摘要
2017年中国科学院海洋研究所"大洋岩石圈与地幔动力学实验室"建成。未来5年,该实验室在国家自然科学基金重点项目(编号:41630968)的资助下,用珍贵的太平洋、大西洋和印度洋洋中脊玄武岩(MORB)、辉长岩和深海橄榄岩(MORP)研究地球化学和地幔动力学的几个基本科学问题:1用Ti-Zr-Hf稳定同位素验证"Nb-Ta和Zr-Hf元素对质量分异的假说";2从MORB演化过程和地幔熔融过程检验目前对铁同位素分馏的基本假说,即重Fe同位素与Fe3+有亲和性,且比轻Fe同位素和Fe2+更不相容;3提出并试图检验地幔高氧逸度是板块构造的结果,即含有大量Fe3+的蛇纹石化大洋岩石圈地幔橄榄岩俯冲到深部地幔所致;4对代表性的MORB样品和中国东部新生代碱性玄武岩样品进行铀同位素研究,检验Andersen等(2015)有关地球演化过程中壳幔循环导致的内、外动力地质过程的相互关系。
This paper discusses some major research to be carried out in the next five years in the newly estab- lished Laboratory of Ocean Lithosphere and Mantle Geodynamics. By using our existing sample collections of global mid-ocean ridge basalts, gabbros and abyssal peridotites from the Pacific, Atlantic and Indian oceans, the research includes： ①Using Ti-Zr-Hf stable isotope methods to test the hypothesis that the observed huge Nb-Ta and Zr-Hf fractionations result from mass-dependent fractionation under mantle magmatic conditions; ②Using a MORB sample suite of uniform ratios of incompatible elements and Sr-Nd-Pb isotopes with large major element compositional variation to test the common hypothesis of iron isotope fractionation, i. e, the affinity of heavy Fe with ferric Fe （ Fe^3＋ ）, and both heavy Fe and ferric Fe （ Fe^3＋ ） being more incompatible than light Fe and ferrous Fe （ Fe^2＋ ） during magma evolution; while using an incompatible trace element and Sr-Nd-Pb isotope highly variable MORB suite to test the same hypothesis during low-degree mantle melting （ i. e, the effect of mantle metasomatism） ; ③Proposing and tes- ting the hypothesis that the high oxygen fugacity of the Earth＇ s mantle is a consequence of plate tectonics by subducting partially serpentinized oceanic mantle lithosphere with abundant ferric Fe （e. g. Fe^3＋/∑Fe〉2） ; ④The recent work by Andersen et al. （Nature, 2015） is a milestone contribution by using U isotope variation in oceanic basahs to hypothesize that the O2-rich atmosphere since the late Archean （ abont 2.4 Ga） mobilized the water soluble U （6＋ vs. 4＋） from continents, transported to the ocean and subducted with sediments to the upper mantle, which explains the low Th/U in MORB （ 〈2.5 ） and the high Th/U （ 〉3.5 ） ocean island basalts （OIB） do not see such U addition effect probably because OIB source materials are all ancient （ 〉 abont 2.4 Ga） if there were subducted component. The Cenozoic alkali basalts
出处
《地球科学进展》
CAS
CSCD
北大核心
2017年第2期111-127,共17页
Advances in Earth Science
基金
国家自然科学基金重点项目“用非传统稳定同位素探索全球大洋玄武岩、深海橄榄岩成因和地球动力学的几个重要问题”(编号:41630968)资助~~
关键词
大洋玄武岩
深海橄榄岩
壳幔循环
地幔动力学
非传统稳定同位素
Seafloor basalt
Abyssal peridotite
Crust-mantle recycling
Mantle geodynamics
Non-traditional stable isotopes.
