caa a22 4500 606149406 CHVBK 20210128100534.0 cr unu---uuuuu 210128e20151001xx s 000 0 eng 10.1007/s00531-015-1168-0 doi (NATIONALLICENCE)springer-10.1007/s00531-015-1168-0 Decoupling of whole-rock Nd-Hf and zircon Hf-O isotopic compositions of a 284Ma mafic-ultramafic intrusion in the Beishan Terrane, NW China [Elektronische Daten] [Ben-Xun Su, Ke-Zhang Qin, Ying-Huai Lu, He Sun, Patrick Sakyi] 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±2.3Ma. 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. Springer-Verlag Berlin Heidelberg, 2015 Nd-Hf isotope decoupling nationallicence Zircon Hf-O isotopes nationallicence Mafic-ultramafic intrusion nationallicence Depleted mantle nationallicence Permian mantle plume nationallicence Su Ben-Xun Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, 100029, Beijing, China aut Qin Ke-Zhang Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, 100029, Beijing, China aut Lu Ying-Huai State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, 100083, Beijing, China aut Sun He Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, 100029, Beijing, China aut Sakyi Patrick Department of Earth Science, University of Ghana, P.O. Box LG 58, Legon-Accra, Ghana aut International Journal of Earth Sciences Springer Berlin Heidelberg 104/7(2015-10-01), 1721-1737 1437-3254 104:7<1721 2015 104 531 https://doi.org/10.1007/s00531-015-1168-0 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00531-015-1168-0 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Su Ben-Xun Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, 100029, Beijing, China aut NATIONALLICENCE 700 1- Qin Ke-Zhang Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, 100029, Beijing, China aut NATIONALLICENCE 700 1- Lu Ying-Huai State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, 100083, Beijing, China aut NATIONALLICENCE 700 1- Sun He Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, 100029, Beijing, China aut NATIONALLICENCE 700 1- Sakyi Patrick Department of Earth Science, University of Ghana, P.O. Box LG 58, Legon-Accra, Ghana aut NATIONALLICENCE 773 0- International Journal of Earth Sciences Springer Berlin Heidelberg 104/7(2015-10-01), 1721-1737 1437-3254 104:7<1721 2015 104 531