气候变化领域集成服务门户(CCPortal): Lithospheric memory of subduction in mantle pyroxenite xenoliths from rift-related basalts

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DOI	10.1016/j.epsl.2020.116365
	Lithospheric memory of subduction in mantle pyroxenite xenoliths from rift-related basalts
	Lu J.; Tilhac R.; Griffin W.L.; Zheng J.; Xiong Q.; Oliveira B.; O'Reilly S.Y.
发表日期	2020
ISSN	0012821X
卷号	544
英文摘要	Petrological and geochemical studies have revealed the contribution of garnet pyroxenites in basalt petrogenesis. However, whether primary mantle melts are produced with such signature or acquired it subsequently remains somewhat controversial. We here integrate new major-, trace-element and Sr-Nd-Hf isotopic compositions of garnet pyroxenite xenoliths in Holocene alkali basalts from Lakes Bullenmerri and Gnotuk, Southeastern Australia, to relate their petrogenesis to mantle-wedge melt circulation and subsequent lithospheric evolution. Results show that the clinopyroxenites have lower MgO and Cr2O3 contents than the associated websterites, and range in compositions from depleted LREE patterns and highly radiogenic Nd and Hf isotopic signatures in relatively low-MgO samples (Type 1), to enriched REE patterns with negative HFSE anomalies, unradiogenic Nd and Hf isotopes, and extremely radiogenic Sr-isotopic ratios in samples with higher MgO (Type 2). Such compositional variabilities suggest that these pyroxenites represent segregates from melts derived from a recycled oceanic lithosphere with a potential contribution from pelagic sediments. Variable LREE contents and isotopic compositions between those of Type 1 and 2 clinopyroxenites are observed in amphibole-bearing samples (Type 3), which are interpreted as Type 1-like protoliths metasomatized by the basaltic and carbonatitic melts, possibly parental to Type 2 clinopyroxenites. The lithosphere beneath Southeastern Australia thus has received variable melt contributions from a heterogeneous mantle-wedge source, which notably includes a subducted oceanic slab package that has retained its integrity during subduction. On this basis, we suggest that the compositional heterogeneity and temporal evolution of the subsequent Southeastern Australian basaltic magmatism were probably affected by the presence of pyroxenite fragments in the basalt source and formed by the tectonic reactivation of this lithosphere during Cenozoic rifting. This interpretation is notably consistent with a trend of Nd-Pb isotopes towards EMII in Older Volcanic Provinces (OVP basalts) and limited Sr-Nd-Pb isotopic variations towards HIMU in the Newer Volcanic Provinces (NVP basalts, including the host lavas), which also exhibit low SiO2, high FeO and high CaO/Al2O3 commonly interpreted as due to pyroxenite contributions. Therefore, the identification of a subduction signature in these rift-related lavas attests to a “lithospheric memory” of earlier subduction episodes (as documented by the xenoliths), rather than a reflection of contemporaneous subduction tectonics. © 2020 Elsevier B.V.
关键词	carbonatite metasomatism clinopyroxenite mantle wedge melt-peridotite interaction recycled sediments Southeastern Australia
英文关键词	Aluminum compounds; Basalt; Calcium oxide; Chromium compounds; Garnets; Hafnium alloys; Iron oxides; Isotopes; Magnesia; Neodymium; Petrology; Silica; Tectonics; Ternary alloys; Trace elements; Volcanoes; Compositional heterogeneity; Compositional variability; Heterogeneous mantle; Isotopic composition; Isotopic signatures; Isotopic variations; South-eastern Australia; Tectonic reactivation; Hafnium; basalt; concentration (composition); geochemistry; isotopic composition; lithospheric structure; mantle source; petrology; pyroxenite; rare earth element; subduction; xenolith; Australia; Lake Bullen Merri; Victoria [Australia]
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202759
作者单位	Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China; Australian Research Council Centre of Excellence for Core to Crust Fluid System (CCFS), GEMOC, Department of Earth and Environmental Sciences, Macquarie University, Sydney, NSW2109, Australia; Instituto Andaluz de Ciencias de la Tierra (IACT), CSIC, Universidad de Granada, Armilla, Granada, 18100, Spain; State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
推荐引用方式 GB/T 7714	Lu J.,Tilhac R.,Griffin W.L.,et al. Lithospheric memory of subduction in mantle pyroxenite xenoliths from rift-related basalts[J],2020,544.
APA	Lu J..,Tilhac R..,Griffin W.L..,Zheng J..,Xiong Q..,...&O'Reilly S.Y..(2020).Lithospheric memory of subduction in mantle pyroxenite xenoliths from rift-related basalts.Earth and Planetary Science Letters,544.
MLA	Lu J.,et al."Lithospheric memory of subduction in mantle pyroxenite xenoliths from rift-related basalts".Earth and Planetary Science Letters 544(2020).