132 Transactions. 



faces, and are set in k {a panidiomorphic groundmass of labra- 

 dorite, serpentinised augite, hornblende, and iron-ore, much of 

 -which is titaniferous. 



55. A coarse-grained basic rock from the Te Kinga quarry, 

 "where it occurs projecting some 15 ft. up from the floor of the 

 ■quarry into the solid granite, which covers it to a depth of 50 ft. 

 The exposed portion, some 12 ft. high by 15 ft. wide at the base, 

 evidently increases in size in depth. The granites show no signs 

 of having been displaced by the intrusion, but the intrusive 

 is surrounded by an aureole of completely altered rock between 

 2 ft. and 3 ft. in thickness, the result of the metamorphism 

 induced by the contact. So completely altered is this envelope 

 that it is impossible to say whether it belongs to the intruded 

 or the intrusive. Near the granite it consists of a granular 

 aggregate of quartz and biotite, which becomes more quartzose 

 close to the granite contact. Part of the mica is in long rect- 

 angular flakes, with longitudinal striation, which does not always 

 extend from end to end of the crystal ; the balance is in shape- 

 less plates. Nearer the intrusive the rock consists of a colourless 

 mica, with chlorite, some very subordinate biotite and quartz, 

 and a little iron-ore, apparently magnetite. The micas and 

 quartz are allotriomorphic : the chlorite appears in radiating 

 sheaves, with a rude suggestion of flow structure, and the rock 

 would certainly be classed as a schist if it occurred under any 

 other conditions. The intrusive rock is soft and close to the 

 contact-zone, partially decomposed, but much fresher samples 

 can be secured from the centre of the mass. It consists almost 

 exclusively of augite, hornblende, and calcite, with very sub- 

 ordinate olivine feldspar and iron-ores. Some of the calcite 

 may represent feldspar, but much of it is of foreign origin, and 

 occurs in cracks. The magnetite is present as dust, and as 

 grains with crystal boundaries. The augite and hornblende 

 have a strong tendency to crvstallographic development, and are 

 idiomorphic to any feldspar that occurs. What little Eeldspar 

 there is is principally anorthoclase, and a lew crystals of basic 

 plagioclase, with high extinction-angles. Patches of serpentinous 

 mineral are present, usually in contact with the calcite. It is 

 birefringent, with lattice structure, but more probably resulted 

 from the alteration of the olivine than hornblende. 



In addition to the basic and basic-alkaline rocks already 

 described, there is an acid-alkaline series, which possibly resulted 

 from a variation of the acid granitic magma from which the 

 granites of the Tuhua series were genetically derived. With 

 our present knowledge of magmatic differentiation it is within 

 the bounds of possibility, although hardly probable, that the 

 wholejof the described rocks, including the ejanites. are the 



