This document discusses trace elements in geology. It defines trace elements as chemical elements that exist in very small concentrations in rocks and minerals, generally less than 0.1% by weight. Trace elements are divided into incompatible and compatible elements based on how readily they substitute for major elements in minerals. Rare earth elements, a group of 15 elements from lanthanum to lutetium, are also discussed. The document outlines several ways that trace elements are important for understanding geological processes, mineral formation, and environmental conditions.

1. Somali National University
Puntland-Baran Branch
Trace Elements
Ismail Katun Mohamud
B.Sc. Geology and Meng Petroleum Engineering

2. TRACE ELEMENTS
 In geochemistry, trace elements refer to chemical elements that exist in very small
concentrations within a rock, mineral, soil, or other geological materials.
 These elements are present in amounts generally less than 0.1% by weight or less than
1000ppm.
 Despite their low abundance, trace elements play crucial roles in understanding
geological processes, mineral formation, and environmental conditions.

3. TYPES OF TRACE ELEMENTS
 Compatibility is a measure of how readily a particular trace element substitutes for a major
element within a mineral. Trace elements could be divided into two groups:

4. 1) Incompatible trace elements
 Elements that are too large and/or too highly charged to fit easily into common
rock-forming minerals that crystallize from melts. These elements become
concentrated in melts. There are two groups of incompatible elements:
a) Large-ion lithophile elements or low field strength elements (LIL or LFSE):
Incompatible owing to large size and low charge (e.g., Rb+, Cs+, Sr2+, Ba2+).
b) High-field strength elements (HFSE): Incompatible owing to large size and
high charge (e.g., Zr4+, Hf 4+, Ta4+, Nb5+, Th4+and U4+).

5. 2) Compatible trace elements:
 These trace elements have a similar ionic radius and charge to the major
elements they substitute for in minerals.
 They are more easily incorporated into the crystal lattice of minerals without
causing significant distortions or structural strain.
 Common compatible elements include elements like magnesium (Mg), nickel
(Ni), and chromium (Cr).

6. RARE EARTH ELEMENTS (REE)
 Group of elements comprising the 15 elements from Lanthanum ( at no. 57 )
to Lutetium ( at no. 71).
 Yttrium ( at no. 39 ) and Scandium ( at no. 21 ) are also sometimes included in
this group.

7. RARE EARTH ELEMENTS (REE)

8. IMPORTANCE OF TRACE ELEMENTS
 Indicator of Geological Processes: Trace elements can serve as indicators of various
geological processes, such as magma differentiation, metamorphism, and alteration.
 Mineralogy and Petrology: The presence or absence of certain trace elements can influence
the mineralogy and petrology of rocks.

9.  The correlation coefficient r is a measure of the linear relationship between two
variables.
 The correlation coefficient is also known as the Pearson product-moment
correlation coefficient.
 The value of r can range from -1 to +1 and is independent of the units of
measurement. A value of r near 0 indicates little linear correlation between
variables; a value near +1 or -1 indicates a high level of correlation.

10.  When two variables have a positive correlation coefficient, an
increase in the value of one variable indicates a likely
increase in the value of the second variable.
 A correlation coefficient of less than 0 indicates a negative
linear correlation.
 That is, when one variable shows an increase in value, the
other variable tends to show a decrease.

11. Consider two variables x and y:
1. If r = 1, then x and y are perfectly positively correlated. The possible values
of x and y all lie on a straight line with a positive slope in the (x,y) plane.
2. If r = 0, then x and y are not correlated. They do not have an apparent linear
relationship. However, this does not mean that x and y are statistically
independent.
3. If r = -1, then x and y are perfectly negatively correlated. The possible
values of x and y all lie on a straight line with a negative slope in the (x,y)
plane.

12.  The quantity r, called the linear correlation coefficient, measures the strength and the
direction of a linear relationship between two variables.
 The linear correlation coefficient is sometimes referred to as the Pearson product moment
correlation coefficient
 The mathematical formula for computing r is:
 where n is the number of pairs of data. Product-moment

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