2026 July LIP of the Month

Quasi-rehealing of the eastern North China craton by the 0.9 Ga Xuhuai mantle plume

Xiangdong Su^1*, Peng Peng^{2, 3*}, Zhuyin Chu², Peng Liou², Yanjie Tang¹

¹Hubei Key Laboratory of Petroleum Geochemistry and Environment, YU-CUGW Joint Research Center on Deep Earth and Surface Dynamic Coupling, College of Resources and Environment, Yangtze University, Wuhan 430100, China; Email: xiangdongsu@outlook.com (X. Su),

²State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; Email: pengpengwj@mail.iggcas.ac.cn (P. Peng).

³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China

Extracted and modified after Su et al., 2026, Earth and Planetary Science Letters 685, 120040; see this publication for full details (Su et al., 2026).

Introduction

Cratonic mantle roots, the deep and buoyant keels that stabilize ancient continents, were long thought to be indestructible. However, an increasing number of studies show that both oceanic subduction and mantle plume events can thin or even remove these keels (Hu et al., 2018; Liu et al., 2021; Shi et al., 2021; Wu et al., 2019). Large igneous provinces (LIPs) are commonly found within ancient craton regions across the globe. Some of these LIPs are believed to be associated with earlier instances of lithospheric thinning and subsequent rehealing beneath the thinned cratons (Liu et al., 2021; Su et al., 2023). However, the question remains: can the newly restored mantle lithosphere regain the stability as its original status. For example, both the eastern North China Craton (NCC) and the Wyoming Craton, which underwent lithospheric thinning and destruction, have undergone LIP magmatism in the past. Could the instability observed today in these cratons, which have lost their mantle roots, be attributed to the influence of LIP magmatism throughout Earth’s history?

Here, by combining trace elements and Sr‑Nd‑Hf‑Os isotopes on mafic rocks from the Xuhuai LIP with Re‑Os systematics of mantle xenoliths, the authors show that while the Xuhuai plume indeed triggered lithospheric thinning and subsequent rehealing, the restored root is only “quasi‑rehealed”, a metastable state that is mechanically weaker and more vulnerable to later destruction than the original Archean keel. This study provides a new framework for understanding why some cratons that experienced ancient plume activity (e.g., Wyoming, eastern NCC) eventually succumbed to delamination.

The Xuhuai LIP

The Xuhuai LIP (also known as the Dashigou LIP; Peng et al., 2011a; Su and Peng, 2025) is an early Neoproterozoic LIP exposed in the southeastern margin of the North China craton (Fig. 1a). It consists of an early far‑field radiating dyke swarm (Dashigou dykes; ca. 920 Ma; Peng et al., 2011a) and central sill complexes (Chulan sills; 940–920 Ma), followed by late near‑center sill complexes (Fig. 2; Chulan sills, Dalian sills and Sariwon sills; 915–890 Ma; Peng et al., 2011b; Su et al., 2018). The total volume is estimated at ~0.65 Mkm², comparable to many Phanerozoic LIPs. Similar field and petrographic features are also observed in the São Francisco–Congo cratons, for example, the Bahia dyke swarm (Fig. 2; ca. 925 Ma). These sills and dykes are composed of mafic rocks ranging from more primitive gabbros (MgO = 6–10 wt%) and Fe-Ti oxides-rich dolerites (MgO = 4 wt%), to highly evolved quartz-bearing dolerites (MgO = 2 wt%, Su et al., 2018). Most of them are tholeiites and the evolution trend of these rocks were controlled by the saturation and crystallization of olivine, plagioclase, clinopyroxene and titano-magnetite, with insignificant crustal components contamination (Su et al., 2026; Su et al., 2020). The evolution of this LIP magmatism (εNd_t = –1.93 to +3.13), under conditions of low oxygen fugacity (∆QFM–1 to ∆QFM) and low water contents (~0.2 wt%). Importantly, the Xuhuai LIP records a temporal geochemical transition: early tholeiites show oceanic‑island basalt (OIB) affinities, whereas later basalts resemble mid‑ocean ridge basalts (MORBs; Su et al., 2020). This transition reflects progressive lithospheric thinning as the plume thermally and mechanically eroded the overriding cratonic root. The initial melting pressures and the potential mantle temperatures (T_P) of the Xuhuai LIP, derived from reverse crystallization modeling and thermo-barometric calculations, are 3.0 GPa and 1520°C (Su et al., 2023), respectively. The unusual high T_P and the radial pattern of the magma plumbing systems indicated that they are driven by a deep mantle plume event. Additionally, the evolution of its magmatic plumbing systems is interpreted as evidence for a subcontinental break-up event (Peng et al., 2011b; Su et al., 2021).

Multi‑isotope evidence for plume–lithosphere interaction

Su et al. (2026) present new Sr‑Nd‑Hf‑Os isotope data for mafic rocks from the Xuhuai LIP, integrated with published datasets. The key findings are:

1. Depleted plume source. A Re‑Os isochron age of 933 ± 37 Ma (MSWD = 3.4) is indistinguishable from zircon/baddeleyite U‑Pb crystallization ages. The initial ¹⁸⁷Os/¹⁸⁸Os ratio of 0.106 ± 0.080 indicates a depleted mantle source, consistent with a deep mantle plume origin. Strongly fractionated PGE patterns (depleted in IPGEs relative to PPGEs and Re) further support a highly melt‑depleted source.

2. Limited crustal contamination. Reverse fractional crystallization modelling shows that the evolution of Xuhuai LIP magmas was controlled mainly by fractional crystallization of olivine, plagioclase, clinopyroxene and titanomagnetite under low water contents (0.2 wt%) and low oxygen fugacity (ΔQFM –1 to ΔQFM), with insignificant crustal assimilation.

3. Significant SCLM interaction (1–10%). Sr‑Nd‑Hf isotopes reveal decoupling: initial ⁸⁷Sr/⁸⁶Sr increases systematically from early to late suites (0.704  to 0.707), whereas εNd_t and εHf_t remain relatively uniform (near‑CHUR to slightly positive). This decoupling cannot be explained by crustal contamination. Mixing models indicate that Xuhuai magmas represent hybrids of depleted plume‑derived melts (dominant) with variable 1–10% contributions from the sub‑continental lithospheric mantle (SCLM). The enriched SCLM end‑member includes both ancient (~2.5 Ga) and younger (~1.8 Ga) lithospheric mantle components, as well as a pyroxenite component.

4. Combined Nd–Os and Sr–Os systematics. The Xuhuai mafic rocks define mixing arrays between depleted mantle (DMM) and enriched SCLM. In εNd_i vs. ¹⁸⁷Os/¹⁸⁸Os_i, samples cluster near the DMM with low initial Os ratios, indicating a plume‑dominated source with minor SCLM input. The ⁸⁷Sr/⁸⁶Sr_i vs. ¹⁸⁷Os/¹⁸⁸Os_i plot also supports binary mixing between depleted plume melts and radiogenic SCLM components. The extremely low initial ¹⁸⁷Os/¹⁸⁸Os of the plume end‑member (0.106 ± 0.080) confirms a long‑term depleted mantle source, with SCLM contribution limited to <10% and negligible crustal assimilation.

Mantle xenoliths and lithospheric rehealing

The most compelling evidence for lithospheric rehealing comes from Re‑depletion model ages (T_RD) of mantle peridotite xenoliths entrained in Cenozoic basalts from the eastern NCC. T_RD ages record the timing of the last major melt extraction event from the mantle. Su et al. (2026) compile a dataset and identify a prominent T_RD peak at 1.0–0.8 Ga, coincident with the activity of the Xuhuai LIP (0.94–0.89 Ga).

This age peak is interpreted as the accretion of buoyant, melt‑depleted peridotite residues generated during plume‑SCLM interaction. As Xuhuai plume magmas traversed the lithosphere, they extracted melts, leaving behind refractory residues that are less dense than the surrounding mantle. These residues accreted to the base of the thinned lithosphere, partially restoring its thickness and buoyancy, a process termed “rehealing”.

Quasi‑rehealing: why the restored root is not as stable as the original

Despite the accretion of buoyant residues, Su et al. (2026) argues that the rehealed lithospheric root beneath the eastern NCC is fundamentally different from, and weaker than, its original Archean precursor. They coin the term “quasi‑rehealing” to describe this metastable state (Fig. 3). Several lines of evidence support this interpretation:

1. Heterogeneous patchwork structure. Unlike the original coherent Archean root that formed through extensive melt depletion and tectonic thickening, the quasi‑rehealed root comprises a patchwork of peridotites with diverse ages and origins (2.5 Ga, 1.8 Ga and 0.9 Ga residues). This heterogeneity inherently lacks the mechanical coherence of a unified cratonic keel.

2. Inherited rheological weaknesses. The plume‑lithosphere interaction zone likely generated or reactivated a mid‑lithosphere discontinuity (MLD), a seismically low‑velocity layer at ~100 km depth with inherently weaker rheological properties. Modern seismic surveys image an MLD beneath the western and central NCC, and a palaeo‑MLD likely existed beneath the eastern NCC prior to Mesozoic delamination (Su et al., 2023). Su et al. (2026) proposed that this weak zone was either created or significantly weakened by the Xuhuai plume‑lithosphere interaction.

3. Prolonged depositional hiatus. A ~400 Myr depositional hiatus (0.9–0.5 Ga, Fig. 1b) overlies the Xuhuai rift succession, interpreted as the surface expression of sluggish, incomplete rehealing.

4. Comparison with fully re‑cratonized cratons. In cratons such as Superior, Rae and Kaapvaal, Proterozoic plume events led to full “re‑cratonization” (Liu et al., 2021). Su et al. (2026) suggest that the key difference may be the presence or absence of subsequent lateral compressional thickening. Cratons that experienced accretionary orogenesis or flat‑slab subduction after plume activity could mechanically strengthen their reheated roots (Pearson et al., 2021), whereas the eastern NCC experienced a prolonged tectono‑thermal hiatus (0.9–0.3 Ga) that allowed no such reinforcement.

Implications for cratonic destabilization and deep mantle dynamics

The quasi‑rehealed state of the eastern NCC lithospheric mantle, combined with the presence of a rheologically weak MLD, effectively preconditioned the craton for its eventual Mesozoic destruction. When the palaeo‑Pacific plate began subducting beneath eastern Asia in the Mesozoic, the already‑weakened lithosphere was primed for delamination. The ~100 km depth of the MLD corresponds precisely to the inferred detachment interface for the wholesale lithospheric delamination documented by (Chen et al., 2023).

This framework has implications beyond the North China craton. The Wyoming craton, which also experienced lithospheric thinning and destruction, contains the 2.01 Ga Kennedy LIP, a potential plume event that may have induced a similar quasi‑rehealed state. More broadly, the recognition that plume‑induced rehealing can produce metastable lithosphere rather than fully restored cratonic stability provides a new perspective on the long‑term evolution of continental roots.

In a companion study, Peng et al. (2025) demonstrate that the global 940–720 Ma LIPs, including the Xuhuai LIP, define a coherent ring around the Rodinia supercontinent that resembles the product of an ancient large low shear‑wave velocity province (LLSVP). This Rodinian LLSVP was partially regenerated (replenished and migrated) to become the Pangean LLSVP, linking the Xuhuai plume event to deep mantle dynamics operating over supercontinent cycles (Peng et al., 2025).

Conclusions

The ~0.9 Ga Xuhuai LIP in the eastern North China craton was generated by a deep mantle plume, as shown by radial dyke geometry, high T_p (1520 °C), and depleted mantle Os isotope signatures (initial ¹⁸⁷Os/¹⁸⁸Os = 0.106 ± 0.080). Sr‑Nd‑Hf‑Os isotopes record progressive thinning of the cratonic lithosphere, from early OIB‑like magmas formed under thick lithosphere to late MORB‑like magmas formed under thinned lithosphere. Re‑depletion model ages (T_RD) of mantle xenoliths show a prominent peak at 1.0–0.8 Ga, coincident with the Xuhuai LIP, providing direct evidence for accretion of buoyant melt residues and lithospheric rehealing. However, the rehealed root is only “quasi‑rehealed”, a heterogeneous patchwork with inherited rheological weaknesses (MLD) and without the mechanical strength of the original Archean keel. This quasi‑rehealed state preconditioned the eastern NCC for its eventual Mesozoic delamination, offering a new framework for evaluating cratonic stability after plume events.

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