Geology Reference
In-Depth Information
(a)
Ignimbrite - Tenerife
•
Juvenile weathered pumice
(yellow),
•
mafic magma with chilled rinds
•
lithic fragments
•
fine ash matrix.
(b)
Porphyritic intrusion -Germany
•
Euhedral pinky/orange alkali
feldspar phenocrysts
•
Milky white subhedral
plagioclase phenocrysts
•
Translucent/grey subhedral
quartz phenocrysts
•
Fine grained matrix
2 cm
(c)
Pegmatite - Greenland
•
Radiating acicular amphibole
cluster
•
Euhedral pink Eudialyte (Zr rich
cyclosilicate)
•
Milky alkali feldspar
•
Found in veins and as coarse
pegmatite segregations
2 cm
(d)
Porphyritic Granite - UK
•
Large euhedral megacrysts of
alkali feldspar
•
coarse groundmass of alkali
feldspar, plagioclase, quartz
and biotite mica.
•
Mafic enclave containing Large
alkali megarysts and plag
pheocrysts
2 cm
Figure 3.4
Examples of textures in some evolved rock types. Note: these textural
types for example, porphyritic (lager crystals in finer ground mass) and pegmatite
and so on. Are found throughout the range of magma compositions.
