134 president's address — section c. 



out of all proportion to their real stratigraphical importance. These 

 beds vary from almost pure quartz through varieties of banded horn- 

 stone, jaspers of great beauty, to almost pure hematite. 



In certain localities these jaspideous beds present a very brilliant 

 appearance, due to the interlamination of red, white, and dark-colored 

 bands with intermediate varieties, the differences of color being due 

 to the occurrence of iron in the form of either limonite, haematite, or 

 magnetite. 



These bands are often intersected by numerous faults, which in 

 some districts are of considerable economic importance, for it is along 

 these fault-lines, generally at right angles to the strike of the quartzites, 

 that rich shoots of gold often occur. In some cases these iron-bearing 

 jaspers attain a very great thickness, over 1,000ft., and have been 

 very much plicated and contorted, whilst in places they have been 

 faulted in a direction parallel to the strike, the fault fissures being 

 often filled with a fault breccia of jasper recemented by secondary 

 silica. In all cases these jaspers and quartzites are vertical or inclined 

 at high angles. In many localities these quartzites and jaspers contain 

 magnetite in such quantities as to render the use of a compass in the 

 vicinity almost impossible. These beds have been styled quartzites, 

 a term implying that they are sedimentary ; they are, however, not 

 of detrital origin, numerous sections in many of the fields show them 

 passing by almost insensible gradations into the enclosing basic schists, 

 the whole appearance suggesting a gradual replacement of the original 

 rock along lines of maximum compression or foliation by silicification — in 

 other words, they represent a case of metasomatosis on an extensive scale. 



It may be of interest to note that these beds invariably occur in 

 the basic schists, in intimate association with auriferous quartz reefs, 

 and are at times themselves auriferous. In order that the present 

 confusion, arising through the want of a name to distinguish infiltra- 

 tion or metasomatic quartzites from indurated sandstones, may be 

 obviated, I hope someone may be able to suggest a convenient means 

 of escape from possible civil war between the field man and the labora-- 

 tory man, to which the present unsatisfactory system of nomenclature 

 rather tends. 



In 1905 the various divisions of these older crystalline rocks, as 

 developed on the Norseman Goldfield, were carefully mapped and 

 investigated, the salient features of which may be briefly summarised. 

 The staple formation consists essentially of a series of highly inclined 

 sedimentary rocks, estimated to reach a thickness — making due allow- 

 ance for repetition by folding — of about 800ft. 



No argillaceous slates appear to occur in the Norseman district, 

 though associated with the metamorphic sedimentary rocks is a bed 

 of very coarse conglomerate. Some of these ancient sedimentary 

 rocks appear to have been permeated by secondary silica and oxide 

 of iron to such an extent as to form very conspicuous bands of laminated 

 quartzites and jaspers, which make a pronounced feature of the field. 

 Associated with the metamorphic sedimentary beds of Norseman 

 are a series of interbedded igneous rocks, some of which are distinctly 



