Li Shuguang graduated from Program of Geochemistry,Dept. of Chmistry, USTC in 1965 and was assigned to teaching in USTC after graduation. From 1983 to 1986 he was doing advanced study in Dept. of Earth and Planet Sciences, MIT. He has been a visitng scholar in Max Planck Institute for Chemistry in Germany and Hongkong University for times. Currently he is serving as professor in USTC, and was elected academician of CAS in 2003.
Prof. Li has done systematic researches in the following field and made a series of innovative research findings. 1) he has made lots of pioneering work in the field of isotopic system in UHP metamorphism and metamorphic chronology theory: found out earlier and proved that there’ are large amount of excess argon in Muscovite of Orogenic eclogites; proved there is disequilibrium of Nd，Sr Isotopic between Ultrahigh-pressure metamorphic minerals and retrograde minerals; was the first to accurately determine the U-Pb ages of Rutile in eclogites. These findings made decisive contributions to accurate UHP dating. 2) he has done long-term and systematic research on the collision process of the North and South China Block and Qinling - Dabie orogenic evolution, and has made significant findings: was the earliest to determine the Sm-Nd age of Coesite-bearing eclogite in Dabie Mountains is Triassic and proved they are the causes of continental crust subduction, which leads to the conclusion that the collosion of North and South China Block happened in Triassic; 3)he was the first to determine a cooling T-t path with two rapid cooling events in UHP rocks, which reveajs a multi-stage rapid uplift history of the UHPM rocks.Based on age and metamorphic grade differences of UHPM rocksin different structural units of subducted continental crust and Pb isotopic mapping in Dabie orogen, he proposed a multi-stage exhumation model for the UHPM rocks in Dabie-Sulu orogen; 4) he applied trend surface analusis, a multi-statistical analysis method, to predict the evolution trend of the rich orebody in Gon Chang Ling iron mine, and concluded a location which was accepted by the Ministry of Metallurgical Industry, a rich layer of 13 meters thick deposit was finally found exactly in the location.Using C Isotopes, he proved that the graphite in magnetite-rich iron ores of Gongchangling is prodused by the metamorphic decomposition of siderite. According to these findings, he proposed a new model for the cause of iron-rich deposit formation. These important contributions to the investigation and formation cause of black rich iron ore won the Second Prize of CAS Science and Technology Award.
All the aboved research findings have attracted much attention from peer experts at home and abroad. He has published over 140 papers, and according to ISI retrieval, from Jan.1,1994 to Oct.31,2004, his 33 papers (as first author) were cited by SCI reference for 667 times, with the average citation frequency of each paper being 20.21 times. His papers’ citation frequency was on the list of top 1000 in the field of Earth Science during the 10 years(Jan.1,1994 to Oct.31,2004). He won Ho Leung Ho Lee Science and Technology Progress Award in 2005 and the Second prize of National Natural Sciences award of China in 2010.
1,Finished project: Metamorphic isotope chronology and collisional process between North China and South China blocks
Accomplished by: Li Shuguang, Liu Yican, Xiao Yilin, Sun Weidong, Li Qiuli
Affiliated with: University of Science and Thechnology of China
Research background: This project represents major achievements in the fields of geochronology, isotope geochemistry and petrogeochemistry.
Studies related to the understanding of continental collision processes and ultrahigh-pressure (UHP) metamorphism have been one of the hottest and most interesting fields in continental dynamics research since the early 1980s, and have provided important knowledge and scientific ideas for developing and improving the plate tectonic theory. The Qinling-Dabie-Sulu metamorphic belt, one of the largest UHP metamorphic terrains discovered so far, formed by the continental collision between the North-China plate and the South-China plate. Studies of the processes and mechanisms of the collision between the two plates and the formation time of the related UHP metamorphic rocks have great significance not only for the development and improvement of the plate tectonic theory, but also for the understanding of the lithosphere evolution under eastern China. For the past 20 years, our group has focused on the geochronology and geochemical investigations on the metamorphic rocks from the East Qinling and the Dabie - Sulu UHP metamorphic belt, aiming to understand the time and geochemical and tectonic evolution related to the collision between the North- and South-China plates and the subsequent continental deep subduction.
Major achievements: The main achievements are summarized into four aspects:
1. We discovered the presence of excess-Ar in phengite from UHP eclogite and thus solved the long-standing problem of Ar-dating results conflicting with ages obtained through other methods. We demonstrated that there is Sr and Nd isotope disequilibrium between eclogitic high-pressure metamorphic minerals and retrograde minerals, which can significantly affect the Sr and Nd dating results for eclogites. Internationally, we reported the first precise U-Pb ages on rutiles from eclogites. Furthermore, we revealed that the bulk Sm-Nd isotopic system of Archean metamorphic volcanic rocks could be reset during their low grade metamorphic process. These discoveries are important contributions to the development of geochronology and continental collision studies, with significant implications for the accurate dating of UHP metamorphic rocks and the correct interpretation of Sm-Nd ages for low grade metamorphic volcanic rocks.
2. We demonstrated before all others that, the collision between the North-China plate and the South-China plate occurred in the early Triassic based on isotopic ages of eclogite. This work settled the long-term debate over the collision time of the two plates. By systematic work, we determined the ages of ophiolites, islan-arc igneous rocks, syn-collision granites, and oceanic crust subduction-related low-temperature eclogites from East Qinling and Dabieshan, as well as the rapid cooling age of the mafic granulites from the Dabie orogen, which revealed the complete chronology of the whole collision process between the North- and South-China plates.
3. For the first time, we determined a cooling T-t path with two fast-cooling stages of the Dabie UHP metamorphic rocks, which revealed a multi-stage rapid uplift history for the UHP rocks. We were the earliest to recognize that different tectonic slices of the Dabie UHP rocks have different Pb isotopic compositions and metamorphic ages. Based on these discoveries, we suggested a multi-stage and multi-slice exhumation model of the UHP metamorphic rocks. According to this model, the subducted contiental crust might have been subjected to detachment or decoupling within the crust along different crust levels to produce multi-slices of UHP rocks which were successively uplifted and exhumed. Such a model is an important improvement on the formerly popular single-slab exhumation model and thus significantly contributes to knowledge about continental plate movement.
4. By systematical investigation, we identified the extensive existence of fluid activity involved during various metamorphic stages throughout subduction to subsequent exhumation of continental crust, and further distinguished the compositional evolution and geochemical characteristics of the fluids and related HP metamorphic minerals (e.g., amphibole). For the first time we obtained strong evidence to show that during continental subduction, fluid/rock interactions may cause significant Nb/Ta fractionation, which is important for understanding the so-called “Nb-Ta paradox” during continental crust formation. Using Sr-Nd-Pb-isotopes as tracers, we found that the subducted South China continental crust could enter the upper mantle for recycling, thus proving that deep subduction of continental crust is an important way for recycling of continental materials.
Significance: These achievements are important and creative contributions to the fields of geochronology, geodynamics and geochemical evolution related to UHP metamorphism and continental collision processes. The above mentioned outcomes of the project were presented as 51 scientific papers published in peer-reviewed international and national journals (38 were collected by SCI). In total, these papers have been cited 1420 times by other authors, of which 8 representative papers (see below) have been cited by other authors a combined 763 times (in the text, the term “cited by other authors” infers citations from other publications in which the authors do not include any author or co-author of the cited paper; based on ISI Web of Knowledge (SCI)). Among the 8 representative papers, three have been cited more than 130 times apiece by other authors, and thus were named “classic papers” in the concerning fields.
2, On going project: “Traceing deep carbon recycle by Ca-Mg isotopes”
Research scientists: Shuguang Li, Shan Ke, Wei Yang, Yongsheng He, Shuijiong Wang, Hongming Zhang
Recycling of marine carbonates into the mantle through subduction zone is an important part of the global C recycles. This process can potentially modify Ca and Mg isotopic variations within the mantle, because marine carbonates typically have lighter Ca and Mg isotopes compared to typical mantle values. Therefore, it is possible to trace deep carbon recycles by using Ca-Mg isotopes. In order to test this hypothesis, a key project of Natural Science Foundation of China (NSFC) “Traceing deep carbon recycle by Ca-Mg isotopes” has been approved in 2012.
This project includes three research contents: (1) Investigation of Ca-Mg isotopic compositions of ultrahigh pressure metanorphic rocks formed by continental subduction and oceanic suduction, respectively, to reveal the possible Ca-Mg isotopic fractionation during dehydration process in subduction zone; (2) Investigation of Ca-Mg isotopic compositions of the Mesozoic and Cenozoic baslts developed in the eastern China and Ermeishan basalts and (3) Investigation of Ca-Mg isotopic compositions of the Mesozoic and Cenozoic mantle derived carbonite rocks and coexisting alkaline rocks developed in western Sichuan province and Shandong province to reveal whether the Ca-Mg isotopic compositions of their mantle sources have been modified by the recycling carbonetes.