28 SCIENCE PROGRESS 



A paper by Dr. A. Holmes on the Pre-Cambrian and asso- 

 ciated rocks of Mozambique is an important contribution to 

 igneous and metamorphic petrology (Quart. Journ. Geol. Soc, 

 1 91 9, 74, pt. I, pp. 31-98). Certain gneisses of the region are 

 believed to be due to concordant injection of granitic magma 

 into a series of ancient sediments, of which the argillaceous 

 facies became granitised with the production of biotite-gneisses, 

 whilst the calcareous and dolomitic facies formed hornblendic 

 and garnetiferous gneisses by interaction with the granite. A 

 novel feature is the correlation of some of the gneisses and 

 granites by means of the lead-uranium ratio in their zircons. 

 The Pre-Cambrian age of a majority of the rocks in the 

 basal complex of Mozambique is thus demonstrated. 



Dr. A. L. du Toit presents an excellent study of the con- 

 tact metamorphism of dolomitic limestone in Natal {Quart. 

 Journ. Geol. Soc, 1920, 75, pt. 2, pp. 119-37). Granitic ema- 

 nations have produced more or less regular zones in adjacent 

 marbles, of which the innermost is rich in diopside and often 

 in scapolite, with forsterite, phlogopite, chondrodite, and spinel 

 farther out. Dedolomitisation is usually perfect ; and in 

 some areas beyond the silicate zone the dolomite has been 

 deprived of the bulk of its magnesia, and has been changed 

 into coarsely crystalline calcite. This change, termed calci- 

 tisation, has probably been due to the action of carbonated 

 waters during the cooling of the plutonic complex. 



F. L. Hess introduces the term tadite as a general name for 

 the rocks formed by the contact metamorphism of limestone, 

 dolomite, or other soluble rocks, into which foreign matter from 

 the intruding magma has been introduced by the agency of 

 hot solutions or gases {Amer. Journ. Set., 1919, 48, pp. 377-8). 



Other important references are listed below. 



Economic Geology : 



Holmes, A., Non-German Sources of Potash, Geol. Mag., 1919,251-4, 



pp. 340-50. 

 Whitman, A. R., Difiusion in Vein-Genesis at Cobalt, Econ. Geol., 1920, 



15, pp. 136-49. 

 Whitehead, W. L., The Veins of Cobalt, Ontario, Ibid., pp. 103-35. 

 Wilson, M. E., Geology and Mineral Deposits of a Part of Amherst Town- 

 ship, Quebec, Geol. Siirv., Canada, 1919, Mem. 113, p. 54. 

 O'Neill, J. J., Preliminary Report on the Economic Geology of Hazelton 



District, British Columbia, Geol. Survey, Canada, 1919, Mem. 110, pp. 51. 

 Bateman, A. M., and McLaughlin, D. M., Geology of the Ore Deposits 



of Kennecott, Alaska, Econ. Geol., 1920, 15, pp. 1-80. 

 Stuart, M., Galena Deposits of North-Eastern Putao, Rec. Geol. Surv., 



India, 1919, 50, pt. 3, pp. 241-54. 

 Stigand, I. A., The Origin of Petroleum, Mining Mag., 1920, 22, pp. 11-22. 

 Dowling, D. B., et alia. Investigations in the Gas and Oil Fields of Alberta, 



Saskatchewan, and Manitoba, Geol. Surv., Canada, 1919, Mem. 116, 



p. 89. 



