​​​​​Orogenic Architecture and Crustal Growth 

from Accretion to Collision

IGCP 662
Leaders
Present state of activities
      There are many activities in the field of the proposed project, as its scope is geologically and geographically broad.
Present state of activities in the CAOB
Chinese activities
      The Chinese research group participated in 4 IGCP Projects (420, 473, 480 and 592) on the CAOB. Dawei Hong and Tao Wang, as leaders of the Chinese working group of IGCP420, undertook research in the Altai Mountains and Inner Mongolia of China.
      The Chinese Government supported many projects to study the CAOB. Three 4-year China National Basic Research Program (973 Program) focusing on the CAOB in China were supported since 2002 (e.g., Wenjiao Xiao, 2011-2014). The National Natural Science Foundation of China (NNSFC) also supported many multidisciplinary studies in China, such as “Accretionary orogenesis in the Beishan (Wenjiao Xiao, 2011-2014)” and “Spatialtemporal distribution of deep ancient and juvenile continental crust and its constraints on metallogenesis of northern Xinjiang and adjacent areas (Tao Wang, 2015-2018). Tao Wang and his colleagues also obtained support for three international (China-Russia) cooperation projects by the NNSFC.
     Tao Wang also undertook several key projects supported by the Geological Survey of China. Recently, Wang and his team conducted isotopic mapping and made new discoveries on the magmatic evolution, continental growth and tectonic division (e.g., Zhang et al., 2016;2017; Yang et al., 2016). At the 35th International Geological Congress in Cape Town, South Africa, 2016, Wang, Isokov, Seltmann et al., organized a symposium related to the CAOB. In addition, Tao Wang participated in the construction of the International Geological Map of Asia (led by Chinese Academician Jishun Ren, 2015) and compiled a map of granitoids and related rocks in Asia and established a coprresponding database.

Russian activity in CAOB studies
     Russian scientists led two IGCP Projects (#480 and # 592) on the CAOB and organized several International workshops and field excursions. The Russian Government also supported many studies of the CAOB. During the last 15 years there were special collaborative projects for Russia-China and Russia-Mongolia teams. From 2003 until 2015 the RAS supported the special Project “Evolution of the lithosphere of the Central Asian Orogenic Belt: from Ocean to Continent”.
      The Novosibirsk group undertook research projects in the Altai-Sayan region and even in the whole of Central Asia (e.g., Safonova, 2017). The Moscow-St. Petersburg group carried out studies on regional geology, igneous rocks (isotopic systems) and tectonics in the central CAOB (e.g., Kovalenko, 2003). The Russian Far East group also undertook extensive research on the tectonics, igneous rocks in the Far East (e.g., Sorokin et al., 2010; Kotov 2013). The Irkutsk group undertook research in eastern Siberia and Mongolia (e.g., Gladkochub et al., 2005-2008). Moreover, D. Gladkochub is co-leader of the multidisciplinary project of the Siberian Branch of RAS (# 0346-2015-0066, 2015-2019).

Progress and open questions on the CAOB
    The above projects and activities led to extensive cooperative research. However, many questions still remain, such as: (1) Detailed orogenic processes: was there Paleozoic subduction-accretion along several huge magmatic arc systems or accretion of oceanic arcs and/or Gondwana-derived continental blocks to the Siberian and North China cratons? (2) When, where and how much crustal growth occurred in the CAOB and what are the proportions of juvenile vs. recycled crust? (3) What are the characteristics of metallogenesis in the CAOB?

Present state of activities on the Tethyan orogen
       International activities in the Tethyan-Himalayan area
      The Tethyan orogen has long attracted geologists around the world for collaborative research. Since the 1980s, numerous cooperative studies were undertaken. These mainly focused on the tectonics and geophysics of the Tibetan plateau (e.g., INDEPTH project). A Himalayan-Karakorum-Tibet (HKT) Workshop is held once every two years. IGCP Project 600 (2011-2015, led by Zengqian Hou) is one of the IGCPs in this domain on Earth Resources. This  project focused on the Tethyan metallogenic belt.
      Chinese activities in the Tethyan-Himalayan area
    Many significant projects supported by China were carried out, such as National 973 projects and key projects of NNSFC. Two National 973 projects focused on collisional tectonics and metallogeny of the Tibetan orogen (led by Hou). Zengqian Hou also led an international cooperation project supported by NNSFC (2014-2018). These investigations proposed a new conceptual framework for the Tibetan metallogenic systems and contributed to an expansion of knowledge about the metallogenetic character of collisional orogens and will promote further understanding of collisional metallogeny.

Other international activities in other relevant orogens
     Chinese geologists (e.g., Guowei Zhang’ group and Yongfei Zheng’ group) have carried out detailed studies on the CCOS (China Central Orogenic systems). The western segment, i.e., the Kunlun-Qinling orogeny is suggested to have been an accretionary orogen (e.g., Yan et al., 2006). The eastern segment, i.e., the Dabie orogen, was a collisional orogen between the North China and Yangtze plates in the Late-Triassic.
      The Appalachian Mountains of eastern North America are part of a famous Paleozoic orogen, and many studies have been undertaken (e.g., van Staal and Barr, 2012). Several recent activities have been organized, such as a field excursion in the Newfoundland Appalachians, led by C. van Staal (2017).
    The Paleozoic Lachlan Orogen of eastern Australia is also considered to be a composite orogen (Fergusson & Coney 1992a). Numerous studies and activities have been undertaken, including many field excursions such as the 2017 Field Symposium on Tectonics of the Australian Lachlan Fold Belt and granite petrogenesis, led by Professor W.J. Collins.
    In summary, extensive cooperative research has been carried out on the sources of granitoids, orogenic processes, crustal architecture and continental growth as well as metallogenesis of the CAOB, The Tethyan belt and other orogens, have also received much scientific attention. Numerous papers in high-impact journals such as Nature, Science, EPSL, Geology, etc. were published. These provided a solid base for further comparative studies, including the source of magmatism and continental growth by isotopic mapping, crustal architecture and metallogenesis. The proposed project will promote continuing studies in following previous ICGP projects and provide a good opportunity to link them for more synthesized and comparative studies and promote quantitative approaches to describe orogenic processes and continental growth.