﻿226 



EVELAND. 



idiomorphic crystals showing zonal growth and considerable po'lysynthetic 

 twinning. The amphibole is normal hornblende and the magnetite seems 

 to occur principally as inclusions in the former, or adjacent to it. In 

 the Bued River canon, where the same rock occurs, a marked peculiarity 

 is developed, which appears to be the presence of inclusions of diorite 

 caught up in the quartzose magma. This "Kugelstruktur" (Rosenbusch) 

 when examined under the microscope, is seen to be due to difference in 

 texture, in fineness of grain, rather than in any difference of mineral- 

 ogical composition, and as before, the sections show plagioclase, horn- 

 blende, magnetite and quartz, with a slight development of accessory 

 sphene and secondary iron oxide. No explanation of this, other than 

 variation in the magma, can be offered. The area covered by this phase 

 of the quartz diorite is considerable, to judge from the length of the ex- 

 posure in the Bued River canon, and over all the area examined, these 

 "inclusions" prevail. Although mapped as a separate mass, the weight 

 of evidence tends to the view that the diorite assumes a more quartzose 

 variation only locally, and that the Batwaan Creek area is a part of the 

 diorite core. 



Many small dikes of basalt cut through this rock, but they are un- 

 important, excepting that the directions of the dikes seem to be quite 

 uniformly along east and west lines. In common with the system of 

 ore deposits in the diorite, the majority of the veins striking east and 

 west, or approximately in that direction, this prevailing direction would 

 point to a line, or rather a direction, of weakness in the main mass of 

 the rock. Three analyses ° of these rocks are as follows : 



Analyses of the basalt. 



Constituent. 



Moisture at 110° (M— 110°) 

 Loss on ignition (M+110°) 

 Silica (Si0 2 ) 



Alumina (A1 2 3 ) 



Ferric oxide (FeoO :! ) 



Ferrous oxide (FeO) 



Calcium oxide (CaO) 



Magnesium oxide (MgO) _ 

 Potassium oxide (K 2 0) __. 

 Sodium oxide (Na 2 0) 



Total 



Per cent. 

 0.14 

 1.61 

 57.49 

 18.40 

 5.46 

 1.71 

 7.61 

 3.05 

 1.99 

 3.38 



II. 



Per cent. 

 0.08 

 1.08 

 58.35 

 16.70 

 4.08 

 3.28 

 7.71 

 3.29 

 2.87 

 2. 62 



100. 84 



100. 06 



III. 



Per cent. 

 0.13 

 0.77 

 57.06 

 20.00 

 3.03 

 3.01 

 7.18 

 3.27 

 3.06 

 2.95 



100. 46 



Numbers I and II are from Antamok River, Number III, from 

 Batuaan Creek exjposures. 



Analyses by Paul J. Fox, Bureau of Science, Manila. 



