Abstract
The article provides an overview of boninitic magmatism occurrences in space and time and shows that the boninite rock series were generated through the entire geological history of the Earth. In modern environments, the genesis of boninites is related to intra‐oceanic subduction initiation. Boninites are typical members of suprasubduc‐ tion zone ophiolite sequences in the Phanerozoic fold belts and also present in the early Precambrian greenstone belts. A comparative study on compositions of the early Precambrian and Phanerozoic boninites indicate their evolu‐ tion through time due to gradual transition from the early thick‐plate tectonics to the modern thin‐plate tectonics. A link between subduction initiation and mantle‐plume impingement at the oceanic lithosphere is discussed.
Highlights
Boninites attracted much attention at the end of the 20th century, primarily, due to deep‐sea studies of forearc slopes in the modern plate convergence zones of the southwestern Pacific
Different types of the boninites have spectra of the same type with distinct negative anomalies of Nb(Ta) and Ti, positive anomalies of Sr and Zr(Hf) and apparent enrichment in large‐ionic lithophile (LIL) ele‐ ments (Rb, Ba, Cs, U, and Th) relative to N‐MORB. Such a kind of the trace elements patterns clearly suggests that (i) petrogenesis of boninite series should be ex‐ cluded any and even a minimum crustal input, and (ii) melting requires a mantle source more depleted in comparison to the mantle lherzolite that generates MORB melts
We reported a fragment of the suprasubduction ophiolites with sheeted dikes in gabbroids and me‐ talavas of the boninite series (~2.8 billion years) in the Iringora locality of the North‐Karelian greenstone belt [Shchipansky et al, 2001, 2004]
Summary
Boninites attracted much attention at the end of the 20th century, primarily, due to deep‐sea studies of forearc slopes in the modern plate convergence zones of the southwestern Pacific. De‐ tailed geochemical studies of many ophiolite sections revealed the presence of boninites unknown for mid‐ oceanic ridges, but abundant in juvenile island‐arc basements. As the boninite findings were ever‐growing in both the classi‐ cal fragments of the ‘ancient oceanic crust’, e.g. the Troodos in Cyprus, and Semail in Oman, or ‘classical sutures’ such as, the Main Urals Fault in Russia, this inevitably raises the question on the ophiolite nature. Another problem concerns the evolution of boninitic magmatism as boninites have been discovered in the early Precambrian greenstone belts. The aims of the paper are to provide an over‐ view of the boninitic magmatism occurrences through space and time, track its evolution, and propose a geo‐ dynamic explanation of this highly informative phe‐ nomenon
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