08 
J. K. H. McWhae. 
per cent., microc-line 30 per cent., oligoclase 20 per cent., biotite 7 per cent., 
hornblende 5 per cent., titanite and magnetite 3 cent. ^ 
Tlio xenoliths in granite are grey, coarse-textured rocks containing 
the same minerals as the granite but with a much higher percentage of 
ferromagJiesians. Occ-asional microcline “ phenccrysts ’ ^ up to one inch ■ 
long occur in tiu- xt'uolitlns tig. 3). Some of the xenoliths are J 
slightly gneissic (text lig. (IB). - 
1 
The lock foi'ining lliese xenoliths apixmrs to be fairl3' constant in i 
character. It has a granitic micro-structure. The minerals luive the same ; 
optical properties as those in the granite, and are biotite with sagenitic j 
rutile webl)ing% (grain-size up to two mm.), greenish-blue hornbhmde, 
(grain-size two to four mm.), sau^.siu'itised oligoclaso with imdusions of 
magnetite ami chlorite, (grain-size four to six mm.), f^tuai'tz and niicro- 
cliiie are clear and vei-y irregular in form and occur in variable ijuantities i 
from two per cent, to 31.) pei' cent, (^)■ain-size two to live mm. except j 
for i-are microcline * * phenocrysts " crowded with inclusions of all the 
other minerals which liave an average size of 2cm. Laigi' (one mm.) j 
ouliedral titanite grains, probably the la'Milt of the alteration of original | 
ilmcnite, have inclusions of inagnetitt' (see text lig, tiA). A])atite, epidot*. ! 
and magnetite' are accessorie^s. Apatite', magnetite, titanite, hornblende, 1 
biotite, and tin' microcline* •‘phenocrysts” are all euln'drah | 
Text Fig. 0. 
Adamellite xenoliths in tlie iiorpliyritic younger granite. 
A. Granohlastic textured, showhig association of titanite and 
magnetite (22317). -Alinerals are hornblende, biotite (b), [dagio- 
clase (slightly turbid), mierooliue (M), (|nartz (Q), titanite and mag- 
netite. 
B. Gneussie structnivd xenolifii showing tlie denelopment of 
titanite idioldasts (22.i81). Section from .sixunmen taken from the 
edge of a xenolith ntNU* the contact Ix'tweeu the granite and the 
xenolith. 
