THE HEEMSKIRK MASSIF 171 



It remains still to investigate the relationships of this chonoUte 

 to the other neighbouring outcrops of similar material, and to those 

 masses which have not been revealed by erosion, but the existence 

 of which we surmise from the observation of dykes and veins 

 identical in character with those found in association with known 

 outcrops. 



IV. — ^The Relation of the Heemskirk Massif to Neighbouring 

 Massifs of Similar Composition. 



If the contention of the author with regard to the nature of 

 the Heemskirk massif is sound, certain difficulties attend the 

 discussion of its relationship to the other developments of granite 

 at the North Pieman and the Meredith Range. These difficulties 

 are not met with if the bathohtic hypothesis with regard to the 

 substructure of the Heemskirk massif is supported ; for the out- 

 crops mentioned (together with several others lying to the north- 

 ward, and shown also upon one of the maps) may be regarded as 

 the surface exposures of one great granite mass which underlies 

 an extremely large proportion of Tasmania. 



All geological evidence supports the view that all these granites 

 are derived from the same source, and that they attained their 

 mise en place synchronously. 



Yet if a chonolitic form be assigned to each massif, a con- 

 tinuous subterranean connection between all of them cannot be 

 assumed (except, of course, at an extreme depth below the surface). 



An alternative hypothesis, which the author offers for con- 

 sideration, as being of possible application to the region under 

 discussion, is as follows : — 



The present visible outcrops of granite are the exposures of 



chonolites of limited extent, though possibly all of 



greater areal dimensions at some depth below the 



present surface than at this level. These chonolites 



extend in a horizontal direction below certain regions, 



and may in certain cases unite with others. The 



distribution of the several chonolites is determined 



by crustal or subcrustal stresses and their results. 



Hence the distribution tends to be more nearly lineal 



than that of the more symmetrical bodies (laccolites) 



which have been injected into unfolded or unfractured 



regions m other parts of the world. Chonolites, between 



which connections exist, are arranged along lines or 



zones of crustal weakness. 



This hypothesis, since it states that any connections that 



may exist between neighbouring chonolites are distributed in 



accordance with zones of crustal weakness and even dislocation, 



demands some treatment of the question of the distribution of the 



igneous rocks and ore-bodies in space. 



Without wishing to enter upon a full discussion of the metalli- 

 ferous provinces of the region to which reference has been made, 

 the author would draw attention to certain already ascertained 



