EXERCISE 5.9 Explaining Igneous Features Found in the Field (continued) Name: Co

Question

EXERCISE 5.9 Explaining Igneous Features Found in the Field (continued) Name: Course: Section Date: (b) The Palisades Sill on the west bank of the Hudson River in New Jersey is a shallow basaltic intrusive. The sill varies testurall, as showni, Einon the oitesturalvariations were pro duced by crystallization of the sill. Schematic cross section of the Palisades Sill Mafic inclusions (xenoliths) in a granitic pluton Wall rock Coarse basalt Fine basalt Zone of olivine (c) In the figure above (right), a thin brown zone of weathering highlights iron-rich zones that separate the host granite from the mafic xenoliths. Based on the magmatic processes described above, suggest an origin for these zones

Explanation / Answer

a)In left figure there is sill which is essentially parallel to country rock .sill composition is mafic but the outer part due to sudden cooling becomes fine grained whereas the inner part due to slow cooling becomes coarse grained.Due to cooling the first formed mineral is olivene.so it is interbedded between fine and coarse grained and forms a layer.

b)xenolith are essentially rock which are brought up by magma having different compositions from that.so the dark minerals were already formed before they come in contact with the latter magam which is felsic in composition Hence this types of configuration results.

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