Talk:Igneous differentiation

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Liquid line of descent - definition needed

This term is used in several places in this article, but is no where defined. I've found a couple definitions on the web. It would be nice if some knowledgeable editor would add a definition to the article, as it seems a fundamental concept.

Liquid line of descent: relates series of liquids derived from single parent magma

Liquid line of descent: The chemical trend (or gradation in composition) exhibited by an igneous rock series if and when such a trend is interpreted to represent a change in the chemical composition of the parental magma of this series due to the process of fractional crystallization. A liquid line of descent is therefore equivalent to "the crystallization path" of the parental magma, and is best shown by plotting the chemical compositions of either aphyric (phenocryst free) or glassy volcanic rocks on variation diagrams.

Figure 12.17 illustrates a magma's chemical evolution, called the liquid line-of-descent, as it undergoes fraction crystallization.

It is often thought, in fact assumed, that variation diagrams represent the liquid line-of-descent, the path of magmatic evolution followed by an evolving liquid. Volcanic rocks, or fine-grained rocks in general, are often considered to represent liquid compositions.

Shenme (talk) 18:28, 4 August 2012 (UTC)[reply]