<P> It consists of two main sequences formed in Proterozoic eon, metasedimentary rock (sedimentary rocks metamorphised under pressure and heat without melting) and metavolcanic rock (metamorphised volcanic rocks) sequences of the Aravalli Supergroup and Delhi Supergroup . These two supergroups rest over the Archean Bhilwara Gneissic Complex basement, which is a gneissic (high - grade metamorphism of sedimentary or igneous rocks) basement formed during the archean eon 4 Ga ago . It started as an inverted basin, that rifted and pulled apart into granitoid basement, initially during Aravalli passive rifting around 2.5 to 2.0 Ga years ago and then during Delhi active rifting around 1.9 to 1.6 Ga years ago . It started with rifting of a rigid Archaean continent banded gneissic complex around 2.2 Ga with the coexisting formation of the Bhilwara aulacogen in its eastern part and eventual rupturing and separation of the continent along a line parallel to the Rakhabdev (Rishabhdev) lineament to the west, simultaneous development of a passive continental margin with the undersea shelf rise sediments of the Aravalli - Jharol belts depositing on the attenuated crust on the eastern flank of the separated continent, subsequent destruction of the continental margin by accretion of the Delhi island arc (a type of archipelago composed of an arc - shaped chain of volcanoes closely situated parallel to a convergent boundary between two converging tectonic plates) from the west around 1.5 Ga . This tectonic plates collision event involved early thrusting with partial obduction (overthrusting of oceanic lithosphere onto continental lithosphere at a convergent plate boundary) of the oceanic crust along the Rakhabdev lineament, flattening and eventual wrenching (also called strike - slip plate fault, side ways horizontal movement of colliding plates with no vertical motion) parallel to the collision zone . Associated mafic igneous rocks show both continental and oceanic tholeiitic geochemistry (magnesium and iron rich igneous rocks) from phanerozoic eon (541--0 million) with rift - related magmatic rock formations . </P> <P> The Aravalli - Delhi Orogen is an orogen event that led to a large structural deformation of the Earth's lithosphere (crust and uppermost mantle, such as Aravalli and Himalayas fold mountains) due to the interaction between tectonic plates when a continental plate is crumpled and is pushed upwards to form mountain ranges, and involve a great range of geological processes collectively called orogenesis . </P> <P> The archean basement had served as a rigid indentor which controlled the overall wedge shaped geometry of the orogen . Lithology of area shows that the base rocks of Aravalli are of Mewar Gneiss formed by high - grade regional metamorphic processes from preexisting formations that were originally sedimentary rock with earliest life form that were formed during the archean eon, these contain fossils of unicellular organism such as green algae and cyanobacteria in stromatolitic carbonate ocean reefs formed during the paleoproterozoic era . Sedimentary exhalative deposits of base metal sulfide ores formed extensively along several, long, linear zones in the Bhilwara aulacogen or produced local concentration in the rifted Aravalli continental margin, where rich stromatolitic phosphorites also formed . Tectonic evolution of the Aravalli Mountains shows Mewar Geniss rocks are overlain by Delhi Supergroup type of rocks that also have post-Aravalli intrusions . Metal sulfide ores were formed in two different epocs, lead and zinc sulfide ores were formed in the sedimentary rocks around 1.8 Ga years ago during Paleoproterozoic phase . The tectonic setting of Zinc - lead - copper sulfides mineralization in Delhi supergroup rocks in Haryana - Delhi were formed in mantle plume volcanic action around 1 Ga years ago covering Haryana and Rajasthan during mesoproterozoic . In the southern part of Aravalli supergroup arc base metal sulfides were generated near the subduction zone on the western fringe and in zones of back - arc extension to the south - east . Continued subduction produced W - Sn (Tungsten - Tin) mineralisation in S - type (sedimentary unmetamorphosed rock) felsic (volcanic rock) plutons (underground crystallised solidified magma). This includes commercially viable quantities of minerals, such as rock phosphate, lead - zinc - silver mineral deposits at Zawar, Rikahbdev serpentinite, talc and pyrophyllite) and asbestos, apatite, kyanite and beryl . </P> <P> Mining of copper and other metals in the Aravalli range dates back to at least the 5th century BCE, based on carbon dating . Recent research indicates that copper was already mined here during the Sothi - Siswal period going back to c. 4000 BCE . Ancient Kalibangan and Kunal, Haryana settlements obtained copper here . </P>

North aravalli region of rajasthan include the following district