THE HEEMSKIRK MASSIF. 167 



The author feels that we may safely accept the following state- 

 ments as being substantially true : — 



1. That the interior of the earth is largely composed of 



metallic ingredients — the " barysphere " of Posepny^ or 

 the " nife " of Suess.^ 



2. That these metallic ingredients are expelled from time to 



time into the outer portions of the earth's mass and thus 

 come into place in the zones which are open to geological 

 investigation. 

 Of the mechanical processes involved in the upward migration 

 of the heavy metals but little can be inferred. 



It is, in the opinion of the author, an indubitable fact that the 

 metallic contents^ of at least many ore deposits have ascended in 

 association with much larger masses of igneous material of different 

 composition. From the ascending materials, in certain cases at 

 least, three principal products are derived, viz. : — 



1. The igneous rock masses (mainly non-metallic). 



2. The metallic ores and many of their gangue minerals. 



3. The juvenile or magmatic vapours and solutions. 

 Rather than state that the igneous rocks or vapours have 



served as carriers of the metallic ores the author would affirm that 

 all three groups together constitute the real essence of the magma. 



The question of the relationship between the metallic ores and 

 the igneous rock masses demands a detailed discussion for each 

 region in which the relationship may be declared to exist. A study 

 of one such region* has been made by the author and his conclusions 

 stated elsewhere. 



In some cases the metallic ores are disseminated through the 

 igneous material with which they have ascended ; in other cases 

 they have been collected with the assistance of the magmatic 

 vapours into certain foci, from which they are expelled during the 

 final stages of consolidation. 



In either case it is evident that the metallic ores and igneous 

 rock materials have ascended together from the deeper portions 

 of the earth's mass. 



With regard to the separation of the metalliferous magma which 

 ascended in the Heemskirk-Comstock-Zeehan district into its 

 several component parts, the author has claimed that a very 

 definite succession of events may be detected from the field evidence. 

 In the evolution of the magma towards the solid state it appears 

 perfectly certain that the granite is the earliest product and that 

 the ore deposits are the latest products of consolidation. 



With the completion of the process of consolidation the period 

 of igneous activity and the metallogenetic epoch closed. It is 

 claimed by the author that the period of complete solidification of 

 the whole magma and the period of cessation of primary ore deposition 

 are coincident and coordinate for this region. 



1" Genesis of Ore Deposits," A.I.M.E., pp. 11, 73, 79. 



2 "The Face of the Earth," Vol. IV., p. 544. 



3 With regard to theTertiarv andesitic goldiields, Dr. Malcolm MacLaren has put forward other 

 hypotheses. Vide "Gold," 1908., p. 61. 



4 The Heemskrk — Comstock — Zeehan region of Western Tasmania. 



