Abstract
We have dated the South Delhi orogeny, Aravalli-Delhi Mobile Belt (ADMB), NW India, using the tectonic fabric, geochemistry, and zircon-monazite geochronology as the proxies. The South Delhi Terrane (SDT), a passive margin domain in the ADMB, consists of multiply deformed (D1–D4) greenschist facies rocks and several granite plutons. The D1deformation is characterized by pervasive isoclinal recumbent F1fold and axial planar tectonometamorphic fabric, S1, developed in all rock types. The S1minerals belong to peak greenschist facies metamorphism, M1, suggesting syntectonic nature of M1with D1. The age of the D1-M1is constrained by the syncollisional peralkaline S type Sewariya granite which is characterized by magmatic/submagmatic fabric (Sm) coplanar with the S1. The margin of the pluton is turned into quartzofeldspathic gneiss carrying the evidence of high temperature deformation. The age of Sewariya granite is estimated at ca. 878 Ma by zircon geochronology. The D1-M1is further constrained by monazite geochronology of the mica schist at ca. 865–846 Ma. The other granite plutons and metarhyolite are pre-D1and emplaced at ca. 992–946 Ma. The D2deformation produced NE-SW trending open upright F2folds coaxial with the F1, and northwesterly vergent F2–axial planar thrusts. Monazite geochronology constrains the D2at ca. 811–680 Ma. The D3is characterized by small to large scale NW-SE folds, and the D4by faults and fractures marking the brittle deformation in the rocks. The D4is constrained by monazite geochronology at ca. 588–564 Ma. There are upper amphibolitic tectonic slivers along the D2-Phulad thrust, belonging to the pre-Delhi rocks, which show ca. 1,638 Ma metamorphism age. From the above study, it is suggested that the South Delhi orogeny belongs to ca. 878–680 Ma marking the final amalgamation of Marwar Craton with the rest of India. This overlaps the early phase of the Pan-African orogeny (900–630 Ma). The brittle deformation, D4, coincides with Kuunga orogeny (650–500 Ma). Our study implies that India, like other continents in the East Gondwana, underwent amalgamation of internal blocks until the late part of the Neoproterozoic.
Highlights
Amalgamation of continents took place through accretion and continental collision giving rise to supercontinental assembly
We studied the South Delhi orogeny of the Archean-Neoproterozoic Aravalli-Delhi Mobile Belt (ADMB) in NW India that consists of several terranes juxtaposed along shear zones (Figures 1A,B)
Our study suggests that the Pratapgath granite is meta-aluminous, I type, and calc-alkaline (Figure 5) and was produced from the remelting of basic igneous rocks at 750–800°C
Summary
Amalgamation of continents took place through accretion and continental collision giving rise to supercontinental assembly. The Aravalli orogeny is marked by subduction along Rakhabdev shear zone (Figure 1F), emplacement of ophiolites at 1.8 Ga, intrusion of granulite and charnockite plutons in the Sandmata Terrane at ca. The South Delhi orogenic cycle initiated during Meso-Neoproterozoic period following Grenvillian orogeny, when the Marwar Craton underwent rifting to form the South Delhi and Sirohi basins (Figure 1G). The South Delhi orogeny is marked by westerly subduction and formation of island arc system with intrusion of Ambaji, Erinpura, and Sewariya granites at 0.88–0.86 Ga (Figure 1H). 966 Ma 960 Ma 840 Ma 967.8 ± 1.2 Ma 966 Ma 970 Ma 955 Ma 863 ± 23 860 Ma 850 Ma 840 Ma 836+7/−5 Ma 822.8 ± 0.8 Ma 818 ± 3.6 Ma 808 Ma 793 ± 18 Ma 771 Ma 765.9 ± 1.6 Ma 765 Ma 765 Ma 765 Ma 763 ± 22 Ma 759 Ma 757.8 ± 0.9 Ma 735 ± 15 Ma 535 ± 15 Ma 509 ± 2 Ma
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