The size of crystals in igneous rocks is generally a function of the rate of cooling. However, within the same rock crystal size does not necessarily reflect the order of crystallization for individual minerals. Without using Bowen’s Reaction Series, how might you determine the order of crystallization of minerals in an individual rock sample? (Hint: Think about the texture).
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2006-06-05 19:42:21 · 2 answers · asked by Megan R 2 in Science & Mathematics ➔ Earth Sciences & Geology
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2006-06-05 21:11:45 · update #1
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2006-06-06 01:40:11 · answer #1 · answered by Anonymous · 0⤊ 0⤋
By looking at the quality and size of the crystats. Early forming crystals have room to expand and are more likely to be euhedral (that is well shaped with regular crystal sides). These crystals generally are larger than later forming crystals. If the magma chamber erupts with melted rock and crystals, the latter are then phenocrysts in a matrix of microcrystalline minerals, or glass. Among larger crystals, growth of one crystal into another can lead to the deduction that one mineral was present and another mineral grew around it. Common sense and deduction skills are sometimes needed to figure the petrogenesis of a rock.
2006-06-06 05:06:31 · answer #2 · answered by Amphibolite 7 · 0⤊ 0⤋