Multiple episodes of thin-layer magma emplacement in the Duluth Complex: Evidence from magma-fluid interactions?

摘要

The Partridge River Intrusion, one of a number ofmineralized intrusions in the Duluth Complex,USA, is made up of a many layers of mafic rock. These rock layers, especially in the lower part of the intrusion,do not seem to follow any typical pattern related to magmatic differentiation. Several hypotheses for the observed pattern have been presented by a number of researchers. We believe that the main cause of the layering is multiple injections of thin igneous layers. This is based upon our interpretation of stable isotope and mineral concentration distributions as a function of depth and their relationship to probable fluid-rock interaction during emplacement.We present data, and interpretations based on it, for two layers that we believe demonstrate this well.