Geochemistry of chromian spinels from the Indo-Myanmar ophiolite belt of Northeastern India

Chromite is commonly used for deciphering the petrogenesis and geodynamic setting of ultramafic rocks. Chromespinels from the Indo-Myanmar ophiolite belt occurring in the form of podiform chromitites associated with the mantle sequence and associated volcanic rocks are studied to characterise their geochemical composition. We have measured major and trace element concentrations of the chrome-spinels. Cr/(Cr+Al) (Cr#) and Mg/(Mg+Fe²⁺) (Mg#) range from 66 to 70 and 66 to 69 respectively in the chromitite and 47 to 56 and 67 to 70 in volcanic spinel. The computed crystallization conditions show that the studied samples crystallized in an upper mantle environment. Using the chrome spinel compositions, parental magma for the chromitite rock is calculated as boninite, and a MORB for the volcanic sample. Minor and trace element (Ga, Ni, Zn, Co, Mn, V, Sc) concentrations in the analysed spinels are comparable to other podiform chromitites hosted in the mantle section of the ophiolite complexes. Chrome-spinel compositions of the two rocks are used to recognize the probable crystallization condition and nature of the parental magma.8 page(s