Abstract
We report a new model of the structure of the crust in Siberia that encompasses two large tectonic regions, the Paleozoic West Siberian Basin and the Precambrian Siberian craton. The area of study covers a significant part of the north Eurasia and extends from the Ural mountains in the west to the Verkoyansk Ridge/Lena river in the east, and from the Arctic shelf in the north to the Tien Shan and Altay-Sayans mountains in the south. The new crustal model is based on our new ("from scratch") compilation of all available reliable seismic data and includes the results of seismic reflection, refraction and receiver functions studies, based on old and newly acquired seismic data (from the late 1960-ies until present). Seismic structure along seismic profiles is digitized with a 50 km lateral spacing which is comparable with the resolution of seismic models. Structural parameters based on gravity modeling, or tectonic similarities, or seismic data reported not along seismic reflection/refraction profiles but as interpolated contour maps are excluded from the new crustal database. Due to uneven quality of seismic data related both to data acquisition problems and interpretation limitations, a special attention is paid to the data quality problem, and quality parameters are incorporated into the new database of regional crustal structure. The present database comprises detailed and reliable information on the seismic structure of the crust for most of the tectonic structures of the region and provides valuable constraints for geophysical modeling of the mantle structure. We observe important spatial correlations between the crustal structure (thickness of the sediments, the basement, and different crustal layers, and average basement velocities) and tectonic and geological settings. Statistical analysis of age-dependence (we use tectono-thermal ages) of crustal parameters allows for distinguishing the effects of various tectonic processes on the crustal structure. The analysis provides the basis for studies of crustal evolution and geodynamic process in the region where the age of tectonic structures spans over ~4 Ga. Archean terranes have a large (39-44 km) thickness of consolidated crust (excluding sediments), which decreases in Paleo-Mesoproterozoic terranes to 34-42 km. Thickness of consolidated crust in Mesozoic and Cenozoic regions is 32-34 km only. The total crustal thickness (including the sedimentary layer) is the largest in the Paleoproterozoic and Mesoproterozoic regions of the Siberian Craton. A block with an unusually thick crust (47-58 km), bounded by the regions of thinned crust, extends in the longitudinal direction across the Siberian craton and cuts major tectonic boundaries which have sublatitudinal orientation. Low surface heat flow (on average around 20-22 microW/m3) and the absence of the high-velocity (Vp>7.2 km/s) lowercrustal layer in the block with the thick crust suggest that eclogitization in the crustal root was subdued, thus allowing preservation of the ultra thick, seismically distinguishable, crust.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | EOS Trans. AGU |
| Vol/bind | 91(52) |
| Sider (fra-til) | S13A-1965 |
| Status | Udgivet - 2010 |