Squeezing of residual liquid due to
earth movements or other means
forming fractions of different
compositions due to
Answers
Answer:
Chemical Variation in Rock Suites
Soon after geologists began doing chemical analyses of igneous rocks they realized that rocks emplaced in any given restricted area during a short amount of geologic time were likely related to the same magmatic event. Evidence for some kind of relationship between the rocks, and therefore between the magmas that cooled to form the rocks came from plotting variation diagrams.
A variation diagram is a plot showing how each oxide component in a rock varies with some other oxide component. Because SiO2 usually shows the most variation in any given suite of rocks, most variation diagrams plot the other oxides against SiO2 as shown in the diagram here, although any other oxide could be chosen for plotting on the x-axis. Plots that show relatively smooth trends of variation of the components suggested that the rocks might be related to one another through some process. Of course, in order for the magmas to be related to one another, they must also have been intruded or erupted within a reasonable range of time. Plotting rocks of Precambrian age along with those of Tertiary age may show smooth variation, but it is unlikely that the magmas were related to one another. If magmas are related to each other by some processes, that process would have to be one that causes magma composition to change. Any process that causes magma composition to change is called magmatic differentiation. Over the years, various process have been suggested to explain the variation of magma compositions observed within small regions. Among the processes are:
1. Distinct melting events from distinct sources.
2. Various degrees of partial melting from the same source.
3. Crystal fractionation.
4. Mixing of 2 or more magmas.
5. Assimilation/contamination of magmas by crustal rocks.
6. Liquid Immiscibility.
Explanation:
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