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Maps, plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes, planches, tableaux, etc., peuvent dtre film6s d des taux de reduction diffdrents. Lorsque Ie document est trop grand pour dtre reproduit en un seul cliche, il est film6 d partir de I'angle supirreur gauche, de gauche d droite, et de haut en bas, en prenant Ie nombre d'images ndcessaire. Les diagrammes suivants illustrent la mdthode. 1 2 3 1 2 3 4 5 6 LAURENTIAN AREA TO THE NORTH AND WEST OF ST. JEROME SOUTH-WEST QUAilTER-SHEET MAP OF THE EASTERN TOWN- SHIPS, PROVINCE OF QUEBEC. »T F. D. Adams, Ma.Sc., PkD. [JReprinted from A-Kiual heport, Oeohgieal Survey of Canada, Yd. VJL, New Seriet.) ^$9 I I« 1 » LAURENTIAN AREA TO THE NORTH AND WEST OF ST. JEROME. By F. D. Adams, Mn.Sc., Ph.D. (Reprii I frnm Annnnl Report, (ieoloijirdl Sarvrii of Cami'lK, Vol. VII., Nnr Seriea.) GENEUAL STATEMENT. The continent of North Americca, as i.s well known, lia.s been L,iurentian gradiuiliy built up by an accumulation of .sediment aljout certain very l"""'"''"*'- ancient land areas which are known as its protaxe.s. Of these the largest and most important is tlio^reat north(!rn protaxis, wliich forms th(! greater part of northern Canada, having an area of somewhat over 2,000,000 square miles and constituting what Suess has termed the Canadian shield or boss. The Laurentian area which forms the extreme north-west corner of the sheet at present under discussion, is a portion of the southern margin of this great northern protaxis and thus represents a part of an extremly ancient land area, fn)m the waste of which the clastic Paheozoic strata to the south were derived. The ai'ea of these ancient rocks eml>raeed in the sheet is small, amounting to about 400 S(i[uare miles; it forms, however, part of a much larger district, stretching to the north V)eyond the limits of this map, the geology of which has been worked out, and a map of which, with full explanatory report, will appear shortly. In the following pages, therefore, merely a brief general description of that portion of this dis- trict lying within the limits of the map accoi ipanying the pre- sent report will be given, leaving the more detailed discussion of the district as a whole, and the many problems which it presents, for the fuller report which will appear later. In the a.spects of its relief, this Laurentian country is sharply Character of marked off from the plains, underlain by the Paheozoic — which bound ''"""*''>'• it on the south. It is a somewhat uneven plateau, the edge of which when viewed from the plains appear.s as a range of hills running in a north-east and south-west direction. The plateau slopes gently to the south-east from an average elevation of about 1000 feet above sea-level at the north-west corner of the map, to about 450 feet above sea-level along the edge of the plain. The depressions in its surface are generally filled with drift, form- ing extensive flats, in which are many picturesque lakes of clear water 1 {Pfiy ^n original Report 93 j) QUEBEC. Tw( IIIIVISIOUS. Grei> villi' series. the larj,'est being Lake L'Achigan in the township of Kilkenny. Four rivers also cross it, namely the North Iliver, the River L'Achigan, the Saint Esprit anil the Lac Ouareau Iliver. Tlio lanilscapo of this Lauii'iitifiii country is of a pronounccrl ty[io which, while lacking on one hand the grandeur and sublimity of high mountain regions and on the other the tranquil beauty of the well cultivated lowlands, has a certain rugged beauty of its own, especially when clothed with the brightly coloui'cd foliage of autumn. The area is about eipially divided between the rocks of the Lauren- tian system and intrusions of anoithositi^ which break through these. TheLaurentian consists of red and gray orthoclas(> gneisses, presenting great variations both in structure and composition, with which are associated crystalline limestones, (juartzites and amphibolites. These rocks often occur in the form of bands or beds alternating with one another, but in some plac(;s the banding is i-eplaccd by a more or less distinct foliation due to a parallel arrangement of the indi\idual grains of the various constituents which go to make up the rock. Both structures are often found in the same rock, and wlien thus occurring together they coincitle in direction. In order that a ))urely objective attitude may be preserved, the term band, rather than bed, is employed in the present report, the latter term being usually associated with the idea of a sedimentary origin, which, howe\er probable, for certain parts at least, of the present district, cannot be considered by any means as demonstrated for the system as a whole. In many other parts of the Laurentian, two divisions can be recognized in the system, namely, an upper series char!ict(»rized by the presence of crystalline limestones, quaitzites and gneisses, having the chemical composition of ordinary sediments as well as a pre- ponderating banded structure, which is called the Grenville series, from a township of that nann; in the County of Argenteuil where it is well developed, and a lower sei-ios of gneisses much more monoton- ous and uniform in character, in which are no limestones, itc, and which possess a foliated rather than a banded structure. This latter series is known as the Fundamental Gneiss, and in many cases closely resembles igneous rocks. In the area at present under discussion the two series cannot be so clearly distinguished. Certain parts of the area can be recognized as belonging to the G'-enviUe series, as, for instance, the extreme easterly portion lying to the south of Rawdon and the westerly portion in the St. Sauveur district. Other portions, as much of the St. Jerome (94 J) •,••;*•! •• •••• •••«•< « .• ,•. ,. ••• ••; .*. LADIIEVTIAN AREA. cliatricb, has the appoanmco rather of the I'-undamontal Gneiss. It has I'undiinienui beeu found impossible, however, to separate the two series and delimit *■"'"**'• them on the map. Breaking through the gneisses are four masses of anorthosite, an intrusive rock belonging to the gahl'ro class, but characterized by a great preponderance of plagioclaso felspar. Of these the two largest, comi)rising portions of the townsliips of Abercronibie and Kil- kenny respectively, are really portions f)f a single very large area, which extends to the north-west beyond the limiti of the map, and has a total area of about 1000 sfjuaro miles. This is known as the .Morin anorthosite area, and is I'udely circular in shape. The anorthosite occurring in the north-west corner of the present sheet, including the township of Abercronibie, is a portion of the southern extension i if the mass, while the anorthosite in the Kilkenny district is the extremity of a large spur, which stalling from the eastern side of the mass runs south, following the strike i)f the gneiss, and finally passes beneath the tlat-lying Paheozoic strata of the plains, being at its southern extremity split in two longitudinally by a wedge of gneiss which runs up into it. Six miles to the north of the limit of the present sheet, these two Anorthosito. masses of anorthosite come together and pass into one another, and thev will, therefore, be treated of as one and the same mass, which they really are. The other two areas, situated about St. Jerome and in the Gore of Chatham respectively, are much smaller and less important. These anorthosite masses are now known to be intrusive. Owing to the fact that in some places they possess a more or less distinct foliation coinciding with that of tlie gneiss through which they cut, Logan and the other early Canadian geologists who first examined the area, thought tb.at they, together with a portion of the associated gneisses and crystalline limestones, formed a series of stratified rocks distinct from and reposing upon the Grenville series. This sup- posed upper series was, therefore, termed the Upper Laurentian, and the anorthosites were considered to ))e its most characteristic membei's. The name Norian was also proposed by Sterry Hunt for these rocks, owing to their petrographical resemblance to the norites of Scandin- avia, which rocks are now also recognized as intrusive. Although intruded through the Laurentian at a time long preceding the Pots- dam, the appearance of these anorthosites antedated at least the termination of the great earth movements which affected the Lauren- tian in pre-Potsdam times, so that they have been squeezed and foliated together with the gneisses through which they cut. n (95 J) 4 (iUKI.KC. OviTkin l.v <*" *•'" uptufiied edges of Uu'so weathered surfaces. Some of the jjneissos are hij;hly acid, consisting essentially of ijuartz and orthoclase feldspar. Most of them, however, contain in addition a eonsidorablo (juantity of biotite or hornblende, while others, owing to the presence of a con- siderable proportion of plagioclase as well as of hornblende or pyr- oxene, with a corresponding diminution in the amount of (juartz present, are properly classcil as basic gneisses. Many of the basic gneisses are closely related to and associated with the anorthosite masses. :\[any of these gneisses differ in no way in composition from igneous rocks. This is especially true of those which from their uniform character and absence of all associated limestones, ciuartzites, etc., are referable to the Fundamental tJniMss rather than to the Gronville series, although many gnei.s.ses in th(; (jirenville series belong to this class aa well. These giuMsses usually show in a marked manner what is known as a cataclastic structure, produced by the mechanical breaking down of the original web of thi; crystalline rock, by movements induced by great pressure, which movements cause in the rock a foliation or paiallel arrangement of constituents more or loss distinct, according to their intensity. In this way a coarse-grained granite may be con- verted first into an augen-gnoiss, and finally into a very finely foliated gneiss in which all the original (piartz grains have the fo.m of thin leaves. This structure is also nMuarkably well seen in the anorthosite, in most places where it occurs in this area, ami will be more particular- ly described in treating of this rock. Many of these; gneisses, at least, were originally of igneous, probably of intrusive, origin. Examples of these aie abundant in that part of the area lying between St. Columban and St. .Jt'rome and between this latter place and Ste. Sophie. In order to ascertain the chemical composition of a typical gneiss of this class, Logan's typical Fundamental (Jneiss from Tivmbling Moun- tain was selected. An analysis of it is given under No. 1. .Siiiiii' |irol)- iilily i>f it^iif (JUS (irigiii. (97 J) AnalyiiiH QUEDEr, I. (iXKIMN. Tntiil'liiJtf Mt. Silica. ,. (11I,'J4 Aliiiiiiim 14-85 Fiirii' iixiili' Ij'ti'i MiiiiHiiniiiiN iixicic •4."» Liiiii' 'J- 10 MiigiK'Hiu "ItT SihIh 4'M) I'otaHDii 4.;i.'t liOSM (111 i;,'nitii)ii ~{} (M»..-.(l 'I'otui iiii^e risin,ij oti tlio east side of 'rremblirii,' Liiko to a, liei;,'lit of 'JoOO feet a I foniiini,' tlu) liigliest jioiiit in tlie ijiureiitiaiis (if lliis part of ( anada. The mountain does not occur williin the area emliraeed l)y tlie present sheet, hut lies about twenty miles to the north-west of its north-western corner. The roelc,howe\ei', resembles closely that ocourrintj at a number of jxiintsiu the iiaui'enlian ai'ea of this sheet. It is I'aUier a tine-grained gneiss, uniform in character and is under the microscope plainly seen to be a crushed or granulated hornblende granite. The analysis shows it to poss(>ss a chemical comjidsition (piite different from that of the other gneisses and slates described below. The silica is liigli but the alumina cdiiiparatively hiw. The alkalies are also high, while the lime preponderates largely over tho magnesia. Tho C(tmposition is that of an ordinary granite. The analysis of a granite from the Carlingf(jrd District in Ireland, by liaughton, given uiuh'r No. ri., will serve to emjihasize this identity. The composition of most, if not all the gneisses belonging to tht; lower or Fundamental Gneiss, could be paralleled among the true igneous rocks. Tho greatest variety in character is found anidiig the gneisses oc- curring in '.he vicinity of the limestone bands. Here the gneisses are usually garnetiferous and (jften c(mtain sillimanite, graphite, rutile, pyrite, and other accessory minerals, the last mentioned mineral when present causing the rock to weather in a very rust'- manner. These rusty gneisses are not found except in association with the lime.stone bands and it is the exception to find tho liniestono unaccompanied by them. (98 j) LAL'KKNTIAN AHKA. ' OwiiiK to tht) peculiar ciuiracter of theso Hevenil KP.«'«8«e'« '""l t'"''"" continuouH usHoi'iation witli tlio '.iinastotH-Maml with liamlsnf (juarl/itc, wliicli rn.ks aiv certainly not of iKiicnuH origin, Imt are luol with m all hijihly nielaniur|.huM'ii Hrdiineiitaiy series, it was helieved that »ome eviilenco ini),'lil he (.l>taine.l, jiointinn to a stulimentary origin in tlwi case of the^e gneisHes aUo. A large number of them were ihero- foro carefully I'xiiininetl. Under the mieruscdpe iheHc do not show the oatai lastic uLructure usually pri'scnted hy the crushed and granulated igne.ius rocks of the system. Thny seom lo hav.» r«crystalli/ed under the influence of th.^ prt'ssun- which has served to crush these other rocks, Tiiey are, how- over, now cniupletely crystalline, no elastic material can he detected iu them, although the .•hara.ter and arrangement of the constituent min- erals is often suggestive of the metamorphwhere, do not, under the microscope, afford anyiliing which could ho taken as conclusive evidence of a clastic origin. Impnrtant ("videnco, however, bearing on tlwir origin was obtained from a study of their chemical compositii,|,.,K.,.|inin amilyses of 'three slates for puri-oses of comparison. Only one of these ^'1;;;!;'.''^;;' '^'""• gneisses, No. V., is taken fiom the i.aurentian area actually enibrncfid in this sluict, the others liowever come from the continuation of this area immediately to the rorth. Analyses Xos. IT., V., VI f. and VIII. were made for mc by Mr. Walter C. Adams, and analysis No. I. was made i)V Mr. Nevil Norton Kvans, Lecturer in Chemistry in .MctJill University. To both gentlemen I desire to acknowledge my groat in- debtedness. I. Gneiss from St. Jean de Matha, province of <,»ucbtc. A fine grained garneliferous siliimanite-gneiss, containing also much ijuartz and orlhoclase. Graphite and pyrite are also present, the latter causing the gneiss to weather to a very rusty colour. It occurs in thick bands iiiterstratiticd with white garnetiferons (piart/.ite, the whole lying nearly flat. IT. Gneiss from the west shore of Trembling Lake, province of (,»ue- bec. A fine-grained dark-gray gneiss composed of (juartj; and orthoclase with mucli l)iotite, and containing little white streaks which were evidently at uiie time continuous little bands. These are composed of sillimanite. Garnets appear here and ther^^ in (99 ..) 8 QUEBEC. Microscopic.-il structur" the (lirkei- portion of the rock. It occurs near a bund of crystal- line limestone which occupies the bed of Trembling Lake. III. An ordinary roofing slate from Wales. Analysed by T. Sterry Hunt. (Phil. Mag., 1854, p. 237.) IV. A similar roofing .slate of Cambrian age, from the large quarries in the township of Melbourm-, in the .southern portion of the province of Quebec. Analysed by T. Sterry Hunt. (Geology of Canadn, 1803, p. GOO.) V. Gneiss from Darwin's Fulls near the \illage of Rawdon, I'ange V. of the township of liawdon, province of (Quebec. It is a highly quartzose garnetiferous gneiss and occuis iji well-defined l)ands interstratified with quartzitc, which is often highly garnotiferous, the bar.ds being from a few inches to several feet in thickness. VI. Red slate from near Tinzen in the district north of the I'^ngadine, Switzerland. Highly siliceous, containing 9-12 per cent of silica as quartz. (Vom Hath, Z. d. G. G., 1857, p. 242.) VII. Gneiss, lot 20, range VII. of the township of Kawdon. Gneiss composed essentially of malacolite, scapolite and orthoclase, and holding a considoiable amount of graphite and of pyrite. Wea- thers very rusty. Occurs in well-dciiiied l)ands, interstratified with a grayi.sh- weather: \ J garnetiferous gneiss. The four gneisses I., II., V. and VII., show no cataclastic structure, but when examined with a microscope seem to have undergone com- plete recrystnllization under the pressure to which they have been sub- jected, no signs of ci-usliing being now vi.sil)le in the tliin sections. The analyses show that tl",' +!rst three of these gneisses have the composition of slate.s. Xos. I. and II. have the composition of ordinary roofing slate, as will be seen by comparing these analyses with analyse'; III. and IV., and are (juite difl'erent in coiiij)osition from any igneous rock. The high content in aluu'ina, the low percentage; of alkalies and the great preponderance of magnesia over lime, characteristic of slate.s will be noted. No. \'. is a gneiss which is so highly quartzose that it might almost be tei-med an impure quartzite, and also has a composition ditroring from tluii of any igneous rock, but one whicli is identical with many highly siliceous slates. No. VI. is such a slate from the Engadine district in Switzerland, and is, as will be .seen, almost identical in composition with No. V. Silicen is bands from the Canadian slate quarries also have a similar composition. The alumina here is low on account of the pi'eponderance of quartz, whidi also lowers the con- (100 ,t) LAURENTIAN AHEA. 9 tent of alkalies. The magnesia preponderates over the lime as before. No. VI. lost 1-92 per cent on ignition before analy.^is, and these figures do not therefore appear in the aiialyois as given above. I. GSEISS. St. Jean de M. II. Gnkiss. Trend.)ling Lake. III. Slate. Wales. IV. Sl.ATE. Mel- bourne. V. Gneiss. Rawdon. VI. Slate. Tinzen. VII. Gneiss. Rawdon. An.al3'si.s of sedimentary gneisses. .Silica Titanic oxide Alumina ... Ferric oxide. Ferrous oxide F'ric 8ul])liiile M'n'ous o.xide Lime Jlagnesia.. . . Soda Potas.sa .... Loss on ignit. Gl!)() l(i() l!)-73 " "i'fio' 1 ■ 'i*i 57 WJ 00-50 04-20 74 70 79-97 54-89 1-00 13 07 1-35 22 83 7-74' 19-70 ■"7-83' 10-80 "'4-23' 8-88 9 -04 8-02 03 4-43 -02 5-(;3 4 70 1 95 8 -.34 (2-70t) trace. ■•^:^ 1-81 •7!) 2 •.■)(> 1'82* trace. 110 3 -.50 •00 5 72 l-.-)0 trace. 112 2-20 2-20 3-lH 3-30 '• -'73' 3-94 3-07 3-20 3-42 -.")0 1-07 1-87 -42 -95 1-05 "■■■70' 1-52 •04 2-30 Total alkalies '.)9a.") 3-29 100 -77 ' 32 KM) -03 5-38 99-05 o.;i3 99-08 1-37 KM) -44 2-94 1(M)-(M) 10-29 The fourth of these gneisses, No. VII., diflfers entirely from the others. The low content of alumina, combined with low silica, the high alkalies and the preponderance of lime over magnesia mark it off as (juito ;listinct from the slates and gneisses just considered. If it be an altered sediment it is one wliich has suffered very little leaching during deposition, and must have been of the nature of a tuffaceous deposit, or one formed from the rapid disintegration of an igneous rock having the comi)osition of a basic trachyte or syenite. It is, there- fore, a rock which, .so far as its composition is concerned, might be either an altered sediment or an altered igneous rock ; and it is impos- sible, consequently, to draw from its chemical composition any definite conclusions as to its origin. In the case of those gneisse.s, then (Nos. I,, IT., V. and VII.,) whose stratigraphical relations and microscopical character suggest a sedimen- tary origin, the first thi'ee have the composition of slates, that is to say, of clay ; in the case of No. V., of clay mixed with sand, while in the case of No.VII., no definite conclusion can be drawn. To sum up, the fore, it may be said concerning che gneisses of this class, that : (1) their association with numerous and heavy beds of limestone and quartzite ; (2) their prevailing banded character, accompanied by a * Water. fWater and graphite (liy difference.) (101 .1) 10 QUEBEC. < ^'uartziti'. Aniiiliilmliti.'. Limestone. Sf. .Siuiveiir. very extensive recrystalllzation ; (3) the f ivcjuent occurrence of graphite in all rocks of the class, and (4) the fact that the gneisses of this class have in many eases at le:ist tlie composition not of igneous rocks but of sands and muds— combine to make it extremely probable that we have, in the case of many of these rocks at least, extremely altered forms of very ancient sediments. The (luartzite occurs in well-defined bands, in the vicinity of the limestones. It is .sometimes quite pure, con>istini,' of translucent or transparent vitreous quart/, but frecpiently holds garnet, sillimanite or other minerals. It is well seen at Darwin's Falls and elsewhere, near the village of Kawdon, as well as all through the Laurentian district to the south of that place. Amphibolite is a common rock, occurring in association with the gneisses in all parts of the area, but usually in oompai'atively .small amount. ■ It is dai'k or nearly black in colour, and is seen uiuler the microscoix' to be composeil essentially of plagio- clase felspar and dark-green liornblende. The latter mineral occasion- ally holds a core of pyroxene, suggesting that the rock was originally a gabbro or diabase. These aniphibolites usually occur as bands in the gneiss and are not confined to the limestone districts, and where the gneiss can be seen to have been greatly stretched or rolled out under the infiuence of pressure, these amphibole bands can invariably be observed to have been puUerl apart into separate pieces, showing that under such pressure they are less plastic than the orthoclase gneiss. The limestones are coarsely crystalline marbles, white or nearly so in colour, sometimes nearly pure, as in portions of the band near St. Sauveur or the occurrence on lot 10 of range VTL, of Kilkenny ; but at other times very impui-e, as in mucli of the New Glasgow band, the impurities consisting of grains of (|uart-<, pyroxene, phlogopite, graphite and othei minerals dissinninated througii thera. So much of this area is occupied by aiiorthosite intrusions, that the limestones are less abundant than usual in districts underlain by the Grenville sei'ies. Ai these limestones, however, are important members of the .series on account of genetic considerations, as well as owing to the light they throw on the stratigraphical relations of the series as a whole, the several occurrences will be specified. Connuencing on the west, there is limestone lyin ,' innnediately to the west and north-west of the village of !-lt. .Sauveur. This is the most extensive deveLipment of Lauivntian limestone in the area. It, for the most part, underlies a low, undulating drifted fact of country (10l'.t) LAUREXTIAN AREA. 11 nave and is associated with basic, often rusty-weathering gneisses. To the north it is cut oil' by the Morin anorthosite, whose southern limit here appears as a high and abrupt cHff' crossing the country. The liii,' stone has at several points been somewhat extensively quarried for the pro- duction of lime, having been burned at intervals for many years — the fact of its being a limestone having been pointed out to the inhabitants by Logan in the early years of the Geological Purvey. Tt is stated to form a very strong lime, l)ut one which from the presence of grains of various silicates disseminated through it, is more or less impure, and which is thus suitable for rough masonry work rather than for interior finishing. Further south in tlie augmentation of r\Iille Isles, similar limestone occurs again, and was supposed by Logan to form a continuation of the same band as that e.xposed near St. Hauveur. Another occurrence of limestone, which, however, is small and St. Jerome, unimportant, is that on the west side of the North Eiver near St. Jerome. It is sen crossing the, road which runs down the west side of the river, a short distance from the town, while blocks or it may be observed at intervals in tlie fields to the south of the road. Further south, the strike would carry it across the Xorth River where it would be covered up by the Paheozoic rocks. It does not appear, however, on the banks of the river, nor could any continuation of it be found to the north. A more important development of limestone, in the form of a liand, Xow Glasgow, which, althougli it can be traced several miles, is still comparatively thin and impure, is found a short distance to the west of the village of New Glasgow, being exposed in the bed of the River Joi-dan near the edge of the Paheozoic. From this point it can be traced in a direction a little east of north, skirting along tlu^ edge of the great anorthosite mass which occupies this part of the sheet, as far as the third range of Kilkenny, a distance of aliout six miles, where it is lost sight of. If it holds tiie course as above described, it would be cut off by th(! anorthosite a sliurt distance to the north of the point where it is last exposed. An isolated occurrence of a fine white crystalline limestone is also p<^iike,i,iy. found oti lot 10 of range 7 of Kilkenny, where it forms a low ridge about 100 yards wide, running north-and-south. In the northern half of the township of Uawdon, beyond the limits jj^^^y^^j^^ of this maj), there is a heavy band of crystalline limestone running through the township from north to south. The southern portion of the township where underlain by the limestone is, however, so heavily (103 ,T) 12 QUEBEC. dnft-covered hat but few exposures are to be sec. On the 4th ran^e along the road between the viHage of Rawdon and Hte. Jul enn a f 'w inulJ exposures of Jin^estone protrude through the drift on bts 13 Z h>, associated with quart.ito and -ueiss which n./v ^ this Wstone to the south, an^f ::; ^ t:!! rr ^r K .0, the hn,estone band is greatly di,ninished in si.e to the soul AiKirthosir, iiitrusiuiLs, TirE AXOBTHOSITE IXTRUSIOXS. As has been mentioned above, about one-half of the Laurentian Tr re*:r:::r'^'^7';r'^"""^^'°"^''^>"'^P' ^^^ ^'^ ^- larger arc eally portions of the same intrusion, known as the Morin anorthosite mass, and unite to the north. This anorthosite is a basic rock belonging to the family of the ^ab- l-os, but characterize,! by the great preponderance of one const itu^nt na-ly, the plag.oclase felspar, which is so abundant tha it oft" a makes up the entire rock. The other constituents are n.onoclinic a. d rhombic pyroxe,i..s and ilmenite. No olivine has been fouml i any 1 be ar.as on this sheet. The rock is usually coarse in < n n it structure being especially well seen on the large weather^l .^c e moutonnee surfaces. In its normal condition the rock hasl anitl •struc ure and is de.p violet, almost black, on a fresh f It^u'; '^ e anorthosite m that portion of the area occupying the extreme no!tl Mo...... west corner of the sheet, in the townships ii^ri^^W^^rt exposed along t^ie road and railway between Ste. Ad.Me u d Ste Agatlie, shows these characters. The same is true of much of t le .morthosite beyond the limits of the sheet to the north. T e rest the Monn anorthosite embraced witliin the limits of the sit t " , re sents peripheral portions of the mass and consequentir ws a marked manner the effects of the great pressure to which tX,; -. w.. ..h,ected before the deposition of the Potsdam. Thr^:^ effec ot this pressure is the production of a brecciated structure n t le anorthosite, especially well seen on large weatherecl suiiaces al ou J ^rgu..te and elsewhere in the easteni part of the towi.::; 7w^. ^ L .^ - •;;;:f^*7 .«^-^*"- - P-duc.., by the partla. ginulation o e .0 k, the resulting rock consisting of fragments of pkgioclase or of the other constituents of the rock, embedded in a species ^f .^^ a. e, nu nidualK. The brecciation being accompanied by a movement banded structure. A very remarkable fact in connection witlr"^ (104 J) Effects of |)ri'.ssure, LAUnENTIAV AHEA. 13 deve opment of this structure is tl.at wherever the rock becomes granu- lated It becon-.fs innch li^^hter ia colour. "This can be observed even in nncroscopical sections, when the phenomena is seen to be due to the disappearance of the dark dust-like inclusions which give to the felspar Its dark colour, wherever the minera? becomes broken up or granulated and so uniformly are thes. two {.rocesses connected, that it is always possible to predict when examining a thin section under the microscope just how n,uch of the rock has been granulated by observing •• s colour' before using polari.ed liglu, by which the extent of the granulation is at once made visible. Hu common is the granulation throughout the area, that even in the most massi^ e and gmnit<.id specimens of the anorthosite, traces of it can usually lie found. When the effects of pressure are more marked, as close to the,, r .• edge of the area or anywhere in the most easterly development of the ' -nu'lly anorthosite m the township, of liawdon and Kilkenny, the -n-anulation '''""""'*^'' becomes much more pronounced and a progres.^ively larg<.r proportion of the rock becomes grvanulated. This is accompanied bv the passage of the streaked structure into a distinct and often perfect foliation whKh coincides with the foliation of the surrounding gneiss, and by a b caching of the rock, until in the ^•arieties showing an advanced stage of granulation only a few small dark remnants of the original coarsdy crystalline plagioclase individuals remain, like augen in an augen-gneiss embedded in a mass of finely granulated plagioclase, often so white that at a distance; the rock cannot be distinguished from marble Tois variety ,s well seen about Xew Glasgow, where it has been extensively quarried for paving stones which are used in Montreal. It is also well seen along the contact near the east end of Lake L'Achigan, gradually becoming dark in colour towards the west end of the lake about St Hippolyte. The anorthosite undergoes no change in chemical composition durin-^ the gramdalion above described-the proc ss, as studied under the microscope, appears to bo a purely mechanical one. It is thus quit? different from that commonly observed and which has been described by Lehman and others in the case of sheared gabbros. In all cases of shearing hitherto .lescribed, the pyroxenes under the influence of the pressure are altered to hornblende, while the plagioc ;,.<. i^ often altered to saussurite, the resulting rock being an amphibolite not a gabbro. There is reason to believe that the movements which affected these anorthosites toek place when the rock was deeply buried and probably also very hot- perhaps near its fusing point. Although, in inosi p, ces, the .Alorin anorthosite comes against the ^ gtiei^s without producing any perceptible alteration, at some parts of its ^""""=""'^'" (105 J) fl 11 yUEIlEC. Black pfiililiv Lakrti,l(l aiiovtluiiite. circurnferoneo, especially north-east of Eelio Lake, where the contact crosses tiie lownships of Abcrcroiubie and Kilkenny, a rather mas- sive, dark, heavy rock, rich ui liisilicates and often holdin-; a little quartz and some untwiiined felspar, bonlers the area and may he a contact product of som(! kind. The Innindary of the typical anortliosite against tills rock is usually pretty sharp, hut the latter passes gradually into the gneiss of the district. This intervening rock, however, has iu the main the composition of gahhro, so that it becomes ditlicult to decide whether it represents a jieculiar and abnormal, possibly altered, form of the gneiss or a contact phase of the anortliosite. Close to the edge of the easterly development of the Morin anorthosite at New Glasgow, and running north for about six miles in a direction very nearly parallel to t!iat of the limestom* band in the gneiss just ,,. west of the contact, is a band of a peculiar gabbro nearly black in colon)', which protrudes through the drift in a series of gr(>at roche moutonnee bosses, conti'asting in a marked manner with the white anorthcsite through which it cuts. The liaiid is narrow, and immediately to the north of New Glasgow sends (.ut an arm about a i|uartei- of a mile long from its eastern side, which cuts across the foliation of tlie anorthosite. Under the microscope, the rock presents an extremely well marked cataclastic structure, the constituent minerals having been completely granulated under the great pressure to which they have been subjected. Of the two smaller areas, that which lies to the west of St. Colum- bin, extending over into the Gore of Chatham and known as the Lake- field area, most closely resembles th(> Morin anoi'thosite just described. It is four and a half miles long and about a mile wide, only about one half of it, however, being embraced in the accompanying sheet. The outer poi'(;i()ns are tine-grained, foliated, very poor in bisilicates and weather white. Tlie inner portion r)f the area is more massive, and appears on the whole to be rather richer i,'i ferro-magnesian constitu- ents, which vary in amount from place to place, often giving the rock an irregular banded structure. A rapid change in strike is ob- servable in this area, the anorthosite and its surrounding gneisses iu the s(mthern part striking on an average N. .30 AV., M'hile about the northern extrenn'ty both rocks strike N. 'M) to 65 E. Less than a mile to the south of the area, at the very edge of the Laurentian escarpment, a diabase dyke cuts through the gneiss, which is here the countrv-rock. The dyke contains angular fragments of white anor- thosite which in many places are so .abundant as to make up the greater part of the whole. These fragments, which were brought up (lOfi ,t) LAUREN'TIAN AUEA. 16 by the molten diabase, probably mark an uiulerground extension of this Lakelield area to the south. Only a portion of the St. Ji'a-ome area, situated as it is immediately st. .Icicnn' at the edge of the Laurentian axis, is exposed to view. The sduthcrn iwrtluwitf. part of it is eovcred uji and concealed liy the Hat-lying Palii'O/oii" beds which conii' in a short distance to the south of the town. What pro- portion of the whole mass is represented by the portion exposed to view it is impossil)]e to say. It differs considerably fiom the other areas, in that the anoi'thositcj composing it is not .so typical in character, as well as in the fact that there intervenes between it and the gneiss a t>road zone of rocks of in- termediate character. The aiiorlhosite, or gabbro as it should in this case more properly bo called, is .seen iuits typical development on ,.,_..a.va.e..3 „,,ui.s a„,l stmiii »li,i,l.)W», these are usually not wul siti ° ulati s.,.„„.le.e. Th„ lar^e n,n .Is „f Pla.^'~''- ^^ ^ ^'^ on the „.he,. , »hieh „... ahuu.la,.. , .,, "I^y^^^f^^ T'-z ;: m T,:: r.; e;^ 'ithe a,; s ,..,. as ,. .. i„„ .„ eKcee,lins well-».arke,l cataelastio structure. This .-.bl,r„ ...ass is surroumlKl l.y a ..,,«• ..t r«cl"' gneiss has been found to follow the windings of the boundary of the Morin anorthosite in a remarkable manner, making it evident that although the anorthosite breaks thr..ugh the gneiss and cuts oti the limestone bands in the latter, the foliation of the gneiss is not altogether an original structure, but is, in part at least, secondary, having been caused by the great pressure to which both rocks were subjected after the intrusion of the anorthosite, which has led to movements in the solid rocks. ECONOMIC RESOURCES. I No mineral deposits of great value have as yet been found within this Laurentian area. The following, however, are worthy of note :- Iron ore-Near St. Jerome, County of Terrehonne.-T^o and a half jn^ ore, St. miles south-west of St. J.rome, on the road which follows the northern bank of the river, there is a deposit of magnetic iron-ore. Phis occurs as several thin bands interstratitied with a dark hornblendic rock and with the red orthoclase gneiss of this part of the -'ea-the whole dipping toward the river at a very high angle. As seen inl 886 the ore was exposed by the removal of the drift deposits at a number of points along its strike, and a shallow opening had been made in it at one place. Subsequently, from October. 1891, until March, 1892, the deposit was worked by the Canada Iron Furnace Company ; during which time about 365 tons of ore was taken out and shipped to the company s furnaces at Radnor and there smelted. The following information has been kindly supplied to me by Mr. Arthur Cole, B. A. Sc, who was engaged in carrying out the work :— ^2 a09.T) AnalyBiH Iron ore, Julit'inu' .g ylKllEC. 1 ► f ,. nit wliicli wlitjn al)iiiuli)iit!(l .'Most of th« ore was taken .mt ot a pit win. h wn The oru-ho.! variocl fioni tw.. and a halt teet to tlue . e< i be,! hart „,.,„we,l dow„ t„ a About ntty to,. we.e takc-n out ^^h:s .^ . n -^ ^^ ^^^ . ^^^^^ feet ileen ami thhty feet long. Woik Nvas nnai > • , .„,„,,le,i " In Septen.be.-, as it was foun-u!X'Ihnng^out in an en,phatic manner the distineti-.n W- Un, an.i >sis „ „.-threlase -neiss and those occunn.g m the tween the .ron-oves ot ^1- '-^^ J ^ ^^^,^^^^^ ,,,,, the ano.thosit^N the former being usuaU> lue althou-h l..ttor u-e rich in this deleterious co.istituent. Ih.s oic altl.ou hittei .tie uui titanium, while occurring so n.>a.' the anorthosite, is quue iie r . .,f the adiacent anorthosite areas always contain a la ge the lron-on^^ ot he adjac. nt ^^^^^ following percentage of tins element. io tl.( >t oeui,, deposits. ,r . , , This denosit is situated near the village near t lie eastti u tuo' ^"- . i,„,.4- Tim r>rp ncurs . .f .anorthosite showrt in the accompanying sheet, the ore occurs bisilicates and striking fr.mi N. 8 W. to ^. - V o (110 J) LAUUKNTIAN ARKA. 19 inchfH to several te.-t m wi.lll. «' >. uu.y ^^^^ .^ tho foliation of the •-•'-';<-''•' '•"\;;,;j:J ., .[^Ue.l, and p.,,, ,,,. ,„,,,hosiU. ana u-on-oro ^ 'f , J \.,, ,,,, .„,,,.t...l it is oft..u .l.tlicult to .letenain. whether ^'^ .' "^.^^^ ,,,, J ,,. through the anc-thosite o. whethe. tl,e ^^^^-\\^ ,„,,,,, , anorthosite are to be attnhutea . U n,^ .^^^^^^.^^^ ^^^^ p,.inci,,al n.ass hen., oxpose.l to, . hou .0) e ^^^^. ^ ^^^, ^^^^^ din-ction. The " ore 'W-- t' ^ ^ ^ J ^^^ ^,.„.,,i,,,o an ore anorthosite, an.l in .nost , a.es .s -^ ^_ .^^_.^^^^ _^^^^ ^^^. i, the i-rnper sense ot U.e t.-nn. It .^ a so > '. y ^. ^^^^^^^ ^^ tains iron pyrites as a frei,e to contau. :- ^^ ^^ ^ ^ Motiillic iron ■ LiKri;rt. luii'iuiit. Titunic ui'iit , . T„„ »„„„«,. i n,,.,..l...i.H..m„«.ou,... t... t.,.„.w,nB results :— ^^ Highly tit»ni ftTO'W. Mctalli'' ii(ii\. 'I'itiUiic aciil. 27 I...' :i:{ f.T in 71 |) t'- found to contain: — :j,> o!t p.c. Titanic aciil ^ .1 • 1 *■ r. am.ill (iiK'nin" has been made We..:fi.d, Jianr I, L"* ' -O" ^^'^ '''.:^'^,? 1 ""^ain amount of in a dark-colontvl heavy tnass.ve ^^ -^ ^j^^ ^ , ^ , ,,„, ,,,iety iron-ore. The tield felattons ntd.cate t at t ts tn ^ ^^^^^^^ of the Morht attorthosite, -^P^^" "^ "^^.^^^ „, p,„ves this to constituents of the fock, and a ^ ^^'i .^H "^o Jis seen to be , ..o., o .. Wex- be the case. Whe.t thin secttons are ^^^^:^^.^^,^ ..d '-'' ,roi.-ore. A not inconsiue ^,.^^^,,. The proportion of iron-ore !^:::;;;z:; It: t,>» e.ii,.e.u,„.-. ..„..„„ «*„ .. following results ; — Metallic iron Insoluble ifsitliie . Titanic aciil •20 ■ '1', per cent. . . 1 joiidcd reaction. ^e,x,rt of Pr„gn..s, deoi. Surv. Can 1876-77, P- 475. (1 1 1 J) 2U gUEHIC. Kifh'uni/, Kang^ VII., Lot 7".— This deposit in an impuro <.chro or limoniti', occurrin« iioar tli« <'(1k." of tl.« Moriii an..ithosit found, however, and the deposit is, I should judge, valueh'ss as a source of iron. A specimen of the limtmite was examined »)y Dr. HoH'mann, and was found to contain ;— NUtallio in.n 2'>73 \m- wml. Innolul.l.' matter '^arge amount. Tt also contained a considtM-al.le ciuantity of manganese, hut no titanium. Anortl..«ite. Anorthosite. This rock, although it has heen hut littlo used for building purposes, might in many cases be employed with advantage for decorative construction. It may he obtained in unlimited amc-nt in the Moiin area, of any colour from deep violet to white. The opalescent varieties oc-ur but sparingly in this district. To judge (.f its appearance when cut and polished, two large blocks, one of tho violet and one of the white variety wore collected and six-inch cul)fc8 were prepared from them. These were exhibited in tho Colonial and Indian Kxhibiti.m held in London in 1H8G. The violet variety was collected on the eastern side of range II. of the township of Morin, and when polished p-esented a handsome appearance, but was rather dark in colour. The white variety, which was taken from the large exposures at New Glasgow, took a high polish Jind in this state was found to bear a striking resemblance to marble. It is more difficult to work than marble, but would be more durable and would retain its polish better, especially in exposed situations, and might well be employed for many purposes in construction. On account of its toughness and durability, this white anorthosite from New Glasgow has been extensively used for paving Btone in the city of Montreal, especially on streets where then - f "ca^-v ireight traffic. A number of small quarries have been opened in the vicinity of New Glasgow, while a larger one is operated about two miles to the north of ^he village. The stone is blasted out in large blocks and is Ihdn dr-^ssed to the reciuired size by means of large hammers. The irJui. !>, which has thus sprung up is quite extensive, up to the time of my iaK visit in August, 1891, 541,000 anorthosite paving blocks having been shippped to Montreal by rail. (112 j)