Cherskii Mountains Study, Sakha Republic

Principal Investigator: David Stone

The original project was set up to understand the present-day tectonic activity and the tectonic history of the Sakha Republic (ex-Yakutia). We started the project in 1990 with a reconnaissance field program to see what cooperative studies could be carried out with the scientists of the Yakutsk Science Center. It has since developed into a major program of paleomagnetic, geochronologic and structural geology studies combined with investigations of present day seismicity. The main focus of the whole program has been to investigate the geologic origin of what is known as the Kolyma Structural Loop (KSL). The KSL stands out on geologic maps of the area east of the Verkhoyansk mountain ranges as a horseshoe-shaped map pattern. This pattern is formed by exposures of rock types that include Paleozoic shelf sediments, island arc volcanic rocks, slices of oceanic crust (ophiolites) and major belts of intrusive rocks.

The principal findings of the geochronologic studies are discussed under 'Geochronologic Studies of Yakutia' and involve obtaining much more precise control over the ages of emplacement of the major intrusive rocks that most clearly outline the KSL, and obtaining data relating to the age and history of the belt of associated ophiolitic rocks and the volcanic rocks representing the ancient volcanic arc.

The main thrust of the paleomagnetic work done so far has been to investigate whether the KSL was originally formed with the horseshoe shape seen today, whether it is an example of oroclinal bending, or whether it is made up of disparate fragments which have more or less accidentally gathered in this pattern. So far the paleomagnetic studies have been plagued with discoveries that most of the rocks have had their original magnetizations completely overprinted by some later event. This magnetic overprint is so pervasive that it has now turned into a major focus of this work. The principal reason for this is the huge area over which this remarkably consistent near-vertical overprinting magnetization is found. We have concluded that since this remagnetization affects rocks of all lithologies it has to represent the effects of a major geologic event, and thus its timing and origin are important to understanding the history of the area. Our preliminary conclusions are that the overprint occurred at roughly the same time that the intrusive rocks were emplaced, but point to a chemical rather than a thermal cause for the remagnetization. Our currently favored hypothesis is that the remagnetization was the result of the migration of hot fluids associated with the compressional events associated with the formation of the major fold and thrust belts of the area.

Current news |Research disciplines| People|Current Research Topics|
Student Research Opportunities|Analytical Facilities| Publications | Home Page