82 The Philippine Journal of Science 1913 



which can be provisionally classed as pre-Tertiary. These are 

 tabulated by Smith x as follows : 



Radiolarian chert Ilocos Norte. 



Quartz porphyry Lepanto. 



Diorites Benguet. 



Gabbros Leyte. 



Pyroxenite Ilocos Norte. 



Peridotite Near Olongapo. 



No definite evidence is advanced to confirm this classification, 

 and while it seems probable that the majority of these rocks are 

 pre-Tertiary, it is also probable that some of the intrusions 

 of quartz diorite were of later geologic age or had suffered indi- 

 vidual uplifts which thrust the diorite alone through the sedi- 

 mentaries or igneous rocks which had previously overlain it. 



One of the above two conditions may have existed in Cebu as 

 shown by the geologic section by Smith 2 where the igneous in- 

 trusion seems to have folded the sedimentaries, and also in 

 Batangas as shown by the geologic section by Smith. 3 The quartz 

 diorite in the Aroroy district, Masbate, has been discussed by 

 Ferguson. 1 It is found intrusive in the Kaal series of sedi- 

 mentaries, which, on account of lack of definite evidence to the 

 contrary, should be classed as Tertiary, since no pre-Tertiary 

 sediments have ever been found in the Philippines. 



Masses of rock similar in appearance to the diorite, but in 

 places slightly porphyritic, are found intruded into the andesite 

 in Gold Creek near the Muyot, Major, and Ascension mines, 

 and in Bued River Valley, Benguet. This rock megascopically 

 is quite distinct from the andesite, but is with difficulty differ- 

 entiated from the diorite intrusions to the east. It is much 

 lighter in color than the andesite, and the contacts between 

 it and the andesite are very well marked. Therefore, it would 

 appear that these intrusions were derived from the diorite 

 magma, but had cooled more quickly on account of their being 

 intruded as small masses. 



In Paracale and in Suyoc we find granite gneiss and granite 

 having a relationship to the veins similar to the diorite in 

 Benguet and Aroroy. The granite and the granite gneiss have 

 been provisionally located in the Tertiary. Therefore, one would 

 be inclined to draw an analogy between the two classes of intru- 

 sives and to place them in the same geologic age. 



1 This Journal, Sec. A (1910), 5, 319. 



2 hoc. cit. 



3 This Journal (1906), 1, 635. 



4 Ibid., Sec. A (1911), 6, 405. 



