Metasomatism of the Kaapvaal Craton during Cretaceous intraplate magmatism revealed by combined zircon U-Pb isotope and trace element analysis
نویسندگان
چکیده
The origins of the mica-amphibole(K-richterite)-rutile-ilmenite-diopside (MARID) and the, presumably related, phlogopite-K-richterite-peridotite (PKP) mantle xenolith suites remain enigmatic. For instance, it is unclear if MARID rocks represent pervasively metasomatised peridotite or veins magmatic material. In Kaapvaal Craton, previous studies employing zircon U-Pb dating in PKP xenoliths demonstrated that ages are broadly coincident with nearby expressions Cretaceous kimberlite orangeite magmatism, implying a genetic link. However, use typically small sample sizes (i.e. few analysed grains) may mask complexities growth history lithologies, as key populations undetected. this paper, we analyse isotopic (U-Pb) trace element composition (n > 40) from three MARID/PKP Kimberley region order to reveal not just timing, but tempo metasomatism. This protocol takes its inspiration detrital clastic sedimentary rocks, which large numbers grains dated, so no important parts record missed. Our data show magmatism magmatism. While range detect mirrors detected by workers, addition larger means can was episodic. By integrating ages, demonstrate older zircon, generally has greater geochemical affinity lamproitic zircon. contrast, most zircons peak have trace-element compositions similar megacrystic - suite crystals thought be connected early high-pressure proto kimberlitic liquids/fluids. These strongly indicate form during localized recurrent melting enriched lithosphere. metasomatizing effects passage varying magmas at shallow depth lithosphere also contribute their complex age signatures. presence span entire intra-cratonic Kimberley, derive both major phases intracratonic single xenolith, necessitates more origin for than simple cumulate. observation argues rocks.
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ژورنال
عنوان ژورنال: Chemical Geology
سال: 2021
ISSN: ['0009-2541', '1872-6836']
DOI: https://doi.org/10.1016/j.chemgeo.2021.120302