The Singhbhum Craton stratigraphy | Singhbhum Craton | location| Map

Introduction of Singhbhum Craton?

Singhbhum Craton covers a triangular area of 50,000 sq. km and consists of a core (8,000 sq. km) of Singhbhum granite, rimmed by supracrustals of varied character and age. It covers Jharkhand, Odisha, and adjoining areas in the eastern part of the Indian Shield.

Location and Boundaries of Singhbhum Craton

The Singhbhum Craton lies in the embrace of two Proterozoic mobile belts—the Satpura Mobile Belt in the east, north, and northwest, and the Eastern Ghat Mobile Belt in the south. The Mahanadi Graben of Gondwana heritage separates it from the Bastar Craton. The arcuate North Singhbhum orogen wraps around Singhbhum granite in the north.

Geological Boundaries of Singhbhum Craton

• North: Bounded by the Chhotanagpur Gneiss, forming the eastern extension of the Satpura mobile belt or Central Indian Tectonic Zone (CITZ), separated by the Tamar-Poropahar (or South Purulia) shear zone.
• South: Bounded by the Eastern Ghats mobile belt, with a tectonic contact marked by the Sukinda shear zone.
• East: Covered under the alluvium of the Bengal basin.

Alternate Names

The Singhbhum Craton is also called Singhbhum-Orissa Craton or Singhbhum Iron Ore Craton, but the name Singhbhum Craton is widely used.

Main Components of Singhbhum Craton

Principal Lithological Associations

1. Singhbhum Granite: Enclaves of Older Metamorphic Tonalite Gneiss (OMTG) and Older Metamorphic Group (OMG) sediments and volcanics.
2. Banded Iron Formation (BIF) Basins: Fringing the Singhbhum granite.
3. Volcanic Basins: Loosely termed as greenstone belts.
4. Flysch-like Sediments and Volcanics: Of the North Singhbhum orogen.
5. Mafic Dyke Swarms
6. Kolhan Basin

Regional Stratigraphy of Singhbum Craton

Iron Ore Group of Singhbhum Craton

Description

There are three basins of iron formation fringing the Singhbhum granite to the west, east, and south, called Noamundi-Koira, Gorumahisani-Badampahar, and Tonka-Daitari. Different authors have grouped them into either a single iron Ore Group or two major stratigraphic groups of the older Badampahar Group and younger Koira Group. The Daitari Group is correlated by many authors with the Badampahar Group.

Singhbhum Granite

Characteristics

The oval-shaped Singhbhum granite is a composite of several bodies, which are assigned to three phases:

• Phases I and II: Geochemically distinguished as Type A (SG-A) (3300-3400 Ma).
• Phase III: Type B (SG-B) (3100 Ma).

Broadly, Singhbhum granite belongs to the granodiorite-adamellite-granite (GAG) suite, containing 3300-3400 Ma old enclaves of OMG and OMTG.

Related Granites

• Kaptipada (Nilgiri) Granite in the east.
• Chakradharpur Granite in the north.
• Bonai Granite in the west.
• Pala Lahara Gneiss: Around Pala Lahara, may also be correlated with Singhbhum granite.

North Singhbhum Orogen (NSO)

Description

The North Singhbhum orogen, about 50-60 km wide, exposes folded sequences in several sub-basins. The orogen is bounded in the north by the Chhotanagpur Gneiss and in the south by the Singhbhum granitic basement. The lithological succession shows a normal order of superposition from the basement granite to the south to the gneisses at the northern margin, denoting a northerly younging trend. The Dalma volcanic belt divides the orogen into two major segments.

Shear Zones

• Singhbhum Shear Zone: A prominent ductile shear zone passes close to the southern margin of the orogen.
• Tamar-Poropahar Shear Zone: A less prominent shear zone at the northern margin, hosting minor copper-uranium-lead mineralization.

Tectono-stratigraphic Domains

1. Dhanjori Domain: Between Singhbhum granite (SG) and Singhbhum shear zone (SSZ), constituting the Marginal Zone of the orogen.
2. Singhbhum Shear Zone: Extending from Porahat to Baharagora.
3. Ghatsila Domain: Between Singhbhum granite and Dalma volcanics.
4. Dalma Volcanics: Folded volcanic-pyroclastic assemblage.
5. Chandil Domain: Between Dalma volcanics and Chhotanagpur Gneiss.

Singhbhum Shear Zone

Description

Also known as the Cu-belt thrust zone, characterized by extreme ductile shearing, multiple metasomatism, and prominent mineralization of Cu-Uranium, Tungsten, and Phosphate. The evolution of SSZ is multi-episodic at 2200 Ma, 1800 Ma, 1600 Ma, and 1000 Ma.

• 2200 Ma: Soda granite emplaced.
• 1800 Ma: Cu-Mineralization.
• 1600 Ma: Uranium mineralization.
• 1000 Ma: Emplacement of Arkasani Granite.

Mineral Assets

Major Mineral Deposits of Singhbhum Craton

1. Iron Ore (Fe): Reserves related to the banded iron formation of the Gorumahisani–Badampahar belt. Intense supergene alteration resulted in rich iron ore deposits of global importance.
2. Manganese Ore: Located just below iron ores in the Jamda–Koira valley, mainly in the shales. Dominant ore is lateroid type; bedded types include pyrolusite, cryptomelane, manganite, and braunite.
3. Chromite (Cr): Over 90% of India’s production comes from Sukinda, Baula-Nuasahi, and Jajihatu–Hatgamaria areas in the Sukinda ultrabasic belt.
4. Copper-Uranium, Apatite-Magnetite, Tungsten: Found in the Singhbhum Shear Zone.
5. Copper-Uranium-Lead: Located in the Tamar-Poropahar (or South Purulia) shear zone