722 W. N. Benson — Origin of Serpentine. 



Serpentine Belt of New South "Wales, the objection is a 

 rather cogent one, for the acidic veins are very rare, and 

 the degree of serpentinization is entirely independent of 

 the proximity of the great batholiths of granite, which 

 invade the serpentine at one place, at others are twenty 

 miles distant (see maps Benson 1913, 1916). It would 

 be of interest to test this point in the great mass of only 

 partly hydrated ultrabasic rocks in New Caledonia, 

 where there does not seem to be any large amount of 

 rock less basic than the peridotites. Lacroix (1911) has 

 noted the occurrence of veins of pyroxenite and anortho- 

 site, and Card (1900) of gabbro and diorite, but appar- 

 ently these occur only in small quantity. There also 

 occur small areas of granite in the serpentine, but it is 

 not clear that they invade it (Glasser 1903, 1904). 



A feature emphasized by Graham (1917) is of interest 

 as affording another indication that serpentinization may 

 follow the invasion of a series of gabbros into peridotites. 

 Where these rocks contain monoclinic pyroxene, lime and 

 more or less alumina must be set free during serpentin- 

 ization; to this process is attributed the formation of 

 grossularite (or topazolite), vesuvianite, epidote, zoisite, 

 and diopside in veins in and near the serpentines. Other 

 lime-silicate veins, somewhat analogous to these, were 

 found in association with serpentine in the Tyrol by 

 Weinschenk (1894), in Eoumania by Murgoci (1900), in 

 Italy by Novarese (vide Eosenbusch 1917, "garnet- 

 ites") ; Kalkowsky (1906) also notes them as occurring 

 in Liguria, Judd (1895) and the writer (Benson 1913) in 

 New South Wales, Ward (1911) and Waterhouse (1916) 

 in Tasmania. Such rocks have been variously inter- 

 preted; Weinschenk (1894) referred them to the inter- 

 action of magmatic waters derived from the peridotite 

 (not from a latter differentiate) upon the chloritic calc- 

 schist into which it had been thrust, though the adjacent 

 central-granites, which Weinschenk considers to have 

 also crystallized from a very aqueous magma under 

 pressure, are considered by some writers to be of more 

 recent origin than the peridotites, and to invade them, in 

 at least one spot (Becke and Lowl 1903). Eosenbusch, 

 after an examination of Weinschenk's material^ con- 

 siders that at least part of it is a highly altered schistose 

 gabbro, or allalinite (Eosenbusch 1907), and that the 

 change in this case was effected without noteworthy chem- 

 ical variation. Murgoci (1900) found included in the 



