SOME GEOLOGICAL FEATURES OF NORTHERN AUSTRALL\. 121 



SUMMARY AND TENTATIVE CONCLUSIONS. 



1. North Queensland, from Cloncurry to C?-pe York, forms 

 part of the North-Central massif of Australia, which is pre- 

 dominantly of pre-Cambrian age, and which has not been, 

 affected by any compressional forces since the early Cambrian. 



2. Festoons of progressively more recent folded rocks 

 envelop the massif. 



3. The massif has been subjected to plateau movements 

 only. As a result, the lodes on it are strong and permanent, 

 with a likelihood of oxidised bodies occurring below the first 

 sulphide zone encountered. 



4. The apically truncated batholiths of the massif and in 

 the Silurian festoon are most favourable for the prospector. 

 Grano-aplites are the characteristic rocks of apically truncated 

 stocks. 



5. Basic eruptives, altered to amphibolites, two quartz, 

 types (blue and wliite), magnetite-hematite-quartz rocks, 

 hematite-quartz rocks in shear zones, and lode graphite, are 

 features of massif petrography. 



6. The North-Central massif of Australia is characterised 

 by Archeean trend lines in a west-north-west direction. Refer- 

 ence to Suess' '■ Das Antlitz der Erde" and to his maps showing 

 the trend lines of the five continents wall show that the dominant 

 trend lines in the southern hemisphere are west-north-west for 

 tropical, and north-west for temperate regions ; and in the 

 northern hemisphere east-north-east for tropical and north- 

 north-east for temperate regions. This feature, being most 

 pronounced in Archaean structures, points to greater plasticity 

 on the earth's crust in Archsean times than in later periods, 

 and affords confirmation of the Lamarckian theory of earth 

 origin. 



7. The Cordilleran belt of Australia, from the Kosciusko 

 massif to WTaitsunday Passage, is essentially a fold region or 

 geosynclmal. Owing to intense folding it is not so favourable 

 for the occurrence of strong continuous lodes as the massif 

 areas . 



8. The Cordilleran belt passes out under sea somewhere 

 north of Mackay, and possibly swings out to New Caledonia, a 

 large portion of the geosynclinal ranges having been resub- 

 merged by extensive trough faulting. 



