258 AUSTRALASIAN ANTARCTIC EXPEDITION. 



EXPLANATION OF PLATES. 



All photographs have been taken in ordinary light unless when otherwise stated. 



PLATE XXXVIII. 



Fig. 1. Fine-grained quartz-dolerite from Horn Bluff (No. 732B). Note typical 

 ophitic fabric. Patches of mesostasis are to bo seen at the centre of the 

 picture and elsewhere, x 27. 



Fig. 2. Quartz-dolerite from Horn Bluff (No. 732A). The felspars, which act as a 

 matrix, may be seen indenting the periphery of the pyroxene. The 

 augite crystal on the left is cut parallel to (100), and shows indistinct basal 

 striation. The mesostasis in which the felspars are set is well shown. 

 x 17. 



Fig. 3. Part of the pegmatitic quartz-dolerite (No. 733) from Horn Bluff. To the 

 right of the vertical diameter is part of a long pyroxene individual twinned 

 on (100) and showing serrated edges. The dark longitudinal band on it 

 represents an alteration area in which the exceedingly fine basal striation 

 is developed. The rectangular sections coming out horizontally from the 

 top of this crystal are cross -sections of augite. At the right-hand side 

 of the long pyroxene some granophyric mesostasis may be seen. Note 

 the variation in the size of the plagioclase. x 17. 



Fig. 4. Basic plagioclase, cut normal to (010) and (001), in graphic intergrowth with 

 augite, in No. 733. Chlorite-stained granophyric mesostasis at top and 

 sides, x 17. 



Fig. 5. No. 733. Most of the field is occupied by mesostatic material, some in the 

 position of extinction, consisting largely of felspar with rod-like or acicular 

 development. To the left this is in contact with a twinned plagioclase 

 crystal whose broad lamellae are extinguished. Crossed nicols. x 59. 



PLATE XXXIX. 



Fig. 1. No. 837. Showing part of a nodule composed of olivine grains with some 

 associated felspar and pyrites. The olivine has been altered to talc (?), 

 the colour of which changes from very pale-green on the left to a 

 greenish-brown on the right side of the nodule, x 17. 



Fig. 2. No. 838. Showing part of a glomeroporphyritic aggregate of plagioclase. 

 Crossed nicols. x 17. 



Fig. 3. No. 449. Containing plagioclase, with granular augite and magnetite. A 

 few small white patches represent interstitial quartz, x 27. 



Fig. 4. No. 459. Showing on the left part of a glomeroporphyritic aggregate of 

 plagioclase crystals whose central portions have been replaced by chlorite. 

 x 27. 



Fig. 5. Essexitic dolerite (No. 208). There may be seen augite, plagioclase, ilmenite 

 (sometimes in rods) and chlorite (light irregular patches at top and right- 

 hand side), x 17. 



Sydney: Alfred James Kent, Government Printer 123. 



