1872.] 



DAINTEEE — GEOLOGT OF QIJEENSLAND. 



311 



With regard to the age of these dykes much has yet to be learned. 

 From all the evidence collected I should be inclined to place their 

 succession in time as follows : — 



1st. The porphyrites and porphyries range from the Metamorphic 

 to the Devonian. 



2nd and 3rd. The diorites, diabases, and serpentines range through 

 all the Devonian period, the action being most intense in the lower 

 portion of the series ; and the interstratified diabase ashes and tufas 

 at Gympie favour this idea. 



4th. The trachytes and felsites are of uncertain date, but are cer- 

 tainly younger than Group 2. 



The true Carboniferous and Mesozoic Carbonaceous of Eastern 

 Queensland 'are constantly penetrated by trap-dykes ; but, ivitli one 

 exception, these are dolerites, differing in no respect from the older 

 and newer Tertiary volcanic series of the colony, and no vein- stones 



Fig. 18. — " Bolerite" Dyke traversing "Desert Sandstone,'''' Grariite 

 CreeTc, Gilbert District, Northern Queensland. 



of arri) hind are found in the bounding strata, neither is alteration 

 observed at the point of contact (see Figs. 18 & 19). 



