Extensional Tectonics from Rifting to Oceanic Basin Formation: Questions and Challenges

Abstract:

Extensional Tectonics has been responsible for opening of the Earth’s large oceanic basins along the passive margins. One important question in regard to extension along the passive margins is this; when and how does extension stop in the large extensional basins such as Atlantic Ocean and the basin starts to contract? Many present day extended terrains such as the Basins and Ranges of North America and the Aegean region of Eastern Europe and Western Asia experienced collisional tectonics preceding large-scale extension and metamorphic core complex formation. A key question in these regions is this: “How does this work?” Is this type of tectonic and petrologic succession “normal” for collisional mountain belts due to gravitational collapse of over thickened crust, or, alternatively, extension may be driven by other forcing factors, such as slab roll-back or continental escape, as in the Aegean Region. This basic question has been debated ever since the discovery of the metamorphic core complexes in the Basins and Ranges of North America in the early 1980s. Other questions of extensional tectonics include determining a) evolution of extensional basins; b) the role of strike-slip faulting in extensional processes; c) amount and percentage of cumulative extension in regions experiencing continental extension; d) geometry of extensional features in the middle and lower crust; and e) seismic hazards. However, there are also extended terrains that did not experience a previous compressional tectonics such as narrow rifting in East African rift valley, and Baikal rıft zone. The main question in the narrow rift zones is this; how do they relate to upper mantle and asthenospheric flow? Extensional basins contain very valuable earth resources, such as oil and gas, precious metals and borate mineral. Therefore, a complete understanding of extensional tectonics processes are very important not only for a better understanding of the Earth’s tectonics evolution, but also for developing a better exploration strategies of the valuable Earth resources.