Abstract

The Morton gneiss, one of a number of granites and granite gneisses referred to the Minnesota Valley granite series, is a hybrid gneiss with complexly contorted structure and variable color. Its hybrid nature is in part the result of lit-par-lit injection, but more important is the strewing out of numerous basic inclusions by the magma producing a "schlieren" gneiss. The contorted structure is probably the result of deformation during the late stages of solidification. Modal analyses show the composition more nearly quartz monzonite than granite.

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