128 C. H. GORDON — SYENITE-GNEISS (LEOPARD ROCk) FROM CANADA. 



d. The crushed condition of the apatite. The smaller deposits are generally more 

 or less reduced to a granular condition. Often the peripheral portion is granular, 

 while the interior consists of coarse grains and fragments of crystals, with fine 

 granular apatite filling the interstices. 



Hypothesis TV assumes that the heterogeneous character of the magma 

 was due to the fusion of inclosed fragments of the pyroxenite and, owing 

 to the differential movement of the mass, the absorbed material became 

 distributed in the magma and cr3"stallized in tlie form ol)served. 



The presence of inclosures of pyroxenite in the syenite-gneiss has been 

 referred to. In specimen 140 a somewhat rounded, subangular mass of 

 pyroxenite appears in contact with the ellipsoidal gneiss. In some places 

 the line of contact is well defined, but in others it is not. Under the 

 microscope, however, the boundary is quite sharp and marked on the 

 pyroxenite side by an abundance of scapolite (wernerite), while no trace 

 of this mineral appears in the ellipsoidal areas. Ho\yever, the pyroxene 

 bands of the latter, which are cut off by the line of contact, are much 

 more prominent adjoining the pyroxenite, gradually diminishing in thick- 

 ness away from the boundary. Another instance is seen in specimen 153, 

 not elsewhere described. In this there appears an irregular fragment of 

 pyroxenite inclosed in the ellipsoidal rock. The structure of the latter 

 is somewhat obscure. The pyroxene appears more abundant in the vi- 

 cinity of the inclosure. Indications of orographic agencies subsequent 

 to the development of the ellipsoidal structure apj)ear in the schistosity 

 of the rock and tiie presence of narrow bands of feldspathic material and 

 rather large plates of biotite, ^vhich extend continuously across both the 

 ellipsoidal rock and the pyroxenite. According to this hypothesis the 

 apatite may be considered to have been derived from the pyroxenite and 

 become more or less crushed and drawn out before the rock became 

 wholly solidified. This hypothesis a|)pears to be sustained ])y a number 

 of considerations. The greater abundance of pyroxene in the vicuiity of 

 the inclosed masses of pyroxenite seems to indicate a partial absorption 

 of the latter. The occurrence of interstitial pyroxene in greater abun- 

 dance in certain areas in the ellipsoidal gneiss may indicate the position 

 of smaller inclosures which have been entirely absorbed. Moreover, the 

 character and condition of the apatite inclosures seem to favor this vie^v. 

 On the other hand, however, difficulties are encountered when we attemj)t 

 to explain by this process — 



The shell-like distribution of the absorbed pyroxenic material prior to 

 solidification, and 



The apparent cataclastic character of the gneissic structure. 



That a more or less completely banded structure may be produced in 



