LATER STAGES OF EVOLUTION OF IGNEOUS ROCKS 75 



COURSE FOLLOWED BY LIQUID AS A RESULT OF REMOVAL OF CRYSTALS 



basaltic 



dioritic 



granodioritic 



granitic (basanitic) 



foyaitic (foyaitic) 

 (The career of the hquid may end at any of these stages on account 

 of its complete freezing and consequent cessation of removal of 

 crystals.) 



II 



MATERIALS FORMED BY ACCUMULATION OF CRYSTALS (rOCKS) 



Extreme sorting. — ^Peridotites, pyroxenites, anorthosites, and 

 other "anchimonomineralic" rocks. 



Little sorting. — Any type formed by the freezing of the liquid 

 at any of the stages in I, in a position where there has been accumu- 

 lation, great or small, of one or more of the kinds of crystals which 

 have recently separated from the liquid. 



Principal Products of the Slow Crystallization of Basaltic Magma 



§ ?• 



Stage 



1. (spinellids) magnesia-iron olivine 



2. magnesia-iron pyroxene 



3. lime-magnesia-iron pyroxene 



4. hornblende 



5. biotite, quartz, orthoclase 



6. biotite, muscovite, quartz, 



orthoclase 



\ hornblende, quartz, 



7. alkalic^ or 



[ pyroxene 



f hornblende, iron olivine, 



8. alkalic< or 



[ pyroxene 



f hornblende, nephelite, 

 9 alkalic < or 



[ pyroxene 

 10. pyroxenes, corundum, nephelite, 

 sodalite 



II. pyroxenes or olivine, analcite 



calcic plagioclase 

 calcic plagioclase 

 medium plagioclase 

 medium plagioclase 

 sodic plagioclase 



f orthoclase, sodic plagioclase, 



[ microcline 



f orthoclase, sodic plagioclase, 



< or 



\ microcline 



f orthoclase, sodic plagioclase, 



or 

 [ microcline 

 r orthoclase, sodic plagioclase, 



or 

 [ microcline 

 f orthoclase, sodic plagioclase, 



or 

 [ microcline 



