Subduction and Exhumation of Ultrahigh-Pressure Rocks: Field and Drilling Studies in Eastern China

ICDP中国大陆科学钻探项目于2005年完成，目标是中国东部的一个超高压（UHP）变质地块。超高压地体是扬子克拉通北缘俯冲至中朝克拉通下方150 km深处形成的。完成了东海主孔（MH）（深度5158 m）、预导孔PP1 （432 m）、PP2 （1028 m）、PP3 （705 m）和容城、日照超镁质体3个浅孔（183 ~ 350 m）的钻探工作。岩心回收率超过钻井深度的85%，包括未风化的片麻岩、榴辉岩、石榴石橄榄岩、泥质和石榴石斜辉石岩样品。根据地表露头的出现情况，预计会遇到橄榄岩，但没有人预测到通过钻探发现的富矿。新的岩心样本现已可供研究，为进一步了解地幔和俯冲过程提供了前所未有的机会。大陆动力学项目资助了由斯坦福大学的JG Liou领导的对ICDP-CCSD岩心样本的多机构、多学科调查，包括来自中国地质科学院、北京、华盛顿卡内基研究所、台湾中央研究院、东京工业大学和早稻田大学的同事。这些pi与30多位中国科学家密切合作，发表了107篇论文。已发表的CCSD核心论文受到研究界的重视，在1996-2007年期间，J.G. Liou在被引用次数最多的地球科学作者中排名第十，而R.Y. Zhang在被引用次数最多的前50位(Thomson？参见ISI科学网。该奖项为完成石榴石橄榄岩岩心样品的地球化学研究提供了额外一年的支持，作为基于成就的更新（ABR）。对石榴石橄榄岩中新发现的硫化物矿物进行Re-Os和硫同位素分析。锆石是一种在橄榄岩中发现的稀有但信息丰富的矿物，将分析其Lu-Hf同位素。对橄榄岩硅酸盐矿物氧同位素的分析将用于测试地幔与地壳的起源。这些新的研究，结合锆石的U-Pb离子显微探针分析，将提供次大陆地幔岩石圈形成的详细年代学，并为俯冲作用在地壳物质污染地幔中的作用提供新的见解。

The ICDP Chinese Continental Scientific Drilling project, completed in 2005, targeted an ultrahigh pressure (UHP) metamorphic terrane in eastern China. The UHP terrane resulted from subduction of the northern edge of the Yangtze craton to 150 km depth beneath the Sino-Korean craton. Several drill holes including the main hole (MH) (5158 m depth), pre-pilot holes PP1 (432 m), PP2 (1028 m) and PP3 (705 m) in Donghai, and 3 shallow holes (183-350 m) in ultramafic bodies in Rongcheng and Rizhao were completed. Core recovery was more than 85% of drilling depth including unweathered samples of gneisses, eclogites, garnet peridotites, dunite, and garnet clinopyroxenite. Encountering peridotites was expected based on occurrences in surface outcrops but no one predicted the bonanza that was found by drilling. The new drill core samples, now available for study, offer an unprecedented opportunity to advance understanding of the mantle and subduction processes. The Continental Dynamics program funded a multi-institutional, multidisciplinary investigation of ICDP-CCSD drill core samples led by JG Liou at Stanford University and has included colleagues from the Chinese Academy of Geological Sciences, Beijing, Carnegie Institution of Washington, Academia Sinica (Taiwan), Tokyo Institute of Technology and Waseda University. The PIs have worked closely with more than 30 Chinese scientists, and published 107 papers. The published work on CCSD cores is valued by the research community as recognized by the ranking of J.G. Liou as the tenth most cited geoscience author and R.Y. Zhang as within the top 50 during 1996-2007 according to Thomson?s ISI Web of Science. This award provides one additional year of support as an Accomplishment Based Renewal (ABR) to complete geochemical studies of core samples of garnet peridotite. Newly recognized sulfide minerals in garnet peridotites will be analyzed for Re-Os and Sulfur isotopes. Zircons, a rare but immensely informative mineral found in peridotites, will be analyzed for Lu-Hf isotopes. Analysis of peridotite silicate minerals for oxygen isotopes will be used to test for mantle vs. crustal origin. These new studies, combined with U-Pb ion microprobe analyses of zircon, will provide a detailed chronology of the formation of sub-continental mantle lithosphere and give new insights as to the role of subduction in contaminating the mantle with crustal material.