Bulletin - Geological Survey of Western Australia, Issues 2-8

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1898 - Geology
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Page 69 - At the date of my visit the old workings, which had opened up a large quartz reef, had been abandoned, and a fresh start made by a party of miners " on tribute," who recommenced work in an " open cut " on the auriferous felsite dyke running parallel to the reef.
Page 78 - The conglomerate covered a much larger area than it at present occupies, and denudation has gone on to a large extent since it formed part of one continuous formation. The thickness of the conglomerate is nowhere very great, operations having shown that it rarely, if ever, exceeds 20 feet. The conglomerate is not of sedimentary origin, but has apparently been formed by the alteration in situ, and" subsequent cementation of the underlying rocks.
Page 64 - ... extensive deposits of sandstone lying beneath the ubiquitous ironstone gravels. These sandstones, which are usually of a light grey colour, are fine-grained and of an even texture. The maximum thickness attained by the sandstone is not less than 150 feet. The quartz reefs all occur in the granite to the west of the diorite, always in close proximity to the junction of the two rocks. The general strike of the reefs is a little to the west of north and east of south, with a high dip to the east....
Page 11 - The interstratified beds of white, yellow, and sometimes ferruginous limestone, attaining the thickness of 30 feet, which occur chiefly in the neighbourhood of Champion Bay, do not seem to be persistent, but are found as it were in patches, which gradually thin out. As the limestone composing them is made up of shells, which in some cases have consolidated into a solid rock, in others have retained their original form, it seems most probable that the accumulation of shells in hollows, in the ancient...
Page 3 - Tinfield, the ore being derived from the disintegration of quartz-porphyry dykes, in which it is associated with tourmaline and titanic iron. Besides iron and manganese, large deposits of kaolin of a very fine quality occur, as well as veins containing mica and asbestos ; but these latter are too much weathered at their outcrop to be of any value. Near Bridgetown a very large deposit of graphite has lately been opened up ; it exists in the form of a bed between talcose schists, about 20 feet in thickness.
Page 122 - Australia shows an enormous extent of Recent and Tertiary strata entering the State at its eastern border, in the Nullabor Plains, and extending without any interruption as far as Israelite Bay. These strata consist of porous limestones associated with beds, into which the rainfall is rapidly absorbed and discharged seawards in the form of fresh water springs. Where these strata have been pierced on the South Australian side of the border, the section invariably shows from 300ft.
Page 116 - ... three beds were passed through. The first of these which outcrops near the mouth of the drive is 28 feet in thickness, being followed by 13 feet of schistose rock, containing a small bed 1 foot 6 inches in thickness, whilst the third bed is 8 feet in thickness. Several other shafts have been sunk, and open cuttings made to test the run of these beds. From one of the former, about four chains to the Westward of the drive, which appears to be upon the large bed, a sample, weighing 25cwt., was sent...
Page 55 - As a general rule the ore deposits have no well-defined walls, but seem to pass insensibly into the surrounding rock. The lodes are often traversed by a network of quartz veins, which ramify in all directions. There is abundant evidence attesting the fact that the rocks have been subjected to profound dynamic phenomena, which has resulted in the production of lines of weakness along which mineral-bearing solutions have found a comparatively easy passage.
Page 86 - Erawandoo form the most prominent summits, is remarkably prolific in iron-bearing schists. The summit of Mount Hale is formed of contorted quartz schists, with bands of hematite, which occur in lenticular masses ; some bands are often as thin as a sheet of paper, whilst others widen out to considerable dimensions. One band measured 70 feet across and outcropped for over a quarter of a mile, but varied in thickness in different parts. There were similar bands parallel to it and equally persistent...
Page 4 - The rocks of this belt consist mostly of hornblende, mica, or talc schists, of which the hornblende schist so closely resembles diorite that it is impossible to distinguish it in a broken specimen. The rocks of this belt are a good deal broken and faulted by granite and diorite dykes and quartz lodes containing gold, iron, and copper. There are also some large magnesia lode-masses rich in fine gold, which will probably prove to be serpentine at a depth. Many of the lodes also contain large quantities...

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