Reviews — The Charters Towers Goldfield. 283 



very useful. Many of the plates recall in a remarkable degree 

 the structures seen in the Mountain Limestone of the North of 

 England. 



XIII. — The Charters Towers Goldfield. ByJ. H. Reid. Geological 

 Survey of Queensland, Publication No. 256. pp. 236, with 

 37 plates, 10 figures, and 25 plans. Brisbane, 1917. 



AT one time Charters Towers had the greatest output of any 

 Australian goldfield, the production in 1899 being 319,572 oz. 

 of fine gold, but in 1916 this had decreased to 42,000 oz., and the 

 writer of this memoir takes a gloomy view of the future. The 

 geological relations of the gold ores are simple and of some interest 

 from the theoretical point of view. The oldest rocks of the region 

 are pre-Devonian schists, quartzites, and metamorphic limestones, 

 penetrated by a batholith of granodiorite, and this again by dykes of 

 aplite, quartz-porphyry, diorite, and porphyrite, the eroded surface 

 of the whole being covered in places by patches of sandstone, 

 possibly Tertiary. Two series of faults later than the dykes 

 determine the position of the lodes, which strike N.-S. and E.-"W. 

 respectively. They may be described as simple and composite 

 fissure lodes, up to 5 or 6 feet wide, with occasional "bulges" 

 up to 50 feet in width. The vein-stuff is quartz, rarely calcite, 

 carrying pyrites, galena, and blende, with occasional tellurides. 

 Most of the gold Avas obtained from highly mineralized pay-shoots 

 of irregular form, diminishing in value in depth. The vein-fillings 

 are clearly of magmatic origin, belonging to Lindgren's type of 

 siliceous gold ores of the middle depths, deposited by ascending 

 solutions derived from the- granodiorite magma. No gold values 

 of any importance are found outside of the igneous rocks, and the 

 association of the lodes with the porphyritic dykes is very definite. 



XIV. — The Geology of the Country around Gatoojta. By A. E. V. 

 Zeallet and B. Lightfoot. Southern Ilhodesia Geological 

 Survey, Bulletin No. 5. pp. 68 and 7 plates. Salisbury, 1918. 

 TIIHIS memoir, written by the late Mr. A. E. Y. Zealley and Major 

 J_ Lightfoot, records the results of a geological examination of 

 about 600 square miles of territory some 200 miles north of 

 Buluwayo, in the years 1912-14 ; about half of it is devoted to the 

 geology, and the other half to the economic development of the 

 region, with descriptions of the mines. The rocks in the area are 

 almost entirely igneous, the dominant feature being a portion of 

 a large granite batholith in the south-east corner, with other granite 

 masses of smaller size on the west. Other rocks include porphyry, 

 felsite, and greenstone, the two last names being wisely used in 

 a very broad sense. One of the most interesting results of the 

 field-work is the discovery that nearly all the " banded ironstones" 

 exposed in the district are ferruginized and silicified felsite and 

 quartz-porphyry. This obviously has an important bearing on the 

 origin of the quartz-magnetite schists of other regions, both in 

 South Africa and elsewhere, and especially the much-vexed 



