Bowen's Reaction Series Overview PDF

**Bowen's Reaction Series** provides a systematic framework for understanding the crystallization of minerals from cooling magma as well as the melting behavior of these minerals when heated. This concept is fundamental in interpreting the mineralogical compositions of igneous rocks. Temperature Ra...

**Bowen's Reaction Series** provides a systematic framework for understanding the crystallization of minerals from cooling magma as well as the melting behavior of these minerals when heated. This concept is fundamental in interpreting the mineralogical compositions of igneous rocks. Temperature Range and Crystallization ===================================== Bowen's Reaction Series describes the temperatures at which minerals crystallize from a molten state and, conversely, the conditions under which they melt. Under standard sea-level pressure (1 bar), the lowest temperature at which minerals crystallize into solid rock is approximately 700°C (158°F), while the highest temperature at which all minerals remain molten is about 1,250°C (2,282°F). Although these values may vary at greater depths due to increased pressure, the sequence and relative relationships among the minerals remain consistent. Diagram and Mineral Groupings ============================= Diagram of Bowen\'s Reaction Series, Y-shpaed with 8 minerals and a temperature scale *Figure 1 The Bowen's Reaction Series. Minerals that crystallize at higher temperatures are at the top (olivine) and minerals that crystallize at lower temperatures are at the bottom (quartz). (Source Colivine, modified from Bowen, 1922)* Figure 1 illustrates the Bowen's Reaction Series, the right-hand column categorizes igneous rocks into four groups arranged from top to bottom: ultramafic, mafic, intermediate, and felsic. A down-pointing arrow indicates an increase in the proportions of silica, sodium, aluminum, and potassium as one progresses from ultramafic to felsic compositions. Conversely, an up-pointing arrow signifies an increase in ferromagnesian components such as iron, magnesium, and calcium. The temperature scale along the left margin of the diagram highlights that minerals, such as olivine and anorthite (a type of plagioclase), crystallize at higher temperatures, whereas minerals like quartz and muscovite crystallize at lower temperatures. Historical Context and Experimental Methodology =============================================== Norman L. Bowen (1887--1956), a pioneering geologist of the early twentieth century, observed that specific mineral assemblages consistently co-occur in igneous rocks, while others are mutually exclusive. He hypothesized that these patterns were closely related to the temperatures at which the rocks cooled. To test his hypothesis, Bowen conducted a series of controlled experiments in which he ground rock samples into fine powders, sealed them in metal capsules, heated the capsules to various temperatures, and then rapidly cooled (quenched) them. Upon examining the quenched samples under a petrographic microscope, Bowen observed that the resulting textures consisted of a glassy matrix enveloping distinct mineral crystals. His extensive experimental work revealed that common igneous minerals crystallize at distinct temperature intervals and tend to occur in assemblages that reflect similar temperature ranges. This understanding also explains the fundamental differences between mafic and felsic igneous rocks. Mafic rocks, which are rich in minerals that crystallize at higher temperatures, differ markedly from felsic rocks, which form from minerals that crystallize at relatively lower temperatures. This temperature disparity is also evident in lava flows, where felsic lavas erupt at temperatures several hundred degrees lower than their mafic counterparts. Significance in Igneous Petrology ================================= Bowen's Reaction Series has become a cornerstone in the field of igneous petrology, providing critical insights into the processes of rock formation and evolution. His seminal work, *The Evolution of the Igneous Rocks* (1928), laid the foundation for subsequent research in the discipline and continues to influence our understanding of the formation and differentiation of igneous rocks. **References** Adapted from OER Geology course by Kimberly Schulte. https://courses.lumenlearning.com/geo/chapter/about-this-course/