|
Stop #6 Contact of Morton and Sacred Heart Oliver Todryk ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Location: Swedes Forest quadrangle 17 west. The final stop made was about a half mile north on County Hwy 7 (towards the river) of the Sacred Heart Granite stop made prior to this stop. This stop was important because it showed the contact between the Sacred Heart Granite and the Morton Gneiss. The Morton Gneiss was seen the previous day and the Sacred Heart Granite earlier that day. Description: Xenoliths (foreign inclusions in an igneous rock) are present in the Sacred Heart Granite which is amphibole rich along the contact. The inclusion of the mafic blocks within the pink (felsic) Sacred Heart and the presence of several adjacent Sacred Heart dikes in the Morton indicate that the Sacred Heart pluton intruded the Morton. There are two different types of the inclusions present here, brittle and ductile. Ductile is when the parent rock breaks apart in straight lines and look more like squares, whereas brittle is where the parent rocks breaks into more circular intrusions.
Figure 6.A Picture of a Xenolith
References: Sims, P. K., Morey, G.B., Geology of Minnesota: A Centennial Volume. Minnesota Geological Survey, 1972, St. Paul,MN.
|
