Transcript Iron Ore Group, Eastern Indian Craton

Iron Ore Group, Eastern Indian
Craton
Asish Basu
University of Rochester
New York 14627
Geological map of the Eastern
Indian Craton in the SinghbhumOrissa region of the Indian
continent (see inset) modified
after [13] and [17]. The current
study area is to the north of Bonai
Granite. The sandstones of this
study are from the Darjing group,
west of Singhbhum Granite.
Samples analyzed are from a
sedimentary succession shown by
the crossed box. Abbreviations:
OMG, Older Metamorphic
Group; OMTG, Older
Metamorphic Tonatile Gneisses.
The ages of the relevant rocks
are: Tamperkola Granite, ~2.8
Ga; Bonai Granite, ~3.2 Ga;
Singhbhum Granite Complex, ~
3.1 Ga; OMTG, ~3.3 Ga; OMG,
~ 3.3Ga. See text for geologiclithologic details.
Nb/Ta ratios vs. Zr/Sm
ratios of the analyzed
sandstones compared to
the Archean tonalitetrondhjemite gneisses
(TTGs) and present day
continental crust and
adakites. Also shown
are modern day
MORBs, OIBs, and
island arc basalts
(IABs)[38]. The
sandstones of this study
are identical to Archean
TTGs, indicating that
the protoliths of the
sandstones formed in
similar petrotectonic
environment.
Upper Lava
Upper Shale with Mn Ore
}
3 Km
Iron Ore Group Banded Iron Ore ~0.7 Km
Lower shale and tuff ~1.9 Km
Lower Lava ~3 Km
Tuffaceous rocks ~30m at
the top; gradational with
Lower Shale
Th/U = 1.7 to 2.5
0.5 mm
1000
100
Upper Lava
Rock/ Chondrite
Rock/ Chondrite
Upper Shale
10
100
10
1
1
La Ce Pr NdSmEu Gd Tb Dy Ho Er Tm Yb Lu
La Ce Pr NdSmEu Gd Tb Dy Ho Er Tm Yb Lu
10000
1000
Tuff (4/03)
Rock/ Chondrite
Rock/ Chondrite
Lower Shale
100
10
1
0.1
La Ce Pr NdSmEu Gd Tb Dy Ho Er Tm Yb Lu
100
Rock/ Chondrite
Lower Lava (Western Limb)
10
1000
100
10
1
La Ce Pr NdSm Eu Gd Tb Dy Ho Er Tm Yb Lu
100
100
10
1
10
1
La Ce Pr NdSmEu Gd Tb Dy Ho Er Tm Yb Lu
Lower Lava (Eastern Limb, Jilling)
Lower Lava (Eastern Limb, Noamundi)
La Ce Pr NdSmEu Gd Tb Dy Ho Er Tm Yb Lu
1
La Ce Pr NdSmEu Gd Tb Dy Ho Er Tm Yb Lu
10000
Rock/ Chondrite
Tuff (4/03)
1000
Age = 3.4Ga
eNd(T) = -4.9
eNd(0) = -38.2
100
10
1
La Ce Pr NdSm Eu Gd Tb Dy Ho Er Tm Yb Lu
10000
Rock/ NMORB
Tuff
1000
100
10
1
0.1
Ba Rb Th U Nb La Pb Ce Sr NdSm Zr Hf EuGd Tb Dy Y Er Yb
100
Rock/ NMORB
Lower Lava (western limb)
10
1
0.1
Ba Rb Th U Nb La Pb Ce Sr NdSm Zr Hf EuGd Tb Dy Y Er Yb
4
Upper Lava
eNd(3.4Ga) = +2.8 to +6.8
# Samples
3
2
1
0
0
2
4
6
8
eNd(3.4Ga)
4
4
Lower Lava (Western limb)
eNd(3.4Ga) = +0.4 to +3.8
3
# Samples
# Samples
3
Lower Lava (Eastern limb)
eNd(3.4Ga) = +0.8 to +6.0
2
1
2
1
0
0
0
2
4
eNd(3.4Ga)
6
8
0
1
2
3
4
5
eNd(3.4Ga)
6
7
8
Geological map of the Eastern
Indian Craton in the SinghbhumOrissa region of the Indian
continent (see inset) modified
after [13] and [17]. The current
study area is to the north of Bonai
Granite. The sandstones of this
study are from the Darjing group,
west of Singhbhum Granite.
Samples analyzed are from a
sedimentary succession shown by
the crossed box. Abbreviations:
OMG, Older Metamorphic
Group; OMTG, Older
Metamorphic Tonatile Gneisses.
The ages of the relevant rocks
are: Tamperkola Granite, ~2.8
Ga; Bonai Granite, ~3.2 Ga;
Singhbhum Granite Complex, ~
3.1 Ga; OMTG, ~3.3 Ga; OMG,
~ 3.3Ga. See text for geologiclithologic details.