Zoned garnets in some Scottish Dalradian pelites

ABSTRACT. Zoning in garnets in Barrovian garnet zone rocks of central Perthshire is shown to be dependent on the continuous prograde reaction histories in which the garnet was involved. In highly aluminous rocks, garnet grows at the expense of chloriioid and staurolite whereas in less aluminous rocks garnet grows at the expense of chlorite. Minerals included in garnet such as ilmenite, plagioclase, chlorite, and chloritoid show compositional changes which with the garnet zoning elucidate the garnet-forming reactions. Where garnet is resorbed to produce staurolite the former loses Fe at its rim to staurolite so that 'reverse ' zoning of decreasing Fe and increasing Mn and Ca towards garnet rim develops. SEVERAL models have been invoked to explain the zoning patterns in garnets. Growth with froze