696 GREAT SERPKNTINE BELT OF NEW SOUTH WALES, vi., APP., 



not return to the west of the Serpentine Line until near Bingara. 



The granites are of the type of the Moonbi, hornblendie 

 granite, with numerous basic inclusions (1, b, p. 696). They invade 

 the limestone on Horsearm Creek, truncate the Serpentine Line, 

 and pass obliquely through the Eastern Series to Mt. Abundance, 

 where the margin of the granite turns to the east. Especially 

 interesting and varied examples of contact-metamorphism occur 

 along the margin of the granite. At the head of Horsearm 

 Ci-eek, the claystones have been entirely recrystallised, with the 

 formation of sillimanite(l, b, p. 704). Nearby, the limestones 

 are intensely altered, especially in Portion 226, Attunga. Here 

 they have been largely replaced by brown garnet, and impreg- 

 nated with orthoclase and albite; while copper-ores have l)een 

 introduced. Many, beautiful, partially oxidised specimens may 

 be obtained from the dump of a small prospecting pit near here. 

 (See, for example, the specimens now in the Mining Museum, 

 Sydney). At the head of Willowtree Creek, the copper 

 minerals are sufficiently abundant, in the contact-altered rock, 

 to warrant exploitation. A brief account of the Attunga Copper 

 Mine here has been given by Mr. Carne(3). The petrological 

 features of these contact-altered rocks have been described by the 

 writer (1, b, pp. 7 13-7 14). 



Very interesting, too, are the contact-effects of the granite 

 upon the rocks of the Igneous Zone overlying the limestone, in 

 which are a number of types of altered tuff and breccia, which 

 ha\e been already briefly described, and may be compared with 

 similar rocks from the head of Seven Mile Creek, in the Tam- 

 worth district, eight miles to the south (1, 6, pp. 7 10-7 11; and 1, e, 

 pp. 607-608). In addition, a massive dolerite has been observed 

 in which the augite has been replaced by strongly pleochroic 

 hornblende, and secondary biotite has been developed (1, b, p.668). 



West of the granite is a series of dykes of lamprophyre, 

 usually pink in colour, with finely divided, ferromagnesian 

 minerals. These are chiefly vosgesites, and occur, e.g., at Bunge- 

 muUagalarno, and on Wiseman's Arm Creek, and at Mundowey 

 to the north. A typical minette was obtained on Willowtree 



I 



