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Evolution of slab dip angle at global subduction zones from 160 Ma to the present day overlain with the spatial distribution of kimberlite eruptions. A large peak in slab flux and kimberlite eruption density occurs at 120 Ma during the breakup of the Gondwana supercontinent, and a second (smaller) peak at 80 Ma associated with the removal of the flat Farallon slab from the base of overriding continental lithosphere in North America. White regions indicate non-oceanic crust, grey regions indicate present-day coastlines. Maps were generated using Cartopy²¹. A full timeseries from 170 Ma to 0 Ma is available as an animation in Movie S1.
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Kimberlites are sourced from thermochemical upwellings which can transport diamonds to the surface of the crust. The majority of kimberlites preserved at the Earth’s surface erupted between 250 and 50 million years ago, and have been attributed to changes in plate velocity or mantle plumes. However, these mechanisms fail to explain the presence of...
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This project focuses on the processing and interpretation of magnetic and IP-resistivity data, which is to understand the subsurface geological structures and identify potential mineral resources. The data acquisition used appropriate geophysical instruments, including data filtering, imaging, inversion, and modeling techniques. The results obtaine...
Citations
... Three recent contributions, Gianni and Navarrete (2022); Gianni et al. (2023) and Mather et al. (2023) invoke low-angle subduction or its remnants, in some cases produced by anomalous thick lithosphere, as responsible for distinctive igneous events in the geologic record. Such possible features are compatible with the hypotheses put forward in this contribution. ...
... Such possible features are compatible with the hypotheses put forward in this contribution. Gianni et al. (2023) and Mather et al. (2023) propose that asthenosphere remnants of low-angle subduction persist for long and would be responsible for some peculiar geochemical magmatic patterns. Gianni and Navarrete (2022) suggest that slab loss by detachment of normal lithosphere from newly subducted, thickened oceanic lithosphere produced a gap in the igneous record of part of southwestern Pangea, by a mechanism distinct from those proposed here. ...
The importance of mantle hotspot traces to driving low-angle subduction beneath the Andes is strengthened by updated South American-Nazca plate reconstructions, including three oceanic hotspot traces, and a new isotopic date compilation. The Juan Fernandez hotspot trace, reconstructed from Pacific-hotspot models to the Nazca-Farallon plate, encountered the subduction zone offshore southern Peru ~65 Ma, broadening arc volcanism; the trace-trench intersection migrated gradually and then rapidly southward, broadening the arc east to Bolivia and northern Argentina; it then stabilized about 13 Ma offshore central Chile, producing the contemporary low-angle Pampean segment. The Easter-Nazca hotspot trace intersected the subduction zone beneath Colombia before 50 Ma and migrated southward beneath Ecuador beginning ~15 Ma, with progressive low-angle subduction implied by migrating volcanic cessation along the Andean crest to southern Peru. The Galapagos-Carnegie trace only recently encountered the subduction zone, apparently inducing a new low-angle segment and cessation of magmatism in Colombia. The reconstructions and magmatic history strongly support a previously proposed genetic relationship of hotspot traces and low-angle subduction. Additionally, reconstructions suggest remnants of older subducted traces in the asthenosphere may have sourced post-rift magmatism into thinning eastern Brazil lithosphere, which cannot be explained otherwise by simple hotspot mechanisms.
... Kimberlites are small-volume, ultrabasic, volatile-rich (CO 2 and H 2 O) igneous rocks originated from sub-lithospheric mantle sources in the diamond stability field (> 150 km;Giuliani, 2018;Pearson et al., 2019;Sarkar et al., 2021). The origin of kimberlite melts is controversial and has been discussed in models that highlight the existence of a mantle plume under thick continental lithosphere (e.g., Torsvik et al., 2010;Giuliani et al., 2023) or the influence of subduction (Mather et al., 2023). Collisional settings can trigger tectonic disturbances beneath cratons that lead to the ascent of kimberlite magmas (e.g., Premier kimberlite; Tappe et al., 2020). ...
Kimberlite magmatism provides insights into periodic tectonothermal processes linked to the evolution of supercontinents. Paleozoic and Mesozoic kimberlites overlapping with the Pangea cycle are exposed in the Amazonian Craton (Pimenta Bueno field) and the Neoproterozoic Brasília Belt. Phlogopite in mantle xenoliths in kimberlites from the Amazonian Craton are characterized by low Cr2O3 (< 1 wt. %) and an enrichment in TiO2 (> 2 wt. %), akin to secondary phlogopite formed by kimberlite magma infiltration in the mantle. Low Ti-Cr (< 1 wt. %) and high #Mg (91–92) grains are linked to extensive metasomatism of garnet peridotites resulting in clinopyroxene-phlogopite rocks. In situ phlogopite Rb-Sr isochron ages of 250–220 Ma constrain the emplacement of pipes in the Amazonian Craton with no age difference between distinct phlogopite compositions (higher and lower TiO2 phlogopite) and microstructures (porphyroclasts, neoblasts, reaction rims). Mantle xenoliths in kimberlite pipes from the Brasília Belt present high TiO2 (> 2 wt. %) akin to secondary phlogopite formed by magma infiltration, and low Ti-Cr (1 wt. %), and high #Mg (> 92) phlogopite akin to primary grains in equilibrium with garnet. In situ phlogopite Rb-Sr isochron ages from all Brasília Belt phlogopite types span 90–80 Ma, constraining the emplacement of diamondiferous and barren pipes, with no relic of older metasomatic events. The kimberlites from the Pimenta Bueno field (Amazonian Craton) are coeval with the beginning of the extension within Pangea that culminated with the Central Atlantic rifting. In fact, the Permian-Triassic kimberlites occur close to intracratonic basins that are crosscut by ca. 200 Ma dykes and sills of the Central Atlantic Magmatic Province. In situ phlogopite Rb-Sr isochron ages spanning 90–80 Ma in the pipes from central and southeastern Brazil (Brasília Belt) may be associated with propagation of far-field stresses linked to opening of the South Atlantic Ocean during the Pangea break-up.
... Each point is also used to extract relevant tectonic parameters from our seafloor grids (where they intersect with the subduction zone), including RAP content, seafloor spreading rate at the formation and age of oceanic crust (in principle, any feature intersecting a subduction zone can be used in our method). At each point, we then calculate a dip angle following Mather et al. (2023), who approximate dip based on a range of subducting and over-riding plate properties including age, thickness, buoyancy and rollback (Hu & Gurnis, 2020). The equally spaced points along the subduction zone, therefore, represent the initiation of a hypothetical subduction isochron-a line drawn along a subducting slab representing the same time of subduction (e.g., Figure 2, analogous to a seafloor spreading isochron). ...
Serpentinization is among the most important, and ubiquitous, geological processes in crustal–upper mantle conditions (<6 GPa, <600°C), altering the rheology of rocks and producing H2 that can sustain life. While observations are available to quantify serpentinization in terrestrial and mid‐ocean ridge environments, measurements within subduction zone environments are far more sparse. To overcome this difficulty, we design a methodology to quantify and offer a first‐order estimate of the magnitude of “slab‐serpentinization” that has occurred over the last 5 Ma within the world's subduction zones by coupling four discrete tectonic and geophysical datasets—(a) raster grids of relic abyssal peridotite (peridotite exhumed from slow spreading mid‐ocean ridges but unaffected by pre‐subduction serpentinization) within ocean basins, (b) slab geometry, (c) thermal profiles and a (d) plate‐tectonic model. Averaged per year, our results suggest that 4.2–24 • 10⁷ kg of H2 per annum could be generated from “slab‐serpentinization” within a subduction zone. Our estimate is 3–4 orders of magnitude lower than what is thought to be produced at mid‐ocean ridges, and 1–2 orders of magnitude lower than what could occur through serpentinization at trench flexure and when including possible mantle wedge serpentinization. Higher hydrogen production is correlated most strongly with the spreading history of ocean basins, underlaying the importance of the tectonic history of a slab prior to subduction.
