Quantitative genetic modelling of the turkel anorthosite, eastern Ghats Belt, Orissa, India

Principal components analysis of the anorthositic and adjoining felsic suite of rocks of the Turkel anorthosite complex suggests that these are unlikely to be comagmatic. This has been supported by delta(18)O values of these rocks. In synoptic principal component space, the compositions of anorthosite, leuconorite and ferrodiorite of Turkel are compared with the chemistry of coexisting phases based on experimental studies on Proterozoic massif-type anorthosite and naturally occurring high-Al gabbros (HAG). Such studies, in congruence with the experimental observations, strongly indicate that the Turkel ferrodiorite represents the residual melt after separation of anorthosite and leuconorite. Major and minor element mass balance computations suggest that an ensemble of 15.32 wt.% anorthosite, 34.74 wt.% leuconorite and 29.71 wt.% ferrodiorite may have originated from a melt which was derived from a HAG magma through fractional crystallisation of 8.86 wt.% olivine and 11.37 wt.% Ca-poor clinopyroxene. Consistent with petrological observations, a small amount of zircon and apatite assimilation from the granitoid country rocks has been invoked to best explain the observed high concentration of Zr and REEs in the anorthositic suite of Turkel. (C) 2004 Elsevier Ltd. All rights reserved.