588 GREAT SERPENTINK-BKLT OF NEW SOUTH WALES, V., 



The zone in which alterations of the limestone are reeoj^nisable 

 is less extensive. The limestone in Seven-Mile Creek is greatly 

 altered within a furlong of the granite, but, beyond that, it is 

 unchanged or merely recrystallised, with the partial obliteration 

 of the fossils. In the more altered parts, the limestone is changed 

 to silicates such as garnet, wollastonite, diopside, and vesuvianite; 

 but sometimes traces of the fossils are preserved among them, as 

 noted by previous authors. 



In the Parish of Nemingha, the limestones are much less altered. 

 All the fossils have been obliterated near the granite, but compara- 

 tively little silicate-mineral has been formed. Where, however, the 

 limestone was originally mixed with tuffaceous material, there are 

 druses filled with calcite, epidote, and vesuvianite; and in the adja- 

 cent, often quartzose, tuffs there are regenerated felspars, w^th 

 diopside and garnet. These druses, doubtless, represent original 

 inclusions of limestone in pyroclastic rock. 



The clayslates and cherts show least sign of alteration. The 

 metamorphic zone extends barely 100 yards from the boundary of 

 the intrusion. The most altered rocks are those which form the 

 small patch of sedimentary rock that is completely surrounded by 

 granite; this occurs in Portion 76, Tamworth. These consist of a 

 highly crystalline, biotite-schist, containing veins and knots of 

 granite and pegmatite. Less altered schists occur at the foot of 

 the hill in Portions 42 and 64, Nemingha, and in Portions 178 and 

 183, Tamworth. Generally, however, the contact of the sedimen- 

 tary rock and the granite is hidden by drift. The greater part of 

 the boundary, as plotted on the map, was obtained by linking up 

 isolated exposures of the contact-line, seen here and there in creek- 

 beds. 



The form of the granite-mass calls for comment. The previous 

 authors showed that the margin of the granite in Seven-Mile Creek 

 is concordant with the strike of the sedimentary rocks, and stated 

 that the latter dip beneath the granite, which, they accordingly sug- 

 gest, is of the nature of a laccoliteO). While unable to confirm 

 this observation, the writer finds that the constant dip of the sedi- 

 ments towards the granite is a marked feature of its western mar- 



