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The Archean Kolar Schist Belt, south India, is a suture zone where two gneiss terranes and at least two amphibolite terranes with distinct histories were accrted. Amphibolites from the eastern and western sides of the schist belt have distinct incompatible element and isotopic characteristics sugesting that their volcanic protoliths were derived from dint mantle sources. The amphibolite and gneiss terranes were juxtaposed by horizontal compression and shearing between 2530 and 2420 million years ago (Ma) along a zone marked by the Kolar Schist Belt. This history of accretion of discrete crustal terranes resembles those of Phanerozoic convergent margins and thus suggests that plate tectonics operated on Earth by 2500 Ma.

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Two sedimentary lithotectonic zones are traditionally recognized in the northwestern Himalayan frontal fold-thrust belt in the Nahan salient: the Lesser Himalaya Zone (LHZ) and the Sub-Himalaya Zone (SHZ). The LHZ is made up of a sequence of Proterozoic to Early Cambrian rocks and the SHZ is made up of Cenozoic rock sequences, which were deposited subsequent to the India-Asia collision. Serial balanced cross-sections show that the structural geometries become increasingly complex from independent ramp anticlines near the foreland through imbricate fan/duplex to stacked-up horses towards the hinterland. Sequential restoration suggests a structural evolution in which a foreland propagating, in-sequence thrusting event was followed by out-of-sequence thrusting in an approximately break-back style. During the out-of-sequence movement, some of the ramps formed during in-sequence thrusting were repeatedly reactivated, leading to very complex structural geometries, particularly in the LHZ. In such a complexly deformed terrain, a rigorous structural modelling approach, combined with a robust geochemical and geochronological database, should be used to carry out calibrated petroleum system modelling, and thus reduce exploration risk.

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