Journal: Mineralogy and Petrology

Abbreviation

Mineral. petrol.

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Springer

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0930-0708
1438-1168

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Publications 1 - 10 of 17
  • Testing the hypothesis of secular thinning and compositional evolution of the lithospheric mantle beneath cratons: Implications for kimberlite magmatism
    Item type: Journal Article
    Sarkar, Soumendu; Giuliani, Andrea; Dalton, Hayden; et al. (2025)
    Mineralogy and Petrology
    The sub-cratonic lithospheric mantle (SCLM) is known for its chemical buoyancy and mechanical strength, which have facilitated its preservation for billions of years. However, the thinning of lithospheric mantle beneath some cratons (e.g., North China, Sao Francisco) indicates that some cratons are not permanently stable. We have assembled a new compilation of SCLM thickness data based on previously published, robustly estimated palaeo-geotherms that are defined by mantle xenocrysts/xenoliths in kimberlites and lamproites globally. These data support a localised and episodic decrease in lithospheric thickness (e.g., Siberian craton) with thin lithosphere (< 200 km) only underlying some kimberlites/lamproites younger than 200 Ma. Some late-Phanerozoic thinning of the SCLM in areas of North America and southern Africa is supported by comparison of the xenocryst/xenolith-based estimates with present-day constraints from geophysical methods. To investigate the effect of lithospheric thinning on the compositional evolution of the SCLM and its implication for magmatism in cratonic settings, we have examined the compositions of olivine xenocrysts sampled by kimberlites and lamproites globally. The average composition of entrained lithospheric mantle olivine exhibits no correlation with kimberlite and lamproite eruption ages, nor with SCLM thickness, suggesting no simple relationship between lithospheric thinning and lithospheric composition over time. Our results further reveal a broad relationship between locally thinner cratonic lithosphere in the last 200 Ma and the frequency of kimberlite eruptions, which hints at more favourable conditions for the formation of kimberlite melts in the upper asthenosphere beneath thinned lithosphere (150-200 km) since the Mesozoic period.
  • Neoproterozoic kimberlite and lamproite magmatism of the Man Craton, Liberia, from a common sub-lithospheric source
    Item type: Journal Article
    Ndimande, Njabulo; Howarth, Geoffrey H.; Giuliani, Andrea; et al. (2025)
    Mineralogy and Petrology
    It has been proposed that, rather than the lithosphere, cratonic lamproites may be derived from convecting mantle sources like those of kimberlites, but with extensive subsequent melt modification via melt-rock reaction with metasomatized, phlogopite-rich sub-continental lithospheric mantle (SCLM). Here we explore this model using samples from kimberlite (Camp Alpha) and olivine lamproite (Weasua) localities in Liberia, West Africa. U–Pb dating of perovskite, performed using in-situ Pb isotope compositions of coexisting (low U/Pb) mica, provides broadly coeval Neoproterozoic ages for Camp Alpha (762 ± 9 Ma) and Weasua (779 ± 6 Ma and 754 ± 7 Ma), indicating emplacement during break-up of the supercontinent Rodinia. The mineralogy and mica compositions along with bulk-rock geochemistry of Camp Alpha kimberlites are consistent with derivation from a sub-lithospheric mantle source. The Weasua lamproite contains perovskite with trace element concentrations (e.g., Sr < 3000 µg/g), trace element ratios (e.g., Th/U, Th/Nb, and La/Nb), and 87Sr/86Sr values (0.7029 to 0.7030) that overlap those of perovskite in the Camp Alpha kimberlites (87Sr/86Sr = 0.7028 ± 0.0002). These data are also similar to those of perovskite in worldwide Neoproterozoic to Cambrian-aged kimberlites but distinct from typical cratonic lamproites, which exhibit perovskite with high Sr contents (> 4000 µg/g) and Sr isotope signatures typical of the enriched lithospheric mantle (bulk-rock 87Sr/86Sri generally > 0.7050). A possible petrogenetic model for the Weasua lamproites entails derivation from a sub-lithospheric source similar to that of the Camp Alpha kimberlites with mineralogical, and hence major-element, variations between these two proximal localities driven by variable assimilation of heterogeneous SCLM material.
  • Sub-solidus Oligocene zircon formation in garnet peridotite during fast decompression and fluid infiltration (Duria, Central Alps)
    Item type: Journal Article
    Hermann, J.; Rubatto, D.; Trommsdorff, V. (2006)
    Mineralogy and Petrology
  • Origin, spectral characteristics and practical applications of the cathodoluminescence (CL) of quartz
    Item type: Journal Article
    Götze, J.; Plötze, Michael; Habermann, D. (2001)
    Mineralogy and Petrology
  • U–Pb dating, Hf-isotope characteristics and trace-REE-patterns of zircons from Medet porphyry copper deposit, Bulgaria
    Item type: Journal Article
    Peytcheva, Irena; von Quadt, Albrecht; Neubauer, Franz; et al. (2009)
    Mineralogy and Petrology
  • Compositional zoning of garnet porphyroblasts from the polymetamorphic Wölz Complex, Eastern Alps
    Item type: Journal Article
    Bestel, Martina; Gawronski, Timo; Abart, Rainer; et al. (2009)
    Mineralogy and Petrology
  • Stabilisation of divalent rare earth elements in natural fluorite
    Item type: Journal Article
    Kempe, U.; Plötze, Michael; Brachmann, A.; et al. (2002)
    Mineralogy and Petrology
  • Pb and Sr isotope and geochemical data from the Pb-Zn deposit Bleiberg (Austria)
    Item type: Journal Article
    Schroll, E.; Köppel, V.; Cerny, I. (2006)
    Mineralogy and Petrology
  • The origin of compositional variations in kimberlites based on comparative petrology and geochemistry of samples from four cratons
    Item type: Journal Article
    Zech, Rebecca F.; Giuliani, Andrea; Weiss, Yaakov; et al. (2025)
    Mineralogy and Petrology
    The term ‘kimberlite’ describes rocks that span a large mineralogical variety including enrichments in mica, carbonates, perovskite, spinel and/or ilmenite. The origin of these compositional variations is addressed here by comparing the petrography, mineral chemistry and bulk-rock as well as groundmass geochemistry of seven representative kimberlite samples (from Wesselton in South Africa; Karowe in Botswana; Diavik and Gahcho Kué in Canada; Majuagaa in Greenland, and Letšeng in Lesotho). These samples exhibit a broad range of mineral and bulk geochemistry covering the whole kimberlite spectrum. Bulk-groundmass compositions are variously enriched in Si, K, Ti, CO₂ and H₂O depending on the dominant groundmass mineralogy – e.g., high K in mica-rich samples. Interaction with mica and ilmenite-bearing lithospheric mantle appears to be the driving factor of K (± Al) and Ti enrichment, respectively. Degassing controls CO₂, and higher SiO₂ in the melt derived from assimilation of lithospheric pyroxenes leads to a decrease in CO₂ solubility. Serpentinization by deuteric and/or crustal fluids governs H₂O concentrations, generally exceeding the H₂O solubility in kimberlitic melts at upper crustal conditions. Even where the groundmass composition closely approximates predicted kimberlitic melts such as at Majuagaa, the low contents of Na require substantial loss of alkalis via fluids during ascent and emplacement. Thus, compositional variations in erupted kimberlites reflect the combination of asthenospheric source variability, lithospheric assimilation, crystallization, degassing and interaction with deuteric and crustal fluids.
Publications 1 - 10 of 17