The Dharwar craton, southern India, interpreted as the result of Late Archaean oblique convergence

Citation
B. Chadwick et al., The Dharwar craton, southern India, interpreted as the result of Late Archaean oblique convergence, PRECAMB RES, 99(1-2), 2000, pp. 91-111
Citations number
113
Categorie Soggetti
Earth Sciences
Journal title
PRECAMBRIAN RESEARCH
ISSN journal
03019268 → ACNP
Volume
99
Issue
1-2
Year of publication
2000
Pages
91 - 111
Database
ISI
SICI code
0301-9268(20000115)99:1-2<91:TDCSII>2.0.ZU;2-O
Abstract
The Dharwar craton comprises two distinct parts separated by a steep N-S si nistral shear zone. In the western part a pre-2900 Ma complex of orthogneis ses, granodiorites and narrow tracts of supracrustal rocks (Sargur Group) f orms the basement to volcanic and sedimentary basins of the Dharwar Supergr oup (ca. 2800-2550 Ma). Late Archaean deformation is characterised by NE-SW crustal shortening and steep N-S sinistral shear zones. The eastern part i s underlain by parallel, steep N-S or NW-SE linear belts of calc-alkaline, anatectic and juvenile granites and granodiorites (Dharwar batholith, ca, 2 750-2510 Ma) with intervening volcanic and sedimentary schist belts (ca. 28 00-2550 Ma). The plutonic belts are 15-25 km wide, up to 150 km long, and b ounded by steep NW-SE high-strain zones up to 2 km wide with sinistral shea r sense (except one which is dextral). Magmatic-state fabrics and structure s in the plutonic rocks are parallel to solid-state sinistral shear fabrics in the high-strain zones, but diffuse magmatic banding is commonly oblique to these zones and coincides with the plane of instantaneous shortening in sinistral shear. Magmatic-state structures, swarms of vertical NW-SE dykes of granite, and the vertical wedge shape of the linear belts are consisten t with emplacement of the batholith during sinistral shear when magma press ure exceeded regional horizontal compressive stress. Upright folds and schi stosity, steep reverse faults and effects of regional HT/LP metamorphism sh ow that deformation was partitioned into NE-SW shortening in the schist bel ts during emplacement of the plutonic belts in the sinistral shear regime. The western part of the craton is interpreted as the foreland to an accreti onary are represented by the batholith and schist belts (intra-arc basins) in the east. NE-SW shortening and sinistral transcurrent displacements in t he foreland and are are consistent with are-normal and are-parallel displac ements during oblique convergence analogous to Mesozoic-Cenozoic convergent settings. (C) 2000 Elsevier Science B.V. All rights reserved.