310 
MANGANESE DEPOSITS OF INDIA : GEOLOGY. [ParT II 
pothesis that tliis mass of rock was an igneous intrusion that had been 
compelled to conform roughly to the strike of the associated rocks by 
being rolled out by tectonic movements subsequent to its intrusion. The 
forking of the mass of manganese-silicate-rock at the eastern end of this 
hill could then be explained as due to the intrusive relations of these 
rocks to the ' country '. [On the metamorphic hypothesis now adopted 
the forking would be explained as due to faulting, and the sudden swell- 
ing out of the manganese-silicate-rock in hill No. 5 as due to its having 
been originally deposited in a deep basin.] The absence of any signs 
of intrusive relations of the manganiferous rocks and ores towards the 
' country ' at every place except Ramdongri might be thought to more 
than overbalance the evidence of Ramdongri. But the pegmatitic and 
granitic rocks, about the igneous origin of which there can be no 
doubt, occurring in association with the manganiferous rocks, are also 
not as a rule clearly seen to be intrusive with regard to their ' country '. 
The general absence of felspar from the rocks of this series might 
have been considered sufficient to settle that they could not be of 
igneous origin. But this constituent is in a few cases present, although 
much more rarely than the macroscopic aspect of the rocks would 
lead one to suspect. 
As the result, however, of a careful microscopic examination of a 
large number of thin slices of the rocks collected in this area, and the 
consideration of the chemical evidence that has since become available, 
it has become clear that these rocks are, as previously explained, meta- 
morphosed sediments. A brief outline of the theory of their origin 
as thus revised is given in the two places, cited above. The evidence justi- 
fying this change will now be given. 
In the north-east parts of the Nagpur-Balaghat area, namely those 
, . parts of the Balaghat district situated to the east 
Evidence for met a- ^. . . * . , , . 
morphic origin of the 01 the Wamganga river, the manganese-ore deposits 
gondite series. have been mapped as occurring in the Chilpi Ghat 
series of rocks, whilst to the west of this river they have been mapped 
as occurring in the metamorphic and crystalline complex. As has already 
been explained the latter type of deposit is characterized by the 
presence of various manganiferous silicates ; whilst those mapped as 
occurring in the Chilpi series are sometimes free from such silicates, 
then containing only manganese-ores with associated and interbanded 
quartzites and phyllites. The key to the unravelling the relations of 
these two apparently different modes of occurrence of the manganese-ore 
deposits Hes in the study of the Balaghat and Ukua deposits. A 
