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Field evidence and geochemistry of komatiites from the Shandiz-ViraniMashhad Complexe, Northeast Iran

AuthorsMobasheri, M.; Garrido, C. J.; Ghasemi, H.; Marchesi, Claudio ; Rahimi, B.; Hidas, K.; Gourabjri-Pour, A.
Issue Date18-Aug-2019
CitationGoldschmidt (2019)
AbstractIn the northeast of Iran,in Shandiz-Virani-Mashhad Complex(SVMC), there are some outcrops of high-Mg ultramafic volcanic rocks. Based ondetailed field observations and geochemical data, the komatiitic nature of these rocks has been well proven.These rocks have a wide range of volcanic facies and accordinglyare divided into three groups of differentiatedflows, undifferentiated flows and pillow lavas. The differentiatedkomatiite flows,have8 different zonesfrom the base to the up: a) the lower marginal zone, b) a peridotite zone including various types of olivine cumulate textures, c) cumulate skeletal zone and harrisitic texture zone, d) intermediate zone or pyroxenite transition zone, e) coarse grained gabbro-pyroxenite zone, f) gabbro zone with branch and dendritic fine grained zone,g) pyroxene spinifex zone, h) upper marginal zone.Undifferentiated komatiitelavasare also zoned, and including three major units:a) joints and polyhedral fracturedzone, b) the skeletal cumulateandmicrospinifex zone, and c)peridotite zone. Whole-rock major and trace element data indicate thatthese rockshave a range of MgO values from 7.06 wt.% to 37.98 wt.%.These komatiitesalsohave low values of Al2O3/TiO2ratiosand high values of Gd/YbNratios, which indicate the relative depletion of them from HREEs.Overally, the SVMCkomatiites containvaluesof[1.4 < GdN/YbN< 1.8, (average 1.6)], [0.6 < LaN/SmN< 1.6, (average 0.93)] and (0.8 ≤ Eu* ≤ 1.3, (averge 1). In this termtheyare classified intothe Al-depleted komatiites.Collidingof an uprisingmantle plume with the Late Paleozoicsubduction zone of Paleo-Tethys in the northeast Iran is asuitable petrogenetic model forgeneration of the SVMC komatiites
DescriptionGoldschmidt, Barcelona (España), 18-23 agosto (2019)
Appears in Collections:(IACT) Comunicaciones congresos
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