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44
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COMMITTEE OF MANAGEMENT.

Chairman; JAMES Loupon, M.A., LL.D., President of the
University.
PROFESSOR W. J. ALEXANDER, M.A., Ph.D.
PRINCIPAL J. GALBRAITH, M.A.
Proressor A. H. REYNAR, M,A., LL.D.
‘PROFESSOR R. RaMSAY WRIGHT, M.A., B.Sc,
PROFESSOR GEORGE M. Wronc, M.A.

General Editor: H. H. LANGTON, B.A., Librarian of the
University.
THE HURONIAN OF THE MOOSE RIVER BASIN

BY

WILLIAM ARTHUR PARKS, B.A.

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A370 558
THE HURONIAN OF THE MOOSE RIVER BASIN

The Moose River, entering the south-west angle of James
Bay, drains an immense triangular area of which the apex is at the
river’s mouth and the base stretches from above Lake Abitibi to
a point west of Kabinakagami Lake. Fach side of this triangle
is approximately 250 miles, and, allowing for’ sinuosities in the
boundary, its area cannot be less than 30,000 square miles.

Explorations in this extensive region have not yet put us
in possession of the minute information desirable. In 1865 Dr.
Robert Bell made certain explorations which are described in his
report to the Geological Survey of Canada in 1875, and at a later
date also he was employed for several years in this district. The
results of his irivestigations may be found in the Report of the
Geological Survey of Canada for 1880-2. Mr. E. B. Borron like-
wise made several journeys, particularly in 1881 and 1882, and re-
ported on his explorations to the Ontario Government.’ In 1896
Mr. Alexander Niven was commissioned to lay down the boundary
line between Nipissing and Algoma, which he extended for one hun-
dred and twenty miles; he was accompanied by Mr. E. Burwash,
whose report on the geology of the region traversed appears in the
Report of the Bureau of Mines of Ontario for 1896. This boundary
line was continued to the Moose River in 1898, and a base lina
carried westward from the 120th post in 1899. The writer accom-
’ panied the two latter expeditions as geologist, and his reports appear
in the Reports of the Bureau of Mines for these years.

With the exception of the above mentioned reports, there is
very little available literature bearing on the region in question.
The southern and major portion of its triangular area consists of
Laurentian gneisses and granites crossed by several bands of
Huronian rocks. The upper part presents limestones, dolomites
and shales of Devonian and possibly also of Silurian age. The
present paper deals with the Huronian alone, and more particularly
with the petrography of the series as here exemplified. For infor-
mation as to the general geology and topography, economic resources
and other points, reference must be made to the reports above cited.

 

1 Report of E. B. Borron, Stipendiary Magistrate, on Part of the Basin of Hudson’s
Bay. Toronto, 1883.
4

The term “Huronian” is applied in this paper to all the rocks
above the Laurentian and beneath the lowest fossiliferous strata.
In this sense the expression is made to include rocks of various age
and different petrographical nature, such as Logan’s original
Huronian, Lawson’s Keewatin and Couchouching series, the Ani-
mikie and Nepigon formations, the gray wacké and associated rocks
of the Sudbury region and the various schists, altered eruptives
and crushed granites characteristic of wide areas in northern On-
tario. In: the region under discussion the Huronian is represented
by a great variety of schists, presumably of clastic origin, and by
others of altered eruptive nature, closely associated with both acid
and basic eruptives in various stages of decomposition. No lime-
stones or sandstones occur anywhere in the region examined by
the writer, although Dr. Bell reports the former rock just south
of the height of land near the Montreal River, and Mr. Burwash
also refers to it.

Tt is in regard to the various schists that the great difficulty
of determination arises. (To establish a fixed nomenclature for
these is almost impossible, as their varieties of colour, structure and
texture are practically innumerable. In a distance of twenty feet
no less than seven distinct varieties were counted on one occasion.
On the other hand, to pass by these rocks with a mere description is
altogether unsatisfactory, as megascopic descriptions by different
observers might leave considerable doubt as to the identity of similar
exposures. ‘For example, the same rock is described as “ dark
quartzite,” “dark gray siliceous schist,” “quartzose schist,” etc.
To the trained scientist these terms, while not petrographically
synonymous, are sufficiently suggestive to recall the rock in ques-
tion. In publications, however, intended for the guidance of pros-
pectors, this method causes great uncertainty. For economic pur-:
poses, it would sutfice to establish the fact that, for a particular
region, a certain variety of rock was ore-bearing, leaving the ques-
tion of its origin to more scientific observers; but there are too many
gradations to render such a classification of any real value. It is
only on the basis of origin that a satisfactory arrangement can be
effected.

_The petrographical peculiarities of the rocks encountered will
first be described, with little or no reference to geographical posi-
tion, and afterwards the great Huronian areas will be outlined and
the location of particular species indicated.
5

J

All rocks are either eruptive or sedimentary in origin, but
such a primary division is useless in the present instance, where
dynamic’ metamorphism has obliterated the dividing line and in-
duced resemblances which force rocks of different origin into the
same group on account of similarity of structure. ‘ Nevertheless
it is to origin that we must look in deciding the more minute
divisions.

We have therefore:—

I. Unaltered eruptives.

TI. Much metamorphosed eruptives and clastics, generally
schistose in structure, which may be embraced in the
term schist.

Among unaltered eruptives are included all those rocks of
primary igneous origin, in which the original structure and mineral
constituents are unaltered or but slightly affected. They may be
grouped and will be considered in the following order:—

(1) Acid or potash-feldspar rocks: Granite, syenite, augite sye-

nite, quartz porphyry.

(2) Basic or plagioclase rock: Diéorite, diabase, olivine diabase,
gabbro, basalt, amygdaloidal trap, pyroxenite, anorthosite.

Granite.—This rock, in an unaltered condition, plays but a
subordinate part in the geology of the district, as far as the Hu-
ronian is concerned. When present in this formation it is gener-
ally in the form of narrow dykes, conforming to the strike of the
schists; the district described as the “second area” is more remark-
able for these rocks. Muscovite, hornblende and biotite granites
have been observed; in all cases they are typical and require no
further notice. Large masses of granite, in some cases probably
eruptive, in others representing the non-laminated portion of the
Laurentian matrix, are common in many parts of the regions of that
age. According to the theory of Dr. Lawson * the granitic portion
of the matrix would be distant from, and the gneissoid portion near
to the Huronian contact. On this assumption much of the granite
observed must be eruptive, for a loss of lamination on approaching
the contact is apparent in many places. Some of these masses are

 

1 Report on the Geology of the Rainy Lake Region. (Report Geol. Surv. Can.,
1887, page 112.) :
‘ 6

mapped as eruptive granite by Dr. Bell. It is not within the scope
of this paper to discuss the point. (For localities see pages 22, 23,
25, 26, 27, 30, 31, 33 and 34.) ;
Syenite-—This rock also is not widespread, typical examples
being very few.. One mass occurs about fifteen miles up the Black
River and shows altered hornblende and feldspar, the character of
the latter being somewhat hard tol determine in the specimen
obtained; but as the general field appearance is decidedly syenitic,
and the microscope reveals scarcely any trace of striation in the
feldspar, it is concluded that the rock is syenite, although it pro-
bably contains some plagioclase. In addition to this exposure and
some narrow bands associated with the schists, all the syenite is,
like the granite, blended with gneiss and syenite gneiss and must be
classed as Laurentian. (For localities see pages 23 and 30.)
Augite syenite——The mass of eruptive which crosses the
Abitibi River, forming the Lobstick and other rapids as well as the
Great Canyon, is represented at its upper or southern margin by a
rock of this nature, which continues with some variations for two
or three miles. It is intersected by small dykes of fine black dia-
base, which present some beautiful examples of miniature faulting
and branching. At the Lobstick Portage it is somewhat schistose in
places and much altered, showing numerous red garnets, a little
quartz, considerable orthoclase and some plagioclase with bright
green augite. At the Oil Can Portage and above it, a section shows
fairly large crystals of augite in a somewhat finer and mosaic-
like mass of orthoclase with a little quartz and plagioclase. The
augite is, in many places, almost entirely altered to fibrous horn-
blende, flakes of brown mica, garnet and magnetite. This rock
presents a grayish-black, somewhat speckled appearance with evid-
ence of flow structure or secondary lamination. In its more altered
parts are seen sphene and mellilite. (For localities see page 33.)
Quartz porphyry.—This rock does not occur in a good state of
preservation, but in an altered and schistose condition it is very
common; in order to carry out the classification adopted, it cannot
be included here but will receive consideration under the schists.
Diorite.—Typical diorite is composed of distinct anhedra of
hornblende and plagioclase, forming a hard, massive and sonorous
rock. In some cases the individual minerals reach’ a size of several
inches, giving the rock a mottled appearance. From this coarse
7

variety all gradations are seen down to that composed of individ-
uals of microscopic size. The finer examples on fresh fracture
still show the crystalline structure, but the mottled appearance is
entirely lost, partly owing to the fineness of texture, but perhaps
more in consequence of discoloration of the feldspar. This type
is common and fairly fine examples are the rule, no very coarse
diorites being seen in the region.

Diorite occurs in large dykes traversing the country rock in
all directions, and also frequently in irregular masses forming the
summits of hills; in some instances the intrusive mass has lifted
the country schists to the summit of the hill, while the diorite
appears on the flanks. By far the most general manner of: occur-
rence is in bands of varying thickness, conformable with the strike
and dip of the schists, which is generally at a high angle. These
thin bands are invariably fine-grained and almost black in colour.
Many of them towards their borders have entirely lost the crystal-
line structure and are homogeneous to the naked eye; the micro-
scope, however, reveals some traces of crystallization in ill-formed
hornblende and magnetite crystals, due, of course, to the more rapid
cooling of the exterior of the mass. An important considera-
tion now confronts us. Are these interbedded diorites contempor-
aneous with the schists, are they subsequent eruptions, or are the
schists themselves derived from the diorites? It is probable that all
these cases occur. The diorites can thus be divided into three
classes, (1) massive eruptives, (2) contemporaneous diorites, (3)
diorites passing into diorite schists.

(1) The class of massive eruptives can be recognized by a
distinct crystalline structure nearly always increasing in fineness
towards the borders and on both sides. All the irregular masses
that form hills, the large dykes crossing the country rock, and many
of the interlaminated sheets show this peculiarity. As far as the
last variety is concerned, the bilateral symmetry of the mass can be
accounted for on no other assumption than that of subsequent in-
jection. The accessory evidence of a sheet of diorite breaking across
from one plane of stratification to another has not been observed
here, although it is well known to occur.

(2) Contemporaneous diorites are generally less crystalline,
more easily weathered and more inclined to show irregularities
of colour and structure. If these rocks were originally overflows
8

they must have consolidated as diabases, because diorite is gener-
ally considered as essentially plutonic. On the assumption that the
original magma was covered by clastic materials which eventually
became metamorphosed into schists, we should expect to find a
difference between the lower and the upper surfaces. This con-
dition has been observed by no means constantly. A sufficient
number, however, on examination gave convincing evidence of
their contemporaneous nature, and it seems advisable to include in
this class most of the narrow bands, perhaps all in which no bilateral
arrangement can be detected.

(3) Rocks of the third class, viz., diorites passing into diorite
schists, consist of ordinary diorite towards the centre of the layer
becoming more and more schistose outwards; and finally fading
away into other schists without any distinct line of demarcation.
This type of rock is doubtless the result of intense metamorphism,
and, while easily recognized, affords very little information as to
origin. While they seem to be best placed in a class by themselves,
they are more probably derived from the second than from the first
group on account of the difference in composition towards the
borders. The outer parts.show much more quartz than the
inner. This could hardly result from metamorphism alone; there-
fore it is concluded that they were more or less mixed with acid
clastics, which would point to a more contemporaneous origin.

Any of these diorites may present varieties, but more especi-
ally those of the first class. While typical diorite consists of horn-
blende and plagioclase, the former ingredient may be replaced
wholly or in part by black biotite, giving a rock known as mica
diorite, or quartz may occur, forming quartz diorite. Both these
varieties are found in the region, as well as quartz mica diorite
(tonalite). The latter generally has a pink feldspar and much
resembles granite; a section to ascertain the nature of the feldspar
is the only sure means of determination.

The passage of diorite into diorite schist and the so-called
“ oreenschists” is a subject of much controversy. The meta-
morphism is accompanied by various phenomena of alteration, as
changes in texture, softening, change of colour, alteration of horn-
blende to actinolite or. chlorite, or even to hematite, magnetite, etc.,
alteration of feldspar to epidote and saussurite and in many places
to calcite. These various changes have produced rocks which are
9

in many instances almost impossible to recognize, and must be
named more or less by analogy. They are included under the
schists and a more detailed description will be given later. (For
localities see pages 28, 25, 27, 28, 30, 31, 32, 33 and 34.)

Diabase.—This rock is by no means as common as diorite
and its examples seem to belong to different periods of injection.
Those of similar age to the diorites and schists are generally much
altered; while a second series, of apparently later age, better retains
the original nature. Rocks of the latter type occur in narrow dykes
crossing the country rock in all directions; they are particularly
‘noticeable in the eruptive region of the Abitibi Canyon. These
belts are uniformly very fine-grained and black in colour; they
commonly show a difference of texture at the periphery, which
weathers smooth while the centre has a more punctated appearance.
“(See pages 22, 23, 24, 26, and 33.)

Olivine eobase: Tange boulders of this rock were found at
the Sextant Portage in the Devonian area, and must have been
‘derived from the neighbouring Huronian, although not seen in
situ. A section shows the usual diabase structure with needles of
‘apatite and irregular patches of olivine, which is much altered to
magnetite.

Gabbro.—The most characteristic examples of gabbro occur on
the northern part of the Abitibi Canyon, and even there it can
scarcely be considered typical. The best exposures are seen at the
deepest part of the gorge, where the cliffs are 100 feet high and of
a dark massive appearance. Under the microscope the augite is
seen in distinct crystals but little decomposed. The feldspar is
represented by both varieties with the plagioclase in excess, whence
it may be termed gabbro, although further south it passes into
augite syenite. (See page 33.)

Basalt, amygdaloidal trap, pyroxenite and anorthosite are of
such rare occurrence that sufficient reference to them will be found
‘in the notes of distribution. (See pages 23 and 33.)

The whole series of Huronian rocks not included under the
unaltered eruptives it is proposed to group together as schists,
although they may not always present a schistose structure. The
use of this term is at the best very uncertain, as is seen’ by the
interpretation placed upon it by Professors Irving, Chamberlin and
Van Hise. “Almost any non-fossiliferous reck presenting in some sort

~
10

a stratiform structure, and more compact and indurated than is usual
with post-archaean strata, has been spoken of as a crystalline schist.
i The near approach of certain foliated fragmental deriva-
tives to typical crystalline schists—indeed their gradation into un-
distinguishable, if not identical, forms, and the passage of massive
eruptives into schistose phases — would render very difficult a
sharply limited consideration of the typical crystalline schists.” *

In this broad sense our region is for the most part made up of
such derivatives, which may be divided into two main groups, (1)
those whose origin was probably eruptive, (2) those whose origin
was probably clastic. ‘The difficulty in distinguishing these two
classes is very great, as they pass imperceptibly into each other and
as a mass of certain ultimate composition whether originally erup-
tive or deposited as a fragmental may give rise to the same rock.
Professor Williams says, “Between undoubted massive rocks ren-
dered schistose by pressure on the one hand, and fragmental tuffs
which have been more or less completely solidified by the same
agency on the other, there must therefore be rocks whose original
form must always remain uncertain.” 2

In this connection see also Irving, Chamberlin and Van Hise,
“The greenschists have been derived by the modification of original
eruptives and present a degradational development which may be
looked upon as offering a contrast to the constructive development
of the crystallines built up from clastic originals.” *

It will therefore be evident that any attempt to classify these
rocks must prove in some manner unsatisfactory; various authors
will adopt different methods, and some overlapping and uncer-
tainty will always exist. The above mentioned authorities classify
the Lake Superior schists thus: —

I. Eruptive derived (metamorphic) erystalline schists.

II. Tuff derived crystalline schists, which were developed
from igneo-fragmental material.

III. Clastic derived crystalline schists, which were developed
from fragmental rocks by secondary growths of the constituent
crystalline fragments.

 

*Congrés Géologique International, Etudes sur les Schistes Cristallins. Lon-
dres, 1888, page 92.

2U. S. Geological Survey, Bulletin 62, 1890, page 133.

%Congrés Géologique International, Etudes sur les Schistes Cristallins. Lon-
dres, 1888, page 105.
11

IV. Clastic derived crystalline schists, which were developed
from fragmental rocks by the conversion of the constituent silicate
fragments into foliated minerals (metasomatic).

V. Chemico-clastic derived crystalline schists, in whose pro-
duction chemical, organic and clastic agencies joined.*

Professor Dr. Albert Heim, after showing the difficulty of
classification and summarizing the various effects of dynamic
metamorphism, says, “Die Beschaffenheit der krystallinischen
Schiefer in den Alpen ist vielfach durch den Gebirgsstauungsprozess
verindert worden. Urspriingliches und mechanisch spater Gewor-
denes sind sehr oft noch gar nicht von einander zu unterschei-
den.” ?

Dr. Andrew Lawson classifies the Keewatin series of the Lake
of the Woods thus:—

I. Basie Volcanic:

Altered diabase and gabbro, massive and schistose with
associated amphibolites or diorites and hornblende schists.

TI. Acid Volcanic:

Altered quartz porphyries, felsite schists, sericite schists,
porphyroids, ete.

III. Voleanic Clastic—pyroclastic:

Ash beds, many graywackés, tuffs, and agglomerates,
both basic and acid.

IV. Detrital—epiclastic:

Conglomerates, quartzites, clay slates, micaceous slates;
soft,,eray, glossy hydromica schists; with chlorite schists,
mica schists, and certain fine-grained gray gneisses, or
rather feldspathic mica schists.

V. Gabbro, serpentine and granite.®

Many of the schists of our region are quite comparable to
Lawson’s series, but many of his members are almost or entirely
lacking, notably the conglomerates, agglomerates, serpentines and
graywackés.

It is not proposed here to deal with theoretical considerations
as to the origin of the various representatives. Such points can
only be determined by a detailed study of a more restricted area

 

1 Ibid, p. 104. 2 Tbid, p. 20.

®Congrés Géologique International, Etudes sur les Schistes Cristallins. Lon-
dres, 1888, page 71. Report on the Geology of Rainy Lake Region. (Report Geol.
Surv. Canada 1887, Part F, page 57 et seq.)
12

\

than that now under discussion. The intention is rather to describe
the various schists and to name and group them according to their
present peculiarities, and, in view of the doubt attending their
origin, to employ that evidence only when the rock seems to be
analogous to some described by good authorities. From this point
of view the following table will give an outline of the method
adopted:—
I. Schists of eruptive origin:

(a) The “greenschists” and diorite schists.

(b) Altered porphyries and porphyrites.

(c) Felsites and crushed granites.

(d) Hornblende and biotite mica schists.

Il. Schists of fragmental origin:
(a) Pyroclastic schists and ash schists.
(b) Quartzites.
(c) Clay slates.
TII. Schists of doubtful origin or belonging in part to both
the above:
(a) Quartzose schists.
(b) Sericite and chlorite schists.

I. Scuists OF ERUPTIVE ORIGIN.

(a) The “greenschists” and diorite schists——As indicated in
the description of diorites, that type of rock passes gradually into
diorite schist, retaining its mineral structure and merely becoming
schistose by dynamic effects. These diorite schists‘are quite char-
acteristic and need no comment; they are widely distributed and ‘
easily recognized, if not in the field, at least by the examination
of a thin section. The “schists” are doubtless eruptives which
have been subjected to more intense metamorphism and while
generally occurring in narrow bands are sometimes massive and of
considerable extent. They do not commonly present a schistose
structure in the hand specimen, and very rarely can such a struc:
ture be made out under the microscope. In the field the weathered
surface is a shade of dirty green; it generally shows a somewhat
punctated appearance and frequently exhibits small whitish specks.
(These must not be confused with the larger and more angular
blotches seen on many altered porphyrites). The freshly broken
surface is rather uneven, greenish to black in colour, and shows a
18

somewhat silky surface, which under the hand glass is seen to be
distinctly radial in structure. Microscopic sections are decidedly
unsatisfactory, showing generally but an indistinct dirty mixture of
kaolinized and saussurized feldspar, a very little quartz and light
green hornblende and chlorite, with accessory pyite, hematite,
magnetite, garnet, mica, ete. Some of these rocks very much
resemble the darker varieties of quartzose schists to be subsequently
described. In the field they may be distinguished from the latter
rock by being more easily abraded by the hammer, and by the fact
that they do not show the same tendency to break into rhomboidal
blocks.

This rock is one of the most frequent occurrence and probably
constitutes the bulk of the first or greater Huronian area, the limits
of which will be indicated in the second part of this paper. The
whole question of the metamorphism: by which these rocks were
produced would fill volumes. As here exemplified they are analo-
gous to the so-called “green MHuronian schists,” and probably
identical with the series described by Professor Williams in the
“Greenstone schist area of Michigan,” where he says:

“There seem to be only three different ways of explaining
the facts as they are plainly and abundantly manifested in each of
the several points examined on the Menominee River. We may.
suppose, as did Foster and Whitney, Whittlesey and Credner, that
the schistose portions of the rocks exposed at these several points
are more or less perfectly metamorphosed sedimentary material,
while the more massive portions represent intercalated beds of
eruptive origin. We may imagine on the other hand, as did
Rominger and Brooks, that all of these rocks, including the most
schistose and the most massive phases, are probably altered sedi-
mentaries, supposing with Rominger that the more massive kinds
are merely the same sedimentary material fused by the intensity
of the metamorphosing action so as to lose all trace of the original
stratification, or admitting with Brooks the possibility, though
great improbability, that some of the more massive phases, like the
gabbro of Sturgeon Falls, are of eruptive origin. Finally, we may
imagine that all phases seen at these several places represent
material of eruptive origin whose stratiform structure is due to
secondary dynamie agencies. (Irving.)’”?

 

1U. 8. Geological Survey, Bulletin 62, 1890, page 66.
14

Here Professor Williams undoubtedly includes other schists
than the variety now under discussion, but from the descriptions
this particular rock must form a large part of his series.

The theory that the massive diorites are intensely altered sedi-
ments is utterly untenable for this region; for proof of this the
reader is referred to the remarks already made regarding the
more massive diorites, to the bilateral arrangement of many of the
bands, to the fact that in many instances they abut with a sharp
line of distinction against entirely dissimilar rocks, and further that
an enormous number of similar belts of diorite traverse the neigh-
bouring Laurentian gneiss, notably on Hay Creek, Misanabie Lake,
Little Misanabie Lake and River and the Laurentian area around
the Pishkanogama and Makozenda or Trout Rivers. Granted then
that the massive variety is eruptive, the frequent and beautiful
gradation into rocks of this type so constantly seen is sufficient
proof that they had a primary eruptive origin. (For localities see
pages 22, 23, 25, 30, 31, 32 and 33.)

In this connection mention must be made of the altered dia-
bases. Rocks of undoubted diabase origin are rare, but the possi-
bility must be admitted that many of our greenschists are of that
nature. The proof of this in many individual cases can never be
obtained. However, greenschist, showing no trace of pyroxene
but exhibiting undoubtedly the structure of diabase has been met
with, notably on Kamiskotaia Lake. This rock is grayish green in
colour, not extremely hard, and only by the microscope is its dia-
base origin revealed; the feldspar is almost entirely altered and the
augite changed to almost colourless hornblende and chlorite, but
the ophitic structure is well preserved.

(b) Altered porphyries and porphyrites——As already men-
tioned, unaltered rocks of this type are absent, but a large series of
altered representatives are met with. Schistose quartz porphyries
present almost invariably a light gray or white surface and very
frequently the quartz individuals stand out on the exposed surface
by the weathering away of the more decomposable, constituents.
Concerning the origin of these rocks Professor Williams says:
“They contain small porphyritic crystals of feldspar and quartz,
and a considerable amount of sericite or hydromica. ok
Rocks of this general type have a wide distribution and have ar-

rested the particular attention of petrographical investigators. In
15

some cases they have been conclusively proved to be the product of
the metamorphism of fragmental rocks—either tuffs or true sedi-
ments—while in other cases they have resulted from the action of
great dynamic forces upon massive rocks of a corresponding con-
formation, 1.¢., quartz porphyries. When it is possible to trace
with certainty the origin of these rocks to stratified deposits they
are usually designated as porphyroids, while in case their mother
rock can be shown to have been quartz porphyry they are usually
called schistose porphyries. In their extreme development these
two types: are often petrographically indistinguishable, and they
present an instructive instance of the production of identical results
by the action of the same physical forces upon matter of the same
average composition, though widely different in origin and struc-
ture.” ?

It is extremely probable that many of the rocks of this gen-
eral| appearance should, in accordance with the above view, be
called porphyroids and as such be included in the clastic division.
It is probable, however, that an eruptive origin, as true quartz
porphyry, is the proper explanation of the presence of most of
them. In many cases, by the loss of the porphyritic individuals,
they pass into felsite schists, a section of which in some instances
much resembles the ground mass or matrix of the altered porphyry.
These rocks are associated with the diorites and greenschists as well
as with the quartzose series; it may be that in the former case they
are of eruptive origin and in the latter belong to the porphyroid
type. A typical section from! near the Montreal River shows a
fine-grained ground mass mostly of quartz but rendered somewhat
dirty and muddy; by decomposed feldspar and small flakes of
sericite. In this are fairly large crystals of orthoclase, much
altered but retaining their angular outline, together with somewhat
smaller quartz individuals which, in nearly all cases, show a
rounded outline. (For localities see pages 25, 26 and 33.)

Many of the so-called speckled and mottled schists as well as
some more massive varieties are altered porphyrites. They may, in
general, be described as gray, green and purplish rocks with
blotches of white matter of an angular form. They are not as
common in this region as in the Huronian around Lake Minnie-
takie to the westward, but exposures are found at the first falls on

 

10.8. Geological Survey, Bulletin 62,1890, page 119.
16

the Frederick House River, on the line of portages between
Matagami River and Porcupine Lake, and in some few other locali-
ties. A section shows a fine-grained matrix, largely of feldspar
and secondary quartz with bright green chlorite, brown mica, etc.
Implanted in this are large much altered plagioclase erystals.

Another peculiar schist which probably belongs here is seen
on the same line of portages mentioned above. It is blackish green
in colour, of a pronounced schistose character and excessively alter-
ed. A section shows plagioclase individuals surrounded by an
exceedingly fine ground mass, in which the secondary minerals,
largely magnetite and chlorite, are arranged in a distinctly

spheroidal manner. (See page 25.)

In addition to these we find a series of very fine-grained schists
of whitish or lightly tinted gray and red colour, readily weathering
and presenting a soft and gray-white surface. They seem to contain
little or no ferro-magnesian mineral and under the microscope
show fine feldspar individuals and quartz which is largely allotrio-
morphic. This matrix is traversed by fine dark lines, probably
representing the remains of mica or hornblende, and is dotted by
relatively porphyritic crystals of plagioclase. This rock passes into
coarser examples (still very fine however), in which the crystals of
plagioclase can just be made out with the naked eye on fresh
surfaces. The coarser of these rocks is undoubtedly a sheared por-
phyrite, and as it passes imperceptibly into the finer variety we
are quite justified in assuming the same origin for the latter. These
schists are very common and have been loosely described as “ white
weathering schists,” “soft fine-grained schists” and possibly as
“fine-grained ash rocks.” (For localities see pages 25 and 31.)

(c) Crushed granites and felsites—Rocks which may with
safety be placed in this group are exceedingly wide-spread and
present many stages of alteration. They are generally pink or light
gray in colour with ill defined dark specks, and occur intercalated
with various schists, particularly near the head of Lake Matagam-
ing. Under the microscope the only well defined mineral is quartz,
and sometimes orthoclase, but the latter mineral is generally much
altered and presents a muddy appearance. The quartz uniformly
shows undulatory extinction and frequently occurs in narrow bands
of a somewhat coarser texture traversing the ground mass of the
rock. The mica or hornblende, as the case may be, is always much
17

changed and drawn out into indefinite patches in one direction so
that it appears as oblong or oval spots with the long diagonals
parallel. In these spots the microscope reveals actinolite threads,
chlorite, magnetite, hematite, pyrite, etc. (For localities see pages
26, 27, 82 and 33.)

(d) Hornblende and biotite mica schists.—The first of these
rocks is a dark gray or green mottled or homogeneous rock accord-
ing to the dimensions of the constituents. It is composed of horn-
blende and quartz and frequently shows little or no schistose struc-
ture. Biotite mica schist is somewhat lighter in colour, with shades
of brown, never green, its schistosity is more pronounced, and it is
much more subject to weathering. Both rocks are more associated
with the Laurentian than with the Huronian, and by the addition
of feldspar frequently pass into gneiss. More or less angular
fragments of these rocks are often seen imbedded in the gneiss,
and they probably at one time played an important role.

In this connection Ch. Lory, in “Les Schists Cristallins des
Alpes Occidentales,” says—“ Les micas schistes se chargent de felds
path et passent 4 des gneiss, avec lesquels ils alternent
Du reste, la séparation entre les deux parties de la série des schistes
cristallins est loin d’étre absolue: de vrais micas schistes, avec des
couches de caleaires cipolins, et méme de vrais gneiss, se rencontrent
jusque dans le groupe supérieur; ils alternent souvent, 4 diverses
reprises, avec les schistes chloriteux ou amphiboliques
Ainsi dans la série des pierres vertes, comme dans celle des vrais
micas schistes et gneiss, les diverses structures schisteuse, gneiss-
ique ou granitoide alternent entre elles, en concordance, sans qw’il y
ait lieu de supposer que le passage de l’une al’ autre soit lié 4
Vintervention de roches éruptives.” *

It will be observed that it is considered better to include here
only typical examples of these rocks, and that many of the dark
gray and green schists, containing, no doubt, hornblende and
quartz, are classified under the quartzose schists. There are two
reasons for this; first, because the amount of hornblende or mica
is so small compared’ with the quartz and is generally so altered
and indistinct that the megascopic appearance does not suggest a
hornblende schist; second, because the associations of these rocks

 

1Congrés Géologique International, Les Schistes Cristallins. Londres, 1888
page 24,
2°
18

point more to a clastic than to an igneous origin. It cannot be
denied however that a sharp line is difficult to draw, and that the

two classes pass one into the other.
Il. Scuists OF FRAGMENTAL ORIGIN.

(a) Pyroclastic schists and ash rocks.—These terms are
practically synonymous, although a distinction is generally drawn,
the former term being applied to examples showing round or
angular fragments imbedded in a matrix, and the latter to fine-
grained gray rocks.

The first type is but sparingly developed in this region, the
best examples being seen! at the head of the south arm of Lake
Matagami. As here seen the rock is green in colour and very fine-
grained; it presents a distinct flow structure around the included
fragments, which vary from a foot in diameter to very small dimen-
sions, and consist for the most part of light gray granite. The rock
is therefore a conglomerate and perhaps graywacké conglomerate.
Mr. Burwash reports conglomerate near Little Hawk Lake.*

The term “fine-grained ash rock” has been excessively em-
ployed to designate strata of a doubtful nature, but in many cases
the expression is used without sufficient consideration. When
the rock can be conclusively proved to have arisen from fine vol-
canic ejectamenta the term is as good as any other, but proof is not
always available. This is possibly the origin of some of the rocks of
our region, but it is preferable to class as quartzose schists and to
ascribe to a doubtful or variable origin rocks which, by some
observers, might be considered as ash derivatives. (See pages 21 and
22.)

(b) Quartzites.—In order to distinguish these rocks from
those which have been called quartzose schists we must restrict the
term to rocks in which no ferro-magnesian or micaceous ingredient
occurs, and in which feldspar plays but a small part. The colour
varies from white to light green or pink. By deepening of colour
owing to increase in accessory minerals the rock passes into quartzose
schist. Two varieties occur:—(1) Compact: a hard rock, almost
pure silica in grains and broken crystals; (2) Saccharine: a loose
friable variety resembling loaf sugar, typically pure white, but
passing into brown and black examples by the occurrence of hema-
tite and magnetite which are frequently seen in beautiful little
crystals. (See pages 24, 25, 26, 28 and 31.)

1 Report of the Bureau of Mines, Ontario, 1896, page 173,
19

(c) Clay slates and micaceous clay slates occur but sparingly
and will be noted later; they are, in some cases, difficult to dis-
tinguish from true schists. (See page 26.)

III. Scuists or DouBtrut oR VARIABLE ORIGIN.

(a) Quartzose schists—This group includes a great number
of rocks of varied appearance, with gradations of colour from al-
most white to dark green and gray. They are uniformly fine-
grained and consist largely of quartz, with occasionally some fine
feldspar, and a small amount of colouring matter, in many cases
difficult or impossible to identify as a distinct mineral. Often, how-
ever, this matter.can be resolved into mineral species, such as pearly
white mica, asbestiform hornblende, hematite, magnetite and
various ferro-magnesian minerals. Many of these schists show a
pronounced rhomboidal cleavage and frequently films of secondary
quartz occur on the planes of parting.

Under this head rocks are included which have been variously
described as ‘ quartzites,’ ‘quartz schists,’ ‘mica and hornblende
schists’ and possibly the whole series loosely designated as ‘ fine-
grained ash rocks.’ The intense metamorphism to which rocks of
this type have been subjected renders the question of their origin
very difficult to answer. That they are altered eruptives is un-
likely on account of their acid nature in contrast to the basic diorites
with which they are so closely associated. Their relation to the
altered quartz porphyries would nullify this conclusion, if it were
not that the latter rock is of much less frequent occurrence. That
they are formed of volcanic ejectamenta is also unlikely on account
of their immense range and from the fact that no volcanic centres
have yet been ascertained in the region. Again, the presence of so
much diorite indicates a basic condition of plutonic activity and not
an acid volcanic state with craters necessarily of some elevation in
order to discharge the amount of ash required to form these schists.
However, it is well to remember that some undoubted pyroclastics
occur, and to the westward of our region are even common, and
also that it has been conclusively proved by Williams and others
that volcanic tuffs do pass into both diorites and acid schists. Any
single example must receive the most minute examination to settle
its origin; as this is impossible over the wide area in question it must
suffice to name these rocks “ quartzose schists,” and leave the ques-
tion of origin for future determination. Speaking generally the
opinion of the present writer is that they are intensely altered
20

sedimentary clastics analogous to quartzites. As might be ex-
pected many varieties occur, a few of which will be described. .

A very pronounced variety, easy to recognize, and very wide-

spread, is-a hard white rock; weathering dull white, and frequently
showing black veins. When broken across the planes of stratifica-
tion it immediately suggests a very fine-grained quartzite. A fresh
surface along the plane of stratification, however, presents small
‘flakes of pearly white mica. This rock seems much like the
novaculite described by Williams in the “ Marquette Iron Region,”
concerning which he says,—“ These are hard, compact, fine-grained
but decidedly schistose beds, locally known as novaculite
The colour of these so-called novaculites is sometimes reddish, some-
times pale greenish or yellowish . . . Under the microscope
they closely resemble the ground mass of the quartz porphyries.
No porphyritic crystals, however, are ever observed, and the
structure is too fine-grained to appear schistose in a thin section.”
(See U. S. Geological Survey, Pulletin 62, page 151 et seq.).
_ Another type is darker in colour, reddish or greenish, frequent-
ly exhibiting rapid changes in colour but always showing a decided-
ly quartz-like appearance on fresh fracture. This variety is seen to
perfection at the third portage on the route between Matagami
River and Kamiskotaia Lake. Examples from this region give from
69 to 78 per cent. of silica.

The third type is dark gray in colour, sometimes containing no
more than 65 per cent. of silica, and is more readily weathered;
it very frequently contains pyrite and it is the variety in which
hornblende, mica and other ferro-magnesian constituents may be
identified. This rock is more closely related to the diorites, which
it somewhat resembles in rough megascopie characters, although
its constitution is entirely. different.

(b) Sericite and chlorite schists—The sericite schists may be
distinguished from any of the preceding rocks by a greater tendency
to cleave; in fact they may be described as extremely fissile. Fresh
fractured surfaces have a silvery appearance and sometimes are
greasy to the touch. Thev are much more subject to sub-aerial
decay; a talus of broken fragments almost always occurs at the
foot of a cliff of this rock. It weathers rapidly and the surface is
frequently rusty and spotted. Under the microscope the schistose
structure is most pronounced. (See pages 22, 28, 25, 26, 28, 29, 30,
-81 and 82.) ,
21

II

The types of rock which form the Huronian in this region
having been briefly described, it remains now to outline the dis-
tribution and to point out some local peculiarities in the various
schists and other rocks encountered. There may be said to be
six distinct Huronian areas in the basin of the Moose River; two
of these are of considerable extent and the others smaller. The
first and greatest belt stretches in a north-west direction from Lake
Abitibi to beyond the Misanabie River. It might well be desig-
nated the Abitibi-Misanabie area, but for brevity’s sake will be
hereafter referred to as the first area.

The southern boundary of this belt crosses the height of land
near Muskegogama Lake, continues north and bending eastward
across Minniesinaqua Lake just touches the south bay of Lake
Matagami. Thence it extends a little east of north and crosses
the Nipissing-Algoma line near the 96th post, to which it con-
tinues approximately parallel up to about the 115th mile (Bur-
wash), when it bends off sharply to the west and crosses the Mata-
gami River at the Wawiatan Portage after sending out a spur
which crosses Lake Kenogamissee as a narrow band. From the
portage it holds north and west to beyond the Pishkanogama River.
There it bends northward and crosses the Trout River in a north-
west direction which it holds to beyond the Misanabie River. The
latter river is crossed by two belts which probably both belong to
this great area, and are so figured by Dr. Bell. The northern
boundary is not so well known. It has been determined on the
Abitibi, Frederick House, Matagami and Misanabie Rivers and is
shown on the map as a continuous line joining these points. In
the description of the rocks of this region they will first be noted
as they occur on the Nipissing-Algoma boundary, and afterwards
on the various rivers and canoe-routes.

The Nipissing-Aleoma boundary crosses the height of land
and enters our region at the 76th mile north of Proudfoot’s line
near Little Hawk Lake. At this point, Mr. Burwash thus describes
the series, “ Reddish thick-bedded rocks cross the line and occupy
the east shore of the lake . . . . They are succeeded on the
north by a greenish gray conglomerate, and this is in turn followed
by gray ash rocks, which in places give way to what appears to be
an amygdaloid, the light coloured amygdules of which weather out
22

at the surface.”’? Ash rocks appear to follow these outcrops to the
north, and at the 83rd mile a small area of reddish crushed granite
is met which is succeeded by a greenish conglomerate. At the 84th
mile Burwash reports a “sericite dolomite schist,” and at the 85th
“schistose rocks stained with iron.” At the 86th mile occurs a
weathered diabase with cubes of pyrites, while to the eastward he
encountered the reddish thick-bedded rocks met with on Little
Hawk Lake. Following these occur weathered diabase, gray ash
rocks and chlorite schist with pyrite. At the 97th mile the line
enters a granite area and continues in it to the 104th mile. This
is, no doubt, the corner of the Laurentian area which extends a mile
and a half east of the line. Grayish sandstone occurs at the con-
tact, and exposures of dioritic schist, reddish slaty rock and chloritic
schists continue to the 111th mile, where the line again enters the
Laurentian, finally leaving it at the 116th mile, and entering
grayish slaty rocks. The rock from here northward is much
obscured by the drift, and it is advisable to continue our section
northward by following the water-course of Night Hawk and
Frederick House Lakes and Frederick House River. Exposures on
the south bay of Night Hawk Lake, and on Starvation Creek,
which enters it, are not numerous and consist largely of altered
diorites or greenschists. After the main body of the lake is enter-
ed the following series is found on the west shore:—Massive green
diorite, altered dioritic schists and quartzose schists with pyrite,
crushed granite (on an island off the mouth of the Redstone River),
coarse hornblende and mica diorites (one and a half miles north of
Redstone), fine-grained hornblende schist and a rather hard sericite
schist (N. 30° E.). North of Porcupine River isa fine-grained
massive diorite and typical chlorotoid schist.

No exposures occur on the river connecting Night Hawk and
Frederick House Lakes, nor are any seen on the latter lake except.
towards the north and on the easterly side, where is presented a
series of dark gray schists with streaks of pyrite exhibiting a banded
spheroidal weathering and showing nuclei of a jasper-like variety

. surrounded by the darker schist. This rock has a decidedly volcanic
appearance and is followed by a fine-grained porphyrite striking
S. E. and dipping 80° from the vertical.

 

1 Report of the Bureau of Mines, Ontario, 1896, page 178.
23

At the first falls, one and a half miles below the lake, occurs
a ridge of much altered porphyrite weathering out in white spots.
At the foot of the fall is a fine-grained gray quartzose schist accom-
panied by altered dioritic rocks, showing under the microscope
feldspar crystals surrounded by radially arranged chlorite. Four
miles below the falls, at the “Three Portages,” a considerable mass
of serpentine filled with magnetite is seen. This is followed by
dioritic rocks resembling those at the falls, and a white-weathered
fine-grained schist. Dark hornblende diorite is the only rock seen
from this point to the Laurentian contact a few miles below. The
contact appears to strike N. 60° W.

Somewhat to the east of this section another is afforded by
the Black River and Abitibi River. A glance at the map will
show the Black River entering the Abitibi at the great bend.
About 20 miles south of this point, the former stream becomes
small and rapid, and we find exposures of pyroclastics with three
inch inclusions, also dark schists with diorite and splashes of quartz
associated with a little sericite. Just below, the river drops 15 feet
over mixed schists with a considerable amount of quartz, alter-
nating with belts of diorite. Six miles below this point occurs a
boss of syenite or possibly hornblende granite on the east side of
the river; it rises to an elevation of 30 feet and is flanked at both
sides by greenschists and some quartzose schists. On the opposite
side of the river is an outcrop of a dark rock with round: white
spots of one-quarter of an inch diameter, exhibiting fluidal struc-
ture in the magma. It is probably an amygdaloid, but the speci-
men brought is too much altered for exact determination. Here
also occurs a rock which is probably a much altered porphyry.

Below this exposure we find fine gray to black schists inter-
stratified with diorites, the whole showing rhomboidal jointing.
Just below, a small rapid is formed by a ridge of pronounced diorite
schist striking N. 35° W. A mile further down a fall of 12 feet
is occasioned by a belt of massive diorite striking N. W. From
here to the mouth of the river, a distance of 13 miles, the only
rocks seen are fine gray quartzose schist with pyrite and diorites of
close texture. From the mouth of the Black River to Iroquois Falls
(5 miles) only one exposure of dark schist is seen. At the falls the
rock is a heavy dark gray weathered diabase. No Huronian ex-
posures occur below this waterfall.
24

To the eastward of the mouth of the Black River, at the “Two
Portages” a similar dark weathered diabase with pyrite is seen.
Although the Huronian area extends further east and embraces
most of Lake Abitibi a detailed description of it cannot be given
here, the writer’s explorations having ceased at the “Two Por-
tages.”

An excellent east and west section of the country between
the Abitibi and Matagami regions is afforded by a canoe route
passing from the mouth of the Black River westward to Frederick
House Lake and from Night Hawk Lake by Porcupine River and
a-chain of portages to the Matagami. The first stretch of this
route, i.¢., to Frederick House Lake, lies up a stream on which
the only exposures are green quartzose schists. From the head
of this stream several portages over high sandy soil bring us to
Frederick House Lake; but no exposures are visible, so completely
is the rock covered by sand. On the Porcupine River however the
rocks are exposed at several places.

One and a half miles up there occurs a dark gray slate-like
schist weathering white with bands of quartzite, strike N. 60° E.,
dip 30°. This exposure well shows the relation previously men-
tioned of the quartzose schists to the quartzites. ‘The next out-
crop above this is a fine quartzose schist with some sericite schist
becoming ferruginous to the north. A mile higher up is a rock
representing the connecting link between quartzites, as previously
defined, and quartzose schist. It is almost pure silica and very
fine-grained. One mile above this deposit is a much altered diabase
with asbestiform hornblende and green hornblende schist. Rocks
of similar nature crop out at intervals as far as Porcupine Lake, a
distance of 30 miles. From Porcupine Lake to the mouth of the
river is only above five miles in a straight line. On the north side
of Porcupine Lake occurs an outcrop of a soft rock resembling
scapstone, with crystals of magnetite and veinlets of chrysotile. Un-
der the microscope the rock appears to be made up of indistinct
fibres of this substance mixed with quartz. It is evidently a much
altered example of the basic eruptive series. On the south side
of the lake occurs altered diabase and gray quartzose schist with
asbestiform partings and veinlets of quartz. On the creek entering
from the south-west were found gray to white fine porphyrite schists,
weathering quite white with stréaks of quartz and pyrite. On the
25

passage overland southward from this lake an interesting series of
rocks is encountered as follows:—Soft mottled sericite schists very
much altered, under the microscope showing irregular and strained
quartz individuals, some feldspar presumably orthoclase, light in-
distinct sericite and considerable calcite; soft schists weathering
with ferruginous stains, associated with bands of quartzite; inter-
laminated bands of quartz and quartzite, striking east and west, and
so filled in places with hematite scales and crystals of magnetite as
to become quite black.

At one and a half miles from the lake were seen diorite schists
followed by soft and hard examples of the sericitic series.

Another exploration line passing 8. E. from about the middle
of the south shore shows the following:—Ridge of granite, east and
west, flanked by soft calcareous sericite schist; hard gray quartzose
schists; sericite schist; streaked quartz rock with pyrite (10 chains):
sericite schist; 20 chains of granite; soft decomposed schists
weathering out in brown spots.

On the first portage westward from Porcupine Lake occur gray
quartzose schists and greenschists. °

On the second portage are seen soft, rusty spotted schists with
sericite showing on the cleavage planes. A fresh fracture across
the planes shows very fine quartz. This is followed by diorite
which is in turn succeeded by hard quartzose schists, and at the
eastern end a rock very similar to that at the west, all striking about
N. 75° E. and dipping vertically.

After crossing a small Jake and a short portage, together about
a mile, the route enters a lake about a mile and a half long in a
north-easterly direction. On the east side of this lake are seen
massive green diorite and diorite schist (pyritous), and on the
westerly side fine gray quartzose schists, possibly altered porphyries,
striking N. E. and 8. W. Two portages, the first of 15°chains and
the second of two miles, are required to reach the Matagami. On
neither of these is any rock exposed.

A. third north and south section of this area is afforded by
the Matagami River and its approaches from the south. The
Huronian is first encountered on the east shore of Muskegogama
Lake, and is represented by diorite and dioritic schists, much con-
torted and mixed with gneiss and bands of quartz. Gneiss again
crops out on the way down the lake, but a massive green diorite is
26

characteristic at the first portage. At the next portage there is a
mass of granite crossed by dykes of fine dark diabase. On the river
below the portage various hard schists and belts of diorite are seen.
On entering Minniesinaqua Lake by the portage connecting it with
the river we first encounter a massive diorite which gives place
westward to diorite schists, passing into a much mixed series of
various quartzose schists, altered porphyries and possibly porphy-
rites, crushed granites and felsites, forming an extremely com-
plicated mass and extending as far as the bend in the lake, 1.e., for
about 15 miles. Here the formation swings eastward, and is
encountered at the south end of Lake Matagami. On the east side
of the bay at the extremity of the lake are seen high bluffs of a
light greenish rock showing the structure of a crushed porphyrite
under the microscope. This is followed by greenish Huronian
schists with one inch to two foot inclusions of gray granite,
evidently conglomerate. Somewhat farther north on the west side,
sheared granite and some bands of diorite form high precipitous
shores. About a mile farther north on the east side, gray and green
spotted micaceous and sericitic schists mixed with bands of granite
and felsite are seen. These strike W. 10° S. and are followed by
mica and hornblende schists passing into gneiss. Dr. Bell describes
the rock on the east side of the southern lagoon as “greenish gray
quartzite, holding transparent grains.” +

A portage from near Fort Matagami extends eastward to Lake
Shattagami where the Huronian is again encountered and is tlius
described by Dr. Bell:—“ On the west side of the narrow cove which
forms both its inlet and its outlet, beds of greenish gray clay slate or
shale, which are full of pyrite, are found, standing vertically, and
striking 8.70" W. About a mile up the south-west side, a soft green-
ish gray rock occurs, which has a dioritic appearance, but is evidently
of a magnesian character. It is rudely stratified, and beds, which
are on edge, run east and west.”

Following the Grassy River eastward we finally arrive at
Little Hawk Lake. The rocks on the route, according to Dr. Bell,
are “prayish quartzite (sometimes of a conglomerate nature) and
greenish diorite.” On Little Hawk Lake he describes a cliff of 200
feet of “grayish red fine-grained quartzite in thick beds, inter-
stratified with others of greenish felsitic quartzite holding red

 

 

1 Geol. Survey of Canada, Report, 1875-76, page 307.
27

grains.” This is doubtless the thick-bedded red rock of Burwash
already mentioned in this paper. “On the north side of Little Hawk
Lake greenish gray clay slate is seen at two points. At the outlet
there is a massive light-green felsitic volcanic ash, marked with specks
of lighter and darker colours than the matrix.”

From this exposure it is about forty miles northward through
Matagami and Kenogamissee Lakes until the Huronian is again
encountered. Here it consists of a narrow spur projecting west-
ward from the main mass to the east. The rocks exposed show
the following series from*south to north:—Fine-grained diorites;
hard gray granite and felsites; mica and hornblende schists; crushed
granite; soft Huronian micaceous schists, striking E. 10° N., and
dipping 30° to N. W.; dark crystalline diorite with white blebs.
The latter rock might be described as a porphyritic diorite.

Some distance north of this series a belt of diorite crosses the
lake near Moore’s house.

The main body of the Huronian is encountered just north of
Wawiatan Portage at the foot of Kenogamissee Lake. It is repre-
sented first by a belt of granite N. 20° W., followed by coarse green
diorite and soft close-bedded white-weathering schist almost ver-
tical and striking north-west. A microscopic examination of . this
-rock shows a very fine-grained ground mass of quartz and feldspar
-with porphyritic crystals apparently of plagioclase, which would
make the rock a porphyrite schist.

Below the rapids few exposures are seen until we reach
Omeemee or Pigeon Rapids. On this stretch, however, quartzose
schists and some clay slate striking N. 75° W. occur.

At the Pigeon Rapids greenish crystalline diorite is mixed
with dark gray quartzose schists and contains bands of quartz carry-
ing gold. Considerable intermixed calcite occurs here.

Only a few exposures of siliceous schists are seen until the
first of the Sandy Portages is reached (Kish-ki-qua-mo), where is
seen a hard gray quartzose schist (gray siliceous and dark bluish
gray clay-slate, according to Bell). Between this and the next
portage occurs a green rock with white spots. A section shows the
white to be entirely altered feldspar and the green mostly chlorite
arranged around the feldspar. It is possibly a much altered por-
phyrite which contained a large amount of ferro-magnesian matter.
It strikes about east and west. At the second portage the rock at
28

the top is hard gray quartzose schist followed to the north by softer
schists (nacreous, chlorotoid and taleoid schists, according to Bell),
with streaks of quartz, strike N. 60° W. At the foot is a large dyke
of green diorite. The rocks at the third portage are vari-coloured
fine quartz schists with a considerable amount of fine decomposable
magnesian matter, striking about north-east and south-west. Dr.
Bell describes them as nacreous and talcoid schists, but it is doubt-
ful if any tale occurs in them; they contain streaks of quartz and
much pyrite. Four or five miles _below. these portages the
Kamiskotaia Sagaigan River enters from the west. On ascending
this stream slaty diorites are first encountered and then hard
quartzose schists. At the third portage on the route to the lake
a splendid development of the quartzose schists is seen. The
country here is bare and rises into hills of considerable size which
give a hummocked aspect to the whole region. The schists are of
many colours, white, green, gray, purple, etc., and strike a little
south of east with a nearly vertical dip. A section shows a pro-
nounced schistose structure with fine quartz exhibiting undula-
tory extinction and sometimes arranged in lenticular patches.
The other ingredient is of variable nature, brown mica being very
common as well as chlorite and perhaps also sericite. These schists
average 70 per cent. of silica. On the stream flowing out of Kamis-
kotaia is seen a fine-grained gray diorite followed by a coarser
variety and on the lake itself is a typical quartz diorite of dark gray
colour.

For a description of the river Matagami below the Kamis-
kotaia Dr. Bell’s report is relied upon,’ as the writer’s investiga-
tions did not extend farther north.

The following is a brief summary of the rocks recorded:—On
the east side, 30 chains helow the branch is an exposure of “massive,
gray, semi-crystalline steatitic rock, holding grains of specular iron,
and cut by small veins of whitish bitter spar.” This is followed for
eleven miles by outcrops of greenish gray diorites, both massive
and slaty. Then occur dykes of green crystalline diorite. Half a
mile further is dark gray quartzite with iron pyrites and clear
quartz grains, N. 80° W. At the end of another half-mile a
massive, light greenish gray siliceous schist resembling diorite runs

 

1Geol. Survey of Canada, Report, 1875-76, page 312 et seq.
29

N. 75° W. (quartzose schist). At Sturgeon Portage, three and a
half miles farther down we find hard greenish gray slaty diorite,
N. 35° to 60° W., cut by a great dyke of greenish gray slate-like
crystalline diorite running north and south. Six miles below the
portage are seen “soft grayish green calcareous talcoid schists, N.
55° W.” Eight miles more bring us to outcrops of “ gray diorite
or volcanic ash, holding sharp crystals of black hornblende, larger
grains of white feldspar, and small crystals of iron pyrites.” At
Loon Portage, three miles down, the rock is “dark, greenish gray
hornblendic schist,” and at Davis’ Rapid, a mile below, it consists
of “chloritie and hornblendic schist.” After this last portage we
pass into the Laurentian gneiss.

On the Ground Hog River the southern boundary of this great
area is considerably farther north than shown on Dr. Bell’s map.
This river was examined for ten miles below the point there repre-
‘sented and the contact was not found; the whole region around
Wawayeskatching Lake and a considerable distance to the east is
gneiss. The same observation holds true on the Pishkanogama
River, the Huronian at the contact being represented by massive
and schistose diorites.

This area is again met with on the Misanabie River, which it
crosses in two belts separated by about eight miles of gneiss. The
more northern of these belts is seven or eight miles wide, at right
angles to the general strike, and the southern not more than six, at
the point where the river crosses it. The rocks in both belts do not
differ materially from those seen in other parts of the area. In the
first belt the average strike is a little south of west, the rocks being
the usual assemblage of gquartzose schists and some mica
schists crossed by belts of diorite. The second belt, towards the south,
shows much quartzose schist and fine hornblende schist. There was
no opportunity to examine these rocks west of the river; the limits
as shown on the sketch are copied directly from Dr. Bell’s map.
: The second Huronian belt extends in a north-easterly direction
for about eighty miles, crossing the Canadian Pacific Railway be-
tween Ridout and Woman River, and terminating near Aquesqua
Lake. The area embraces Sa-ge-tow-wash-ka, Matagaming and
Ground Hog Lakes, and it was along this route that it was exam-
‘ined. On passing down the river from Rice Lake gneiss is en-
countered as far as the third portage, a distance of about three and
30

a half miles. Here, however, gray hornblende schists crop out,
followed by granite with inclusions of dark hornblende schist
in such numbers as to indicate a sort of giant breccia. From
this point to Lake Sa-ge-tow-wash-ka extends about a mile
and a half of swamp showing only occasional exposures of gray
granite and green diorite.

At the prominent point one and a half miles from the mouth
of the river on the east side is a massive green diorite. North
from here, on the west side of the lake, a typical hornblende
granite extends for some miles along the shore. On the bay from
which the river flows out are first seen very fine-grained white
schists, almost pure quartz but probably containing some fine
sericite, for they weather out a dull white. These rocks much
resemble the variety described as novaculite. They are followed
by green chlorite schists, mixed with greenish hornblende granite,
to the foot of the bay. Between this lake and Lake Matagaming
there is a fall of 150 feet; the country is very rough and the rocks
varied and: well exposed.

At the first portage, immediately on leaving the bay, are seen
dark green chloritic and hornblende schists passing into lighter
mottled schists to the north. At the next portage, one and a half
miles down, green rocks like those above are seen splashed with
quartz. Another mile and a half intervenes to the third portage,
where are found a syenitic rock, greenschists with pyrite and a fine-
grained sheared granite showing under the microscope a large
percentage of fine quartz, a very little greenish mica and scattered,
relatively large, crystals of orthoclase. A short distance north a
series of vari-coloured schists cross the stream. These rocks are
somewhat soft and sericitic in places and contain small seams
of quartz. Very similar rocks, striking east and west, are
seen on entering Matagaming Lake; they rise into considerable
hills, having a banded appearance of white, green, reddish, purple,
etc. Nearly half a mile of porphyritie hornblende granite follows,
occurring in belts, interlaminated with gray quartzose schists °
and light green chloritic schists, striking north-east and dipping
40° to the north-west. Whitish schists are common about a mile
beyond the wide granite belt. At the point where the lake begins
to open out we encounter dioritic schists followed by hard gray
and light green varieties. About a mile lower down, where the
31

lake bends to the east, soft sericite schist is found, striking east
and west and dipping 20° to the north. Opposite are seen hard
quartzose schists. Very little more rock is seen on the lake or on
the river below as far as Ground Hog Lake.

Half a mile north of Ground Hog Lake soft friable whitish
schists run east and west, dipping at a high angle. Three miles below,
the river is broken by the Kaskamene Rapids, where are seen soft
micaceous slate-like rocks suitable for whetstones. Two miles
below these rapids sericite schists crop out, striking east and west.
Two and a half miles from this point a heavy rapid, Mekesewasun,
occurs. Here a dyke of heavy diorite crosses the rivera few degrees
north of east; above it are seen gray and green schists, and below
five or six varieties of closely banded quartzose schists. On an
island a mile and a half farther down we find hard gray quartz
schists and diorite with pyrite. The Laurentian contact occurs
just below, but a dyke of massive diorite N. 20° W. is found at
the Ostandigististagan Fall a little farther down.

This area is also visible on the canoe route between Ground
Hog and Pishkanogama Rivers. The trail leaves the former river
a few miles below Ground Hog Lake. On the third portage gneiss
is encountered, but towards the end of the trail it gives place to
bright green fissile schists, probably chlorite. On the small lake
succeeding, similar schists are observed striking east and west and
mixed with sugary quartzite. Similar rocks are seen on the next
portage, and the northern and eastern shores of the following lake
are of gneissoid muscovite granite, while gray micaceous Huronian
schists occur to the south and west. A creek connects this lake with
a larger one on which are seen in order, fine gray gneiss, pro-
tovermiculite (?) schists, striking north-east and south-west, pray
quartzose schists striking east and west and dipping 20° N., soft
friable sericitic schists striking north-east and south-west and
dipping vertically, soft brown highly ferruginous examples splashed
with quartz; fresh specimens seem to indicate an extremely altered
porphyrite infiltered with secondary silica.

Near this last exposure a small stream enters another lake on
which are found green sericitic schists and sugary quartz, massive
green and schistose diorites with pyrite, soft white schists, and hard
white spotted varieties, probably altered porphyrites. Fresh speci-
mens are much greener than the surface samples, and under the
33

microscope show fine-grained feldspar decomposition products and
indistinct light green chlorite with a little quartz. The second por-
tage beyond this lake joins a stream flowing into the Pishkano-
gama; on it occur hard gray quartzose schists.

The Huronian area crosses the Pishkanogama River in three
narrow belts. The most northerly has a width of about three miles
and shows but few exposures of white, gray and green schists aver-
aging north-west in strike and dipping to the south-west. Near the
foot of Pishkanogama Lake the second belt crosses and shows green
foliated schists apparently more quartzose than dioritic. The third
belt is found as a narrow band about three miles up the lake, and
consists of foliated green talcose schists, striking east and west, with
a dip of 30° to the north.

From this description it will be observed that the basic erup-
tives are found towards both the north and south borders of the
area, and that they are not at all common towards the;centre. This
is also true of the altered basic eruptives, diorite schist, greenschists,
etc. The quartzose schists, crushed granites and more acid rocks
generally are far more characteristic of this belt than of the first,
where altered basic eruptives probably constitute a large percentage
of the area. ‘

The third great Huronian area occurs on the south-west arm
of Misanabie Lake, where it is exposed for about eight miles; it
narrows to a point towards the north and crosses Long Lake as a
spur. On approaching this region from the east we first encounter
bands of diorite cutting the gneiss nearly north and south and
dipping 20° E. Four miles west of Ferry Point we enter a region of
mixed schists striking about north and south. Red, green and gray
quartzose schists and crushed granites are interlaminated with
diorite, diorite schists and much greenschist or altered diorite.
These rocks form high bare hills the summits of which seem to be
occupied by massive diorite while the various schists form the
flank.

The fourth Huronian area crosses the Abitibi River, extending
from the Lobstick Portage to below the canyon, a distance of about
seven miles. The average strike is a little north of west and the
effect on the river is remarkable; a series of heavy rapids are form-
ed followed by a distinct canyon two miles in length. This
formation is decidedly eruptive in origin, little trace of schists of
any kind being observed.
33

The first indication of the presence of this belt is seen on an
island above the Lobstick Portage, where the gneiss passes into
mica schist striking north-west and south-east with a dip of 20°
to the north. On the east side the rock is diorite and at the south
side it is augite syenite with some plagioclase, and with numerous
garnets in the more weathered parts; it varies in structure from
massive to quite schistose and towards the south-west corner
is hornblendic and highly pyritous.

At the Lobstick Portage is seen first a highly hornblendic
schist followed by streaks of dark gray schist with pyrite, which
is succeeded by augite syenite and quartz porphyry, becoming more
granitic in appearance down stream.

Augite syenite occurs about two miles down and is traversed
by narrow bands of fine black diabase, running in all directions and
showing beautiful examples of dislocation and miniature faulting.
This rock seems to pass into diorite or rather alternates with
diorites; a rock occurring above the Birch Portage presents a much
altered appearance and may be a syenite or diorite with sphene
and mellilite. Above the Oil Can Portage a highly feldspathic
augite syenite of coarse structure is seen; at the foot of the portage
the rock is somewhat the same but contains rather more plagioclase,
and is grayish black and speckled in appearance and shows evidence
of flow structure running N. 30° W. Some small veins of fine erystal-
line calcite occur throughout this belt. At the head of the canyon
the rock is practically the same as at the Oil Can Portage. Three
quarters of a mile down a small amount of anorthosite occurs, and
a little beyond a much decayed granite. One mile down the cliffs
are nearly 200 feet high and are formed of dark gabbro mixed with
irregular masses of granite and traversed by numerous calcite
bands. A crushed granite or perhaps quartz porphyry succeeds to
the north and continues, with a north and south strike, to the end
of the rough water.

How far the belt may extend east and west is not known. Dr.
Bell does not mention it on the Matagami, but describes numerous
eruptive dykes, which may represent it. On the Misanabie, nearly
in the required line of the strike, a Huronian belt crops out which
is possibly continuous with this, but lacking proof of the continuity
we must regard it as a separate area. On ascending the river it is
encountered about a mile below the point where the river makes

8
34

the great bend to the eastward and is represented by a heavy rock
of trappean aspect; this is followed by various schists of dark
colour, interlaminated bands of diorite and belts of granite and
felsite. Unfortunately want of time prevented the obtaining of
specimens, a microscopic examination of which would have estab-
lished or disproved the identity of these rocks with those at the
canyon of the Abitibi. The formation continues to the foot of the
Long Portage, a distance of about five miles. (See Dr. Bell’s
Report, page 333).

Near St. Peter’s Portage some narrow bands of Huronian
rocks intersect the gneiss; these consist of both dioritic and quart-
zose schist, but it is doubtful if they are of sufficient extent to be
classed as a Huronian area.

The only other Huronian belt is that lying to the westward
of Trout Lake as determined by Dr. Bell. The writer had no
opportunity of seeing this area and depends entirely on Dr. Bell’s
observations that. the rocks here consist of “rather dark coloured
hornblendic schists, with an east and west strike.”
35

SUMMARY.

As a petrographical series most of the rocks of these various
regions may be described as altered eruptives, both acid and basic,
which have, for the most part, been subjected to intense metamor-
phism. Mixed with them are other schists of clastic origin consist-
ing very largely of quartz. The whole complex shows evidence of
much dynamic metamorphism and represents a more or less con-
stant schistose structure, with the laminae dipping at high angles.
While a great similarity exists between the different areas there
are, in a general way, some peculiarities belonging to each. The
first or great area is, on the whole, more basic than the second, the
most important rock being diorite with its derivatives diorite schist
and greenschist. These basic rocks seem to form the centre of the
area and the more acid representatives, quartzose schists, altered
porphyries, etc., appear to be distributed more towards the borders.

The second area is decidedly more acid with a preponderance
of crushed granites, felsites, altered quartz porphyries and acid
schists. ,

The third division shows considerable diorite of a somewhat
massive nature, frequently forming hills, which are flanked by the
same series of schists as in the other regions.

The Huronian area of the Abitibi canyon is quite different
from any of these and must be regarded as a large eruptive dyke
composed principally of augite syenite passing into gabbro.

The schistose areas seem to be comparable to Lawson’s Kee-
watin series, at least in part. ‘They may also be compared to the
greenstone schist area of Marquette. Their origin is probably
similar to that of the regions mentioned and will not be discussed
here; the reader is referred to Bulletins 62 (1890) and 86 (1892)
of the U. 8. Geological Survey, and to the Report of the Geological
Survey of Canada, Part F, 1888.

The sketch map accompanying this paper is compiled largely
from Dr. Bell’s map of the region, corrected in places by the more
recent determinations on the base and meridian lines of Alexander
Niven, O.L.S., as well as by the compass surveys conducted by the
writer of this paper along most of the canoe routes. It cannot claim
any great accuracy but will serve to indicate, in a general way, the
distribution of the rocks in question. Owing to the small scale it
was thought advisable to introduce but few names other than those

mentioned in the text.
   

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