ALKALINE ROCKS OF S. QUEENSLAND. 253 



A. — The sedirneiitary rocks in each of the four districts consist 

 essentially of sandstones, shales, and cong-lomerates of Upper Trias- 

 Jura age. 



B. — Most of the rocks west of the line dividing the Palaeozoic 

 from the Mesozoic fomiations are metajnorphic. The rest are ig-neous 

 in origin. The metamorphic rocks I am discussing in a separate 

 paper. 



C. — The non-alkalime igneous rocks comprise granites and 

 syenites (Cooran, Woondum, Obi-Obi, Woodford, Leacey's Creek),, 

 rhyolites (Tuchekoi Eange, Blackall Range, in part, Toolburra Range, 

 Mount Archer, &c.), quartz porphyry (Upper Mary River), andesites 

 (Blackall Range, in part, Little Livei-pool Range, in part), basalts 

 (Woondum, Blackall Range, Moimt Mee, Little Liverpool Range, &c.), 

 and dacites (Glass House Mountains, Yandina, and Mount Fhnders), 

 gabbro at Milora on the Boonah line. 



D.— The alkaline- rocks with which we are specially concerned 

 here comprise: — 



{a) Pantellarite. — Tinbeerwah,, Peregian, Bottle and Glass, 

 Nindherry, Eerwah, Ngun-Ngun, Trachyte Range; also in 

 isolated places on and near Mount Flinders and on the 

 Little Liverpool Range. Some of the pantellarites possess 

 a trachytic fabric with flow structure ; others are hyalo- 

 pilitic ; some are pilotaxitic, and a few orthophyric. The 

 pantellarites are darker in colour, and have a higher iron 

 and lime percentage than the following class. 



(h) Comendite. — Cooran, Cooroora, Coolum, Conowrin, Tibro- 

 gargan (Tiberowaccam), Beerburrum, Ewin, Mount 

 French, Spicer's Peak, Mount Mitchell, &c. The comendites 

 are all light in colour, greyish, bluish white, or yellowish ; 

 their fabric is microgranitic or orthophyric, and the 

 dominating constituents are sanidine or sodasanidine and 

 aegirine, riebeckite or arfvedsonite. Quartz is also pre- 

 sent. 



(c) Leucocratic Soda-Trachytes. — Beerwah, Mount Flinders, and 



the Little Livei-pool Range. These rocks are similar in 

 colour to the comendites, but have a trachytic fabric. In 

 composition they differ from the comendites only in being 

 quartz-free or nearly so. 



(d) Melanocratic Soda-Tirachytes. — These differ from the above 

 in being much darker in colour — from grey-blue to almost 

 black. They are easily recognised in hand specimen from 

 basalts and andesites l3y their silky lustre. The dominant 

 minerals are anortlioclase, microcline microperthite, and 

 oegirine, with or without magnetite. Such rocks have 

 been described in my papers from the Round Mountain, 

 near Caboolture, Mount Flinders, and various points on 

 the Little Livei-pool Range. Occasionally nosean and 

 pseudo-leucite forai important constituents in these rocks. 



(e) Momonite has been described from Mount Cooroy. 



if) Quartz-keratophyre has been described from Mount Byron, 

 near Mount Mee. 



