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NEW SOUTH WALES,
Enclosure 1 in No. 3.
Encl. 1 in No. 3. RETURN of the Quantity and Value of Gold exported from the Colonies of New South
Wales and Victoria for the Quarter ended 31st March 1853.
LETTER from the Rev. W. B. CLARKE, to the Honourable the COLONIAL SECRETARY, ON
the geological structure of the western slopes of the highlands of New England, between the summits of the Cordillera and the interior, in the basins of the Gwydir and Macintyre Rivers.
Tarahmbwoan, Ranger's Valley, Severn River, SIR,
May 7, 1853 DURING the period which has elapsed since I had the honour of forwarding my Report, I have been engaged in exploring the western falls of New England, and a considerable tract in the district of the Gwydir; but I have had to contend with, at least, seven weeks of rainy weather, and, therefore, the interval that has occurred has been extended longer than I anticipated. I trust, however, that the following remarks will show, that I have not been neglectful of the objects of my expedition.
In the instructions which I had the honour of receiving from His Excellency the Governor-General, I was directed to follow down “ the westerly waters towards the meridian of Warialda,” and to “examine so much of the adjacent country as time might allow."
I have now the honour of stating, for his Excellency's information, that I have followed down in succession every main creek and river for a considerable distance to the westward, between the Rocky River and the Mole inclusive, that I have examined the Macintyre River, (crossing it at seven different points, between its source and its junction with the Severn,) and that I have followed the Gwydir to the termination of the ranges to the westward of Warialda, having seen the sun set upon an horizon as level as the Pacific, in the direction of Moree, where Major Mitchell, in his expedition of 1832 (about 9th January) reached the Gwydir. As I was within less than 100 miles of the point on the Karaula where that expedition terminated, and as I have seen a considerable portion of the upper part of that river, as well as crossed the tracks of the late Mr. Cunningham, in his expedition of 1827, I did not consider it necessary to pursue my journey further west, into what is known to be an almost level country, with scarcely a rise of a few feet above the elevation of the interior; and as the desert traversed by the late Mr. Kennedy, between the Warrego and the Culgoa, lies not more than 250 miles to the westward of my last station, I consider that I have completed the observations necessary for a due west and east section from that desert to the highest part of the Cordillera, having carried a chain of barometrical observations backwards and forwards, between the commencement of the interior and the summit of the “Dividing Range."
As it is my intention to complete the section, on the same west and east course to the tidal waters, should I be enabled to succeed, I feel confident that this undertaking will not be considered unimportant in its results to the physical history of this country, especially as respects its geological structure.
I have further to state, for the information of his Excellency, that I have made careful barometrical observations on every summit, in succession, of the Ben Lomond Range, for
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the purpose of assisting in the settlement of a doubtful determination, and have obtained data, by the barometer and theodolite, for the calculation of the differences of level throughout a considerable part of the area under discussion.
Lastly, I have, during this survey, explored the Gold Field on the Bingera, and associated creeks falling into the Gwydir.
It is now my duty to lay before his Excellency a succinct account of the general geological results at which I have arrived.
I wish, however, to premise, that one of the objects which I had in view, in examining so many
of the creeks and rivers in succession, was to ascertain, whether an opinion expressed by me in my Report of the 15th November 1852, was correctly formed, and if so, what is to be considered the northern boundary of the auriferous tract alluded to in the following extract from the Report in question.
· Looking at the disposition of the waters between this neighbourhood,” (the Peel River,) " and the head of the Hastings, on the one hand, and Bingera, on the other, I expect that " in a north-west direction from Cobrabald to the latter Gold Field, the precious metal “ will be found generally distributed over a breadth of country, perhaps, thirty miles " wide,” &c.
From what I had since seen, I think I might have safely written sixty or eighty instead of thirty miles; but I would wish to explain, for the benefit of persons in Europe, who may perchance be misled by the interpretation of the word “miles," that I do not, of course, allude to miles of solid gold, but to miles of land in which gold, more or less, may be found. From some expressions in English journals, which have, I fear, wilfully or carelessly misled many intending emigrants, whose imaginations and cupidity overreach their common sense, I deem it right to repudiate any such exaggerated accounts as the evil genius of Mammon has invented out of expressions, which are strictly true as relating to the superficial area of certain auriferous tracts of country, but literally false if they are to be received according to the meaning which, it seems, for purposes best known to the interpreters, has been assigned to them. I have always been very anxious to avoid any exciting language, and I have been sorry to learn, that out of those statements which I thought I had guarded by much caution, (for which caution I have been sometimes blamed by persons in the colony,) the invention of the designing, or the eagerness of the covetous, have distilled a conclusion which my published statements do not justify, and to which no private letters of mine to persons in or out of the colony lend any authority. Having universally refused, when solicited, to give any information to Gold-dealing Companies, and having referred to these Reports to his Excellency as the only exposition of my views for which I hold myself responsible, I deem it right, and a solemn duty to the Government, to the Legislature, to the in-coming population of the colony, and to myself
, to declare that if, as I have been informed, my name has been employed in deceiving any persons at home, it has been without my sanction or knowledge, and against the fairest interpretation of the words which I may have used in describing such parts of the country as I have found to be auriferous,
I can appeal with satisfaction to many persons in the Gold Fields, who have expressed their confidence in these Reports by stating that, after following my tracks, they have found that I have never “ deceived them.” Such persons would not interpret an auriferous tract eighty miles wide, to mean eighty “miles of gold;" and it is in the desire of saving disappointment to some who may be unfitted for the labourious occupation of gold-seeking, and the doubtful results of even diligent work in a rich Gold Field, that I take occasion to introduce this warning, in my own defence, and for their benefit, that though gold may be procured easily enough in some localities, and though it may occur in an area of 80 miles wide, and 150 miles long, the success will, probably, be obtained by few, and disappointment be felt by many.
The geological formations, of which the present area is composed, consist of various granites, porphyries, serpentine, and ordinary trappean products : metamorphic and unchanged slates, quartzites, and limestone; a series of carboniferous deposits, identical with that of the Hunter and Wollondilly basins; and alluvial deposits derived from the preceding, which are either spread locally, and of no considerable thickness, on the slopes of the rocks from which they have been produced, in the bottoms of dried lagoons, now forming muddy plains; or, as in the case of the interior, in deep stratified drift, through which the great rivers wind their sluggish way in droughty weather, or in times of flood pour a muddy torrent to the far interior, between banks which they have cut in their passage through the slightly declining country.
It will simplify the description of this region, to arrange the formations under separate heads.
I. GRANITE.—Rocks of this description, apparently of more than one period of emission, have been already described in my former Reports. They may be considered as forming a narrow band on the western side of the table land, between Boorolong and Maryland, sometimes cresting the Cordillera, but generally occupying a position subordinate in elevation to the trappean rocks, which form the frequent peaks and platforms, and which have forced their way through the granite or connected porphyry which it has overflowed. At the back of Maryland, the grey granite is flanked by red granite, which also appears in various points between Warwick and Maryland, and between the latter place and the Severn, to the north-west of which line the country is chiefly slate.
The grey granite which is auriferous on the Rocky River is continued down the SOUTH WALES. Bundarra or Gwydir to the neighbourhood of Mount Drummond, and is more or less
Granite, also auriferous, occurs about the Dividing Range at Boorolong, and as far as Larrayanuar (Sandy Creek); at the heads of Clarendon Creek and Sandy Creek, in both of which I found particles of gold.
Cope's Creek runs through granite and is also auriferous.
Granite occupies a considerable area at the head of that creek, as at New Valley, and on the Macintyre between the junction of Ouerra Creek with that river and Newstead Creek. Paradise Creek also flows in part through granite. In the two last mentioned localities I found no gold, the character of the rock being different to that of the Bundarra.
Granite also occurs in the lower part of Graham's Valley, and at Stonehenge, and Beardy Plains as well as near Dundee, where it is metalliferous, but, so far as I have seen, without gold. A singular grey hornblendic granite occurs about the junction of the main branches of the Severn, at Tarahmbwoan (meeting of the waters), and about Ranger's Valley.
Granite appears slightly near Nullamana ; at the head of Frazer's Creek; and somewhat to the eastward of the junction of the Severn and Macintyre. Between Ottley's Creek and the latter river, I traversed a wide range of granite, the character of which induced me to think, that gold will be found in small quanity in that range. It appears in the low grounds at Bannockburn, near the head of Byron Creek, and in the same way at Gurahmin, but rises to some elevation between the latter place and the Macintyre, at Bukkulla. It extends for seventeen or eighteen miles to the northward of Gurahmin. It is probably connected with the appearance of the same formation between the falls of Cope's Creek and Keera. The Gwydir there breaks through the ranges in such an abrupt manner, as to render the country impassable. It has, in this respect, an analogy with the Snowy River, near Biddi; it is in each case due to the direction of the main joints traversing the rock. A third instance is supplied by the Macintyre, south of Coorubarumbarate, which traverses, for some distance, a vertical gorge of granite, giving to the river a character very much in contrast with its usual features. The Mole also flows in part through a gorge of granite. Grey granite occupies a portion of the country below the range, east of Terrahihi, between the Weah-waa and Horton's River, and on the latter; and I think may be found in some of the deep defiles which intersect the broken knot of mountains of the Nundawar Range, as between Tyreel and Caroga, on the west side of the former range.
Although it is very probable, that other localities, which my time did not allow me to explore, might prove a still more extended existence of granites, the above examples are sufficient to show, that it is widely distributed in the area under discussion, and in connection with the already described tracts of granite on the Upper Namoi and Gwydir, which are known to be auriferone, it is probable that other auriferous patches may exist in the basal granitic region, or in some of the creeks not yet explored, in the higher portions of it. As granite exists on the table land of New England, and on the deep and precipitous falls to the Clarence on the geology of which river, I hope, hereafter, to be able to report) and, about Maryland, rises into lofty domes of striking outline as seen from the westward, we shall perceive that the solid nucleus of the mass of the couutry represented by the Districts of New England and the Upper Clarence, and in part by those of the Gwydir and Liverpool Plains, is granite of some kind, and that some of these granites may be the oldest formations, though from their connection with other igneous masses it is equally probable that other portions of the granites are of later eruptions. The granite about Mount Mitchell is auriferous.
I have not deemed it necessary to particularize the numerous observations I have made on the changes of mineral constitution and structure of these granites; it may suffice to say, that their texture varies, and that their composition passes, on the one hand, by sensible or insensible gradations into ordinary trappean rocks, and on the other, into binary and simple rocks, in which felspar and quartz respectively exclude all other materials. I wish, however, to mention, that at one spot (Bannockburn), the granite holds numerous lumps of stratitic matter, partially decomposing, which seems to disclose a connection with magnesian rocks, of which there are abundant examples in the serpentines hereafter to be mentioned, and the localities of which are not very far distant. At any rate, this granite contains more than the usual proportion of magnesia.
These granites are occasionally traversed by quartz veins, as well as veins of felspar, the latter mineral having been segregated on each side of a thin fissure, instances of which occur at Guralı min.
The whole of the granites betray marks of erosion and decay, and some singular instances of rocking stones may be noticed in almost every granite locality ; they are not, however, so well developed as in the grey variety, nor do they present the lofty pyramidal terminations which are so striking in the southern counties, being generally rounded, peeling off in concentric flakes. Crystals of blue, smoky, and brown quartz, as well as limpid rock crystal occasionally occur. Tourmaline in radiating masses is also met with.
Of metals beside gold I have met with sulphuret of antimony, as near Mount Mitchell and in the Boorolong Run (as well as from the neighbourhood of Gara); graphite in
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radiating masses occurs in the granite east of Dundee, and in more plentiful quantity near New Valley; wolfram and oxyde of tin, with tourmaline, occur near Dundee and in Paradise Creek, and it is probable that this ore of tin is plentifully distributed in the alluvia of other tracts, as I have found it amidst the spinelle rubies, oriental emeralds, sapphires, and other gems of the detritus from granite. Iron also occurs in various modes in the veins traversing granite; and I am informed, that both copper and lead have been detected in granite along the Peel; I saw the specimens but did not find them.
Such indications as the above prove that a granitic region is not so barren as some persons may be inclined to suppose.
If the ore of antimony should be found in any quantity hereafter, it will be valuable, but the experience of geologists is against the probability that it will be found abundant in or near granite of the age to which I am inclined to refer its matrix in New England. Graphite is also a valuable mineral, useful in the arts, and since a new method of employing the compressed scales and dust of graphite has been discovered, and the supply of the mineral from the Boroodale mines of English Cumberland is fast diminishing, it may be worthy the consideration of colonists how far graphite in Australia may be available.
Whilst thus naming metals from the district of New England I take occasion to correct an error in my fourth Report, which was accidental, by substituting the word lead for galena. The spe. gr. showed that the metal was not common galena or sulphuret of lead, but native lead, a mineral of very rare occurrence, and respecting the existence of which in other countries there has been much discussion among geologists. On looking into some notes made years ago, I find that I had recorded, as existing in the neighbourhood of the Peel, the occurrence of green malachite and a yellowish-white highly magnetic metal having spe. gr. 8.0 and a hardness of 5.5, the form also and other characteristics of placodine (an arsenical nickel); it dissolved readily in nitric acid, but was partly oxydised superficially. It has since been found on Weare's Creek, further to the south-west.
It may be interesting to mention, that the loftiest elevation at which I have found granite in this journey, was about 4,800 feet above the sea, and the lowest about 800 feet, on the same north-westerly slope from the Cordillera. The direct distance being 64 miles, the declivity of the planes (supposing it continuous) would be 62 feet per mile: the fall of the waters being very much less, we have a plain proof, that the river channels must run in deeply fissured rocks, as I have shewn in the case of the Macintyre and Mole, or that the granites are, probably, of different epochs.
Before I quit this section, I would remark, that independently of the resemblance which I have seen in this region amongst granitic and associated rocks to those characters which I saw granites, &c., assume in the European Alps and in Devon and Cornwall, there are some circumstances mentioned in the recent history of Professor Forbes' scientific “ Travels through the Alps of Savoy,” (a work of whiclı, probably, not two copies have found their way to this Colony,) which appear to me to bear upon the age of the rocks respecting which I ain writing. I beg leave, therefore, to cite the following passages, premising that I have already in one of my former Reports (28th August 1852), mentioned from another authority that gold occurs in the Alpine granite of the region described by Professor Forbes :
“ The mass is granite, in which sapphires are found, though rarely in the Couloir im
mediately beyond the angle ;” (the locality is on the Mer ile Glace of Chamouni.) · I “ have found a singular porphyrytic rock amongst the fragments, containing felspar and
epidote, which it is difficult to refer to any class of primitive rocks.” (p. 78.)
“ The glacier of Bosson's has brought down beside and beneath it a great mass of debris “ of the rocks of Mont Blanc, including serpentines of doubtful origin.” (p. 180.)
I add, also, from Sir H. de la Beche's Report on the Geology of Cornwall and Devon, that his friend “Mr. R. W. Fox obtained small nests of plumbago” (graphite) “from one “ of the elvans near Deveron, the only instance, we believe, of the occurrence of this “ mineral which has yet been noticed in Cornwall.” (p. 182.) The same author also says, that Mr. Fox obtained“ oxyde tin in the form of crystals of felspar;” (p. 390 ;) it is in similar form that I have seen oxyde of tin in New England, and the graphite of Dundee occurs as that of Deveron.—These resemblances may not do much towards the settlement of a question of epochs, but when there are other points of resemblance, they must not be forgotten.
II. PORPHYRY.-Connected with true granite there is in this region an immense display of porphyries of various composition. In some places they appear to pass insensibly from and into masses of true granitic type; at other localities, they put on a form which unites them with ordinary trap. Thus from a porphyritic granite to eurite, and thence to cornean bases with interspersed crystals of quartz, or larger masses of that mineral which again assumes the condition of dykes or veins, or to mixtures of quartz and steatitic crystals in such a base, there is every variety of composition, colour, texture, and structure.
There is also an abundance of hard porphyry with double six-sided prisons of quartz and pale felspar crystals embedded in a base of felsparite, which sometimes so closely resembles the famous Roborough stone of Devonshire as to lead me to suspect that some of this New England porphyry exists as elvans amidst the granite, though the porphyry under one or another of its characters occupies wide tracks and assumes the forms of long ranges, the sweeping curves or rounded bosses of which are due to the diffent conditions
NEW of hardness. In general, I have found the granite nuclei surrounded by porphyry; but SOUTH WALES. occasionally there is a distinct evidence at the planes of junction of some extraordinary
transmutation. The porphyries are often divided by fissures and joints which, for some distance, are persistent, and so arranged as frequently to give the notion or stratification, but this appearance is as often cut off by a fresh arrangement of joints and a nodular structure, so that the joints resolve themselves into fissures produced by the coaling of boss-like swellings under irregular tension of the mass.
That this formation exists under some of the country now covered by black or red trappean alluvia was proved to me by my examination of the matters thrown from wells attempted to be sunk on some of the so called plains. In one instance, at King's Plains, I found that under the black surface soil the upper part of the hard porphyry was decomposed and loose, and completely altered by the long abode of water upon it, before the upper
soil had accumulated, and that the double hexagonal pyramids of quartz had been accumulated in heaps by the recent rains.
The porphyry contains veins of quartz on the heights above Moredun Creek; at the junction of Ouerra Creek with the Macintyre River, and at Corajin (Gragin) Creek; on the heights above Turracabad, and above Yarrabarra, and in other places near Ranger's Valley.
It appears to be associated with quartz rock on Pinduri Creek, (as at Tower Hill Station,) and near Weean Creek, and the intermediate change is marked by quartz porphyry along Frazer's Creek from Tolkiva to Gunnygeeren, and between that creek and Bukkulla, on the western side of the N. by E. strike which it there assumes ; ridges of iron stone, containing iron which merely requires heating once or twice to become malleable, separating it from the trappean track along the Macintyre which thus flows in a trappean channel on that point, between quartz porphyry and the granite range before mentioned as extending from Bannockburn. Quartz rock also occurs on the Beardy water branch of the Severn River at Yarrowford, and is connected with the porphyry which ranges thence for 30 or 40 miles towards the north-west. At that spot there is a little gold.
The base of the whole country, with the exceptions I have pointed out under the former section, and with some few which I may not have noticed, is composed of these different porphyritic rocks in the area, roughly defined by the following limits. From Larraganum on Sandy Creek, were it joins the granite, about 8 miles from Boorolong, to Ollera (George's) Creek, Limestone Creek, (so called from nodules of alluvial calcareous matter in the surface soil,) Moredun Creek, Ouerra Creek, to Wellingrove Creek and Strathbogie, including the ranges at the heads of the Karaula or Macintyre River, Undúnbalah or Paradise Creek, Coorubarúm barat or Newstead Creek, Furracabad Creek, and the western sources of the Severn, to Talkibon and Taramboi feeders of the Mole River, (Deepwater and Castlereah Creeks,) thence crossing the Severn to Arawatta and Frazer's Creek and to the head of Byron Creek, and so along the ranges separating the waters of the Macintyre from those of the Gwydir, we have an irregular but general outline of about 3,700 square miles, in which porphyritic rocks under various modifications are strikingly developed.
In such an area there must, I think, be metals of some kind, but save the ores of iron I fell in with none: the abundance of quartz veins leads me to believe that further research amidst the broken country and rough defiles which I but hastily examined, might detect what has escaped my observation. But if, as I have already inferred, the porphyry assumes the nature of elvans, the metals about Dundee may belong to the porphyry rather than the granite, which at the point in question assumes a porphyritic character and finally merges into porphyry. The occurrence of porphyry of this class on the edge of an auriferous region in New England is quite in analogy with the occurrence of similar porphyry on the edge of the granitic gold field of the Araluen district. (See Report of 21st October, 1851.)
III. TRAPPEAN ROCKS.—Bursting through both granite and porphyry and overfiowing them, basalts amygdaloids and a small proportion of greenstone form a third kind of igneous rocks in the area under discussion.
They form the culminating points of the Cordillera on the Benlomond Range, and break out along the spurs from that range in various places on the western falls. That they have issued from the granite is shewn very remarkably by several examples along the banks of the Macintyre a little below the junction of Ouerra Creek, and upon the broken ranges between the head of Paradise Creek and the junction with the river. The granite exists in the former place in well rounded disintegrating masses, and it is in the midst of these and overflowing them, that a singular lumpy basalt forms semi-columnar ridges and platforms, presenting at a little distance the appearance of deeply fissured beds of conglomerate. A similar fact was noticed at a spot called Goodunbyangee. The trap is in a state of disintegration and covers the slopes with its fragments. The granite was in a weathered condition before this trappean outburst.
On the ranges before alluded to, at least 600 feet above the other locality, and the exact spot of which I cannot define, because it is in the midst of the mountains, I found a similar instance, accompanied by a distinct change in the underlying rock, which is there a porphyritic granite over coarse crumbling granite. Between the trap and the porphyritic rock there is interposed a soft layer of reddle, a substance very common on porphyry near trap, as at Ollera, and which was deposited from the trap upon the older formation.