MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 71 
changes taking place in direct continuation of the consolidation of 
the magma by reason of the action of magmatic end-stage emanation 
products on already crystallized mineral grains. As used by Seder- 
holm, the term was confined to microscopic intergrowths along the 
margins of two grains at their contacts. 
“ Deuteric’’ is here extended to cover mineralization and other 
end processes of magmatic origin, involving the actual magmatic 
replacement or change of rock matter by the ultimate end-stage 
concentration products of magmatic differentiation. 
Graton and McLaughlin??? evolved the terms “ orthotectic,’ for 
ore deposits of strictly magmatic origin concentrated by crystalliza- 
tion in the ordinary course of cooling of an igneous magma; and 
“ pneumotectic”’ for products of magmatic consolidation which were 
modified by and controlled by gaseous constituents or “ mineralizers ”’ 
which accumulated by elimination, from the preceding orthotectic 
stage. 
The term “ orthotectic”’ is not properly applied to the magnetite ; 
nor does the term “ pueumotectic”’ exactly fit the case, since the 
word involves rather vague ideas with respect to control by “ gases ”’ 
and “ mineralizers,’”’ especially gases. 
Hence the term “deuteric,’ implying changes produced by or 
mineralization caused by the action of the ultimate magmatic end- 
stage consolidation products, essentially in aqueo-igneous solution, is 
used as descriptive of the processes involved in the deposition of the 
magnetite. Figures 2 and 3, plate 6, are in a small measure illustra- 
tive of some of the “deuteric”’ effects. 
Evidence for magmatic origin. The evidence for the mag- 
matic origin of the magnetite may be stated briefly as follows: 
1 The magnetite is always intimately associated with typical peg- 
matites of unquestionable igneous source. It occurs intergrown with 
the pegmatites (simultaneous crystallization), both cuts them and is 
cut by them, and is distributed interstitially as an end product in them 
(contemporaneous, with overlapping stages). One or both of the 
pegmatites invariably form part of the walls of the ore bodies and 
they are so involved with and so intimately related to the ore as to be 
undoubtedly from the same source. 
2 The magnetite contains within it minerals of co-related origin, 
such as apatite, pyrite, pyrrhotite and end-stage quartz. These are 
of igneous character and habit. 
B) 
122 Graton, L. C., & McLaughlin, D. H. Further Remarks on the Ores 
of Engels, California. Econ. Geol. 13: 81-99. 1918. 
