ORIGIN OF AMPHIBOLITES OF LAURENTIAN AREA IT 
undulatory extinction and the structure of the rock is suggestive of 
the ‘‘mortel’’ or granulated structure seen in the granite gneisses. 
In this remarkable occurrence, therefore, the crystalline limestone 
can be seen under the influence of the granite intrusion to have changed 
into a typical hornblende feldspar amphibolite, having passed through 
the intervening stage of a pyroxene scapolite hornblende feldspar 
amphibolite (pyroxene scapolite gneiss). 
Three specimens of these amphibolitic rocks from Maxwell’s. 
Crossing, chosen to represent three steps in the progressive change 
from limestone to amphibolite, were selected for analysis. The 
analyses were made by M. F. Connor, B.Sc., of the Geological Survey 
of Canada. The figures given are in every case the mean of two 
determinations which agree closely with one another. The results 
of these analyses are as follows: 
No. 1 
No. 2 No. 3 
(a) (0) 
SLO Bera etsiNees 32.88 50.20 50.00 50.83 
ANOS hernia 0.49 0.75 0.82 L120 
IN AO Rs siaio ago Q.04 13.80 18.84 18.64 
HesOne ea ine 0.77 1.18 Dotty) 2.84 
INXS OSG Ba peo 3.48 Soe iS aia 5-97 
ITT © Sei eterarcteilhias ye bueeeeet Maul nme ally wise Woe i 0.08 0.10 
CaO aes 30.90 Li. 7E 10.65 7.50 
INUGO cence aet 4.18 6.38 4.63 4.90 
Te Oe Mieco t: 0.85 1.30 1.18 TS3 
Nias Oe cian G7, T70 4.46 4.22 
COs eGo hone TIGA 2 OM yin liiwliyieend tral eea 0.10 Ont 
rc dlane as RUT LS Ey nie Cai wren stevdy: 0.10 0.03 
Seo 6 en oe (DAU IEIER | car ENA ass Rae ee 0.03 0.01 
lel Q) aes nance: 1.08 1.66 I.00 I.40 
100.04 100.08 99-97 99.48 
No. 1 represents the first stage of alteration and was made from a 
specimen which shows an alternation of narrow lighter and darker 
colored bands. ‘The specimen was broken across the strike of the rock 
and thus included several of each of these bands, giving in this way 
an approximate average of the composition of the rock as a whole. 
Under the microscope the lighter colored bands are seen to consist 
of calcite, pyroxene, and a little hornblende. In the darker bands. 
the calcite is largely replaced by the silicates, the constituent minerals. 
