MINERAL CHEMISTRY OF CHROMITE FROM ULTRAMAFIC ROCK IN SOUTH SULAWESI, INDONESIA

-Mineral chemistry compositions of chromite from chromitite rock in South Sulawesi\ud Ultramafic rock were determined using Scanning Electron Microprobe (SEM) method. Chromite\ud occurs either as podiform lens and layers ranged from 10 ??? 40 cm in size in ultramafic rocks from\ud Bantimala and Barru blocks, Indonesia. Both chromitites from these two blocks showed a very\ud different composition mineral chemistry. Those from Bantimala block has much lower Cr2O3 content\ud (17.1 ??? 21.1 wt%) compare to those from Barru block ( 52.9 ??? 57.7). The Bantimala block chromitite\ud have Cr/(Cr+Al ) ranges from 0.95 ??? 0.96, Mg# ranges from 0.06 ??? 0.08 and Cr2O3 content varies from\ud 17 to 21 wt% with extremely low vale of Al2O3 (0.6 to 0.65 wt%). On the contrary, those from the\ud Barru block show relatively lower value of Cr/(Cr+Al ) which range from 0.75 ??? 0.84, Mg# from 0.59 ???\ud 0.66 and Cr2O3 content vales ranges from 52to 57 wt% with relatively normal value of Al2O3 (7 to 12.5\ud wt%) . This result showed that these two chromitites were originated from different mechanism,\ud which the former derived from the crystallisation of parental melt in island arc environment whereas\ud the latter formed from crystallization of extrusive boninitic lava