338 DEPARTMENT OF THE INTERIOR 



2 GEORGE V, A. 1912 



Boundary survey. The following description of the monzonite is taken from a 

 manuscript written by Dr. G. A. Young, one of the joint authors in the forth- 

 coming report on the mining geology of the Rossland district. The writer is 

 very greatly indebted to Dr. Young for the favour of using this material in 

 advance of publication, as well as to Mr. R. W. Brock, who has generously 

 supplied the hitherto unpublished results of Mr. Connor's analysis of the 

 monzonite. Quotation marks indicate the part of the present text supplied by 

 Dr. Young. 



' The monzonite body underlies about one-half of the total area of 

 the map sheet (accompanying the special report) and as already stated, 

 represents only the western portion of a roughly oval mass about five miles 

 long in an east and west direction and having a maximum width of about 

 one and three-quarter miles. That part of the monzonite mass lying inside 

 of the area of the map has a very irregular boundary which, commencing 

 on the summit of Deer Park Ridge, first trends northeasterly and then 

 north, passing along the western side of Center Star gulch. The boundary 

 swings across this valley a short distance beyond the northern boundary 

 of the area and pursuing a very irregular course, follows along the top of 

 Monte Cristo mountain and thence diagonally down the southern face of 

 C. and K. mountain, sending a tongue across the summit of the latter. 

 Beyond the eastern limits of the map sheet, the boundary of the monzonitt' 

 curves around the east face of C. and K. mountain towards the great 

 body of Nelson granodiorite on the north, then turning back on itself, 

 extends eastward across the valley of Trail creek to the slopes of Lookout 

 mountain. The southern boundary of the monzonite from the greatest 

 eastern extension of the body, takes a general westerly course, entering 

 the area under discussion, along the side of Cherry ridge near the south- 

 eastern corner of the map sheet and with a bow to the north, strikes west- 

 ward to the top of Deer Park mountain near the southwestern corner of 

 the area. 



' Within the mass thus outlined are. several intrusive bodies of por- 

 phyritic monzonite and pulaskite as well as a few areas of the bedded 

 series and of the augite porphyrite. The greater part of the monzonitic 

 body is surrounded by the Carboniferous sediments and associated augite 

 porphyrite, the igneous mass cutting sharply across the general strike of 

 these formations. Towards its western end the monzonite is limited by 

 the considerable area of Nelson granodiorite found in the valley of Sheep 

 creek. 



' The large area of monzonite with its very irregular boundary, is 

 not occupied by a simple body but by a number of varieties of rock having 

 certain characteristics in common but still presenting much diversity in 

 general appearance and composition. In colour they vary from nearly 

 black to light gray; in grain from very fine to coarse; and in structure 

 from granular to semi-porphyritic. Different types at times cut one 

 another and along the contacts, the younger varieties not infrequently are 



