What would cause a plagioclase feldspar to have a dark interior and a lighter ex
ID: 236347 • Letter: W
Question
What would cause a plagioclase feldspar to have a dark interior and a lighter exterior?
a. It represents a change in the composition of the magma. Initially the melt was rich in calcium which created the dark color of the interior, then, as the magma changed composition, the plagioclase used more sodium in its crystal structure which caused the change to a lighter color.
b. The change is tied directly to the temperature of the magma. Early high temperatures allowed only iron and magnesium to be tied into the crystal structure of the plagioclase feldspar. This created a dark color. Later, as the temperature dropped, aluminum and oxygen began to be incorporated into the crystal structure to make the outer layers lighter in color.
c. Color change in the plagioclase feldspars is releated to where the crystal formed. The darker colored crystal formed deep in the magma chamber. Lighter colored crystals form near the top. A crystal that has a dark interior and a lighter exterior represents a crystal that moved upwards during the crystallization process.
d. The change in color deals with the processes of weathering. Once exposed at (or near) the surface, the more soluable elements like iron and magnesium begin to leach out. The removal of these elements causes the plagioclase to lighten from the outside towards the center
a. It represents a change in the composition of the magma. Initially the melt was rich in calcium which created the dark color of the interior, then, as the magma changed composition, the plagioclase used more sodium in its crystal structure which caused the change to a lighter color.
b. The change is tied directly to the temperature of the magma. Early high temperatures allowed only iron and magnesium to be tied into the crystal structure of the plagioclase feldspar. This created a dark color. Later, as the temperature dropped, aluminum and oxygen began to be incorporated into the crystal structure to make the outer layers lighter in color.
c. Color change in the plagioclase feldspars is releated to where the crystal formed. The darker colored crystal formed deep in the magma chamber. Lighter colored crystals form near the top. A crystal that has a dark interior and a lighter exterior represents a crystal that moved upwards during the crystallization process.
d. The change in color deals with the processes of weathering. Once exposed at (or near) the surface, the more soluable elements like iron and magnesium begin to leach out. The removal of these elements causes the plagioclase to lighten from the outside towards the center
Explanation / Answer
Answer is a It represents a change in the composition of the magma. Initially the melt was rich in calcium which created the dark color of the interior, then, as the magma changed composition, the plagioclase used more sodium in its crystal structure which caused the change to a lighter color,so would be a cause plagioclase feldspar to have a dark interior and a lighter exterior.
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