exciv Proceedings of the Asiatic Society of Bengal. [N.S., XV, 
deposits in the Dharwars of India to the activity of acid rather 
than of basic igneous rock 
IV. Summary. 
now summarise briefly the views expressed in 
this address. Discussing the conflicting opinions of Dr. Smeeth 
and Mr. Middlemiss as to the origin and relationships of the 
Dharwars, we find it probable that the rocks constituting the 
Dharwar formation are in part of sedimentary and in part of 
of autoclastic ws al and no undoubted case of the pear ws 
resting with a basal sedimentary conglomerate on an olde 
es series oy been found. The so-called “ fanelisanital 
whi e Dharwars often appear to rest, frequ- 
itty nike ‘inisive relationships towards the Dharwars, and 
consists partly of ered post-Dharwar granites but is perhaps 
in part composed of pre-Dharwar granites or gneisses re-melted, 
so that they now pteukiit intrusive contacts towards the Dhar- 
wars, and must be treated from the ae point of 
view as ick Dia arwar. In fact, asfar as we know, the Dhar- 
wars must be regarded as the oldest known rocks in India 
this basis the Archaeans of India may be classified as 
follows :— 
(1) the oldest aes known representatives ; 
(2) the Dharwar 
(3) the oldest sh obiete re-melted and now post-Dharwar ; 
(4) tena intrusives, comprising peridotites, gra- 
ga 
dioritey and elaeolite-syenites. 
This classification applies to what may be termed the 
hot 
gneisses. 
In discussing problems of ore genesis, I have confined my 
attention a the Chota Nagpur type of Archaeans, and have 
given brief accounts of the three chief groups of Indian Arch- 
aean ore-deposits, viz. :— 
(1) metamorphosed syngenetic ween olen ore- — 
represented (a) by the quartz-iron-ore roc ocks 
mangan re deposits of the Central Provinces ; 
(2) syngenetic ig a ore-deposits represented by the 
chromite deposits of Singhbhum, Mysore and Salem ; 
_ (3) epigenetic veins and impregnations in the Dharwars 
which, for three different areas, viz. Singhbhum, 
(wolfram, apatite, magnetite, copper, argentiferous 
