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amphibolitization involves first a loss of carbonates and a development 
of feldspar and pyroxene in their stead. In the second stage all car- 
bonates are replaced by pyroxene, feldspars, and scapolite, and finally 
the rock becomes in texture like a fine-grained igneous rock composed 
of feldspars, hornblende, and pyroxene. Without presenting analyses of 
the fresh limestones, the authors assume that this change involves loss 
of lime and carbonic acid from the limestones and transfusion of silica, 
alumina, iron, and magnesia with some alkali and titanic acid from the 
granite to the limestones. From the data presented this conclusion is 
only valid if the change took place without loss of mass. The lime- 
stones and dolomites are also altered in many places to serpentine 
marbles. Microscopic studies show, however, that the change to serpen- 
tine is preceded by the development of other silicates such as pyroxenes 
and amphiboles. 
The gabbros and diorites occur either as stock-like masses piercing 
the limestones and altering them to aniphibolite, or as dikes cutting the 
limestones, and as sheet-like masses whose relation to the limestone 
is uncertain. Some of the latter may be altered pyroclastics. The 
dikes and sheets have the character of granular amphibolites. 
Relatively small masses of acid volcanic orthophyre with distinct 
flow structures are intercalated with the limestones. 
The nepheline corundum-bearing syenites occur between the granite 
gneisses and the limestone and with one exception within the limestones, 
thus seeming to corroborate Daly’s hypothesis of the genetic relation- 
ship of syenites to limestones. All contain limestone inclusions. 
Certain phases consist largely of nepheline with few femic constituents, 
others almost entirely of femic minerals, while in some plagioclase feld- 
spar is the dominant mineral. 
The greatest petrographic unit of the area, the granite gneisses, 
presents three principal phases. About 82,per cent of its area, the red 
gneisses, is composed mainly of oligoclase, with some potash feldspars, 
quartz and femic accessories; the remainder of the area consists of gray 
gneisses, high in femic constituents, and amphibolite inclusions, derived 
mainly from the metamorphosed invaded limestones. ‘The amphibolite 
inclusions vary in extent from acres to minute lenses, and present all 
stages of dissolution. Some are still angular and massive, others are 
pierced by pegmatitic phases of the granitic magma, while pieces which 
have flowed many feet from each other are separated by fine-grained 
gneiss. Clear cases of the solution of the amphibolites in the granites, 
while uncommon, suggest that some of the gray gneisses may have 
developed in this way. In general, however, the amphibolite inclusions 
