A seminar on the CAOB in the University of Hong Kong
Organizers: Prof Guochun Zhao; Ass. Prof. Zhonghui Liu
Talk 1 "Continental Construction in Central Asia and Deep Mantle Processes" by Inna Safonova
Talk 2 "New data on lake evolution in northern Central Asia"
by Sergey Krivonogov
IGCP Project #592
"Continental construction of the Altaids
(Central Asian Orogenic Belt) compared to actualistic examples from the Western Pacific"
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 the Western Pacific.
The main goal is to undertake a broad-scale and multi-method investigation of continental construction in the Central Asian Orogenic Belt (CAOB or Altaids) 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 (formation of juvenile crust);
2) crustal formation (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 of the CAOB and across them within the whole orogenic belt.
Four geological transects crossing these areas will be studied:
1) Russian Altai-Chinese Altai-Mongolian Altai;
2) Kazakhstan-Kyrgyz-Chinese Tienshan;
3) Sayan-Transbaikalia (Russia) - northern Mongolia-Southern Mongolia - Inner Mongolia (China);
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.
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, Indonesia, Tasmania, Australia).
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.
Areas of Interest (AOI) and transects (Tr) to be studied in the frame of IGCP#592
Schematic cartoon for four stages of continental construction
(modified from Groves et al., 1998)