Lab 3 // Igneous Rocks Flashcards
Granite
Texture: phaneritic Minerals/Groundmass: potassium feldspar, Na-rich plagioclase, quartz, biotite Rock type: felsic Processes: -low temperature -intrusive
Granodiorite
Texture: phaneritic Minerals/Groundmass: Na-rich plagioclase, quartz, biotite Rock type: felsic Processes: -low temperature -intrusive
Basalt
Texture: aphanitic Minerals/Groundmass: black groundmass Rock type: mafic Processes: -high temperature - extrusive / intrusive
(porphyritic) Dacite
Texture: (porphyritic) aphanitic
Minerals/Groundmass: light grey groundmass with amphibole phenocrysts
Rock type: felsic
Processes:
-low temperature
-intrusive or intrusive
- two stages of cooling - slow first forming the phenocrysts and then fast to form the groundmass
(porphyritic) Rhyolite
Texture: aphanitic / porphyritic
Minerals/Groundmass: light pink groundmass / red groundmass with quartz phenocrysts
Rock type: felsic
Processes:
-low temperature
-intrusive or intrusive
- two stages of cooling - slow first forming the porphyritic sample
Diorite
Texture: phaneritic Minerals/Groundmass: mainly amphibole and Na-rich plagioclase Rock type: intermediate Processes: -intermediate temperature -intrusive
Peridotite (olivine)
Texture: phaneritic Minerals/Groundmass: olivine Rock type: ultramafic Processes: -very high temperature -intrusive (earth's mantle)
Scoria (vesicular basalt)
Texture: aphanitic and vesicular
Minerals/Groundmass: rusty red (oxidized) groundmass
Rock type: mafic
Processes:
-high temperature
-extrusive (with gas escaping to form the vesicles)
Gabbro
Texture: phaneritic Minerals/Groundmass: mostly Ca-rich plagioclase (striations), minor pyroxene (dull black) Rock type: mafic Processes: -high temperature -intrusive