Heavy accessory minerals of the Val Verde tonalite

Study of the heavy accessory minerals of igneous rocks by means of concentration of the heavy fractions is a fairly recent development in the field of petrology. Originally, work of this type was intended as a means of demonstrating the parent rock from which heavy minerals of various sedimentary deposits had been derived. In this direction, investigations have been of undoubted value. More recently, various workers have advocated the use of accessory minerals of igneous rocks as a means of correlation of igneous intrusions. In many cases their use has yielded results apparently of positive value. However, data on the precision of this type of correlation are still being gathered, and studies concerned with accessory minerals and their variation are of some importance at present.