Dating Kimberlites: Methods and Emplacement Patterns Through Time

Heaman, Larry M.; Phillips, David; Pearson, G.

doi:10.2138/gselements.15.6.399

Cited by 38 publications

(33 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These lines of evidence suggest that kimberlites might sample deep mantle sources similar to OIBs. However, kimberlites have been emplaced in continental regions since at least ∼2.1 Ga and perhaps, since 2.8 Ga (22) and hence, provide a record of deep and ancient mantle components that spans a time window more than an order of magnitude longer than that represented by OIBs (i.e., <200 Ma).…”

Section: Significancementioning

confidence: 99%

Remnants of early Earth differentiation in the deepest mantle-derived lavas

Giuliani

Jackson

Dalton

2020

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The noble gas isotope systematics of ocean island basalts suggest the existence of primordial mantle signatures in the deep mantle. Yet, the isotopic compositions of lithophile elements (Sr, Nd, Hf) in these lavas require derivation from a mantle source that is geochemically depleted by melt extraction rather than primitive. Here, this apparent contradiction is resolved by employing a compilation of the Sr, Nd, and Hf isotope composition of kimberlites—volcanic rocks that originate at great depth beneath continents. This compilation includes kimberlites as old as 2.06 billion years and shows that kimberlites do not derive from a primitive mantle source but sample the same geochemically depleted component (where geochemical depletion refers to ancient melt extraction) common to most oceanic island basalts, previously called PREMA (prevalent mantle) or FOZO (focal zone). Extrapolation of the Nd and Hf isotopic compositions of the kimberlite source to the age of Earth formation yields a143Nd/144Nd-176Hf/177Hf composition within error of chondrite meteorites, which include the likely parent bodies of Earth. This supports a hypothesis where the source of kimberlites and ocean island basalts contains a long-lived component that formed by melt extraction from a domain with chondritic143Nd/144Nd and176Hf/177Hf shortly after Earth accretion. The geographic distribution of kimberlites containing the PREMA component suggests that these remnants of early Earth differentiation are located in large seismically anomalous regions corresponding to thermochemical piles above the core–mantle boundary. PREMA could have been stored in these structures for most of Earth’s history, partially shielded from convective homogenization.

show abstract

Section: Significancementioning

confidence: 99%

Remnants of early Earth differentiation in the deepest mantle-derived lavas

Giuliani

Jackson

Dalton

2020

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Some rare superdeep (sub-lithospheric) kimberlites may have ascended from as deep as 800 km [ 14 – 17 ], although these diamonds could have been transported to the base of the lithosphere before being entrained by kimberlite magmas [ 18 ]. The kimberlite record extends deep in geological times [the oldest known kimberlite pipe is 2.85 Gyr old; 19 ] and is considered to be episodic from 2 Ga [ 20 – 22 ]. Over 60% of known kimberlite pipes erupted during Mesozoic and Cenozoic times [ 22 ], which could be either the result of the preferential preservation of younger kimberlites or of increased eruption rate during the last 200 Myr [ 23 ].…”

Section: Introductionmentioning

confidence: 99%

Mapping global kimberlite potential from reconstructions of mantle flow over the past billion years

2022

View full text Add to dashboard Cite

Kimberlites are the primary source of economic grade diamonds. Their geologically rapid eruptions preferentially occur near or through thick and ancient continental lithosphere. Studies combining tomographic models with tectonic reconstructions and kimberlite emplacement ages and locations have revealed spatial correlations between large low shear velocity provinces in the lowermost mantle and reconstructed global kimberlite eruption locations over the last 320 Myr. These spatial correlations assume that the lowermost mantle structure has not changed over time, which is at odds with mantle flow models that show basal thermochemical structures to be mobile features shaped by cold sinking oceanic lithosphere. Here we investigate the match to the global kimberlite record of stationary seismically slow basal mantle structures (as imaged through tomographic modelling) and mobile hot basal structures (as predicted by reconstructions of mantle flow over the past billion years). We refer to these structures as “basal mantle structures” and consider their intersection with reconstructed thick or ancient lithosphere to represent areas with a high potential for past eruptions of kimberlites, and therefore areas of potential interest for diamond exploration. We use the distance between reconstructed kimberlite eruption locations and kimberlite potential maps as an indicator of model success, and we find that mobile lowermost mantle structures are as close to reconstructed kimberlites as stationary ones. Additionally, we find that mobile lowermost mantle structures better fit major kimberlitic events, such as the South African kimberlite bloom around 100 Ma. Mobile basal structures are therefore consistent with both solid Earth dynamics and with the kimberlite record.

show abstract

“…Such DSRs in kimberlites have been identified exclusively on mantle‐derived zircons. This mantle‐derived population of zircons with DSRs includes the megacrystic zircons common in kimberlites (i.e., kimberlitic zircon; Belousova et al., 2002; Heaman et al., 2019; Kamenetsky et al., 2014), and zircons associated with mica–amphibole–rutile–ilmenite–diopside (MARID; Giuliani et al., 2015; Robles‐Cruz et al., 2012), phlogopite–K‐richterite–peridotite (Hoare et al., 2021), and veined harzburgite (Kinny & Dawson, 1992) mantle xenolith suites. Only one DSR has previously been dated and was found to have an identical age to the host mantle zircon (Davis, 1977), and there is no solid evidence for the growth conditions of DSRs.…”

Section: Introductionmentioning

confidence: 99%

Desilicification Rims of Zircon Xenocrysts Record the Timing of Kimberlite Emplacement

Мельник

Korolev

et al. 2022

JGR Solid Earth

View full text Add to dashboard Cite

Kimberlites are deep and relatively rare mantle‐derived igneous rocks, which provide key insights into the lithospheric mantle composition beneath continents (i.e., from the entrained mantle materials) at the time of magma emplacement. In addition, the temporal distribution of kimberlites throughout Earth's history may reveal secular changes in global geodynamics. However, alteration and abundant exotic material (i.e., xenoliths and xenocrysts) of different ages, both typical of kimberlites, often hinder reliable dating of these rocks. In this study, we investigated zircon xenocrysts and their replacement by desilicification reaction rims (DSRs), which consist mainly of baddeleyite, in the metamorphosed Kimozero kimberlites from the Karelian Craton, Russia. Similar DSRs have been identified previously on mantle‐derived zircons in numerous kimberlites, but the precise timing and location of formation of these rims remain unclear. U–Pb isotope dating of mantle zircon xenocrysts in the Kimozero kimberlites indicates that these rocks were emplaced at ca. 1.97 Ga. DSRs with similar textures and baddeleyite chemistry occur on both the 1.97 Ga mantle and 2.70–2.38 Ga crustal zircon xenocrysts in these kimberlites. Pb–Pb isotope dating of the DSRs yields the same age (i.e., ca. 1.97 Ga) as the mantle zircons. The data constrain the formation of DSRs to crustal levels and, more importantly, indicate that these rims record the timing of kimberlite emplacement. Therefore, we suggest that such baddeleyite reaction rims are a new and promising material for kimberlite geochronology.

show abstract

Dating Kimberlites: Methods and Emplacement Patterns Through Time

Cited by 38 publications

References 22 publications

Remnants of early Earth differentiation in the deepest mantle-derived lavas

Remnants of early Earth differentiation in the deepest mantle-derived lavas

Mapping global kimberlite potential from reconstructions of mantle flow over the past billion years

Desilicification Rims of Zircon Xenocrysts Record the Timing of Kimberlite Emplacement

Contact Info

Product

Resources

About