A Raman spectroscopic study of diamond and disordered sp3-carbon in the coesite-bearing Straumen Eclogite Pod, Norway

摘要: Raman spectral point analysis and mapping have been applied to study the nature of carbon-bearing microinclusions C3-1 C5-1 within zircon in phengite–kyanite–coesite eclogite sample 62a from Straumen Eclogite Pod Western Gneiss Region (WGR), S.W. Norway. Graphitic carbon is always present with a degree structural disorder comparable that found other ultra high pressure metamorphic (UHPM) terranes; it compatible an origin by partial retrogression coexisting diamond due depressurization exhumation. Hematite coexists C3-1. In both microinclusions, wavenumber position peak varies point, ideal value 1332 cm−1, frequently down ∼1328 cm−1 sometimes ∼1322 cm−1 The bandwidth also increases proportionally. Some spectra reveal doublets peaks at ∼1328 even triplet. These data are discussed terms one or kind sp3-carbon, for example metamictization, overtemperature overpressure, nitrogen impurities especially stacking disorder, is, possible existence coexistence 3C, 2nH and/or 3mR polytypes mixture same monocrystal. question contamination disordered sp3-carbon slide evaluated; numerous arguments favour UHPM origin. new contribute ongoing debate on various petrological geodynamical models (including deviatoric stress) creation rocks general. This locality Straumen, fourth WGR but first southwestern part area WGR, provides minimum estimate UHP metamorphism ∼3.5 GPa. Taken together published P–T estimates, 3.75 ± 0.75 GPa covers all estimates coesite-, diamond- orthopyroxene-bearing types WGR.