Projet 592 - Continental construction in Central Asia

Understanding how does continental crust form, overgrow and evolve is a highly important Earth Science problem. The focus of the newly proposed IGCP project is continental crust construction in Central and East Asia and its desktop comparison with Western Pacific. The project is planned as a successor to IGCP 480 (Tectonics of Central Asia), 420 (Phanerozoic Crustal Growth) and, to some extent, 283 (Evolution of the Paleo-Asian Ocean). The complementary projects could be regarded IGCP 574 (Bending and Bent Orogens and Continental Ribbons), 516 (Geological Anatomy of East and South East Asia), 473 (GIS Metallogeny of Central Asia), 436 (Pacific Gondwana Margin), 321 (Gondwana Dispersion and Asian Accretion), and 224 (Pre-Jurassic Evolution of Eastern Asia) and a separate USGS-Russia project on "Metallogenesis and Tectonics of Northeast Asia".

However, none of those previous and current IGCP and other projects addressed key goals, objectives, questions and tasks of this proposal in their interrelationships, whereas we will build upon those precursor data, fill the remained gaps, solve the unanswered questions and introduce all previous and new data into a single holistic pattern of continental construction.

The main goal is to undertake a broad-scale and multi-method investigation of continental construction in the Central Asian Orogenic Belt (hereinafter CAOB) in order to prove that the Phanerozoic was an important period of juvenile continental crust formation versus an idea of its dominantly Archean origin.

The specific goals are linked with distinguishing main stages of continental construction:

1) crustal growth (juvenile crust) and

2) crustal formation (recycled crust);

3) continental growth (accretion minus tectonic erosion);

4) continental formation (collisional processes).

All these stages will be carefully reconstructed within each individual orogenic belt and across them within the whole orogenic belt: Altai-Sayan and Transbaikalia (Russia), Eastern and Central Kazakhstan, Kyrgyz Tienshan, Chinese Altai and Tienshan, Russian Far East.

Four geological transects crossing these areas will be studied:

1) Russian Altai-Chinese Altai-Mongolian Altai;

2) Kazakhstan-Kyrgyz-Chinese Tienshan;

3) Transbaikalia (Russia) - northern Mongolia-Southern Mongolia - Inner Mongolia (China);

4) Primorje-Japan-Korea. The reconstruction will be based on the currently available and expected future data (mainly geochronological, geochemical and geophysical).

The inferred processes, events and mechanisms of continental construction will be carefully compared in relative aspects (geochronological isotopic ages, geochemistry, structural styles, tectonic patterns, lithology, etc.) with the present-day or recent/Quaternary examples from the Western Pacific (north to south: Japan, Korea, East China). These regions have been better studied than the Central Asian Orogenic Belt and will be used for comparison, i.e. for desktop studies.

Another important specific goal to be reached is which social benefits or geohazards are related to the formation of huge orogenic belts, such as the Altaids including formation of minerals deposits and surface/environmental impact through volcanism and seismicity.

All this would finally allow us to reconstruct a whole evolutionary pattern of this huge orogenic system. During previous projects many questions have been solved, however, much more new appeared and their solution requires truly integrative activity of a multi-country team with leaders directly from the countries within the region of investigation (Russia, China) and those who have obtained a great experience in organizing and performing scientific research in that region during many years (UK, France). Undoubtedly, such a team will be capable not only to organize scientific meetings, but to accomplish the whole regional and methodological spectrum of field and analytical works and thus will guarantee the successful performance of the Project.

The Project will be based on an interdisciplinary approach including U-Pb and Ar-Ar isotope geochronology, igneous and metamorphic petrology, isotope (Hf-Sm-Os-O) and major/trace element geochemistry, lithology, sedimentology, micropalaeontology, tectonics, structural analysis, palaeomagnetism, geophysics, metallogeny and environmental geology.

Retour en haut de la page