DOI: 10.1007/s00531-015-1168-0
Scopus记录号: 2-s2.0-84942364155
论文题名: Decoupling of whole-rock Nd–Hf and zircon Hf–O isotopic compositions of a 284 Ma mafic–ultramafic intrusion in the Beishan Terrane, NW China
作者: Su B.-X. ; Qin K.-Z. ; Lu Y.-H. ; Sun H. ; Sakyi P.A.
刊名: International Journal of Earth Sciences
ISSN: 14373254
出版年: 2015
卷: 104, 期: 7 起始页码: 1721
结束页码: 1737
语种: 英语
英文关键词: Depleted mantle
; Mafic–ultramafic intrusion
; Nd–Hf isotope decoupling
; Permian mantle plume
; Zircon Hf–O isotopes
Scopus关键词: hafnium
; igneous intrusion
; isotopic composition
; mafic rock
; mantle plume
; neodymium isotope
; oxygen
; Permian
; ultramafic rock
; zircon
; Beishan
; China
; Nei Monggol
英文摘要: Abundant Permian mafic–ultramafic intrusions in the Beishan Terrane, NW China, are parts of the Tarim large igneous province. Among these intrusions, Luodong intrusion is composed of dunite, wehrlite and gabbro. These rocks have whole-rock Sr–Nd–Hf and zircon Hf–O isotope compositions that display significant decoupling. The decoupling of these generally well-correlated systems demonstrates contrasting evolving trends. Systematic compositional and mineralogical controls on decoupling have been investigated. Wehrlites and gabbros show MORB-like trace element patterns with negligible crustal contamination. They have high initial 143Nd/144Nd [εNd(t) = +6.6 to +11.2] and 176Hf/177Hf [εHf(t) = +12.2 to +16.9] and low initial 87Sr/86Sr [(87Sr/86Sr)i = 0.702949–0.704098] ratios and plot within the MORB field, indicating that their parental magmas were derived from a depleted mantle source. The enrichment features are present in the zircon crystals separated from the gabbro. These homogeneously unzoned zircon crystals have high U concentrations, low Th/U ratios and a U–Pb age of 284.0 ± 2.3 Ma. They are therefore interpreted as having formed rapidly in a highly fractionated/evolved magma. Their εHf(t) and δ18O values range from −9.3 to −6.7 and +10.25 ‰ to +11.42 ‰, respectively. The decoupling is linked with crustal contamination by ancient crust (probably Proterozoic schist in the Beishan Terrane) that occurred during zircon crystallization. However, the contamination signature in the whole-rock composition was soon overprinted by magma mixing process. The inference is evidenced by zoning textures preserved in plagioclase, clinopyroxene, spinel and particularly olivine, and the presence of coeval diabase dykes cutting through the intrusion. The isotope decoupling observed in this mantle-plume-related mafic–ultramafic intrusion supports the idea that Nd–Hf decoupling and Lu/Hf and Sm/Nd parent/daughter variations exist only on a small hand-size scale in a particular growth environment and prevailing kinetics. © 2015, Springer-Verlag Berlin Heidelberg. URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942364155&doi=10.1007%2fs00531-015-1168-0&partnerID=40&md5=b306852072cec6c9c95142a247478495
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/70246
Appears in Collections: 影响、适应和脆弱性 气候减缓与适应
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作者单位: Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing, China; Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China; State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing, China; Department of Earth Science, University of Ghana, P.O. Box LG 58, Legon-Accra, Ghana
Recommended Citation:
Su B.-X.,Qin K.-Z.,Lu Y.-H.,et al. Decoupling of whole-rock Nd–Hf and zircon Hf–O isotopic compositions of a 284 Ma mafic–ultramafic intrusion in the Beishan Terrane, NW China[J]. International Journal of Earth Sciences,2015-01-01,104(7)