Identify the following igneous rocks based on their texture and ...

[Jipu 123]

Identify the following igneous rocks based on their texture and mineral content.
 
  What will be an ideal response?

Question 2

What processes can form intermediate and felsic magmas from a melt that is originally mafic?
 
  What will be an ideal response?

[Ptupou85]

Answer to Question 1

a. Fine-grained rock with 0 quartz, 0 potassium feldspar, 61 plagioclase feldspar, 13 biotite, 17 amphibole, 9 pyroxene, 0 olivine
b. Fine-grained rock with 0 quartz, 0 potassium feldspar, 67 calcium-rich plagioclase feldspar, 0 biotite, 0 amphibole, 25 pyroxene, 8 olivine
c. Coarse-grained rock with 0 quartz, 0 potassium feldspar, 52 calcium-rich plagioclase feldspar, 0 biotite, 0 amphibole, 32 pyroxene, 16 olivine
d. Coarse-grained rock with 0 quartz, 0 potassium feldspar, 0 plagioclase feldspar, 0 biotite, 0 muscovite, 0 amphibole, 56 pyroxene, 44 olivine
e. Fine-grained rock with 32 quartz, 26 potassium feldspar, 26 sodium-rich plagioclase feldspar, 5 biotite, 11 amphibole, 0 pyroxene, 0 olivine
By reference to text Figure 4.3: Andesite, Basalt, Gabbro, Peridotite, Rhyolite

Answer to Question 2

Fractional crystallization: Removal of early-formed, relatively low-silica minerals leaves a melt that is more silica-rich.
Magma assimilation: Mafic magma may melt more silica-rich surrounding rock; the resulting silica-rich melt blends with the originally mafic magma to produce an intermediate or felsic magma.
Magma mixing: A mafic magma may mix with a felsic magma to produce an intermediate magma.