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Chromian spinel compositions from Madawara ultramafics, Bundelkhand Craton: Implications on petrogenesis and tectonic evolution of the southern part of Bundelkhand Craton, Central India
Author(s) -
Mohanty Niranjan,
Singh Surya Pratap,
Satyanarayanan Manavalan,
Jayananda Mudlappa,
Korakoppa Madiwalappa Mallappa,
Hiloidari Sikha
Publication year - 2018
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3286
Subject(s) - chromite , peridotite , magnetite , geology , olivine , geochemistry , ultramafic rock , craton , spinel , gabbro , mafic , mineralogy , igneous rock , mantle (geology) , tectonics , paleontology
Madawara ultramafic complex (MUC) in the southern part of Bundelkhand Craton, Central India comprises peridotite, olivine pyroxenite, pyroxenite, gabbro, and diorite. Coarse‐grained olivine, clinopyroxene (Cpx), amphibole (Amp), Al‐chromite, Fe‐chromite, and magnetite with rare orthopyroxene (Opx) are common minerals in peridotite. Chromites are usually coarse‐grained euhedral found as disseminated crystals in the olivine matrix showing both homogeneous and zoned texture. Al‐chromite, primarily characterizes Cr‐spinels and its subsequent fluid activity and alteration can result in the formation of Fe‐chromite, chrome magnetite, and magnetite. Mineral chemistry data suggest that Al‐chromite is characterized by moderately high Cr 2 O 3 (38.16–51.52 wt.%) and Fe 2 O 3 (3.22–14.51 wt.%) and low Al 2 O 3 (10.63–21.87 wt.%), MgO (1.71–4.92 wt.%), and TiO 2 (0.22–0.67 wt.%), whereas the homogeneous Fe‐chromite type is characterized by high Fe 2 O 3 (25.54–47.60 wt.%), moderately low Cr 2 O 3 (19.56–37.90 wt.%), and very low Al 2 O 3 (0.06–1.53 wt.%). Subsequent alteration of Al‐chromite and Fe‐chromite leads to formation of Cr‐magnetite and magnetite. The Cr# of Al‐chromite varies from 55.12 to 76.48 and γ Fe 3+ # from 8 to 19, whereas the ferrian chromite has high Cr# varying from 94.27 to 99.53 while its γ Fe 3+ # varies from 38 to 70. As a whole, the primary Al‐chromite shows low Al 2 O 3 , TiO 2 contents, and high Fe#, Cr# values. Olivines have forsterite ranging from 75.96% to 77.59%. The bulk‐rock geochemistry shows continental arc geochemical affinities indicated by the high concentration of large‐ion lithophile elements and U, Th relative to the low concentration of high‐field strength elements. These petrological and mineralogical as well as primary Al‐chromite compositions plotted in different discrimination diagrams suggest an arc environment that is similar to Alaskan‐type intrusion.