47

C.—9

Opinion has been and still is to some extent divided on the question of deep mining in the slate country, and various different theories as to the whence of the gold in the reefs of the ThamesTokatea and Kapanga groups are responsible for this. Those who maintain that the gold is by thermal agencies derived from deep-seated rocks, and with its associated silica now forms ore bodies traversing formations diverse in character, as are the slates and superimposed volcanic rocks, find no difficulty in postulating the existence of rich metallic and auriferous deposits in the slate country. On the other hand, there are those who maintain that the gold from its primary source has been brought to the surface or near to the surface by being included in and as forming part of the volcanic ejectamenta that covers and forms so large a part of the Cape Colville Peninsula. These theorists cite in support of their views the usual presence of small quantities of gold and silver in the volcanic rocks themselves; the numerous strings and small leaders of quartz, often auriferous, that from the superior rocks feed into and supply as it were the main lode itself; the fact also that special volcanic rocks are the principal repositories of the gold; and, finally, that the gold-bearing veins in the slates are almost exclusively but the continuation downwards of auriferous lodes that are present in the overlying volcanic rocks, or have been, where these and the upper part of the lodes have been removed by denudation. As is usual in such cases there may be truth on both sides, and amid a conflict of evidence it were unwise to attempt a solution of the problem before the whole of the facts have been placed in review. One important locality in connection with mining in the slates has yet to be considered. This is the slate area forming part of the Kuaotunu Peninsula. Within this, the evident influences that have been the main agent in the deposit of the principal quartz reefs are thermal waters, the source of which, though not distant from the scene of volcanic action, is not directly from volcanic rocks. There can be no doubt whatever that the vast accumulations of siliceous sinter that form such a prominent feature on the higher part and eastern slope of the Waitaia Range have been derived from the slate country that underlies and forms the bulk of that range, or from unknown rocks of a more siliceous type underlying these. Neither need it be doubted that the principal reefs of the Kuaotunu field have been deposited by thermal agencies bringing their burden of silica and more valuable products from below, and not from any volcanic rocks at or near the surface. In view of these considerations it may therefore be prudent to defer judgment on a matter on which so much may be advanced on both sides, and simply acknowledge in this place the fact that goldmining in the slates has not hitherto, on the west side of the Peninsula, been a successful venture; while, on the other hand, the bulk of the gold obtained from the Kuaotunu field has been taken from reefs in slate country, the material and contents of which could not have been supplied from adjacent or overlying volcanic rocks. The principal line of reef at Kuaotunu appears to have had one main shoot of gold declining at a low angle from north to south, the direction of the lode. And this having been passed through, although the quartz as a thick reef continues, the amount of gold present is not sufficient to pay the cost of raising and treatment of the stone, and at the same time yield a profit to the shareholders. This being so, there next arises the question of the probability of other shoots of gold lying at lower levels in the reef, and the warranty there may be in justification of any venture in search of gold at lower levels, either by boring or shaft-sinking. The success of any such venture, it will be readily seen, depends on which of the two theories of the immediate source of the gold to the reef proves to be the correct one. The facts at Kuaotunu appear to be in favour of the supposition that other shoots of gold may be found at levels below those yet reached in the Try Fluke and Kapai-Vermont Claims, and other claims along the same line of reef. Bemarks. —The Carboniferous rocks of the Cape Colville Peninsula are vastly older than any of the superincumbent formations that rest upon them. Whether rocks of the Older or Middle Secondary systems were ever present within the area of the Peninsula cannot now be determined. If such ever were present, it is certain that over the areas where slates now appear at the surface these had been denuded away, prior to the deposit of any part of the Cretaceo-tertiary or coalbearing series that, as regards those of this Peninsula, are usually considered the next oldest rocks in succession to those of the Maitai series. As seen in the neighbourhood of Cabbage Bay, the outlines of the old land, the surface on which the coal-measures repose, indicates the existence of a hilly if not a mountainous country, and the lowest deposits of the coal-bearing series is confirmatory of this view. Also, it is a well-known fact that between the deposit of the Mataura or Putataka series of Jurassic age and the earliest deposits of the Cretaceous period, as these are preserved to us in New Zealand, a great gap in the geological record intervenes, and it was during this period that the land within the New Zealand and neighbouring areas had its main line of extension, and the axes of its mountain-chains in a north-west and south-east direction, as indicated in a former part of this report. Cape Colville Peninsula was therefore at that time probably a flanking range on the west side of the great mountain axis of the old land. It is of great importance to determine whether the coal-bearing series was the first deposit of post-Jurassic date, and this is a matter that, in the present state of our knowledge, cannot be determined. It is possible that the volcanic rocks of the Thames-Tokatea group antedate the sedimentary rocks of the Cretaceotertiary period, and in that case the former must be regarded as appearing about the middle or beginning of the Cretaceous period. Until further evidence makes this manifest, it is preferred to adhere to what is generally the conclusion respecting this matter, and to treat of the Cretaceotertiary coal-bearing series as being the second in age of the rock formations of the Peninsula. Cretaceo-tertiary or Coal-bearing Formation. Rocks belonging to this series, as forming a distinct formation among the various groups present in the Cape Colville Peninsula, were first described by Mr. Cox, late Assistant Geologist, who, during the latter part of 1880, examined the Thames and Coromandel district, and at the same time paid a