Magmatic and Tectonic Setting of Archean Granitoids in the Southeastern Singhbhum Craton, India: Developing constraints with major and trace element geochemistry and geochronology

The Singhbhum craton is one of five Archean nuclei comprising Peninsular India. It is a composite Archean block that includes the Older Metamorphic Group, the Older Metamorphic Tonalite Gneisses, the Singhbhum Granite, and the Iron Ore Group as its major units. The ages of these components range from ~3.5 to ~3.1 Ga, although overlapping ages and similar rock types confound their genetic relationships. Plutonic felsic rocks from the southeastern Singhbhum craton (BK1: a foliated tonalite, KP1: a non-foliated granite, and SG14: a non-foliated granite) yield U-Pb (zircon) ages of 3321 ± 2 Ma (BK1), 3301 ± 1 Ma (KP1), and 3261 ± 1 Ma (SG14) that coincide with a pulse of Singhbhum Granite emplacement at 3.27 to 3.33 Ga. REE patterns and tectonic discrimination diagrams based on major and trace element ratios suggest a subduction zone setting for these rocks. We report major and trace element data for and compare them to previous works in order to characterize the Archean felsic plutonic history of the craton.

Genetic significance of trace elements in certain rocks of Singhbhum, India

SummaryThe distribution of trace elements is studied in different acid and basic rocks, adjacent to the copper lodes in the Mosaboni mines, Singhbhum, and adjoining the thrust zone, as well as of areas far away from the mineralized zones. Specific differences in composition and trace constituents in these rocks especially as regards S, Cu, Ni, and Co, suggest that the relationship of the Singhbhum granite with the soda granite is most unlikely, and that there is a connection between the soda granite and the sulphide ore-fluid ; a genetic relationship of sulphide mineralization with the epidiorite is doubtful. The possibility of the existence of a common source for the Chotanagpur granite and the Singhbhum granite is inferred.

Soda-granites from South of Tatanagar, Bihar, India

The nature and origin of some soda-granites from the western part of the Singhbhum shear zone, Bihar, India, are discussed. These soda-granites are responsible for copper sulphide, apatite-magnetite, and uraniferous mineralization within the shear zone. Earlier workers regarded these rocks as sheared materials representing a portion of the high sodic residual liquid from the neighbouring Singhbhum granite magma. The present work indicates that these rocks are migmatitic in nature and are the products of progressive replacement of pre-existing pelitic and semi-pelitic schists by felspathic materials. Migmatization is essentially post-shearing in age while the Singhbhum granite is pre-shearing in age. The migmatitic materials appear to have been derived by the partial melting of the Singhbhum granite during shearing, particularly in depth, as a result of sudden release of confining pressure consequent upon shearing and generation of heat caused by friction at the base of the shear zone. The resulting liquids, which were albite rich, found easy passage through the shear zone and brought about migmatization and mineralization in its wake.