Fifteen years of the Chinese Continental Scientific Drilling Program

Science Reports Sci. Dril., 22, 1–18, 2017 www.sci-dril.net/22/1/2017/ doi:10.5194/sd-22-1-2017 © Author(s) 2017. CC Attribution 3.0 License. Fifteen years of the Chinese Continental Scientific Drilling Program Zhiqin Xu1,2 , Jingsui Yang2 , Chengshan Wang3 , Zhisheng An4 , Haibing Li2 , Qin Wang1 , and Dechen Su2 1 State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China 2 Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China 3 School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China 4 State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China Correspondence to: Qin Wang () and Dechen Su () Received: 24 October 2016 – Revised: 10 March 2017 – Accepted: 13 March 2017 – Published: 31 May 2017 Abstract. Continental scientific drilling can be regarded as “a telescope into the Earth’s interior” because it provides process insight and uncompromised samples of rocks, fluids, and even sampled from the deep biosphere from the Earth’s surface to great depths. As one of the three founding members of the International Continental Scientific Drilling Program (ICDP), ICDP China has made great achievements in many scientific drilling-related research fields. Based on the ICDP participation it attracted global attention of scientists and set up not only the Chinese Continental Scientific Drilling (CCSD) Program in 2001 but also a growing number of ambitious drilling projects in the country. The 5158 m deep borehole of the CCSD project at Donghai County in the Sulu ultrahigh-pressure metamorphic terrain demonstrates that large amounts of crustal rocks of the South China Block have been subducted to at least 120 km, followed by rapid uplift. After successful completion of drilling at Donghai, several continental scientific drilling projects were conducted with funding of the Chinese government and partially with support of ICDP, resulting in a total drilling depth of more than 35 000 m. These projects encompass the Continental Environmental Scientific Drilling Program of China, the Scientific Drilling Project of Wenchuan Earthquake Fault Zone, the Continental Scientific Drilling Project of Cretaceous Songliao Basin, and the Program of Selected Continental Scientific Drilling and Experiments. On the occasion of the 20th anniversary of the ICDP and the 15th anniversary of the CCSD Program, this paper reviews the history and major progress of the CCSD Program. 1 Introduction Flying into the outer space, going into the Earth’s interior, and investigating the deep ocean floor have been dreams of mankind for the exploration of the nature. Numerous exploration projects to the space and the ocean floor have been carried out since 1950s. Twenty years have passed since the foundation of the International Continental Scientific Drilling Program (ICDP) in 1996. Symbolized as “a telescope into the Earth’s interior”, the ICDP aims to provide fresh samples from great depths to reveal the complex com- position and structure of the continental crust, the Earth’s fluid system, microbiological distribution, geothermal energy, and earthquake mechanisms. Chinese scientists were involved in many ICDP projects and contributed to the success of the ICDP in many research fields. The ICDP only supports projects that address fundamental scientific issues of global significance. One of the most exciting discoveries in the last 3 decades is the global distribution of coesite- and diamond-bearing ultrahigh-pressure (UHP) metamorphic terranes, demonstrating that low-density continental material could be rapidly subducted to depths greater Published by Copernicus Publications on behalf of the IODP and the ICDP. 2 Z. Xu et al.: The Chinese Continental Scientific Drilling Program than 100 km and then exhumed to the surface (Zheng, 2012; Hermann and Rubatto, 2014; Liou et al., 2014). Hence, continental subduction played a critical role in plate tectonics and material recycling between the crust and the upper mantle. Since the discovery of coesite and microdiamond from eclogites and their country rocks in the Dabie Mountains (Okay et al., 1989; Wang et al., 1989; Xu et al., 1992), extensive studies have shown that the Dabie–Sulu orogenic belt is one of the largest ( ∼ 30 000 km2 ) and best exposed UHP metamorphic terranes in the world (Liou et al., 2014). As the first ICDP project in China, the Chinese Continental Scientific Drilling (CCSD) project began to drill the 5158 m deep borehole in Donghai County (Jiangsu Province) on 4 August 2001, which marked the starting point of the CCSD Program (Xu et al., 2009a). Uplift of the Tibetan Plateau in the Cenozoic has had profound influence on the global climate change and inland aridification. In order to study the evolution of Asian monsoon and its relationship with regional tectonics and global climate change, the Lake Qinghai Drilling Project was conducted in 2005 to obtain high-quality geological and biological core records (An et al., 2006, 2012). On 12 May 2008, the Mw 7.9 Wenchuan earthquake happened along the Longmenshan thrust belt in the eastern margin of the Tibetan Plateau. In order to better understand the intracontinental earthquake mechanisms, Chinese scientists started the Wenchuan earthquake Fault Scientific Drilling (WFSD) project just 178 days after the earthquake (Li et al., 2013, 2014). The ongoing Continental Scientific Drilling Project of Cretaceous Songliao Basin started in April 2014 and will recover continuous highresolution terrestrial achieves and Cretaceous climate change (Wang et al., 2008, 2013a, b). Besides these ICDP projects, from 2008 to 2012 the Chinese government also supported the Program of Selected Continental Scientific Drilling and Experiments, which consists of seven drilling projects on some key problems in continental dynamics. These projects provided scientific and technical preparation for the future superdeep borehole (over 10 000 m) in China. On the occasion of the 20th anniversary of the ICDP and the 15th anniversary of the CCSD Program, we present a brief review of history and achievements of the CCSD Program. 2 2.1 The Chinese Continental Scientific Drilling project History of the CCSD project Preparation for the CCSD project can be traced back to 1988. Encouraged by the drilling projects of the Kola superdeep borehole and the Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland (KTB), Chinese scientists proposed a continental scientific drilling plan in mainland China in 1988. The Ministry of Geology and Mineral Resources of China, which was combined in the Ministry of Land Resources of China in 1998, started to investigate potential sciSci. Dril., 22, 1–18, 2017 entific drilling sites in 1991. After years of investigation and d (...truncated)