171 TJbc Goolcxjy of the Gold Fields of BritUh Gidana. 



The Malali llapids ai-e over coarse-textured dialjase at the lowest 

 rapid, where it contains in places some cau<;ht-up pieces of granite; the 

 rock becomes much coarser at the second and tliird rapids, where it 

 contains much diallage, which gives it an appearance that probably 

 misled Sawkins {Qnartprly Journal of the Geological Society, vol. 

 xxxvii., p. 427, "Geological Reports," p. 53) into the statement that 

 the rapids were over "granitoid schist." The top rapid is over 

 moderately coarse diabase. Diabase extends for some distance up the 

 river beyond the rapids. 



Near the mouth of the Kwitaro Creek exposures of coarse granitite 

 occur for about a mile and a half along the course of the river. At 

 SericamVjra, near the Kwitaro Creek, the granitite is traversed by an 

 el van of augite -syenite, while at Kurua there is an exjaosure of 

 pegmatite or gi-aphic granite. 



For two miles above the granitite to near Saka many exposures of 

 diabase occur, the northerly ones trending north-east and south-west, 

 the southerly ones striking north and south. A coarse diabase in the 

 Marimai'i Ci'eek trends up the river north and south. About a mile 

 south of Arampa Hill, at Omakwia, a dyke, about sixty yards across, 

 of coarsely granular diabase passes through white sandy clay, probablv 

 the residua from granitic rocks. Near Surabaro Creek a partially 

 decomposed granite is visible, and from here to Yawarusaru similar 

 rocks are exposed at intervals, the banks of the river generally being 

 granitic decomposition-products. 



From Yawarusaru the upward course of the river changes from a 

 southern to a westerly one, and passes in about ten miles to the 

 Kumaparu path, through a district frequently traversed by dykes of 

 diabase of varying textures. In this part of its course the bed of the 

 river and the sides of the hills are in many places covered with 

 concretionary ironstone-gravel. The diabase from here to the Waracabra 

 Rapids, varies in texture from fine at Sibalikabra to medium at 

 Mecropai. At Waracabra it has a coarse structure, and it consists 

 of quartz-diabase and of very coarse enstatite-diabase. About two 

 hundred yards above the foot of the rapids the rock gradually changes 

 into a fairly fine-grained one, where it is last seen at the end of the 

 Kumaparu path. 



From near the end of the Kumaparu path the river resumes 

 its southerly course, and its banks indicate that it traverses a 

 gneissose district. About a mile north of tlie great falls of Ororu 

 Malali coarse hornblende-granitite-gneiss is exposed on the east bank 

 and at intervals from there to the foot of the falls. The falls are 

 caused by a great Vjelt of diabase of very coarse texture, which cuts 

 through the gneissose rocks in an easterly and westerly direction. The 

 effects of the intrusive mass are distinctly noticeable on the gneiss 

 at about fifty yards from the contact, and are very marked 

 near it, where the gneiss assumes a granitic structure, the 

 foliation gradually becoming obliterated. At the falls near the diabase 

 the gneiss resembles a porphyritic granitite with crystals of orthoclase 

 and oligoclase, with rounded outlines surrounded by hornblende and 



