Tectonic setting of kimberlites

Jelsma, Hielke A.; Barnett, Wayne; Richards, Simon; Lister, Gordon

doi:10.1016/j.lithos.2009.06.030

Cited by 183 publications

(136 citation statements)

References 39 publications

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“…We took 2 milliard years as the central value in our estimate above. Now on the other hand the times of the creation of the kimberlites in South Africa seem [36] to be dominantly less than about 200 million years ago, although a few are indeed older. Thus effectively the upper limit for the age of the detected kimberlite pipes lies in the interval from 2 * 10 8 years to 4 * 10 9 years.…”

Section: Uncertainty Estimate For Number Of Kimberlite Pipes/clustersmentioning

confidence: 99%

“…Now, however, it must be admitted that we have a problem for this picture of the origin of kimberlite pipes. The times of creation of various kimberlite pipes have been estimated [36,37] and a distribution found, even in regions where Archean pre-Cambrian rocks were exposed, with clustering in various geological eras. In particular there is a concentration of kimberlite emplacements in a couple of clusters during the Cretaceous period earlier than about 200 million years ago.…”

Section: • Explosion Energy Is Comfortably Smaller Than the Estimatedmentioning

confidence: 99%

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Tunguska dark matter ball

Froggatt

Nielsen²

2015

Int. J. Mod. Phys. A

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It is suggested that the Tunguska event in June 1908 was due to a cm-large ball of a condensate of bound states of 6 top and 6 anti-top quarks containing highly compressed ordinary matter. Such balls are supposed to make up the dark matter as we earlier proposed. The expected rate of impact of this kind of dark matter ball with the earth seems to crudely match a time scale of 200 years between the impacts. The main explosion of the Tunguska event is explained in our picture as material coming out from deep within the earth, where it has been heated and compressed by the ball penetrating to a depth of several thousand km. Thus the effect has some similarity with volcanic activity as suggested by Kundt. We discuss the possible identification of kimberlite pipes with earlier Tunguska-like events. A discussion of how the dark matter balls may have formed in the early universe is also given. * colin.froggatt@glasgow.ac.uk † hbech@nbi.dk 1

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Section: Uncertainty Estimate For Number Of Kimberlite Pipes/clustersmentioning

confidence: 99%

Section: • Explosion Energy Is Comfortably Smaller Than the Estimatedmentioning

confidence: 99%

Tunguska dark matter ball

Froggatt

Nielsen²

2015

Int. J. Mod. Phys. A

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“…The trans-lithosphere discontinuity of the Lucapa structure played a very important role by favoring a thermal perturbation, melt production, and mantle upwelling [28,29], and in the evolution of the host rocks. The integration of petrography, geochemistry, and geothermobarometric studies of the less altered samples from six kimberlites in the northeastern Angola suggests that these kimberlites originated from different sources in spite of the fact that they are all located in the same tectonic corridor.…”

Section: Discrimination Among Kimberlitesmentioning

confidence: 99%

“…The reactivation of old deep-seated faults during the Paleoproterozoic, the Permo-Triassic, the Cretaceous and the Cenozoic [29] probably is an important factor in some of the different pulses of diamondiferous kimberlites. Thus petrography, geochemistry and Sm-Nd isotopic data from these kimberlites provide interesting tools to recognize possible diamondiferous kimberlites in the area.…”

Section: The Underlying Mantle In the Northeastern Angolamentioning

confidence: 99%

Major- and Trace-Element Compositions of Indicator Minerals that Occur as Macro- and Megacrysts, and of Xenoliths, from Kimberlites in Northeastern Angola

et al. 2012

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Abstract:In this study, we compare the major-and trace-element compositions of olivine, garnet, and clinopyroxene that occur as single crystals (142 grains), with those derived from xenoliths (51 samples) from six kimberlites in the Lucapa area, northeastern Angola: Tchiuzo, Anomaly 116, Catoca, Alto Cuilo-4, Alto Cuilo-63 and Cucumbi-79. The samples were analyzed using electron probe microanalysis (EPMA) and laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). The results suggest different paragenetic associations for these kimberlites in the Lucapa area. Compositional overlap in some of the macrocryst and mantle xenolith samples indicates a xenocrystic origin for some of those macrocrysts. The presence of mantle xenocrysts suggests the possibility of finding diamond. Geothermobarometric calculations were carried out using EPMA data from xenoliths by applying the program PTEXL.XLT. Additional well calibrated single-clinopyroxene thermobarometric calculations were also applied. Results indicate the underlying mantle experienced different equilibration conditions. Subsequent metasomatic enrichment events also support a hypothesis of different sources for the kimberlites. These findings contribute to a better understanding of the petrogenetic evolution of the kimberlites in northeastern Angola and have important implications for diamond exploration.

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“…However, seven different eruptive centres were distinguished, associated to tuff ring and maar morphologies ( Figure 1; Campeny et al, 2014). The emplacement of the Catanda volcanic carbonatites is associated to the extensional domain of the Lucapa belt, which is a rift corridor defined by the NE-SW trending fractures of the Quilengues-Andulo fault system (Jelsma et al, 2009). The first magmatic activity reported in the Lucapa corridor is from the Paleoproterozoic (Sykes et al, 1978) but magmatism was also significantly important in the Upper Cretaceous, associated to the break-up of Gondwana and the corresponding opening of the South Atlantic Ocean (Moulin et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Recent carbonatitic magmatism in Angola: the dykes of the Chiva lagoon maar

Campeny¹,

Melgarejo²,

Mangas³

et al. 2017

BSGM

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RESUMEN ABSTRACTChiva is a circular lagoon with a diameter of 900 m, located in the vicinity of the Catanda graben (Angola). This area is largely covered by Quaternary lacustrine sediments, however, a few dykes of carbonatitic composition have been found near the SE shore of the lagoon. The intrusion of these carbonatitic dykes has been linked to the occurrence of recent volcanic events in the Chiva area and interpreted as feeding channels of an eruptive centre with maar morphology. The Chiva carbonatitic dykes show a finely porphyritic texture formed by phenocrysts of subhedral calcite (60 %), apatite (30 %) and magnetite (10 %) hosted in a fine calcite-rich ground mass that also contains accessory minerals such as pyrochlore, perovskite and kimzeyite. The mineralogical and compositional features of the Chiva dykes are similar to those described in some of the carbonatitic lavas from the Catanda graben, suggesting that both volcanic events are genetically related. The finding of this new eruptive centre enlarges the carbonatitic domain of Catanda and opens the door to the discovery of new carbonatitic outcrops in this region of Western Angola.

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Tectonic setting of kimberlites

Cited by 183 publications

References 39 publications

Tunguska dark matter ball

Tunguska dark matter ball

Major- and Trace-Element Compositions of Indicator Minerals that Occur as Macro- and Megacrysts, and of Xenoliths, from Kimberlites in Northeastern Angola

Recent carbonatitic magmatism in Angola: the dykes of the Chiva lagoon maar

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