IGCP-649 project “Diamonds and Recycled Mantle” has successfully organized the 4th IGCP-649 Diamonds and Recycled Mantle Workshop at The University of Queensland (Australia) and an 8-day field trip after the workshop in New Caledonia during 5-14, July, 2018. This workshop was efficiently organized, presented numerous warm discussions, and was combined with a substantial field trip. Eight attendees from China University of Geosciences (CUG-Wuhan) included Prof. Jian-Ping Zheng, Prof. Chang-Qian Ma and other scholars in the field of geology, geochemistry and geo-engineering. All CUG-Wuhan attendees felt that this fantastic workshop and following field trip was extremely helpful for their geological understanding and critical thinking. The main features of this workshop and field trip were:

(1) A large group of young scientists attended the international conference. More than 70 attendees are from China (including Hong Kong), Australia, New Caledonia, USA and Russia, and 60 of them attended the after-workshop field trip. The Chinese attendees come from more than 10 distinguished institutes, including the Institute of Geology in Chinese Academy of Geological Sciences, Peking University, Nanjing University, China University of Geosciences (Wuhan), The University of Hong Kong, Northwest University (Xi’an), Jilin University, University of Science and Technology of China, Institute of Geology and Geophysics in Chinese Academy of Sciences, Guangzhou Institute of Geochemistry in Chinese Academy of Sciences, and Xi’an Center of China Geological Survey. Prof. Jonathan Aitchison from the University of Queensland and Prof. Dominique Cluzel from the University of New Caledonia led the field trip and gave very detailed descriptions and explanations of the geology in New Caledonia. The young scientists played a significant and active role in this workshop, not only with the oral and poster presentations but also with the field-trip discussions. The oral and poster presentations of young scientists have accounted for 64% and 52%, respectively, of the presentations.

(2) The workshop lasted two days at The University of Queensland, and included 25 oral talks and 21 poster presentations. The talks covered a wide range of scientific aspects, such as the origin and formation mechanism of diamonds in different types of oceanic peridotites and chromitites, the comparison of chromitite features and genesis from the whole world, the investigation of high-pressure and ultrahigh-pressure metamorphic rocks and subduction fluids in the world-class orogens, and the reconstruction of paleo-oceanic tectonic framework and paleo-environment. Most of the talks were innovative, interesting, and warmly discussed.

(3) The field trip in New Caledonia was well organized and included plenty of classic geological phenomena. The main basement of New Caledonia was rifted and derived from East Australia during the end of late Cretaceous, and then experienced a series of complex geological processes, including the oceanic plate subduction, arc-continent collision, exhumation of high-pressure rocks and obduction of ophiolites. New Caledonia’s tectonic history has left numerous classic geological “foot-prints” in New Caledonia and preserved accumulations of economically important metals (Cr, Ni, Co) originating from the mantle, the subduction factory and the Earth’s surface weathering environment. The observations and discussions of the geology among attendees have expanded our understanding, inspired our thinking, increased our knowledge and promoted our friendship.

In summary, this workshop concentrated on frontier topics such as the evolution of oceanic lithospheric mantle, the formation processes of ophiolite and the origin of chromitite; in addition, the outcomes presented in the workshop represent the recent research progress in several geoscience fields. The field investigation of the biggest “red soil”-laterite type of Ni deposits and the chromitite ore deposits in New Caledonia has greatly promoted our understanding of the geological background for metallogeny, and will help to provide new clues and ideas for targeting nickel and chromitite prospects in China and all over the world. We suggest that we have to: (1) choose typical ophiolites, chromitite deposits and subduction systems in the world for the future field investigations, (2) facilitate international cooperation, and (3) enhance geological training for young scientists. Carrying out the above suggestions will ensure that Chinese scientists will lead the research in mantle recycling and chromitite formation in the world.

18-July-2018