Permian palaeomagnetism of East Kazakhstan and the amalgamation of Eurasia

Most of Kazakhstan belongs to the Ural–Mongol belt, the tectonic evolution of which is poorly understood as demonstrated by disparate tectonic models suggested thus far. We undertook a palaeomagnetic study of Upper Permian basalts and andesites from two localities in east Kazakhstan in order to evaluate the final stages of the evolution of this belt and Eurasian amalgamation. Thermal demagnetization revealed a single pre-tilting characteristic component of ubiquitously reversed polarity from all samples. The mean declination of this remanence from one locality agrees rather well with the Permian European palaeomeridian, whereas that from the other is clockwise rotated by 28°± 8° . The overall mean inclination of −49°± 4° differs by 9.7°± 4.2° from the reference inclination calculated, for our localities, from the Eurasian mean pole for the 245–260 Ma interval and is in agreement with 260–275 Ma data. We account for the observed pattern by either a slightly erroneous rock age (lithologies are somewhat older than indicated by geological data) or non-dipole (octopole) components of the geomagnetic field. Because significant relative motion of the study area with respect to Eurasia is not demonstrated, we conclude that welding of Kazakhstan, Europe and Siberia was essentially completed by Mid-Permian time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73262/1/j.1365-246X.2003.01879.x.pd

Unraveling the early-middle Paleozoic paleogeography of Kazakhstan on the basis of Ordovician and Devonian paleomagnetic results

It is a common concept that different tectonic units in the western part of the Central Asian Orogenic Belt were united into the landmass of the Kazakhstania continent in the Paleozoic but many important details of its history remain enigmatic and controversial. Recently published paleomagnetic data from this region demonstrate that the ~. 2000. km long horseshoe-shaped Devonian Volcanic Belt was created by oroclinal bending of an originally rectilinear active margin of Kazakhstania. Still, the Silurian and Devonian paleomagnetic results which this interpretation is based upon are limited and unevenly spread along the belt, and additional middle Paleozoic data are highly desirable. Accordingly, we studied three mid-Paleozoic objects from different segments of this volcanic belt. Two of the three new objects yielded paleomagnetic directions that fit perfectly into the oroclinal scenario, whereas the third one provided no interpretable data. The earlier history of Kazakhstania, however, remains misty. We obtained three new Ordovician results in north-central Kazakhstan and found similar inclinations but widely dissimilar declinations. Previously published data show a large scatter of Ordovician declinations in South Kazakhstan and Kyrgyzstan as well. We analyzed all seven Middle-Late Ordovician paleolatitudes and came to the conclusion that a nearly E-W trending active margin of the Kazakhstania landmass had existed at low (~. 10°S) latitudes at that time. We hypothesize that this margin of the Kazakhstania landmass collided with another island arc, called Baydaulet-Akbastau, and with the Aktau-Junggar microcontinent by the Ordovician-Silurian boundary. As a result of this collision, subduction ceased, and regional deformation, magmatism, and rotations of crustal fragments took place in most of Kazakhstania. In Silurian time, Kazakhstania moved northward crossing the equator and rotating clockwise by ~ 45°. This changed the orientation of the Kazakhstania to NW-SE, and thereby established the (rectilinear) predecessor of the modern curved Devonian Volcanic Belt

Geochemistry, mineral chemistry and Re–Os isotopes of refractory peridotites of the North Balkhash ophiolite zone in the West Central Asian Orogenic Belt (Central Kazakhstan): multi-stage melt evolution of a Late Precambrian forearc mantle

Supplementary Figure S

Geochemistry, mineral chemistry and Re–Os isotopes of refractory peridotites of the North Balkhash ophiolite zone in the West Central Asian Orogenic Belt (Central Kazakhstan): multi-stage melt evolution of a Late Precambrian forearc mantle

Supplementary Figure S