THAMES DEEP LEVELS.

Thames Star, Volume XLV, Issue 10616, 16 January 1909, Page 2

THAMES DEEP LEVELS.

AjND THEiIiR. FUTURE PROSPECTS

AN INTERESTING ARTICLE.

(By Chas. B. Storie,. Mining and Metallurgical Engineer.)

Ait the present time much attention, is being devoted to the subject of "The future development of th-3 deeper areas of the Thames goldfield, and, as the subject is of the most vital importance to the Thames ? n particular, and minings generally throughout the' Cape Oolville Peninsul.ai, it behoves the mining and: investing community to carefully study the evidence that Is available, both for aSnd againat thei .pi*bposod under-

takings^-,. ?■/'■', v t.. ■ \ .'.', , It is considered advisable thai a comprehensive statement of the position, free from teohn.icalit.es>, shonil-1 be placed befoi-e the puWc, in ander to enable them to the salient features and complex problems that are sure to arise from time to tinie. The problem, that is receiy'ng the greatest aitteintion at , i^he present time is the relative merit® "of two different propositions for driv'ng; a level from the Queen :;of Beauty

shaft at a depth 6t 1000 ft, towams the northern portion of the goldfield. Before arriving at any definite conclusion regarding the merits of the altormvt've routes proposed,* it would, probably, he wise to consider the main geological and mineoloisical features tha.t hare been, rHsi closed and tlemionstrated hv mining operations actuailly carried out. 1 —S'jnple Statement of the Thames i Geology.— To begin, with, it may be stated that the Thames Goldfield, is built [up of a series of volcanic laya flowsj 1 oonsistinig maioly of a rock oommontj ■ly called ': "andesite." It is claimed by some •authorities that the successive, lava flows which 'brought these rocks from great depths, took place beneath the sea, and in consequence thesei 'ejections womdd be classed as i from submarine volcanoes.

Wfalatever may ihaive been the mode of origin -does not concern the prac-,. tical miner, but what is of material importance from a mining point of view, is the fact that some of :the lava flows have been subjected to such intense miheralisaition, by - ol> scure forces, that certain, fractures and channels in them have become repositories for valuable metals and minerals, and to such an extent us to constitute deposits. of economic; value and importance, and constitute a goldfield. On. the other hand, some of these lavas have been subjected to'"such a relatively meagre amount of mineralisation .that the vftluW that- hare been^concanitrated in them are not considered of sufficient importance to be classed as payable miinieral deposits, and theise rocks are therefore "relaitively" barren. ," : When the term zqne is usied. :t refers to one or another of tihie above njimtioned lava flows, and is generally classed as a produotjye or umproducv tive zone respectively;' • —"The-Effect of the Mbanataiari

Fault.—» - - i After the mineral deposits wer^ formed, most of which occurred as quartz reefs, a violent disturbance took placet, Which produced & huge fracture riuinilng im a northerly and southerly direction through the goldfifijd. " Th> fracture is what Is* known as tba Moawataiari '.'fault,' and, in, consequence of this '■ "fault' having taken place, the rock mass, on the. seaward side of it, subsided, and was precipitated downwards: and westwards for a. distance (tentatively determined) of 800-IOOWt. This movement** along'" 1 the "fault" was what is now termed the Moaniataiavi slide'and the immediate effect of this slide waft to dislocate all of tihe reefs that ran in a hillward direction and precipitate them Jlownw^rds to tht> distance corresponding to the movement thikt had : taken place. It will thus Ibe seen that the rich "zones" of country on the seaward side of the slide, would, when: tho rock mass came to rest, abut against a poor or unprodluotive "zone" ou the hillward side, and the confusion thus caused has led to the complex prospeetimigi operations that have been carried out by the mining companies in, the endeavour to "pick up" the continuation of the rich runs of stone! that were ieo succesefully ; cut ploited in the early days of the goldfield. ' ' .

It is not difficult, to-form a-mental picture of what the original goldfield was like before the slide took place.' Qpe can easily imagine that if the whole of the flats and foreshore upon which the townships of Thames and ■j&orth^^a^/'now^ibuilt 1' were reelevated! and placed! back in the position, that .'they originally - occupied^ the Brian Boru Hotel, for example, would occupy a position about where Rolleston *aaid Richmond streets now intersect, but.at «un elevation corresponding approximately to the highest point |of TJnai Hill, and the Thames .Stair office would* occupy a position about vertically over the highest point in. Ajlbert street, but at «.-n elevationi nearly as high as the Al burnia shaft. \ These homely illustrations will give some ideia, of the extent of the i movement that has takeni place, ani, •m prospeotin^' on the hillw»rd> side of), thai B|ulfef?ot';th© con|.'.n;tratioh of tne' rich runs of stone that existed ai Crrahanistown, this displacement must be talten Into consictartatioji. (These''illustrations aire purely relative, and dot not take into consjderationi the great thickness of gravels, etc., on the flats, etc.) 1/ —(Number of Zones.—

So far as it has been, demonstrated by actual mining operations there appears to have been at least five of these "zones." Those had a very low dip from the horizontal. in, both ;\ westerly and a southerly direction ; in other words, the general dip was south-westerly. . . For example, a crosscut at Grahamatown, from, the foreshore towards Dixon's wef -would initerßeot precisely the .same* "zone*" as a crosscut from the Karaka towards, the same point and at the same level. : It will thus b© seen that, for all practical purposes, the Maanataiari

tunnel and the workings at tho to;j of the h 11 iyive proven at least three - of'the "zones" of country that were nearest' the surface, and with practically negative results as far as Bonanza mines are concerned.

(To be continued.)