The 4th workshop in Australia and NC
Source:    Publish Time: 2018-07-27 16:25   261 Views   Size:  16px  14px  12px

            The fourth IGCP 649 Workshop successfully held in Australia and New Caledonia


   IGCP-649 project has successfully organized the 4th 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 is sponsored by the IGCP-649 project “Diamonds and Recycled Mantle” and led by Prof. Jingsui Yang (CARMA, Institute of Geology of CAGS, China) and Prof. Jonathan Aitchison (School of Earth and Environment Sciences, The University of Queensland, Australia). The workshop was efficiently organized, presented numerous warm discussions, and was combined with a substantial field trip.

More than 70 scientists from China (including Hong Kong), Australia, New Caledonia, USA and Russia attended this workshop, and 60 of them participated in the after-workshop field trip. The Chinese attendees come from 12 distinguished institutes, including 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, the Institute of Geology in Chinese Academy of Geological Sciences, the Institute of mineral resources in Chinese academy of geological sciences, and Xi’an Center of China Geological Survey. A large group of young scientists attended the international conference. They played a significant and active role in this workshop, not only with the oral and poster presentations but also with the field-trip discussion.

 The workshop was held on 5th and 6th July, 2018 and hosted at the School of Earth and Environment Sciences at the University of Queensland, St Lucia Campus, Brisbane. It included 25 oral talks and 21 poster presentations, which covered different scientific issues, such as the origin and formation mechanism of diamonds in different types of oceanic peridotites and chromitites, the features and genesis of different types of chromitites worldwide, the HP and UHP metamorphic rocks in the world-class orogens, and the reconstruction of paleo-oceanic tectonic framework and paleo-environment.

The post-workshop filed trip was composed of seven days (7th-14th July) to investigate the ophiolite and chromitites in New Caledonia. New Caledonia is one of the best examples anywhere of an arc-continental collision system. It consists of a collage of Cretaceous to Paleogene terranes that developed along, or were accreted to, the NE margin of a rifted fragment of the Australian plate. The basement of New Caledonia includes rocks that were once accreted to the continental margin of eastern Gondwana. It is overlain by Upper Cretaceous to Eocene sedimentary rocks deposited during Gondwana dispersal. A vast, but now erosionally dissected nappe of ultramafic rocks, the New Caledonia Peridotite Nappe, structurally overlies much of the island. It is interpreted to have been emplaced during collision between an intra-oceanic island arc and the above-mentioned continental fragment that had rifted-off from the eastern margin of Gondwana. Eocene sediments on the island record the arrival and obduction of the structurally underlying Poya basalts. The famous blueschist to eclogite facies rocks, which crop out in the NE of the island are inferred to have experienced high-P metamorphism in response to the attempted subduction of the crustal basement terranes of New Caledonia beneath the Eocene oceanic island-arc subduction system. 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). 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 geology in New Caledonia.

IGCP-649 is a global research programme, which is undertaken by Center for Advanced Research on Mantle (CARMA) of Institute of Geology, CAGs. This project will conduct extensive and systematic researches on peridotites, chromitites and related unusual minerals (diamond, moissanites and other unusual minerals) from different ophiolites in global orogenic belts, to discuss and understand new scientific problems such as the formation and origin of deep-mantle minerals in oceanic lithosphere, the origin of carbon source for “Luobusa-type” diamond, the evolution of earth mantle and the dynamic process of ophiolite emplacement. IGCP-649 project lasting for five years (2015-2020) were awarded and sponsored by UNESCO and IUGS. In August of 2015, the First Ophiolite Workshop was held in Xining of Qinghai Province, China. After the workshop, participants were organized to investigate the Early Paleozoic ophiolite and high-pressure metamorphic belt in Qilian Mountain. The Second Ophiolite Workshop was held in Cyprus. Field trip was organized to investigate the world-renowned Troodos ophiolite. The Third one was held in Cuba, and organized to investigate the Mayarí-Baracoa ophiolite and chromitites in eastern Cuba. 


The geological sketch of New Caledonia (Pirard et al., 2013, JP)


Conference welcoming address given by Prof. Jonathan Aitchison, Head of School of Earth and Environmental Sciences, The University of Queensland, Australia.


Prof. Jingsui Yang, a leader of IGC-P649 project made an introduction of IGCP-649 project.


 


Dr. Vladimir Shmelev, Institute of Geology and Geochemistry, Ural Branch of RAS, Russia gave a talk named Diamond-bearing occurrences of the Ural-Timan Fold Belt (Russia): The result of ultra-deep subduction?



Prof. Peter Olds from College of Alameda, United States of America gave a talk named Impacts and exposed lithospheric mantle: A way to recognize large terrestrial impact basins?



Dr. Pengfei Zhang from The University of Hong Kong, Hong Kong gave a talk about Melt events in a nascent mantle wedge: Implication from the Luobusa ophiolite, Tibet.










Prof. Dominique Cluzel from the University of New Caledonia gave descriptions and explanations of geology in New Caledonia in the field.



Outcrops of dunite/pyroxenite cumulates in the Moho transition zone



A locality famous for early Eocene-aged boninites in which twinned clinoenstatite crystals may sometimes be observed.



Outcrops of pillow lavas in the Koh terrane, an intra-oceanic island arc system of Carboniferous/Permian age.



Investigation on the Tiebaghi Cr mine in the Tiebaghi massif. The massif, which represents less than 2% of the total peridotite cover, has supplied more than 80% of New Caledonia chromite production and was once the largest chromite mine in the world and in 1941 alone, produced about 54,000 tons in a single year.



  Hand specimens of different types of classical chromite ore in the Tiebaghi Cr mine.


 

 Outcrops of lherzolite with clinopyroxene veins in the Tiebaghi massif.



Investigation on classic high P/T metamorphic rocks in the NE of Grand Terre



Outcrops of eclogite and blueschist in the Diahot and Pouebo terranes.



Discussion and communication in the field



Discussion and communication in the field



Discussion and communication in the field



Discussion and communication in the field



Discussion and communication in the field



Discussion and communication in the field



Group photo in the filed of the fourth International Workshop of IGCP-649 Project