Print this pageThere has long been controversy on the characteristics, the evolution, and the tectonic significance of the Altun fault zone, a Cenozoic crustal scale strike-slip fault zone in mid-Asia. This paper presents some of the results of macro- meso- and microscopic analysis on structural styles in extensively metamorphosed and highly deformed blocks of different origins in the fault zone, which suggests a complicated progressive history of fault zone development.
A main stage of deformation with the occurrence of mylonites occurred at T: 270-350°C and P: 0.05-0.45GPa using mineral thermometer and barometer of, e.g. chlorite and phengite from midProterozoic, Paleozoic and Jurassic rocks. Sinistrial displacement up to 400km is deduced from the correlation of sedimentary and structural characteristics of the two displaced counterparts (Qilian mountain and Hongliugou) of a Paleozoic aulacogen on both sides of the fault zone. The present oil- and gas-bearing Qaidam and Tarim basins separated by the fault zone are of an united basin in Jurassic and Tertiary, which is indicated by: 1) extension of Jurassic sedimentary facies from Qaidam basin to Tarim basin; 2) the continuous distribution of heavy minerals in Tertiary and Jurassic sediments acrossing the fault zone; 3) the occurrences of Mesozoic-Tertiary sedimentary rocks on the top of the Altun Mountain. They further suggest the Cenozoic (since late Oligocene) development of sinistrial strike-slipping of the Altun fault zone due to the progressive collision of Indian with Eurasian plates.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid