CLASSIFICATION OF IGNEOUS INTRUSIVE BODIES 499 



No generally accepted name has yet been proposed for such 

 irregular intrusions. "Laccolith" cannot be used, since that term 

 denotes a definite form, and also implies a special mode of intrusion 

 different from that here conceived. The writer has not been able to 

 find a simple English word for the purpose, and suggests a name 

 formed from the Greek on the analogy of "laccolith," "bysmalith," 

 and "batholith." It is "chonolith," derived from %w^o?, a mold 

 used in the casting of metal, and \i0o<i a stone. The magma of a 

 "chonolith" fills its chamber after the manner of a metal casting 

 filling the mold. Like a casting, the "chonolith " may have any shape. 



A "chonolith" may be thus defined: "an igneous body (a) injected 

 into dislocated rock of any kind, stratified or not; 1 (b) of shape and 

 relations irregular in the sense that they are not those of a true dike, 

 vein, sheet, laccolith, bysmalith, or neck; and (c) composed of magma 

 either passively squeezed into a subterranean orogenic chamber or 

 actively forcing apart the country-rocks. 



The chamber of a "chonolith" may be enlarged to a subordinate 

 degree by contact fusion on the walls, or by magmatic "stoping." 



An example of a "chonolith" is illustrated in Fig. 7. 



Many intrusive bodies that have been mapped and illustrated 

 with sections seem to belong to this same category. Among these 

 may be mentioned a few taken from works dealing with the western 

 Cordillera of the United States. 



In the Little Belt Mountains folio of the U. S. Geological Survey, 

 several "stocks" of granite, diorite, etc., are sectioned with relatively 

 narrow feeding channels from below. The Three Forks (Montana) 

 folio contains a map and section of a "laccolith" in non-laccolithic 

 relations. Section "M-M" of the Ten Mile District Special folio 

 shows a mass of granite injected after the manner of a "chonolith." 

 South of Mount Stuart, Washington, the Mount Stuart folio illustrates 

 an irregular intrusion of peridotite with " chonolithic " relations. 



Cross 2 states that the intrusive body of Mount Carbon, Colorado, 

 is injected and irregularly cross-cutting; it is not a true laccolith, 

 but appears to be best placed in such a class as that here proposed. 



1 The term "injected" is used here and elsewhere in this paper in a sense defined 

 in the third paragraph of the following section on the principles of classification. 



2 Op. cit., p. 191. 



