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Archean Metallogeny and Crustal Evolution in the East Indian Shield
Issue:
Volume 4, Issue 4-1, July 2015
Pages:
1-14
Received:
20 March 2015
Accepted:
26 March 2015
Published:
29 July 2015
Abstract: East Indian Shield bears the evidences of Archean metallogenic and crustal evolution like the other major shield areas of the world. The primordial continental crust in the form of more silicic bodies were floating like metallurgical slags over the hotter and denser ultramafic-mafic lithosphere (UM-ML) before 3800 Ma. Earliest sediments, now represented by the Older Metamorphic Group (OMG) , were deposited in small basins the basement of which was made of UM-ML containing rafts of primitive silicic bodies. Possibly the earliest greenstone rocks (some banded iron formation, associated high-Mg basalts and ultramafics) formed in the OMG with deformation and metamorphism continued upto about 3500 Ma. Partial melting of the lower amphibolitic crust due to underplating and asthenospheric sagging formed the tonalitic magma around 3500 Ma (Older Metamorphic Tonalitic Gneiss or OMTG) and subsequently Singhbhum Granite Type-A (Phase-I and Phase-II) around 3300 Ma both of which intruded the folded and metamorphosed OMG rocks. The major event of greenstone belt formation took place during 3500-3200 Ma both in the eastern part and in the western part of the Singhbhum granitic craton. The general trend of these two greenstone belts is NNE-SSW and they were the repositories of the Iron Ore Group (IOG) sediments, volcanics and ultrmafic-mafic rocks. The IOG rocks formed prolific mineralization of Fe,Mn,Cr,Ti,Cu,Ni,Au and platinum group elements(PGE). Multiple phases of tectonism and partial melting of crustal materials ultimately led to the formation of Singhbhun Granite Type-B (Phase-III) around 3100 Ma which later intruded the folded and metamorphosed IOG rocks. From 3000 to 2500 Ma cratonization of the East Indian Shield formed the batholitic mass of Singhbhum granitic complex at the central part with the greenstone belts on either side. Around 2500 Ma the Singhbhum craton became tectonically active again with the formation of three mobile belts – Dalma in the north, Dhanjori-Simlipal in the east and Jagannathpur-Malangtoli in the west.The sediments and lavas of these mobile belts are the major resources of Proterozoic Fe, Ti, Au, U, P, Cu, Pb, Mo, W and Ni mineralization
Abstract: East Indian Shield bears the evidences of Archean metallogenic and crustal evolution like the other major shield areas of the world. The primordial continental crust in the form of more silicic bodies were floating like metallurgical slags over the hotter and denser ultramafic-mafic lithosphere (UM-ML) before 3800 Ma. Earliest sediments, now repres...
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Titaniferous Magnetite Deposits Associated with Archean Greenstone Belt in the East Indian Sheild
Riya Mondal,
Tapan Kr. Baidya
Issue:
Volume 4, Issue 4-1, July 2015
Pages:
15-30
Received:
4 May 2015
Accepted:
7 May 2015
Published:
29 July 2015
Abstract: In the East Indian Shield, occurrence of titaniferous magnetite deposits associated with the Archean Greenstone belt occur in Kumhardubi, Betjharan and Nuasahi areas of Odisha and Dublabera area of Jharkhand. The ore bodies comprise lenses, veins, bands and patches within gabbroic rocks. Petrogenetic studies have revealed the primary and secondary mineral constituents of the ores such as titanomagnetite, ilmenite, hematite, spinel, cobaltite, goethite, martite, rutile and silicate gangue minerals. Various crystallographic intergrowths are resulted from exsolution & oxidation at different temperatures during cooling of the sub-solidus magma. Chemical analyses show that the ore contains 10.35 -17.68 wt.% TiO2, 0.148 – 0.227 wt.% V2O3 and 32.75 – 67.39 wt.% Fe2O3. Different geochemical composition diagrams confirm their tholeiitic origin. The formation of the massive ore bodies is referred to late magmatic crystallization from tholeiitic magma followed by Fe-Ti enriched residual liquid injection within the host rocks. Syn to late formation of the magnetite ores along with gabbro-anorthositic intrusive with respect to the Archean Greenstone Belt of East Indian Shield is suggested
Abstract: In the East Indian Shield, occurrence of titaniferous magnetite deposits associated with the Archean Greenstone belt occur in Kumhardubi, Betjharan and Nuasahi areas of Odisha and Dublabera area of Jharkhand. The ore bodies comprise lenses, veins, bands and patches within gabbroic rocks. Petrogenetic studies have revealed the primary and secondary ...
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Iron and Manganese Mineralization Associated with Archean Greenstone Belt in Joda-Noamundi Sector, Odisha, East Indian Shield
R. Ghosh,
D. Chakraborty,
M. Halder,
T. K. Baidya
Issue:
Volume 4, Issue 4-1, July 2015
Pages:
31-39
Received:
4 May 2015
Accepted:
6 July 2015
Published:
29 July 2015
Abstract: Iron and manganese mineralization in the Joda-Noamundi sector is associated with Banded Iron Formation of the Archean Iron Ore Group of rocks (3.5-3.0 Ga).Both Mn and Fe mineralization is stratiform and stratabound. In the Noamundi basin the estimated reserve of Fe and Mn -ores are 3.3 Gt and 130 Mt respectively. The Fe and Mn-mineralization are also genetically related to each other. A detailed petrology, mineralogy and mineral chemistry of the ores show their evolution with respect to different tectonic phases. During the first phase of deformation and metamorphism Fe-protolith generated magnetite and Mn-protolth generated bixbyite, hausmannite, jacobsite and braunite. During second phase martitized magnetite and hematite in Fe-ore and hollandite, psilomelane and pyrolusite in Mn-ore were generated. During supergene events low temperature higher oxide minerals were generated from the metamorphic and hydrothermal Fe and Mn –ore minerals. The stratigraphic status of the Fe- and Mn- ores with respect to crustal evolution has been established
Abstract: Iron and manganese mineralization in the Joda-Noamundi sector is associated with Banded Iron Formation of the Archean Iron Ore Group of rocks (3.5-3.0 Ga).Both Mn and Fe mineralization is stratiform and stratabound. In the Noamundi basin the estimated reserve of Fe and Mn -ores are 3.3 Gt and 130 Mt respectively. The Fe and Mn-mineralization are al...
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Gold Mineralisation in Chigargunta Area of the Kolar Schist Belt, South India- A Part of the Archean Greenstone Belt
Issue:
Volume 4, Issue 4-1, July 2015
Pages:
40-45
Received:
23 April 2015
Accepted:
5 May 2015
Published:
29 July 2015
Abstract: Gold mineralisation is reported for the first time in ‘Champion gneiss’ (quartzo-feldspathic schist) a felsic unit,in the eastern sector of the Chigargunta area (Lat: 120 430300N, Long:780 150 000E) of the Kolar schist belt, South India, during 1979-80. Quartzo-feldspathic gneiss and hornblende schist are the predominant rock types of the area. These rocks are characterised by a strong pervasive foliation trending N50E –S50W to N200E - S200W with easterly dips of 70-85. In the northern part of the area the rocks are folded with the foliation which is axial planar. Lower to middle amphibolite facies metamorphism is widespread in the area. Gold mineralisation is localised along shear zones which are ductile to brittle in nature. These zones are parallel to subparallel to the trend of foliation in the host rock and are characterized by strong mylonitic fabric, profuse quartz venation and hydrothermal alteration. Pyrite and pyrrhotite are the dominant sulphides. Gold occurs in native form. This felsic hosted gold mineralisation termed as E-2 lode (for exploration purpose) is estimated to contain a reserve of 3.13 million tonnes averaging 4.7 g/t gold. Besides, this lode there are several loads ( E-1,E-3, etc) occur within mafic units as well as in felsic unit adjacent to E-2 lode with different reserves, within the schist belt. Epigenetic gold mineralisation shows a close temporal and spatial relationship to late Archean (2700-2500 m.y) crustal accretion, stabilisation and granulite formation in the South Indian Shield. The present work delineate, the nature of mineralization in felsic unitwithin the schist belt which was not considered as source rock of gold mineralization during the period and left untouched until the present work
Abstract: Gold mineralisation is reported for the first time in ‘Champion gneiss’ (quartzo-feldspathic schist) a felsic unit,in the eastern sector of the Chigargunta area (Lat: 120 430300N, Long:780 150 000E) of the Kolar schist belt, South India, during 1979-80. Quartzo-feldspathic gneiss and hornblende schist are the predominant rock types of the area. The...
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