Abstract:
The Singhbhum craton of the eastern Indian shield
consists of two major crustal provinces viz., Chotanagpur
Gneissic Complex (CGC) and Singhbhum Granite
Complex; separated by a Singhbhum Mobile Belt. There
are a number of geological evidences suggesting that CGC
is a cratonic block rather a mobile belt. A number of mafic
dykes, both Mesoproterozoic and Cretaceous, are emplaced
within the CGC. Field relationships reveals that E-W to
WNW trending the Mesoproteozoic mafic dykes are
intruded within the Precambrian basement complex,
whereas NE to ENE and NNW to WNW the Cretaceous
mafic dykes are mostly intruded within the Damodar
valley, however some of them are also intruded the CGC
too. Two Mesoproterozoic and two Cretaceous mafic dyke
swarms are identified. Petrographic characters of the
studied Mesoproterozoic mafic dykes classify them as
metabasites and metadolerite, whereas Cretaceous mafic
dykes are classified into high-Ti dolerite (HTD) and low-Ti
dolerite
(LTD). Available ages on Cretaceous mafic dykes suggest
their emplacement ~110-115 Ma and indicate their relation
with the Kerguelen mantle plume activities. Geochemistry
of the Mesoproterozoic dykes suggests their derivation
from primary mantle melts. On the other hand, geochemical
characteristics of the Cretaceous mafic dykes suggest that
they are emplaced in an intra-cratonic rift-setting and fed
from two different melts generated through plume
tectonics.
