THE SUDBURY LACCOLITHIC SHEET 777 
Calculating the normal minerals we find: 
@uariZ ae wis 0 Sorel ve a ere Seah ee i BOO 
Orthoclase se 9c lez then eck atk ath ene eRe aT ALA 
UNM DIte yates ee seen g Au Se ea, |) eee 2OL20 
PAT OTEN TLCS MMe carey 9c aoa eign tr eee ue YOO 
iypersthenegetuge vr ge ach gas canes mare 62 
Rerricoxide: <3 Wamawi: ere ee PAs .63 
Probably some of the soda belongs to the orthoclase, since the 
extinction angles of the plagioclase correspond to oligoclase. Accord- 
ing to the new system the rock may be called Omeoze, a dopotassic, 
peralkalic rock belonging to the order Brittanare, near the boundary 
of Columbare. 
The basic norite and the acid granites just described are thought 
to have sprung from the original nickel-bearing magma, because they 
follow so closely the southern edge of the main nickel range; but it 
must be admitted that they bear little resemblance to the basic and 
acid phases of the nickel eruptive itself. 
The Ramsay Lake gabbro band.—There are, however, a few bands 
of gabbro which have some points of likeness to the nickel-bearing 
norite, though they do not occur in close connection with it. The 
most notable runs for 9 miles parallel to the southern nickel range as a 
chain of hills separated from it by 3 or 4 miles of Huronian sediments 
and earlier or later eruptives. 
This irregular band of gabbro has pushed up and sometimes 
partly overturned the stratified Huronian graywacke around its mar- 
gin, and a few strips of the Huronian run up its flanks at the widest 
part, suggesting a chain of elongated laccoliths, or possibly the blunt 
edge of an eruptive sheet having a nearly vertical attitude. As the 
gabbro differs markedly from the nickel-bearing norite, it is believed 
that there is no direct connection between them, but that the southern 
band probably split off from the magma before the main sheet occu- 
pied its present position. 
The rock is medium- to coarse-grained and usually greatly weath- 
ered, though occasionally fresh enough to show its original composi- 
tion of labradorite, making up about half the sections, diallage and 
enstatite, the rhombic pyroxene being in somewhat smaller amounts 
than the monoclinic. There is a very little quartz in interstices 
