[Proc. Roy. Soc. Victoria, 32 (N.S.), Pt. I., 1919]. 



Art. VII. — The Diabases and Associated Rocks of the Howqua 

 River near Mansfield, with reference to the Heathcotian 

 Problem in Victoria. 



By E. O. TEALE, D.Sc, F.G.S. 



With an account of the Petrography of the Diabases by 

 Prof. E. W. Skeats. 



(With Plate IV., 4 Text Figures and Map). 

 [Read July 10th, 1919]. 



Contents. 



1. Introduction. 



2. Position and Access to the Howqua Region. 



3. Physiographical Features. 



4. General Geology. 



5. Lower Palaeozoic Rocks (Heathcotian to Silurian). 



A . Diabases : — * 



(a) Normal Diabase. 



(b) Soda Rich Diabase. 



(c) Platy Diabase. 



B. Tuffs and Agglomerates, 



C. Alteration features of the Diabase : — 



(a) Red Jasper. 



(b) Siliceous — carbonate rocks. 



(c) Talc rocks. 



(d) Serpentine and Chrysotile. 



(e) Minei'alization of the Diabase — Auriferous sulphides, eta 



D. Tlie Sediments : — 



(a) 'i'heir Lithological features. 



(b) Apparent structural relationships. 



(c) Phosphatic Deposits. 



E. Concerning the Age of the Diabase and Cherts — a comparative- 

 review. 



6. The Upper Palaeozoic Rocks. 



A . Devonian : — 



(a) Dacite-porphyry. 



(b) Grano-diorite. 



(c) Dioiite. 



B. Lower Carboniferous : — 



(a) Basal conglomerates. 



(b) Rhyolite. 



(c) Conglomerate. 



(d) Sandstones. 



(e) Purple shales. 



7. Summary and conclusions. 



i 



