DR. HECTOR ON THE NEW ZEALAND GOLDFIELDS.

Westport Times, Volume III, Issue 542, 14 August 1869, Page 2

DR. HECTOR ON THE NEW ZEALAND GOLDFIELDS.

At a meeting of the New Zealand Institute, last week, the following remarks on this subject were made by Dr Hector:— In the Province of Otago the alluvial gold is obtained on the denuded surface of metamorphic schists, and originally came out of some portion of these rocks. Metamorphic rocks are those which, originally sedimentary, have during a long course of geological periods been subjected to chemical agencies, and have, as a result, acquired a very diiferent structure. All rocks deposited as sediments consist of the fragments of otber rocks aggregate in the form of conglomerate sand or impalpable mud. Metamorphic action has had the effect of rearranging the component parts of these rocks into the form of simple minerals. In the South Island, wherever a large area of these rocks is exposed, in every depression or ravine, gold may be found—sometimes in enormous quantities, and without there being any distiuct lodes or reefs to which its origin can be traced, excepting in a few cases. In the district of "Westland the alluvial gold has been found in the western slope only of the dividing range of the Islands, and on this slope are found all the varieties of metamorpbic rocks. The absence of gold on the eastern slope, where unaltered palceozoic rocks are chiefly to be found, except in a few localities where there is a local reappearance of the metamorphic rocks, has a remarkable significance. In the western district of the Nelson Province we find that the gold occasionally occurs under conditions which differ both from those in Otago and in AVestland, being derived from rocks which are never auriferous in the south, but which has been locally metamorphosed by being involved complicated dislocations of this part of the earth's crust, accompanied by the injection of a variety of igneous rocks, and we are entitled "to infer that the gold and otber metals found in this rich district have been introduced through their agency. Turning now to the North Islaud we find an extensive area, about one-third of the whole, occupied by the unaltered palceozoic strata which overlie the metamorphic rocks of the South. He then pointed ont on the geological map [the distribution of these rocks, indicating those portions of the map derived from actual observation. The rocks comprise sandstones and slates, trequeutij- indurated and jointed, but no trace of true meu»moT.nTii<>

rocks have yet been discovered in the North Island. Gold has been found at the Thames District, and in the neighborhood of Wellington, which are almost at the two extremities of the island, and doubtless many intermediate places will yet be discovered. He then described the structure of the Colville Peninsula, on the western side of which the Goldfields are situated, and exhibited a map showing the position and comparative area of each, calling attention to the very insignificent portion of the country which had as yet been tested by the miners. The rocks found in the Peninsula consist of lofty ridges of the slate rocks interbedded with which occur strata formed from very ancient eruproeks. Enveloping these ridges to a height above the sea of many hundred feet, are deposits of tertiary tufa, a stratified rock consisting of volcanic ash intermixed with ejected fragments of recent geological date. This tufaceous rock presents a very marked variety in its character, in some localities forming a very fine-grained rock containing a large quantity of auriferous pyrites dispersed through its substance. This is the characteristic rock in which all the richest lodes have been found at the Thames. In all the auriferous areas yet examined igneous dykes occur, the composition of which shows that they are allied to those fouund accompanying the dislocations previously alluded to as occurring in the South Islands and which no doubt account for their presence in these superficial rocks. From the foregoing considerations we find that in the South where the gold in most widely spread, we have the metamorphic rocks on the surface ; in Nelson, dislocations, igneous dykes, and rocks locally metamorphised; at the Thames, igneous dykes; and at Wellington, dislocations; so that in these latter cases we have evidence that the existence of a communication between deep seated and chemically altered rocks and the surface i 3 the essential accompaniment of the gold. He mentioned, in conclusion, that thermal waters escaping by such lines of communication are generally admitted as sufficient to effect the transport of any metal.