a—6.

1886. NEW ZEALAND.

THE OWEN REEFS, NELSON (REPORT ON), BY W.C. WRIGHT, Esq.

Laid on the Table by the Hon. Mr. Lamach, with the Leave of the House.

Mr. W. C. Weight to the Chief Surveyor, Nelson. Sir,— Survey Office, Nelson, 31st May, 1886. I have the honour, by your instructions, to furnish the following report on the Owen Reefs, which I have prepared from survey, and from a careful examination of the different lodes and of the locality generally. In following this report it will be borne in mind that the reefs described are in no way developed, but are outcrops of quartz, frequently of great magnitude, which even in the older claims have in no case been opened up. These outcrops are numerous, but those only are shown which come within the limits of actual survey. Plan No. 1. —The area described is contained by the watershed of the Owen Biver and its tributaries, and is in length twelve and in width eight miles. It is enclosed on the north-east and west by lofty mountains, and on the south by the Buller River. The Owen junctions with the Buller on the coach-road from Nelson to Reefton at a point distant sixty miles from the latter and seventy-six from the former place. In following down the Buller River from Nelson, at about ten miles before reaching the Owen, a belt of syenitic granite occurs, being about five miles wide and extending northward from Mount Murchison, which is also of granite! This belt appears to be tho eastern termination of the gold deposits of the Buller, which, although rich below this line, have produced no yields of any importance above it. Prom this fact it may be inferred that the rocks which have so enriched the river and its tributaries are lying westward of and above the granite. This granite, as a continuous and lofty mountain range, forms the eastern watershed of the Owen, and the superincumbent strata in the Owen Valley are beds of slate and sandstone, a formation most favourable to the existence of mineral lodes. The slates change greatly in character, from a bright-brown argillaceous rock, with a regular cleavage, to a dark, semi-crystalline, and brittle mass with angular fracture. They are both, however, traversed by numerous quartz lodes and veins all more or less auriferous, but the brighter coloured slates appear to contain all the richer reefs at present discovered. These rocks change to blue in mining, and iron pyrites on the cleavage surfaces of the slate takes the place of the oxide of iron nearer the surface. The strike of the strata is nearly north-west and the dip south-west, the angle of dip being about 50°. The quai'tz lodes which are found cropping to the surface at almost every spur, and which are frequently exposed by the creeks and rivers, are in systems of parallel reefs; the crops are frequently immense bodies of stone; the hanging-wall well defined, with a strong selvage of a greyish clay. Their strike is about 33° north-west, and the underlie conforms nearly with the dip of the strata. The foot-wall varies in every case both in strike and underlie, in some places bearing nearly north and south, and standing almost vertical. From this peculiarity it is evident that the reefs will not be found lying between two regular and almost parallel walls, but in the shape of huge blocks of quartz, forming in the south-east probably, and dropping into the hanging-wall as they are traced northward—a formation difficult to follow where the blocks are small; but on this field the blocks appear to be of immense size, and the quantity of stone, if it contains sufficient gold, should fully compensate for the trouble of prospecting for them. (See Sketch No. 1.) In every case where I could test the hanging-wall, I found it to be richer in gold than any other part of the reef; and other minerals that usually accompany gold near-the surface—oxide of iron, magnetic iron ore, lime, &c.—have given a peculiar honeycomb character to the stone in that direction. The quartz on the foot-wall is more frequently found hard and massive, and contains much less gold and very little other mineral. 1 C.-6.