72 
J, R. H. McWhae. 
of firebricLs at CJaekliiie for some years (2(), p, II; 10, p. 13). The sillimaiiite 
content of the clay is estimated to vary from ^^^e to 10 per cent, of the rock 
(26, p. 12). 
(ii) SamL 
A pure white quartz sand derived from the quartzites in the west of 
the area is being utilised by the Clackline Firebrick Company. 
n. CHARCOAL IRON. 
Banded iron ore dei^osits occur two miles west-north-west from Clack- 
line Railway Station. These have been niapi>ed and described by Hobson 
(G.S.W.A. File 237/1910) who states that up to the end of 1907 they had 
produced 18,253 tons of iron ore for use as a iiux. These deposits are 
the result of latcritisation of iron-rich metajaspilites of the Jimperding 
Series. The area of iron-inch rocks is approximately 60 square chains accord- 
ing to Hobson’s ma^i; and the average iron content is 45.5 per cent. A plant 
is being erected at Wundowie, about 10 miles to the west-south-west of 
Clackline, to obtain jiig iron from similar ore, using charcoal as a fuel for 
smelting. 
IHob.son's Map and Rciport '•Proposed drilling in the vicinity of the Clackline iron- 
stone deposits” has since been published in the W.A. Mines Dept. Ann. Kept, for 1945, 
pp. 58-00.— Ed.] 
Vr. HISTORY OF THE AREA. 
1. In early Pre-Cambrian time argillaceous, arenaceous and iron-rirdi 
sediments (jaspilites) were dei>osited along with contemporaneous tuffs and 
basic igneous lava flows or sills. 
2. An orogenic period accompanied by the intrusion of a granitic 
magma followed. 
At this stage the, sediments suffered regional metamorphism under silli- 
manite zone conditions and considerable jilastic fiowage took place in the 
less competent argillaceous facies. There was no further orogeny or re- 
gional metamorphism after this period. 
3. The granitic magma did not com])letely crystallize until after the 
folding had cea.sed (23, p. 109). It consolidated as granitic gneiss sills of 
huge size which indicates that the folding had taken place at considerable 
depth (4, p. 294, 2, p. 81). 
4. A relatively short lime, geologically speaking, after the coinpletel 
consolidation of the granitic gneiss, palingenesis of the granitic gneiss and 
sediments of the Jimperding Series took i>lace. At the end of the orogenic 
period the base of the orogene Avonld be at a great depth and under great 
pressure due to the superincumbent loa<l of sedinumt. A lag in isostntic 
adjustments appears to occur after orogeny in whicli the surface projections 
of the orogene are eroded. The erosion of the surface part of the orogene 
would reduce the pressure on the acid rocks at depth so that jialingenesis 
may have followed (18, pp. 336-332). 
This palingenie granite magma (the Younger Granite) was now in- 
truded into the Jimperding Series. Some contact metamorphism was effected 
by this intrusion, probably the most important change being the retrograde 
metamorphism of the earlier formed high-grade silliinanite and cordierite 
to sericite. 
