1. seminar
on
sandur schist belt

2. contents
INTRODUCTION.
STRATIGRAPHY OF SANDUR.
SHRIMP U/Pb AGES OF ACID VOLCANIC ROCKS.
SEDIMENTATION OF SANDUR SCHIST BELT.
METAMORPHISM OF SANDUR SCIST BELT.
STRUCTURE OF SANDUR SCHIST BELT.
CONCLUSION
REFERENCES.

3. Introduction
o Sandur schist belt is the one of the green stone belt situating
in the eastern dharwar craton.
o It is a is prominent boat shaped belt , sited over northern part
of closepet granite in eastern Dharwar craton.
o It covers an area of 960 sq km only.
o It is structurally highly disturbed and squeezed by the younger
closepet granite
o The succession of sandur is younging from southwest to
northeast.
o some of the richest accumulation of manganese and iron are
concentrated in this.

4. Geological map of sandur

5. Imagery of sandur schist belt

6. stratigraphy of sandur
• Lithological association in this belt is similar to that of the
Chitradurga belt, with different types of sediments in margins
and a volcanic complex in the middle.

7. Yaswanthpura formation
 In the southwest margins of schist belt, amphibolites and
ultramafic abound, associated with rare quartzite.
 Which is correlate with Bababudhan group of WDC, but for
the main difference that these rocks are intruded by gneissic
veins, as in Jawanahalli belt.
Deogiri formation
 The Deogiri formation consist of manganiferous and
calcareous greywackes with convolute bedding, cross bedded
quartzite, stromatolitic limestone, volcanic and BIF.
 It is similar to the Vanivilas subgroup of the Chitradurga
group.

8. Ramanmala and Donimalai formation
 The Ramanmalai and Donimalai formations consist essentially
of pillowed basic volcanics and BIF with minor greywackes.
 The normally cherty BIF is associated with an unusual granular
type of BIF, is called GIF.
 The GIF contain fragment chert and iron oxide, and show
graded bedding.
 GIF is usually proterozoic type iron formation, but its
developed in archean belt, confirming dichronity in crustal
evolution.

9. Taluru or Sultanpura formation
 The Talur or Sultanpura formation formation is a volcanic
complex with pelgic sediments, polymictic conglomerate,
chert and BIF .
 The pillowed mafic volcanic rocks are tholeites and high Mg
basalts.
 Trace elements, REE, and Nd isotopic data suggest their
derivation from primitive mantle, and contaminated by
continental crust.
 The associated triomolite-actinolite schists of Taluru
formations are visualized as layerd basic intrusions , and as
komatiites , like those commonly found in the other archean
greenstone belts .

10. Cont….
The trimolite actinolite schists are geochemically komatiitic
in composition , but conformation by textural evidences
and detailed mapping is necessry to resolve this isuue.
This is important because tremolite , actinolite ,
anthrophyllite , cummingtonite , etc are usually
metamorphic amphiboles of needle like habit that form
sheaves and resembles the igneous spinifex texture.

11. Vibhutigudda formation
 Talur and Vibudigudda formations are similar to Hiryur
formation , in Talur formation volcanics are dominant.
 Vibudigudda formation consisting of greywacke, polymictic
conglomerates , cross bedded quartzite , BIFs, meta basalts,
and acid volcanics , that are closely inter-bedded with granite-
clast volcanic conglomerate.
 Spectacular felsic volcanic breccias are seen in Belikallugudda
and Sanganakallu.
 The association of felsic lavas , pyroclastics and volcanic
conglomerate is similar to Champion gneiss forming the
eastern tectonic margins of most of the eastern greenstone
belt.

12. SHRIMP U/PB zircon ages of acid volcanic rocks in
sandur
o It’s carried out by, Nutman AP, Chadwick Brian, krishna Rao b,
Vasudev BN.
o SHRIMP U/Pb dating of zircon grains from a schistose acid
volcanic rock in the Vibudigudda formation yielded ages of
2658 ± 14 and 2691 ± 18ma.
o Zircons from high strain grey gneisses which appears to be the
oldest recognizable compnent of the late archean granite
complex adjacent to the belt have an age of 2719 ± 40ma .
o Zircons from the youngest recognizable granite adjacent to
the belt have also yielded younger age of 2570 ± 62 ma.

13. Cont….
o The age shows that granite emplacement and deformation
adjacent to the Sandur schist belt took place in a period of
150ma.
o The imprecise ages of zircon in the acid volcanic rocks in the
sandur group and adjacent granites are related to neo
proterozoic loss of lead which may have been an effect either
weathering or regional thermal event.

14. SEDIMENTATION OF SANDUR
o Quartzites, stromatolitic limestones and BIF occuring in the
lower part of the sequence indicate shallow marine setting.
o The greywacke-polymict conglomerate unit represents
turbidites and debris flow.
o GIF represents transgression –regression cycles related to
submarine volcanism.
o The central volcanic complex marks major event of submarine
volcanism.
o The granite clasts in the polymict volcanic conglomerate are
similar to those of surrounding intrusive granites, suggesting
rapid unroofing of the terrain.

15. METAMORPHISM
o Metamorphism of sandur belt took place around as an effect
of the regional high thermal gradient associated with the
intrusion of late archean post tectonic granites.
Structure
o Originally the structure was described as double syncline with
an intervening anticline.
o Recent studies have shown that the eastern and western arms
of the belt represent upright synclinal sheath folds, both folds
being seperated by a steepend thrust called Sandur valley
discontinuity.
o The effect of deformation are more serve in the marginal
meta sedimentary units than in the central volcanic complex
that has experienced only low strain.

16. Conclusion
o Sandur schist belt is prominent boat shaped belt , sited over
northern part of closepet granite in eastern Dharwar craton.
o The main formations of sandur schist belt are, Yeshwantnagar
formation, Deogiri formation, Raman mala formation,
Donimalai formation, Taluru formation, and vibudhigudda
formation.
o SHRIMP U/Pb dating of zircon grains from a schistose acid
volcanic rock in the Vibudigudda formation gives an ages of
2658+_ 14 and 2691+_ 18ma.
o Different types of sediments indicating different types of
depositional environment.
o Metamorphism in sandur is mainly due to the intrusion of
younger clospet granite.

17. References..
Books
 M.Radhakrishnan & R.Vaidhyanathan (2010), GEOLOGY OF
INDIA , Volume1, Geological society of India, pp147-151.
 B.P.Radhakrishna & R.Vaidhyanathan (2011), GEOLOGY OF
KARNATAKA, 2nd edition, Geological society of India, pp123-
127.
 B.P.Radhakrishna, PRECAMBRIAN GEOLOGY OF SOUTH
INDIA, pp14-16.
Sites
 http://repository.ias.ac.in/21598/
 https://inis.iaea.org/search/search.aspx?orig_q=RN:28000029