lOO HAYDEN: GEOLOGY OF SPITl. 
4 
garnetiferous and a non-garnetiferous ; of these the former appears to be 
Garnetiferous basic "^"^^ the older, and has been found only in the 
rocks. (( Xso iMoriri gneiss," at numerous localities near 
the northern end of that lake, near Tso Kyagar, and between Shakshang 
and Puga. All the intrusions are similar to one another, apd consist 
of a garnetiferous amphibolite, composed chiefly of actinolite and 
garnet, with muscovite, some untwinned felspar and quartz. No intru- 
sions of this rock have been found in the schists which represent the 
younger palaeozoics, although both they and the Rupshu granite are 
often penetrated by dykes of the second or non-garnetiferous class ; 
there is therefore no direct evidence of their age, but it seems probable 
that, were they post-carboniferous, they would be found intrusive 
in the beds of that system"; it is of course possible that a more detailed 
examination of this very interesting area may prove that they occur 
among the sedimentary beds as well as in the gneiss. 
The non-garnetiferous rocks consist chiefly of forms related to 
Basic rocks without augite-norites, and resemble the basic intru- 
garnets. sives found in Spiti. In the present state of our 
knowledge of the petrography of Rupshu, detailed descriptions of 
isolated specimens would be of no particular utility, but it is perhaps as 
well to record the fact that they occur as dykes among the carboni- 
ferous and permian beds and in the Rupshu granite ; they therefore 
constitute the youngest intrusive rocks of Southern Rupshu, and are 
probably related to the pyroxenites and other basic igneous rocks found 
further to the north, specimens of which have recently been described 
by General McMahon.^ 
> Memoirs, G. S, I., vol. XXXI, pp. 303—329. 
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