Zhang Xubo

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Last Name
Zhang
First Name
Xubo
ORCID
0000-0002-4015-9169

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  • Article
    Effects of hotspot‐induced long‐wavelength mantle melting variations on magmatic segmentation at the Reykjanes Ridge: insights from 3D geodynamic modeling
    (American Geophysical Union, 2022-03-10) Zha, Caicai ; Lin, Jian ; Zhou, Zhiyuan ; Xu, Min ; Zhang, Xubo
    Spatial variations in mantle melting induced by the Iceland hotspot have strong effects on meso-scale mantle upwelling and crustal production along the slow-spreading Reykjanes Ridge. The ridge-hotspot interaction has been recorded by diachronous V-shaped ridges and troughs extending away from Iceland, as well as by changes in ridge segmentation since 37 Ma. The origins of V-shaped structures are widely debated, while the causes of the gradual erasion of ridge segments bounded by transform faults are rarely investigated. Through 3D time-dependent geodynamic modeling, this study investigates how the hotspot-induced regional mantle melting variations affect ridge segmentation. Periodic temperature perturbations were initially imposed beneath the melting zone to trigger buoyant upwelling cells, which corresponded to the offset ridge segments at the Reykjanes Ridge. Iceland hotspot-induced long-wavelength mantle melting variations were generated by applying a regional linear temperature gradient at the bottom of the model domain. Modeling reveals a two-stage evolution of the buoyant upwelling cells that characterizes the segmentation transition at the Reykjanes Ridge. In Stage 1, the regional mantle melting variations trigger along-axis pressure-driven mantle flow, which alters the segment-scale mantle upwelling and promotes the propagation of segment boundaries away from the region with relatively higher mantle temperature. In Stage 2, buoyant upwelling cells are destroyed progressively as along-axis mantle flow dominants, leaving V-shaped diachronous boundaries between the segmented and unsegmented crust. These results advance our understanding of the effects of long-wavelength mantle melting variations induced by regional mantle heterogeneities on ridge segment evolution at slow-spreading ridges.
  • Article
    Mantle heterogeneity and melting processes in the South China Sea: thermal and melting models constrained by oceanic crustal thickness and basalt geochemistry
    (American Geophysical Union, 2021-01-13) Zhang, Xubo ; Lin, Jian ; Behn, Mark D.
    We simulate mantle flow, thermal structure, and melting processes beneath the ridge axis of the South China Sea (SCS), combining the nominally anhydrous melting and fractional crystallization model, to study mantle heterogeneity and basin evolution. The model results are constrained by seismically determined crustal thickness and major element composition of fossil ridge axis basalts. The effects of half-spreading rate, mantle potential temperature, mantle source composition, and the pattern of melt migration on the crustal thickness and magma chemical composition are systematically investigated. For the SCS, the east and southwest (SW) subbasins have comparable crustal thickness, but the east subbasin has higher FeO and Na2O contents compared to the SW subbasin. The estimated best fitting mantle potential temperatures in the east and SW subbasins are 1,360 ± 15 °C and 1,350 ± 25 °C, respectively. The mantle in the east subbasin (site U1431) prior to the cessation of seafloor spreading is composed primarily of the depleted mid-ocean ridge basalt mantle (DMM), and is slightly contaminated by eclogite/pyroxenite-rich component. However, the mantle source composition of the SW subbasin (sites U1433 and U1434) contains a small percentage (2–5%) of lower continental crust. Basalt samples at the northern margin of the east subbasin (site U1500) shows similar chemical characteristics with that of the SW subbasin. We suggest that the basin-scale variability in the mantle heterogeneity of the SCS can be explained by a single model in which the contamination by the lower continental crust is gradually diluted by melting of DMM as the ridge moves away from the rifted margin.