It. A. Daly — Secondary Origin of Certain Granites. 191 



Table I. 

 Mineralogical composition of Rocks showing secondary deriva- 

 tion of Granite. (Essential minerals noted in italics.) 



I. Moyie Sill. 

 Intermediate rock. 

 Hornblende 

 Biotite 

 Andesine 

 Quartz 

 Chlorite 

 Titanite 



Titanif. magnetite 

 Apatite 



Gabbro. 

 Hornblende 

 Labradorite 

 Quartz 

 Titanite 

 Biotite 

 Apatite 



Gr anophyre-granite . 

 Biotite 



Soda orthoclase 

 Microperthite 

 Micropegmatite 

 Quartz 

 Andesine 

 Muscovite 

 Titanif. magnetite 

 Apatite 

 Calcite, epidote, kaolin 

 Country rocks: highly acid mica-bearing quartzite, sometimes 

 slightly feldspathic, containing quartz, biotite and muscovite 

 (sericite) as principal constituents, with orthoclase, epidote, 

 titanite, magnetite, pyrite, zoisite, chlorite, leucoxene and zircon 

 as subordinate minerals. Occasionally a thin layer or parting of 

 more argillaceous composition. 



II. Pigeon Point. 

 Intermediate rock. 

 Hornblende 

 Anorthoclase 

 Plagioclase 

 Quartz 



Micropegmatite 

 Chlorite 

 Magnetite 

 Apatite 

 Rutile 



Gabbro. 

 Olivine 



DiaUagic augite 

 Basic labradorite 

 Apatite 



Titanif. magnetite 



Granoph y re-granite. 

 Anorthoclase 

 Oligoclase 

 Quartz 



Micropeg mat ite 

 Chlorite 



Augite (occasional) 

 Muscovite 

 Rutile 

 Leucoxene 

 Hematite 

 Apatite 

 Country rocks : feldspathic quartzite and slate, containing 

 quartz, orthoclase, plagioclase, chlorite, green mica, biotite, mag- 

 netite, leucoxene. Feldspar sometimes 75 per cent of the quartzite. 



III. Sudbury District. 

 No rite. Intermediate rock. 



Hypersthene Hornblende or 



Augite Hypersthene 



Bytownite Biotite 



Quartz Oligoclase-andesine 



Biotite Orthoclase 



Ho rnb 1 en d e Microperth ite 



Apatite Quartz 



Magnetite Epidote 



Sulphides Apatite 



Magnetite 



Country-rocks : sandstones, gray wackes, slates, conglomerates, 

 greenstones, volcanic tuffs and granitoid gneiss. 



Granopkyre-granite. 

 Biotite 



Orthoclase 

 Micropegm atite 

 Microperth ite 

 Microcline 



Oligoclase 



Quartz 

 Epidote 

 Ilmenite 

 Titanite 



