PETROLOGICAL ABSTRACTS AND REVIEWS 
ALBERT JOHANNSEN 
Miter, Witi1amM J. Geology of the North Creek Quadrangle, 
Warren County, New York. Bull. Univ. of the State of New 
York. N.Y. State Museum Bull. No. 170, 1914. Pp. go, 
figs. 10, pls. 14, map. I. . 
Rocks described are diabase, pegmatite, gabbro, syenite, granite, 
and various metamorphosed rocks. Chemical analyses and recomputa- 
tions into the norm are given, as well as volumetric modal analyses for 
many rocks which have not been chemically analyzed. Nine varieties . 
of reaction-rims are reported. Differentiation was found in a gabbro 
mass. The composition varies from syenite to gabbro in the same mass, 
but the different phases are irregularly distributed and seem to follow 
no law. Contact phenomena are described, and the volumetric compo- 
sition of the rock, which varies from typical gabbro to typical granite, 
is given for nine different zones. 
The geological history of the region is told and a few pages are 
devoted to economic geology. 
Mitter, Wittiam J. “Magmatic Differentiation and Assimila- 
tion in the Adirondack Region,” Bull. Geol. Soc. Amer., XXV 
(1914), 243-64. 
The writer describes the effects of the intrusion of great masses of 
syenite and granite in the Grenville rocks of the Adirondack region. 
He cites the older literature with regard to the differentiation in this 
region and shows, by his personal observations, that the inclusions of 
rocks of the Grenville series, varying from a few feet to a few rods in 
length, have been either partially or wholly fused and melted into the 
granite or syenite. While the author believes that stoping and engulf- 
ment of portions of the Grenville series was a common process in this 
region, he says that there is no positive evidence that the composition of 
the igneous intrusive was thereby appreciably changed. 
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