79 



belong, mostly, to the diabase types (see Benson, "Basic 

 Rocks of Blinman," Roy. Soc. S. Austr., xxxiii., 1909). The 

 amount of alteration induced in the adjacent rocks by con- 

 tact metamorphism varies considerably with the dififerent 

 dykes. In some cases, little or no alteration can be detected, 

 while in others some quartz and allied minerals appear to 

 owe their development to contact with the dyke. Siderite, 

 hematite, limonite, and copper ores are frequently found in 

 dolomitic limestones near the junction of these beds with an 

 igneous dyke. It is an interesting fact that on the south- 

 eastern spurs of Mount Remarkable a small field of igneous 

 dykes occur, having similar petrographical features to those 

 found near Blinman, and which intrude rocks of a similar 

 geologic age (see Thiele, Roy. Soc, S. Austr., xl., 1916, 

 p. 680). 



The association of igneous dykes, dolomitic limestones, 

 and copper ores is a characteristic feature of the Blinman 

 mining field. Dr. Lander's mine, which I visited, situated 

 near to Blinman, about a quarter of a mile to the southward 

 of the old Blinman to Parachilna road, is typical of most 

 of these mines. The ore occurs in bunches, immediately 

 below an igneous dyke, which is intrusive at a low angle. 

 The carbonates and oxides of copper, siderite, and hematite, 

 together with some quartz, are distributed through a metalli- 

 ferous zone, mixed with vein stuff, up to 9 ft. in diamet-er. 

 Below the ore zone is a broken-down shale, containing a little 

 ore, and this latter rests on dolomitic limestone. 



The Scenic Aspects of the Flinders Ranges are often 

 very striking, and certainly unique in South Australian 

 scenery. Under arid conditions, the weathering agencies have 

 sculptured the country into sharp and rugged outlines, pro- 

 ducing bare hills and mural cliffs. The prevailing red colour 

 of the rocks also gives an unusual tone to the landscapes and 

 lends itself to uncommon colour effects. When standing on 

 some vantage point, commanding a view of the surrounding 

 hills, especially with the slanting rays of the setting sun 

 thrown upon the scene, the picture is full of a weird beauty. 

 The bare scarps of the ranges look like enclosing walls, the 

 red rocks possess a higher colour* by reflecting the lurid sun- 

 set, and the glow on the rising mists of the valleys all combine 

 to give the appearance of a vast furnace or the floor of a 

 smoking volcano. 



XVIII. Tectonic Phenomena. 

 The main geological structures of the region under 

 description are relatively simple. The great fault-scarp, 

 facing west, by which the Flinders Ranges are suddenly cut 



