Sandy Saha: added.

2025-05-28T13:28:39Z

added.

New page

{{short description|Overview article}}
{{Use dmy dates|date=May 2022}}
{{Use Indian English|date=May 2022}}
[[File:1 Aravalli Range in Rajasthan India.jpg|thumb|The Aravalli Mountain Range in Rajasthan, India]]
[[File:India Geographic Map.jpg|thumb|upright=1.5|The Aravalli Mountain Range is in the northwestern part of India.]]
The [[Aravalli Range|Aravalli Mountain Range]] is a northeast-southwest trending [[orogenic belt]] in the northwest part of [[India]] and is part of the [[Indian Shield]] that was formed from a series of [[craton]]ic collisions.<ref name=":0">Mishra, D.C.; Kumar, M. Ravi. Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints. Geoscience Frontiers. 2013 March. 5: 25–41.</ref> The Aravalli Mountains consist of the Aravalli and Delhi fold belts, and are collectively known as the Aravalli-Delhi orogenic belt. The whole mountain range is about 700 km long.<ref name=":1">Mckenzie, N. Ryan; Hughes, Nigel C.; Myrow, Paul M.; Banerjee, Dhiraj M.; Deb, Mihir; Planavsky, Noah J. New age constraints for the Proterozoic Aravalli–Delhi successions of India and their implications. Precambrian Research. 2013 November. 238: 120–128.</ref> Unlike the much younger [[Himalayas|Himalayan]] section nearby, the Aravalli Mountains are believed much older and can be traced back to the [[Proterozoic]] Eon. They are arguably the oldest geological feature on Earth.<ref>{{Cite journal |last1=Verma |first1=P. K. |last2=Greiling |first2=R. O. |date=1995-12-01 |title=Tectonic evolution of the Aravalli orogen (NW India): an inverted Proterozoic rift basin? |url=https://doi.org/10.1007/BF00240560 |journal=Geologische Rundschau |language=en |volume=84 |issue=4 |pages=683–696 |doi=10.1007/BF00240560 |bibcode=1995GeoRu..84..683V |issn=1432-1149 |s2cid=129382615|url-access=subscription }}</ref> The collision between the Bundelkhand craton and the Marwar craton is believed to be the primary mechanism for the development of the mountain range.<ref name=":0" />

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

== Geology of the Aravalli Mountains ==
{{see also|Aravalli Range#Geology}}
The Aravalli Mountain Range features a [[Horst (geology)|horst]]-like structure and consists of a series of Proterozoic rocks that are intensely deformed and [[Metamorphism|metamorphosed]].<ref name=":2">Verma, P.K.; Greiling, R.O.. Tectonic evolution of the Aravalli Orogen (NW India): an inverted Proterozoic rift basin?. Geol Rundsch. 1995 August. 84: 683–696.</ref>

=== General formation ===
Three main subdivisions of rocks constitute the stratigraphy of the mountain range, with the Archean Bhilwara [[Gneiss]]ic Complex basement being the lowest strata, followed by the overlying lower Aravalli Supergroup and the upper Delhi Supergroup.<ref name=":1" /> The northern part of the mountain range only consists of the Delhi Supergroup, and this has given to its name of ‘North Delhi Belt.<ref name=":1" /> On the southern side, however, both the Aravalli and Delhi supergroups are present. The mountain range is bounded by the Eastern and Western marginal [[Fault (geology)|faults]], where the former is also termed as the Great Boundary Fault.<ref name=":2" />
{| class="wikitable sortable mw-collapsible"
|+
! colspan="3" |<big>General geological formation of the Aravalli Mountains</big>
|-
| rowspan="3" |Delhi Supergroup
|Ajabgarh Group (=Kumbhalgarh Group)
|[[Carbonate rock|Carbonate]], [[mafic]] [[Volcanic rock|volcanic]] and [[argillaceous]] rocks
|-
|Alwar Group (= Gogunda Group)
|[[Arenaceous]] and mafic volcanic rocks
|-
|Raialo Group
|Mafic volcanic and calcareous rocks
|-
| rowspan="3" |Aravalli Supergroup
|Jharol Group
|[[Turbidite]] [[Facies (geology)|facies]] and [[Argillite|argillaceous]] rocks
|-
|Debari Group
| rowspan="2" |[[Carbonate rock|Carbonates]], [[quartzite]], and [[Pelite|pelitic]] rocks
|-
|Delwara Group
|-
|Archean basement
|Banded Gneissic Complex (BGC)
|[[Schist]]s, [[gneiss]]es and composite gneiss
Quartzites
|}

=== Archean Bhilwara Gneissic Complex basement ===
The Bhilwara Gneissic Complex basement is about 2.5 Ga old.<ref name=":1" /> It is made up of a group of metamorphic and [[Igneous rock|igneous]] rocks that are mainly [[amphibolite]] to [[granulite]] grade, [[Tonalite|tonalitic]] to [[Granodiorite|granodioritic]] gneisses and intrusive [[granitoid]]s with a minor amount of [[metasedimentary]] and [[metavolcanic rock]]s.<ref name=":3">Kaur, Parampreet; Zeh, Armin; Chaudhri, Naveen; Gerdes, Axel; Okrusch, Martin. Archaean to Paleoproterozoic crustal evolution of the Aravalli mountain range, NW India, and its hinterland: The U-Pb and Hf isotope record of detrital zircon. Precambrian Research. 2011 March. 187: 155–164.</ref><ref name=":4">Lente, B. Van; Ashwal, L.D.; Pandit, M.K.; Bowring, S.A.; Torsvik, T.H.. Neoproterozoic hydrothermally altered basaltic rocks from Rajasthan, northwest India: Implications for late Precambrian tectonic evolution of the Aravalli Craton. Precambrian Research. 2009 January; 170: 202–222.</ref> The basement is categorized into two subdivisions: the Sandmata Complex and the Mangalwar Complex.<ref name=":5">Rao, V. Vijaya; Prasad, B. Rajendra; Reddy, P.R.; Tewari, H.C.. Evolution of Proterozoic Aravalli Delhi Fold Belt in the northwestern Indian Shield from seismic studies. Tectonophysics. 2000 June. 327 (1–2): 109–130.</ref><ref name=":6">Sinha-Roy, S.; Malhotra, G.; Guha, D.B.. A transect across Rajasthan Precambrian terrain in relation to geology, tectonics and crustal evolution of south-central Rajasthan. In: Sinha-Roy, S., Gupta, K.R. (Eds.), Continental Crust of NW and Central India. Geological Society, India. 1995. 31: 63–89.</ref> The Sandmata Complex refers to gneisses and granitoids while the Mangalwar Complex refers to the metasedimentary and metavolcanic series which are considered to be metamorphosed older [[Greenstone belt|granite-greenstone belt]].<ref name=":5" /><ref name=":6" />

=== Aravalli Supergroup ===
On top of the Archean basement, the Aravalli Supergroup overlies with clear [[Unconformity|unconformities]] separating the two strata.<ref name=":2" /> The Aravalli Supergroup is divided into three groups: lower Delwara Group, middle Debari Group, and Upper Jharol Group.<ref name=":7">Meert, Joseph G.; Pandit, Manoj K.. The Archean and Proterozoic history of Peninsular India: tectonic framework or Precambrian sedimentary basins in India. In: Mazumder, R. & Eriksson, P. G. (eds), Precambrian Basins of India: Stratigraphic and Tectonic Context. Geological Society, London. 2015 March. 43: 29–54 </ref> The lower and middle groups shared similar lithology, where both groups are dominated by [[Carbonate rock|carbonates]], [[quartzite]], and [[Pelite|pelitic]] rocks, thus suggesting a [[Continental shelf|shelf]] depositional environment. [[Turbidite]] facies and [[Argillite|argillaceous]] rocks are prominent in the upper Jharol group, thus suggesting a deep marine depositional environment.<ref name=":7" /> The depositional age of these sequences ranges approximately from 2.1 to 1.9 Ga.<ref name=":1" />

Three major episodes of deformation and metamorphism were involved in the Aravalli Supergroup, including [[Fold (geology)|foldings]], [[Shear (geology)|shearing]], kink bands and [[crenulation]]s etc.<ref name=":7" /> Metamorphic grades of the rocks generally range from greenschist facies to amphibolite facies.<ref name=":7" />

=== Delhi Supergroup ===
The upper Delhi Supergroup overlies on the Aravalli Supergroup with a clear unconformity.<ref name=":2" /> This supergroup hosts two main types of rocks: a thick sequence of volcanic rocks that is of continental affinity; and sedimentary rocks that represent [[fluvial]] and shallow marine environments and deep marine depositional environment.<ref name=":2" /> The depositional age of these sequences is approximately from 1.7 to 1.5 Ga.<ref name=":1" />

In the ‘North Delhi belt’, the Delhi Supergroup is classified into three groups: lower Raialo Group, middle Alwar Group, and upper Ajabgarh Group.<ref name=":3" /><ref>Roy, A.B., Jakhar, S.R., 2002. Geology of Rajasthan (Northwest India). Precambrian to Recent. Scientific Publishers (India), Jodhpur, 421 pp.</ref> The Raialo Group consists predominantly of [[mafic]] [[Volcanic rock|volcanic]] and calcareous rocks.<ref name=":1" /> The Alwar Group mainly consists of [[Arenite|arenaceous]] and mafic volcanic rocks.<ref name=":1" /> The Ajabgarh Group is dominated by carbonate, mafic volcanic and argillaceous rocks.<ref name=":1" /> In the southern part, similar rock types, despite different names, are identified, where they are Gogunda Group (equivalent to Alwar group) and the Kumbhalgarh Group (equivalent to Ajabgarh Group).<ref name=":3" /><ref>Gupta, S.N.; Arora, Y.K.; Mathur, R.K.; Iqbaluddin, Prasad B.; Sahai, T.N.; Sharma, S.B.. The Precambrian geology of the Aravalli region, southern Rajasthan and northeastern Gujarat. Geological Survey India. 1997. 123: 262.</ref>

== Four phases of tectonic evolution ==
The tectonic evolution of the Aravalli-Delhi orogenic belt can be divided into four phases:<ref name=":5" />
# Bhilwara Gneissic Complex (~ 2,500 Ma)
# Aravalli Orogeny (~ 1,800 Ma)
# Delhi Orogeny (~ 1,100 Ma)
# Post-orogenic evolution (~ 850 – 750 Ma)
Two phases of [[rift]]ing, [[sedimentation]], [[Convergent boundary|collision]] and [[Suture (geology)|suturing]] were documented in the tectonic evolution of the Aravalli-Delhi orogenic belt.<ref name=":5" /> During Proterozoic Eon, N-S convergence between the Bundelkhand and Bhandara cratons at the Satpura Mobile Belt, and E-W convergence between the Bundelkhand and Marwar cratons at the Aravalli-Delhi orogenic belt have synchronously occurred in India.<ref name=":0" /> This resulted in an overall resultant force of NE-SW convergence of the Aravalli-Delhi orogenic belt, and also led to the arcuate shape of its convergent zone.<ref name=":0" />

=== Evolution of the Archean basement ===
The Aravalli Mountains basement started with an older [[sialic crust]] evolving into extensive [[Granite|granitic]] [[batholith]]s by the emplacement of granitic bodies during the period ca. 3.0 to 2.5 Ga.<ref name=":2" /> This subsequently led to rapid [[cratonization]] and rapid thickening of crust to about 20–25 km.<ref>Choudhary AK, Gopalan K, Sastry CA (1984) Present status of the geochronology of the Precambrian rocks of Rajasthan. Tectonophysics 105: 131–140.</ref><ref>Naqvi SM, Divakar Rao V, Hari Narain (1974) The protocontinental growth of the Indian Shield and the antiquity of its rift valleys. Precambrian. Res 1: 345–398.</ref> The main crustal source is believed to be old crustal components of the area.<ref name=":3" /><ref>Condie, K.C.; Beyer, E.; Belousova, E.; Griffin, W.L.; O’Reilly, S.Y.. U–Pb isotopic ages and Hf isotopic composition of single zircons: the search for juvenile Precambrian continental crust. Precambrian Research. 2005. 139: 42–100.</ref> The region subsequently experienced a large scale metamorphic event that granite is partly metamorphosed into [[gneiss]]ic rocks, forming the Archean Basement.<ref name=":2" /> These cratonization processes continued together signifying the end of amalgamation of cratonic nuclei that constitutes the development of an early continental crust.

=== Aravalli Orogeny ===
During the [[Paleoproterozoic]] Era, the opening of Aravalli oceanic basin separated the eastern Bundelkhand craton and the western Marwar craton.<ref name=":5" /> Sedimentation of the Aravalli Supergroup took place simultaneously with basic magmatism and followed by a gradual subsidence of the Aravalli Basin floor.<ref name=":2" /><ref>Mathur, RK; Prasad, B; Sharma, BS; Iqbaluddin. Synsedimentational shoreline volcanism in Aravalli of Rajasthan. Geological Survey India News. 1978.</ref>

Soon after the rifting phase ended, the compressional phase took place where the eastern Bundelkhand craton [[Subduction|subducted]] under the western Marwar craton.<ref name=":5" /> As collision continued, the subduction zone steepened, leading to the development of an [[island arc]] between the two cratons.<ref name=":5" /> After collision had proceeded for a certain period of time, the uplift of the Aravalli Supergroup was induced at around 1800 Ma.<ref name=":1" /><ref name=":5" /> In the last stage of convergence, the [[thrust fault]] further steepened and the colliding blocks eventually become sutured.<ref name=":5" /> The suture zone is marked by the Great Boundary Fault.<ref name=":7" />

=== Delhi Orogeny ===
During the [[Mesoproterozoic]] Era, another rifting phase began.<ref name=":5" /><ref>Deb, M., Talwar, A.K., Tewari, A., Banerjee, A.K., 1995. Bimodal volcanism in South Delhi fold belt: a suite of differentiated felsic lava at Jharivav, north Gujarat. In: Sinha-Roy, S., Gupta, K.R. (Eds.), Continental Crust of NW and Central India. Geol. Soc. India, Memoir 31, pp. 259–278.</ref> At that time, the Bundelkhand-Aravalli-BGC and the Marwar craton lie on the eastern side and western side respectively as the rifting phase separated the Bhilwara Gneissic Complex (BGC) from the Marwar craton.<ref name=":5" /> The oceanic basin created in the course of rifting received the Delhi Supergroup sediments.

The compressional phase that followed led to eastward subduction of the western Marwar craton.<ref name=":5" /> Continuous subduction of the western block might have created another island arc, and similar to the Aravalli orogeny, further collision between the two blocks with island arc in between gave rise to the development of the Delhi orogeny around 1100 Ma.<ref name=":3" /><ref name=":5" /> The suture zone between the two cratons is marked by the Western Marginal Fault and the emplacement of the Phulad [[Ophiolite]] Suite in the region.<ref name=":7" />

=== Post-orogenic evolution ===

==== Acid magmatic events ====
The epilogue of the tectonic evolution was marked by granitic and [[Rhyolite|rhyolitic]] [[magma]]tic events, namely the emplacement of the Erinpura granite and the Malani Volcanics on the western side of Aravalli-Delhi orogenic belt.<ref name=":2" /> This event is ranked third among the largest igneous province in the globe, with a total area of about 52,000 km<sup>2</sup> in India.<ref name=":7" /> Malani Igneous Suite is a collective term for bimodal volcanic and plutonic rocks aged 873–800 Ma in the area.<ref name=":7" /> The lithologies of the rock suite are predominantly rhyolitic and rhyodacitic volcanic rocks with granitoid intrusions overlying unconformably or intruding through the Delhi Supergroup.<ref name=":4" /><ref name=":7" />

==== Purana basins formation ====
Apart from the vigorous post-orogenic magmatic event, a large number of so-called ‘Purana’ basins was actively developing near the orogenic belts.<ref name=":7" /> The word ‘Purana’ means ‘ancient’ and was used to depict the group of isolated sedimentary basins with thick Proterozoic sedimentary strata that are relatively undeformed on the Indian Shield.<ref name=":1" /> The Vindhyan Basin and the Marwar Basin are part of the Purana basins that sit near the Aravalli Mountain Range.

* Vindhyan Basin
The Vindhyan Basin is located on the southeastern side of the Aravalli Mountain Range where its formation is believed to be associated to the large downwarp of the crust after Delhi Orogeny.<ref name=":7" /> It spans an area of about 104,000 km<sup>2</sup> in the northwestern part of India overlying on the Archean Bhilwara Gneissic Basement.<ref name=":8">Turner, Candler C.; Meert, Joseph G.; Pandit, Manoj K.; Kamenov, George D.. A detrital zircon U-PB and HF isotopic transect across the Son Valley sector of the Vindhyan Basin India: Implications for basin evolution and paleogeography. Gondawa Research. 2013 June. https://dx.doi.org/10.1016/j.gr.2013.07.009</ref> The Vindhyan Supergroup is classified into two fundamental strata, lower and upper Vindhyan, with a large unconformity representing 500 million years interval between the strata.<ref name=":1" /> Within each stratum, it is further categorized into major groups. The lower Vinhydan comprises the Semri Group while the upper Vinhyan consists of the Kaimur Group, Rewa Group, and Bhander Group.<ref name=":1" /> The earliest sedimentation forming the lower Vindhyan can be traced back to Paleoproterozoic and stopped somewhere around early Mesoproterozoic (~1,721 Ma to 1,600 Ma).<ref name=":8" /> Sedimentation forming the upper Vindhyan resumed again in the Mesoproterozoic and ceased in Neoproterozoic.<ref name=":8" /><ref>Azmi, R.J.; Joshi, D.; Tewari, B.N.. 2008. A synoptic view on the current discordant geo- and biochronological ages of the Vindhyan Supergroup, central India. Journal of Himalayan Geology. 29: 177–191.</ref> Vindhyan Supergroup portrayed transitional to shallow marine depositional environment, such as [[alluvial fan]], [[River delta|delta]], [[Mudflat|tidal flat]], carbonate ramp etc.<ref name=":8" />

* Marwar basin
To the west of the Aravalli Mountain Range and far beyond the Vindhyan Basin lies the Neoproterozoic-to-[[Cambrian]]-aged Marwar Basin.<ref name=":7" /> The Marwar Basin sits on the Malani Igneous Suite and contains a sedimentary section of 2 km in thickness.<ref name=":7" /> Similar to other Purana basins, the Marwar Supergroup is less deformed and unmetamorphosed. The Marwar Supergroup is classified into three major groups: the lower Jodhpur Group, the middle Bilara Group, and the upper Nagaur Group.<ref name=":7" /> [[Arenaceous rock]]s, [[calcareous rock]]s and [[evaporite]]s are the dominant rock type in the Marwar Basin.<ref name=":7" />

== Association with supercontinent cycles ==
The tectonic events and basin developmental phases are thought to be correlated to the amalgamation and breakup of plates during [[supercontinent cycle]]s of [[Columbia (supercontinent)|Columbia]], [[Rodinia]], and [[Gondwana]].

The Aravalli orogeny (~1,800 Ma) began with the development of oceanic basin. The rifting process is believed to be associated with the formation of the Columbia supercontinent, which happened from 2.5 Ga to 1.8 Ga and was coeval with the onset of Aravalli orogeny's rifting basin.<ref name=":7" /> The opening of another sedimentary basin during the Delhi orogeny (~-1,100 Ma) coincided with the time where the supercontinent Columbia broke up, and the cessation of basin development followed by a compressional phase was concurrent with the assembly of [[Rodinia]].<ref name=":7" /><ref name=":8" /> The deposition of the upper Vindhyan Supergroup may also denote the final episode of Rodinia formation.<ref name=":7" /> Several geochemical analyses show that detrital [[zircon]] samples obtained from the Marwar basin are highly linked to the breakup phase of Rodinia and the assembly phase of [[Gondwana]].<ref name=":7" />
== Map gallery ==
<gallery mode="packed-hover" heights="250">
File:Paleoglobe NO 1590 mya-vector-colors.svg|Reconstruction of Columbia supercontinent
File:Laurasia-Gondwana.png|Godwana supercontinent
</gallery>

== See also ==
* [[Geology of India]]

== References ==
{{Reflist}}

[[Category:Geology of India]]
[[Category:Aravalli Range]]

Tectonic evolution of the Aravalli Mountains - Revision history

Sandy Saha: added.