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A short-term cooperative visit of Chen Jie and Tan Jintang to Swiss University of Lausanne in 2013

2014/5/22 18:20:39

Under the sponsorship of “Formation Process of the Active Tectonics and Plateaus in the Northeastern Part of Pamir Syntax”, an independent project of the State Key Laboratory of Earthquake Dynamics, at the invitation of Prof. Frederic Herman of University of Lausanne, Researcher Chen Jie and Postdoctor Tan Jintang of the Institute of Geology, CEA paid a 9-day cooperative visit to the Institute of Geosicence, University of Lausanne from August 31, 2013 to September 9, 2013, with a theme of “luminescence low-temperature thermochronology of Pamir”.

Main purposes of this visit: 1) To learn Pecube 3-dimensional thermal motion simulation program; 2) To exchange available results of luminescence thermochronological elevation profile; 3) To establish a standard for sharing luminescence thermochronological data in future cooperation between the two sides; 4) To discuss the research papers of luminescence low-temperature thermochronology to be contributed in the near future as well as the emphasis of the work in the next step.

During the visit, we carried out sufficient exchange and discussion with the members of the research group led by Prof. Frederic Herman on luminescence low-temperature thermochronological measurement and thermal simulation of historical data. Prof. Herman determined the concrete agenda of the visit through discussion with Chen Jie and arranged his colleagues to train us on the program or analyze luminescence measurement data with us based on the specialties of the laboratory personnel. In addition, Prof. Herman and Researcher Chen Jie discussed the conception for further research on the nearly 60 low-temperature thermochronological bedrock samples taken from the Gaizi valley this July and assisted us with the debugging of Pecube program so that the program can run smoothly on different operating system platforms used by us. Dr. Thibaud Simon-Labric was responsible to train us to use the Pecube program. Based on the latest-version Pecube program, Dr. Thibaud gave detailed explanation and hand-on operation guidance in several aspects, including parameter setting of data input documents, possible format errors, how to convert DEM data to make them match the data input requirements of Pecube, and accurate setting of geometric models of faults. In the end, under the guidance of Dr. Simon-Labric, we successfully imported the DEM images of the Kongur Mountains – Gaizi Vvalley of Pamir into the Pecube program, assumed several situations of tectonic uplift and terrain changes, predicted chronological space distribution of each thermochronological system in a normal direction under these situations and compared them with the available measured thermochronological data.

Dr. Pierre Valla and we jointly sorted luminescence thermochronological measurement data, exchanged ideas in relevant calculation procedures and established a standard format for sharing and exchange of data about luminescence thermochronology. Dr. Tan Jintang questioned Swiss calculation result of the abnormal decay rate of IR50C signals of fledspar and pointed out its mistakes. Dr. Valla also introduced a theoretical model for low-temperature infrared luminescence thermochronology of fledspar established by him and the postdoctoral student Benny Guralnik of Prof. Herman and the encouraging latest results achieved by applying the model in German KTB deep drilling samples, and discussed the possibility to apply the model in the obtained elevation profile of low-temperature infrared luminescence thermochronology of Pamir. Researcher Chen Jie also discussed in depth with Dr. Valla on the writing of the research articles based on the existing low-temperature infrared luminescence thermochronology data of Pamir, and determined the rough structure of the articles, preliminary progress that needs to be reported, and core issues to be discussed. The two sides also discussed the experimental work in the next step.

Dr. Geogina King exchanged ideas with us on the latest progress of luminescence dating in measurement methodology, particularly measurement instrumentation reported by international peers at the 2013 British Conference for Luminescence and Electron Spin Resonance held from August 27 to 30 (Note: Researcher Chen Jie and Dr. Tan Jintang planned to attend this conference in Britain before visit to Switzerland, but as the foreign-related approval document of CEA was not available till mid August, British visa and Swiss visa couldn’t be obtained within such a limited time. After deliberation, we had to give up the plan for attending the conference in Britain). Dr. King currently is responsible for construction and operation of the Luminescence Dating Laboratory of University of Lausanne. According to the original plan, during the visit, we would use Swiss Photon Timer and Pulsed OSL Unit to measure the pulse infrared luminescence signals of Pamir thermochronological samples on nanosecond – microsecond scale, but as the radiation system of the instrument was faulty, we couldn’t realize the goal on schedule. Before leaving, we decided after consultation with Dr. King to leave some samples; and when the problem of the instrument is solved, she will assist us completing the measurement.

During the visit, on the one hand, we actively and modestly learned the operating method of Pecube program and drew on their experience in luminescence measurement. On the other hand, we actively introduced them the progress that our research group made in the research of tectonic deformation and geomorphologic process on the northern margin of Pamir in the recent years. Researcher Chen Jie made a lecture titled “Feldspar IRSL-Thermochronology in the Kongur Shan, Eastern Pamir, China”, and systematically displayed the research status of the tectonic evolution history of Pamir, thermochronological dataset relating to the Pamir plateau, particularly, the data of low-temperature infrared luminescence thermochronology of the Konqur tension system completed in the recent two years, arousing great interest of the people attending the meeting and inspiring heated discussion on details of the concrete measurement procedures of luminescence thermochronology and the explanation of thermochronology. Particularly, during free discussion after the report, the two sides came up with new research ideas and planned to explore the basic process involved by luminescence thermochronology by using the unique accessories installed on Swiss laboratory luminescence measurement instruments. Prof. Mark Brandon, a senior scholar in the international low-temperature thermochronology field, from Yale University also attended the report meeting and showed great interest in the report of Researcher Chen Jie. He put forth a few new perspectives and new possibilities to look at the current data and discussed with Researcher Chen Jie on the possibility of future cooperation.

In addition to indoor discussion and exchange, Prof. Frederic Herman also arranged the two people to go to Mont Blanc, the highest peak of Alps for field study together with all the members of his research group on September 4. Mont Blanc is a typical example for applying low-temperature thermochronology in horizontal distribution samples of a tunnel to restore a geomorphic evolution history. During the study, people from University of Lausanne introduced geological structure, fault distribution, geomorphic evolution and remanants of glacial activities. Particularly, people attending the study discussed classical remnants of glaciations at Little Ice Age and glacial recession in the recent years in Alps.

Generally, the content of the visit in 9 days is rich. We basically knew the use of the method and logical framework of Pecube program and displayed the preliminary understanding of Chen Jie’s research group on the tectonic evolution history of Pamir and their unique advantage in luminescence dating samples and measurement technology; effectively summarized the multi-system thermochronological data obtained in the early stage, particularly the low-temperature infrared luminescence thermochronological data. And meanwhile we established the research task and objective in the next step, which is to constrain the thermal stability of mineral luminescence samples by using the samples with temperature measurement record obtained from the diversion tunnel of Bulunkou Hydropower Station on Pamir and to correct the influence of topographic relief on apparent uplift speed by using these samples.

During the visit, we made utmost effort to learn the Pecube program, but the time of nine days was too short, we could only complete the part of normal simulation in the expected goal. Swiss experts strongly suggested that we arrange more sufficient time to visit Switzerland in 2014 so that the two sides may work together to apply the Pecube program in normal and reverse simulation of available thermochronological results and restoration of the activity history of the Kongur normal fault and the geomorphic evolution history of its neighboring areas.

The short nine days’ cooperative visit provided us a chance to exchange ideas face to face with international topnotch scholars in the field of low-temperature thermochronology and made us quickly know the cutting edge of international research on luminescence thermochronology and familiarize the current technical bottlenecks. It raised our sense of urgency and boosted our confidence. In the future bilateral cooperation, we should continue to play the advantage of our luminescence dating laboratory in luminescence dating methodology and technology, explore, from the aspect of luminescence measurement, luminescence signals more suitable to the research of thermochronology, and develop more concise and accurate methods to extract thermal information from thermochronology. Swiss scholars have rich experience in explanation and numerical simulation of thermochronological data. We will take it as an opportunity of cooperation, learn modestly from Swiss scholars by all chances and raise our ability in the research and exploration of numerical simulation and quantitative expression of the influence of tectonic activity on earth surface process.