Identifying deep recycled carbonates through Miocene basalts in the Maguan area, SE Tibetan Plateau

Lei, Hangshan; Zhao, Zhidan; Niu, Yaoling; Zhang, Shuangquan; Cousens, Brian; Ma, Qian; Teng, Fang‐Zhen; Liu, Dong; Miao, Zhuang; Yang, Yu-Jun; Wu, Jin-Hui; Wang, Qing; Zhu, Di‐Cheng

doi:10.1016/j.lithos.2021.106356

Cited by 4 publications

(1 citation statement)

References 73 publications

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“…O'Reilly and Griffin (2010) suggested that if mantle xenoliths are hosted in magma, the magma possibly spent 8-60 h travelling from the depth of 80-200 km to the surface. In the study area, there are many mantle xenoliths and xenocrysts in the Hainan basalts (Fan and Hooper, 1989;Xu et al, 2002;Liu et al, 2015;Jiang et al, 2017), indicating that magma ascended rapidly, without enough time to assimilate the crust (Liu et al, 2015;Sun et al, 2018;Lei et al, 2021).…”

Section: Crustal Contaminationmentioning

confidence: 92%

Carbon Enrichment in the Lithospheric Mantle: Evidence from the Melt Inclusions in Mantle Xenoliths from the Hainan Basalts

Tian

Zhang

et al. 2023

Acta Geologica Sinica (Eng)

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It is generally believed that the lithospheric mantle and the mantle transition zone are important carbon reservoirs. However, the location of carbon storage in Earth's interior and the reasons for carbon enrichment remain unclear. In this study, we report CO2‐rich olivine‐hosted melt inclusions in the mantle xenoliths of late Cenozoic basalts from the Penglai area, Hainan Province, which may shed some light on the carbon enrichment process in the lithospheric mantle. We also present a detailed petrological and geochemical investigation of the late Cenozoic basalts and mantle xenoliths from northern Hainan Island. The collected samples of late Cenozoic Hainan Island basalts belong to both alkaline and subalkaline series, showing fractionated REE patterns with high (La/Yb)N values of 3.52–11.77, which are typical for OIB. Based on Al‐in‐olivine thermometry, the temperatures estimated for the mantle xenoliths can be divided into two groups. One group has temperatures of less than 1050°C, and the other group has temperature ranging from 1050°C to 1282°C. Clinopyroxene (La/Yb)N–Ti/Eu and clinopyroxene Ca/Al–Mg# diagrams indicate that the mantle peridotite experienced metasomatism from both silicate and carbonate melts. Melt inclusions in the olivine of mantle xenoliths include (1) CO2 bubble–rich melt inclusions; (2) multiphase melt inclusions (glass + CO2 bubble + daughter minerals); (3) pure glass melt inclusions. Magnesite is a daughter mineral in the olivine‐hosted melt inclusions, which could be interpreted as a secondary mineral formed by the interactions of CO2‐rich fluids with an olivine host, due to post‐entrapment effects. The glasses in olivine‐hosted melt inclusions have high SiO2 contents (60.21–77.72 wt%). Our results suggest that a considerable amount of CO2‐rich melt inclusions are captured in the lithospheric mantle during metasomatism. The lithospheric mantle can therefore act as is a ‘carbon trap’, with much CO2 being absorbed by the lithospheric mantle in this way.

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Section: Crustal Contaminationmentioning

confidence: 92%

Carbon Enrichment in the Lithospheric Mantle: Evidence from the Melt Inclusions in Mantle Xenoliths from the Hainan Basalts

Tian

Zhang

et al. 2023

Acta Geologica Sinica (Eng)

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Miocene Alkaline Basaltic Magmatism in Northeastern Tibetan Plateau: Implications for Mantle Evolution and Plateau Outward Growth

Che,

Liu,

Zhao

et al. 2024

Geochem Geophys Geosyst

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The widespread Cenozoic alkaline magmatism within and around the Tibetan Plateau offers a prime opportunity to probe the nature of the mantle at the depths where basalt magmas originate. The close temporal and spatial relationship between volcanism and regional strike‐slip fault systems also helps better understand the geodynamics of outward growth of the plateau in response to the continued India‐Asia convergence. We present a comprehensive study of the deeply sourced alkaline basalts formed along the Kunlun strike‐slip fault with the aim of understanding their petrogenesis and the composition of mantle sources beneath the northeastern Tibetan Plateau. High Nb/U and Ce/Pb ratios and relatively depleted bulk‐rock Sr‐Nd‐Pb isotope compositions corroborate the mantle origin of these alkaline basalts. Homogeneous and low 87Sr/86Sr of clinopyroxene indicates negligible crustal contamination during magmatic evolution. Low δ26Mg in the alkaline basalts and positive correlations with Hf/Sm and Ti/Ti* indicate that the basalts were derived from mantle that was metasomatized by melts derived from sedimentary carbonates during the Paleo‐Tethyan seafloor subduction. Based on 40Ar/39Ar dating results, it appears that the alkaline basaltic magmatism in the northeastern Tibetan Plateau occurred simultaneously with Kunlun strike‐slip faulting. These observations suggest that the India‐Asia convergence must have reactivated ancient subduction plate boundaries and resulted in strike‐slip faulting along these suture zones within and around the Tibetan Plateau. The eruption of low‐volume and deeply rooted alkaline basalts may have been controlled by fractures associated with the strike‐slip fault systems.

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Identifying Recycled Materials Using Mo Isotopes in Intraplate Alkali Basalts From the Southeastern Margin of Tibetan Plateau

Xu,

Qi,

Wang

et al. 2024

Geochem Geophys Geosyst

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Mantle heterogeneity in lithology and geochemistry is often attributed to recycled subducted materials. While distinct mantle end‐members are identified by radiogenic isotopes, the specific recycled materials contributing to this heterogeneity remain debated. This study presents Mo‐Sr‐Nd‐Pb isotopic data for OIB‐like alkali basalts from the Maguan area in the southeastern Tibetan Plateau, focusing on slab inputs' role in mantle heterogeneity. The Miocene (ca. 13 Ma) Maguan alkali basalts are divided into two types based on petrographic and geochemical characteristics, showing similar Sr‐Nd‐Pb isotopic signatures but different Mo isotopic compositions. Type I basalts exhibit a wide δ98/95Mo range (−0.31‰ to −1.03‰, average −0.47‰ ± 0.06‰, 2SD = 0.40‰, n = 13), while type II basalts have heavy and constant δ98/95Mo values (−0.11‰ to −0.17‰, average −0.14‰ ± 0.01‰, 2SD = 0.05‰, n = 6). The unique low δ98/95Mo value (−1.03‰) in type I basalts is among the lowest reported in OIB‐like continental basalts. Type I basalts likely originate from an enriched asthenospheric mantle metasomatized by melts from recycled dehydrated oceanic crust and sediments, whereas type II basalts are derived from partial melting of an enriched asthenospheric mantle metasomatized by melts from recycled serpentinized peridotites. The residual Tethys oceanic slabs in the deep mantle significantly contribute to the mantle source of the Maguan basalts. The formation of Maguan Miocene magmas may be linked to mantle upwelling induced by the subduction of the West Burma plate. This study highlights the Mo isotopic system's utility in tracing complex slab fluxes generating mantle geochemical heterogeneity.

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Identifying deep recycled carbonates through Miocene basalts in the Maguan area, SE Tibetan Plateau

Cited by 4 publications

References 73 publications

Carbon Enrichment in the Lithospheric Mantle: Evidence from the Melt Inclusions in Mantle Xenoliths from the Hainan Basalts

Carbon Enrichment in the Lithospheric Mantle: Evidence from the Melt Inclusions in Mantle Xenoliths from the Hainan Basalts

Miocene Alkaline Basaltic Magmatism in Northeastern Tibetan Plateau: Implications for Mantle Evolution and Plateau Outward Growth

Identifying Recycled Materials Using Mo Isotopes in Intraplate Alkali Basalts From the Southeastern Margin of Tibetan Plateau

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