Aravalli evolution

GEOLOGICAL EVOLUTION OF THE ARAVALLIS

 • Aravalli mountains are believed much older and can be traced back to the proterozoic eon.

• They are arguably the most oldest geological feature of the earth.

• The collision between the Bundelkhand craton and the Marwar craton is believed to be the primary mechanism for the development of the mountain range.

• The precise evolutionary processes responsible for the Aravalli mountain range remains controversial today, and there are diverse theories put forward for the tectonic history.

PHASES OF ARAVALLI FORMATION

The geological evolution of the Aravall-Delhi orogenic belt can be divided into four processes:–

1. Bhilwara Gneissic Complex(BGC):

• The Aravalli mountain basement started with an older sialic crust evolving into extensive granitic batholiths.

• This subsequently led to cratonization and rapid thickening of crust to about 20-25km.

• The BGC, Sadmanta Complex and supracrustal sequences collectively known as the Aravalli craton were developed by multiple accretionary-crystal processes from 3.3 to 0.7Ga.

2.   Aravalli orogeny:

• During the paleoproterozoic era the opening of the Aravalli oceanic basin separated the western Bundelkhand craton and the western sedimentation of the Aravalli supergroup took place simultaneously with basic magmatism and followed by a gradual subsidence subsidence of the Aravalli basin floor.

• Soon after the shifting phase ended a compressional phase took place the eastern Bundelkhand craton subdued under the western Marwar craton.

• In the last stage of convergence, the thrust fault further steepness and the cooling blocks eventually became sutured.

• This suture zone is marked as the Great Boundary Fault (GBF).

3.   Delhi Orogeny:

• During the mesoproterozoic era another rifting phase began.

• At that time the Aravalli-BGC and the Marwar craton lie on the eastern side respectively as the rifting phase of the BGC from the Marwar craton.

• The oceanic basin created in the course of rifting received the Delhi supergroup sediments.

• The compressional phase that followed led the eastward subduction of the western Marwar craton.

4.   Post orogenic evolution:

• The epilogue of the tectonic evolution was marked by granitic and rhyolitic magmatic events namely the emplacement of the Ernipura granite and Malani volcanics on the western side of the Delhi orogenic belt.

• Apart from this vigorous post-orogenic magmatic event a large number of so-called 'purana' basins developed near the orogenic belts.

These tectonic events and developmental phases are thought to be correlated to the amalgamation and breakup of plates during the super continent cycles of Columbia, Rodinia and Gondwana.