Plate Tectonics 2.5 Billion Years Ago: Evidence at Kolar, South India
E. J. Krogstad 1,
S. Balakrishnan 2,
D. K. Mukhopadhyay 3,
V. Rajamani 2, and
G. N. Hanson 1
1 Department of Earth and Space Sciences, State University of New York, Stony Brook, NY 11794, USA
2 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India
3 Department of Earth Sciences, Roorkee University, Roorkee 247667, India
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.
Submitted on October 31, 1988
Accepted on February 1, 1988
