INCLUSIONS OF BASIC PLUTONIC ROCKS AT KIAMA. 69 



the typical isotropic base of the monchiquites is well shown. 

 The olivine phenocrysts are more or less automorphic and 

 may be partly or entirely serpentinised. The augite is 

 automorphic and slightly pleochroic, some of the smaller 

 phenocrystalline individuals may form glomero-porphj^ritic 

 aggregates. Magnetite is abundant in small crystals. 

 Felspar occurs in the groundmass to some extent. Altered 

 leucite is probably present. The base is abundant." A 

 comparison of these two descriptions will show that the 

 two rocks are essentially the same. 



Similar Occurrences. 

 In 1893 the presence of a " Ohromite-bearing Rock in 

 the Basalt at the Pennant Hills Quarry, near Parramatta 

 was pointed out by Prof. T. W. E. David and Messrs. W. F. 

 Smeath and J. A. Wall, in a paper to this Society. Since 

 that time numerous fragments of gabbro, peridotite and 

 allied rocks have been obtained from this locality; the 

 basalt in which they are enclosed occurring in the form of 

 a volcanic neck. In 1902 Mr. G. W. Card 1 in the Records 

 of the Geological Survey of N.S.W., wrote as follows : — " It 

 may be noted that enclosures of a basic character are by 

 no means uncommon in the basalts traversing or overlying 

 the Hawkesbury formation. Thus boulders of gabbro occur 

 in this way at the Pennant Hills Quarry, Dundas, near 

 Sydney, and gabbro also occurs in olivine basalt from Glen 

 Alice, Oapertee. Colourless pyroxene, resembling that of 

 eelogite has been detected in basalts from Mount Wilson, 

 Rooty Hill, Thirlmere and Long Bay near Sydney. In the 

 nepheline basalt from Burragorang a pyroxene containing 

 picotite has been noted. At Bulli a dyke contains large 

 lumps of an aggregate of hornblende, olivine and picotite. 



1 An Eelogite-bearing Breccia from the Bingera Diamond Field by- 

 George W. Card, a.r.s.m., f.g.s., Records of the Geological Survey of New- 

 South Wales, Vol. vu., part ii. 



