1919. ] The Sixth Indian Science Congress. elxxix 
of division (3) should also be poor in related ore-deposits. This 
leaves for consideration the Dharwar sediments and the post- 
Dharwar intrusives, and in practice we find that nearly all the 
varieties of epigenetic deposits formed of minerals introduced 
uring and since the folding and metamorphism of the Dhar- 
wars; in particular, ores of copper, gold, lead, and zine, with 
rarer ores of iron, tungsten, and uranium. As will be shown 
below, the presence of these ores is in all probability due in 
many cases to granitic intru 
Of the post-Dharwar intrusives the eo — 
do n 
monly carry valuable ore-deposits, having, as a rule, in course 
rw 
ae mica deposits cars so metimes, in Se i pockets o' 
ores of the rarer metals, such as uranium (pitchblende and 
Seharekies and tantalum (columbite and tantalite), as in Chota 
Nagpur and Nellore. The epidiorites are commonly devoid of 
valuable Accueil: but may occasionally carry Pe ap of 
titaniferous magnetite, as in Singhbhum; otherw ere is 
little evidence that the doleritic intrusions of various ages in 
deposits have been found in connection with the few known 
occurrences of elaeo lite- svenites, although i in Coimbatore asso- 
ciated felspar-rock carries ‘corundum in large quantities. 
may, therefore, suitably confine our attention to 
Classification of Indian three gro ups of ore- deposits in the 
Archaean ore-deposits. Archaean, viz. :— 
(1) the Aike aniee sedimentary deposits of the Dharwars, 
mplifi by i iron and manganese deposits 
(2) he clack igneous post-Dharwar deposits exempli- 
fied by chromite deposits in peridotite ; an 
(3) the — ore-deposits (mainly in the Dharwars) 
due to granitic intrusions, exemplified by lodes 
of copper, lead, zinc, gold, ete 
A. Syngenetic sedimentary ore-deposits of the Dharwars. 
Tron-ores. 
The banded rocks composed of magnetite, hematite, and 
quartz, or a fine-grained jasperoid or cherty form of silica, are 
