PowerPoint Presentation - Chapter 9a Trace ELementsPowerPoint演示文稿-第9A微量元素.ppt

PowerPoint Presentation - Chapter 9a Trace ELementsPowerPoint演示文稿-第9A微量元素
Figure 9-1. Harker Diagram for Crater Lake.
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Example: hypothetical garnet lherzolite = 60% olivine, 25% orthopyroxene, 10% clinopyroxene, and 5% garnet (all by weight), using the data in Table 9-1, is:
DEr = ( · ) + ( · ) + ( · ) + ( · ) =
Trace elements strongly partitioned into a single mineral
Ni - olivine = 14
Figure 9-1a. Ni Harker Diagram for Crater Lake. From data compiled by Rick Conrey. From Winter (2019) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
Incompatible trace elements concentrate  liquid
Reflect the proportion of liquid at a given state of crystallization or melting
Figure 9-1b. Zr Harker Diagram for Crater Lake. From data compiled by Rick Conrey. From Winter (2019) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.
Trace Element Behavior
The concentration of a major element in a phase is usually buffered by the system, so that it varies little in a phase as the system composition changes
At a given T we could vary Xmelt from 20  60 % Mg/Fe without changing the composition of the melt or the olivine
Trace element concentrations are in the Henry’s Law region of concentration, so their activity varies in direct relation to their concentration in the system
Trace element concentrations are in the Henry’s Law region of concentration, so their activity varies in direct relation to their concentration in the system
Thus if XNi in the system doubles the XNi in all phases will double
Trace element concentrations are in the Henry’s Law region of concentration, so their activity varies in direct relation to their concentration in the system
Thus if XNi in the system doubles the XNi in all phases will double
Because of this, the ratios of trace elements are often superior to the concentration of a single element in identifying the role of a specific mineral
K/Rb often used  the importan