPHIC ROCKS: MINERALOGY AND GEOCHRONOLOGY ( example of the Salair-Kuznetsk Basin transition )
I.S. Novikov, E.V. Sokol, A.V. Travin, S.A. Novikova
Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Combustion metamorphic complexes; paralava; clinker; geochronology; 40Ar/39Ar dating; neotectonics; Kuznetsk Coal Basin
Pages: 378-396
Abstract
Cenozoic combustion metamorphic (CM) complexes produced by fossil natural coal fires are widespread at range-basin junctions worldwide. Large-scale fires accompany the initial orogenic phases as fresh coal-bearing strata become drawn into the aeration zone as a result of crustal deformation. In combustion metamorphism, the protolith melts to different degrees either into ferrous basic paralava or in glassy clinker. The melt rocks have a phase composition favorable for 40Ar/39Ar dating of ignition coeval with the onset of each episode in Late Cenozoic orogenic events. We suggest an algorithm providing correct 40Ar/39Ar age determination of CM rocks followed by well-grounded geological interpretation and test the new approach on melt rocks from the Kuznetsk Coal Basin.
Paralava samples were dated by 40Ar/39Ar incremental heating and the isotope ratios were corrected for Ca-, Cl-, and K-derived Ar isotopic interferences. The interpretation of age-spectrum results was checked against internal and external criteria. The former were plateau and isochrone ages and the latter included the so-called
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