SEGREGATION GRANITES 165 



perature is low. In other words they are "secundine"' to the 

 great series of basalts and gabbros. 



The primary water-content (exceeding the average for rocks of 

 similar composition) which Anderson and Bailey emphasize as 

 characteristic is very suggestive. The analysis (i) of the glassy part 

 of the leidleite may be very nearly that of the anchieutectic solu- 

 tion that once filled the acid interstices and that wandering off by 

 itself would make red rocks and even hornblende granites. That 

 though central it is glassy may be due partly to great viscosity and 

 less power of crystallization, due to less lime, iron, and magnesia, 

 and more silica, partly to a more rapid passage through the crystalli- 

 zation range of temperature, even though later. 



If we study these analyses (see following table) , i and 2 given 

 by Anderson and Radley, and compare with 3 and 4, Bowen's 

 analyses of Canada diabase and dike granite and with the average 

 igneous rock as given by Clarke and Daly we find, (i) that they 

 are not very far from the average igneous rock, (2) that they are 

 not very far from the eutectic trough or line to which I called 

 attention in 1904,^ (3) that they are not very far from the analyses 

 of the red rocks given by Grout and Wright, etc., (4) that the 



' I have found the followmg classification of dikes with the appropriate adjectives 

 to have some value : 



1. Invasive. — Forced more or less slowly into cavities formed by the extra hydro- 

 static pressure of the invading magma; contacts irregular and often close-welded. 



2. Suctive. — Forced quickly into a crack otherwise opened, by fault or earthquake 

 relieving strain, aided by gravitative suction, owing to the condensation by cooling 

 of the gases from the magma; contacts generally fairly straight and not close- welded. 



Nearly parallel is a classification according to the hot or cold condition of the 

 country rock as follows: 



1. Secundine (Latin secundine = SiiteThirih). — Injected into a hot country rock; 

 contact generally irregular, close- welded, the grain generally equal throughout, 

 either finer or coarser at or near the margin. 



A characteristic mode of occurrence of lamprophyres, aplites and pegmatites. 



2. Subsequent. — Injected into a cold country rock, with fine-grained selvages 

 (the zones of increasing grain amoimting to from one-quarter to one-tenth of the 

 breadth of the dike) with straight and not close-welded contacts. 



A characteristic occurrence of dikes not closely connected with larger masses or 

 volcanic centers, and in composition close to Bvmsen's normal basaltic magma or 

 more basic. 



The anchieutectic rocks which we are discussing are generally invasive secundine, 

 but in case of shrinkage cracks, due to loss of heat or contact metamorphism, may be 

 suctive and secundine too. 



" Jour. Geol., (1904), p. 91. See also Wet and Dry Differentiation, "Tufts 

 College Studies," Vol. Ill, Pt. I. 



