The little universe of man: By C. D. Darlington. 1978. London: George Allen & Unwin. A vol. in-8°, 308 pp., figs, tabs, bibl., index. Bound £6.95

Abstract

Southeast Asia comprises collage of continental blocks that were rifted out in phases from the northern parts of the Gondwanic Indo-Australian continent during the Paleozoic-Mesozoic time and were accreted through continental collision process following closure of the Paleo- and Neo-Tethys. The South China and Indo-China blocks were possibly rifted during early Palaeozoic, whereas, the Tibetan and SIBUMASU blocks were rifted during Permo-Carboniferous when the said margin was under glacial and/or cool climatic condition. The Indo-Burma-Andaman (IBA), Sikule, Lolotoi blocks were also rifted from the same Indo-Australian margin but during late Jurassic. This was followed by break-up of the Indian and the Australian continents during early Cretaceous. The opening of the Indian Ocean during the Tertiary was synchronous with closing of the Tethys.India-Asia collision during early-middle Eocene was a mega tectonic event. Apart from initiating the Himalayan orogeny and the eastward strike-slip extrusion of the Indochina block from the Southeast Asian continental collage along the Ailao Shan — Red River shear zone, it also caused early-mid Eocene continental-flood-basalt activity in the Himalayan foreland basin. Indian continent's post-collisional indentation-induced syntaxial buckling of Asian continental collage at its eastern end possibly caused late Paleogene highly potassic magmatism around the Gongha syntaxial area that was located close to the sutured margin of South China continent with Indochina block at the outer fringe of Namche Barwa syntaxis. These magmatic bodies are soon after left-laterally displaced by the Ailao Shan — Red River shear zone. The nature and chemistry of magma at these two settings indicate that both groups result from similar petrogenetic and tectonic processes representing deep-seated melts due to mantle decompression. Some deep faults produced at the edge of flexed Indian continental lithosphere and responsible for the development of the foreland basin may have produced continental-flood-basalt and related magma by decompressional melting of enriched sub-continental mantle. The site-specific location and time sequence of magmatism from the marginal parts of South China continent and located at the outer fringe of Namche Barwa syntaxis are strongly significant. It suggests that these magmatic bodies may also be genetically related to the India-Asia collision process and indentation-induced syntaxial buckling of upper mantle beneath the marginal parts of the South China rigid continent.