صور الصفحة
PDF
النشر الإلكتروني
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small]

II. Showing the quantity and value of, and duty on, gold exported from Otago between 3rd August, 1861, and 31st March, 1862.

[blocks in formation]

III. Showing the quantity and value of all the gold exported from the whole of New Zealand up to 31st March, 1862.

[merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

Tables I. and II. are compiled from statistics given in the 'Otago Daily Times' of April 6, 1862, and Table III. from those given in the 'Otago Colonist of July 15, 1862.

On the Geology of the Gold-fields of Auckland, New Zealand. By W. LAUDER LINDSAY, M.D. & F.R.S. Edinburgh, F.L.S. & F.R.G.S. London, &c. The author had personally made a geological examination of the Coromandel gold-field, in the province of Auckland, in February 1862, having previously spent several months on a similar survey of the Otago gold-fields. He described Coromandel as a different type of gold-field from Tuapeka (Otago), and, as such, of interest as illustrative of the general geology of the New Zealand gold-fields. The main results of his observations and deductions may be concisely stated thus:— 1. The geology of the northern gold-fields of New Zealand, including those of Nelson as well as of Auckland, does not differ essentially from that of the southern or Otago gold-fields (as the geology of the latter is described in his paper "On the Geology of the Otago Gold-fields," save in so far as regards certain minor details. The parent slates, for instance, are in the north more frequently of a clay-slate or argillaceous character than in the south; the auriferous quartzites are frequently developed to an extent as yet unknown in Otago; the evidences of trappean disturbance are more numerous, and the metamorphism of the slates by the contiguity of the erupted or intruded traps better marked. Nor does the character of the gold differ materially, save in so far as, in certain localities, it is more generally associated with its quartz matrix.

2. The Coromandel Peninsula consists mainly of a mountain ridge, running nearly north and south; the mountains having a bold serrated outline, and varying in height from 1000 to 2000 feet. The valleys between the spurs given off laterally by this main or dividing range are of the character generally of ravines or gorges, occupied by mere mountain streams; the "flats" or alluvial tracts at their mouths, and on the coast, are inconsiderable.

3. This mountain-range consists apparently of slates of Silurian age, generally of argillaceous character, but greatly altered by contact with, or proximity to, numerous outbursts or intrusions of trappean and other rocks. The mountains are so densely wooded, and so difficult of access, that it is only here and there in the gorges of the streams that sections of these slates may be examined. In these sections the slates are frequently found to resemble Lydian stone or the slaty varieties of basalt (such as clinkstone); while they are disposed more or less vertically, their irregular upturned edges affording the most convenient and abundant "pockets" for the detention and storage of the alluvial gold washed from the higher grounds.

4. [Local geologists describe the fundamental rock of the Coromandel mountainsystem as granitic, and the granite as forming here and there the "aiguilles" of the dividing ridge. The author met with no granite in situ; nor did he discover granitic boulders or pebbles in the boulder-clays of the auriferous drift, or in the shingly beds of the mountain streams about Coromandel Harbour.]

5. The Coromandel slates are characterized by their prominent and numerous quartz "reefs," consisting of auriferous quartzites. Here and there, where the dense vegetation admits, these reefs are met with in situ, frequently as "dykes," standing prominently above the general level of the slates; sometimes forming the top of the dividing ridge itself. The proximity and abundance of such quartzites are sufficiently indicated by the immense numbers of huge quartz-boulders or blocks which bestrew the low ground and occupy the ravines and gorges, which blocks are characterized by comparative angularity. The quartz is frequently of the porous, light, spongy character so prevalent in the gold-fields of Australia, Nova Scotia, California, and other auriferous countries; and its colour is frequently buff, brown, ochrey, or vermilion, the result, apparently, of different degrees of ferruginous impregnation.

6. The auriferous drift is mostly of the charac.er of the newer or upper Tertiary drifts of the Otago gold-fields, consisting essentially of-a. variously coloured clays; b. boulder-clays, also variously coloured; and e. gravels, of the chopped slate"

character, the débris of the component rocks of the parent ranges, which gravels rest immediately on the "bed-rock or slate. In this gravel, as at Otago, the gold chiefly occurs; hence to these gravels are, as yet, mainly directed the operations of the miner.

7. The gold itself occurs in the form of dust, scales, or nuggets-frequently as scaly nuggets or "pepites," but still more generally dendritically disseminated in quartz-pebbles, which are usually ochrey or brownish in colour.

8. It is largely associated with iserine (titaniferous iron-sand), apparently of the character of that so abundant at Taranaki. This mineral, indeed, appears to be associated with gold in almost all the New Zealand gold-fields.

9. The prevalent volcanic rocks, which burst through, overlie, or are otherwise associated with the slates, are mainly various trachytes, tuffs, basalts, and syenites. A hard breccia, consisting to a great extent of fragments of jasper and flint, resembling somewhat the "cement" or quartz conglomerate of the older or lower Tertiary auriferous drifts of the Otago gold-fields, occurs on Beeson's Island, in Coromandel Harbour, which island is mainly or altogether tufaceous. Boulders of basalt and syenite bestrew the tops of the hills which form the greater part of the said island; and basaltic boulders are associated with quartzose ones in the shingly beds of the mountain-streams of Coromandel and in the boulder-clays of the auriferous drift.

Contrasting the Tuapeka (Otago) with the Coromandel gold-fields, the author indicated the following respective peculiarities:

At Tuapeka (Otago):-a. The bare open country, resembling the Lammermoors of Scotland, consisting of gently undulating "ranges," of a height generally of from 500 to 1500 feet. b. The abundance of the auriferous drift, and the comparative insignificance or scarcity of the parent quartzites. c. The scarcity of timber for fuel and slabbing; but, on the other hand, the presence of lignites. d. The inclement climate. e. The difficulties of land-communication with the capital (Dunedin), arising from insufficient roads. f. Unlimited powers of "prospecting" and "working," arising from the absence of a native population.

At Coromandel:-a. The precipitous mountain-ranges, densely covered with a jungly vegetation to the top; the hill-bases impinging directly on the sea-margin, without the intervention of" flats," save to an insignificant extent. b. The scarcity of the auriferous drifts, and the abundance of the parent quartzites. c. The abundance of timber for fuel, mining-works, and dwellings. d. The superior climate, arising from its geographical position, 800 miles more northerly. e. The facilities of water-communication with the capital (Auckland), 45 or 50 miles distant. f. Difficulties and dangers of prospecting and working, arising from the presence of a jealous, hostile proprietary native population.

From his observations at Coromandel and Tuapeka, as well as in the other parts of New Zealand he visited during his tour of 1861-62, the author makes the following statements, inferences, or predictions::

1. That while there is, at Coromandel, a very limited and insignificant field for alluvial digging, there is ample scope for quartz-mining.

2. That the auriferous resources of Coromandel will only be fully developed in the course of many years by the application of all modern improvements in chemistry and mechanics to systematic mining, which must become one of the permanent industrial occupations of the province of Auckland, and which will demand the sinking of a large capital in the first instance.

3. That slates similar to those of Coromandel, with associated auriferous quartzites, will be found to occur over a comparatively large area of the province of Auckland.

4. That new gold-fields remain to be discovered in that province; though experiment only, and on a suitable scale, can determine where, and whether "payable," gold-fields exist.

5. That whereas lignites are widely distributed over the province of Auckland, it is most desirable to ascertain whether they are of similar geological age to those of Otago, and associated with the same auriferous drifts.

6. That whereas, in Australia and other auriferous countries, gold is not confined necessarily to metamorphic slates or their derived drifts, but occurs occasion1862,

6

ally in granitic and hornblendic (syenitic) rocks or their débris; and whereas, though this is rare in New Zealand, there is, according to the testimony of Mr. Haast, the Government geologist of the Canterbury province, at least one good instance of such an occurrence in the province of Nelson (in the beds of the rivers Roto-iti and Roto-roa, where the gold could apparently only have been derived from the decomposition or degradation of rocks of a syenitic or hornblendic character);-the attention of prospectors and miners, not only in the province of Auckland, but in that of Otago and, indeed, in all the New Zealand provinces (all of which will probably be found to be to a greater or less extent auriferous), should be directed to drifts derived from granitic and hornblendic rocks, as well as to those resulting from the detrition of Silurian and other slates.

7. That it is probable the auriferous system of rocks (the supposed Silurian slates) extends from the province of Otago into the adjacent provinces of Southland and Canterbury-from Nelson (where they are already known to exist to an extent second only to that in Otago, and where, indeed, "gold-fields" have been successfully worked for a considerably longer period) into Canterbury-and from Auckland into Wellington and adjacent districts-though to what extent remains to be determined by actual survey and experiment.

8. Contrasting the Northern with the Middle Island of New Zealand, it is probable that the latter is more extensively and largely auriferous than the former; that in the former the auriferous quartzites are developed out of proportion to the derived drifts, while in the latter the reverse is the case; and that, should this supposition prove to be correct, the character of the gold-mining in the two islands will necessarily differ most materially.

9. Speaking in general terms, auriferous rocks may be said to extend throughout the New Zealand islands, the exceptions being where they are interrupted by recent volcanic formations, traps of various ages (mostly Tertiary), limestones of various ages, extensive Tertiary beds, and other geological series or systems.

The author concluded by strongly advocating the necessity of an immediate systematic Geological survey of the province of Auckland-one implying a duration of about five years, with an expenditure on staff, travelling, and publications of about £10,000. He recommended this equally for all the New Zealand provinces of which geological surveys have not yet been made; pointing to the example of Otago, which has recently appointed a Government geologist, who is now engaged on a three years' survey of that, geologically, most interesting province.

On the Paleontology of Mineral Veins; and on the Secondary Age of some Mineral Veins in the Carboniferous Limestone. By CHARLES MOORE, F.G.S. The author's attention was directed to this subject by the very fissured character of the Carboniferous Limestone of the Mendip Hills, and by observing that many of the fissures had subsequently been filled with deposits containing organic remains of later geological ages, some of them being probably as young as the inferior oolite. In a quarry near one in which the author had previously found the Microlestes, Placodus, &c., there were as many as fifteen vertical fissures within a length of 200 feet, passing down through inclined beds of Carboniferous Limestone, one of them being 15 feet in breadth at the base. These contained organic remains belonging to the Carboniferous Limestone, the Rhætic bone-bed, and the Middle Lias. In the upper portions of some of the fissures, galena, sulphate of barytes, and iron-ore were present, showing that in these instances the above minerals must be of Secondary age.

In further investigating this point, the mineral deposits of the Mendips, near Charter House, were examined. In descending a lead-mine at this place, the author found the vein-stuff very varied in its character-sometimes a conglomerate, then almost composed of Encrinital stems, with a few Corals, all much abraded by the action of water; and at a depth of 175 feet a deposit of eight feet of blue marl containing 7 per cent. of galena. In this he found about 130 species of organic remains, consisting of part of an Ammonite, Belemnites, ten species of Brachiopoda, together with numerous univalves and Foraminifera. Fish-remains were also abundant, of different species; and there were also pieces of drift-wood which had been converted into jet. It was thus evident that the Mendip lead-veins had been

within the influence of the ocean during the Secondary period, and that the minerals they contained could not be of more ancient date. Somewhat similar results attended an examination of the districts around Bristol and Weston-super-Mare.

The author next examined samples furnished from six mines, in Carboniferous Limestone from Shropshire, Yorkshire, and Cumberland. From Weardale, out of twenty-seven small samples, organic remains were obtained from fourteen, the lowest being 678 feet from the surface; and the same result occurred from Alston Moor and the White Mines, Cumberland. In one small sample from the Grassington Mines, Skipton, which when washed was reduced to half an ounce in weight, not less than 156 specimens were found. These include the author's genus Zellania, hitherto never observed in any stratified bed lower than the middle lias; and numerous Conodonts, which have never been found higher than the Ludlow bone-bed. It was argued that we had no evidence of the contents of mineral veins having been derived from volcanic agency, nor by any electrical action removing the minerals from the adjoining rock and redepositing them in the veins. The author's view was, that what are now mineral veins were once open fissures which were traversed by the ancient seas of the period, and their derived contents deposited; and that whilst these infillings were proceeding, the minerals, which might previously have been held in solution in the water, were by the operation of electrical and other causes precipitated, and that thus, instead of being due to volcanic action, they were to be attributed to aqueous and sedimentary deposition.

Contributions to Australian Geology and Paleontology.

By CHARLES MOORE, F.G.S.

After noticing the evidence recently obtained of the presence of Mesozoic rocks in Australia by Mr. Gregory, the Rev. W. B. Clarke, and Mr. Hood, the author remarked on the paucity of organic remains that had yet been obtained from these rocks-in the whole probably not more than thirty species. He then referred to a series of fossils he observed being exhibited at a meeting of the Somersetshire Archæological and Natural History Society, by Captain Sanford, of Nynehead, to whom they had been forwarded by Mr. Shenton from Western Australia. They appeared to have been chiefly derived from beds of oolitic age, and probably from the same district as those sent to the Exhibition by Mr. Gregory; the Trigonia, Cuculla, Belemnites, &c., being of the same species. Captain Sanford's collection, including a number of duplicates, comprised about sixty specimens, and also a block of stone about 10 in. by 6 in., which, on being closely examined, showed that the bed from which it was derived must have been very rich in organisms; for on its surfaces the author was able to make out about thirty species, or as many as had previously been discovered from all the Australian Mesozoic deposits. It contained an Ammonite, Trigonia (allied to T. costata), Pecten, Lima, Cucullæa, Avicula, Ostrea, Turbo, and other univalves, Rhynchonella variabilis, Pentacrinites, &c.

Amongst the Ammonites in this collection were several allied to the A. radians, and appeared to indicate for the first time the presence of the Upper Lias in Australia. There were also several specimens of the Myacites liasianus, found only in the ironstone zone of the Middle Lías in this country; and, singularly, the matrix containing the Australian specimens yielded 52 per cent. of metallic iron.

In the absence of sections, and from the different lithological characters of the shells, the author supposed them to have been obtained from beds of different geological ages, and that, from their abraded character in some instances, they were probably found in derived deposits, and not in the parent rock; and that it was not improbable, for the same reasons, that this applied also to the other Mesozoic remains that had hitherto been found in Australia.

On the Fossils of the Boulder-clay in Caithness. By C. W. PEACH. The author first mentioned that, as so little was known of the fossils of this formation, he thought that a short communication on the subject might be acceptable to the Section. The Boulder-clay occurs more or less all over Caithness. In some places it is very deep, especially on the banks and estuaries of rivers, sides of burns, &c., where it is found in some places to the depth of 60 or 80 feet, and at various

« السابقةمتابعة »