Evidences of Magmatic Differentiation of Karaj DamIgneous Rocks

Category Petrology
Group GSI.IR
Location 21th symposium on geosciences
Holding Date 21 May 2008

Abstract:
      Detailed petrographical, geochemical and mineral chemistry studies of Karaj dam?s plutonic complex are presented. Lower and upper margins of the complex have effects of contact chilled associated with porphyry texture. The porphyry texture changes to isogranular gradually from margins toward central part of the complex. Likewise, the asymmetrical differentiation sequence, turned from gabbro to diorite and then to monzonite. This fact represents magmatic differentiation in the form of separation and settling the crystalline phase. The changes of chemical composition of clinopyroxene and plagioclase indicate the high ratio of Mg/Fe and Ca/Na in the primary magma.
   These ratios decrease from beginning to end of differentiation process. Also, SiO2 values and incompatible elements increase during the process, where as the MgO ratio and compatible elements decrease.

   General:
     Detailed petrographical, geochemical and mineral chemistry studies of Karaj dams plutonic complex are presented. Lower and upper margins of the complex have effects of contact chilled associated with porphyry texture.
   The porphyry texture changes to isogranular gradually trom margins toward central part of the complex. Likewise, the asymmetrical differentiation sequence, turned from gabbro to diorite and then to monzonite. This fact represents magmatic differentiation in the form of separation and settling the crystalline phase. The changes of chemical composition of clinopyroxene and plagioclase indicate the high ratio of Mg/Fe and Ca/Na in the primary magma. These ratios decrease from beginning to end of differentiation process. Also, SiO2 values and incompatible elements increase during the process, where as the MgO ratio and compatible elements decrease.

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