A N:o 1) Igneous Rocks of Sviatoy Noss in Transbaikalia. 15 
The composition of the large massif is fairly uniform, its 
varieties ranging from subalkalic. granites to granodiorites. 
The porphyritic rocks are frequently intersected by dikes 
of lamprophyric and aplitic rocks, and the massif seems 
to be bordered towards the migmatite area by a zone of 
aplitic granite. As the latter is often seen to cut the porphyr- 
itic coarse-grained rocks, while the opposite case was never 
observed, the latter have been solidified earlier, though 
great difference in the age is not by any means probable. 
Porphyritic coarse-grained gran o- 
/ diorite. ; 
As representative of the chemical composition of these 
coarse-grained porphyritic rocks a specimen taken about one 
kilometer northwest of Mys Besimyanniy on the east shore 
of the Tshivirkouy Bay, was analyzed by the writer. The 
result was as follows. | 
Mol. |i Mol. 
DER MÖR 07, Nörm 
SiO, | 65.06 | 1084 | 71.27 | Quartz....... "14.102, Q=14.10 
Al,O, |: 15.84 | 155 | 10.19 | Orthoclase ...... I) | 
Fe,0, | 1.74] — 110] ALDIber ba Rd aa 35.11) - F=73.76 
| FeO 2.51 i 3.81 | Anorthite ........ 0 öd) | 
"MnO | 0.08 | Z sal 87.86 
| MgO Sal 33 | 2.50 CaSiO, 1.97 
CaO 3.28 60 3.94 | Diopside . .Y MgSiO, lg 
Na,O 4.16 67 4.41 l FeSiO, 0.79) | P == 7.51 
F-K;O 4.82] 51:| 3.35 MgSiO, 2.20 f 
HO, |. 0,63 261,00.53 Hypersthene | FeSiO, äs)?05 
P30; 0.26 21] — Magnetifet öste sve va 2.55 
Fl Ho 0.57 Ilinenite «..... . . io 2 STR 
APAELLC TNG mat site AS ehe e 0.67 A = 0,67 
; Z fem 11.95 
99.81 
100.26 | 100.00 | 
