EarthByte Group, School of Geosciences, The University of Sydney, Sydney, 2006, Australia.
Sci Rep. 2023 Jun 6;13(1):9216. doi: 10.1038/s41598-023-36250-w.
Kimberlites are sourced from thermochemical upwellings which can transport diamonds to the surface of the crust. The majority of kimberlites preserved at the Earth's surface erupted between 250 and 50 million years ago, and have been attributed to changes in plate velocity or mantle plumes. However, these mechanisms fail to explain the presence of strong subduction signatures observed in some Cretaceous kimberlites. This raises the question whether there is a subduction process that unifies our understanding of the timing of kimberlite eruptions. We develop a novel formulation for calculating subduction angle based on trench migration, convergence rate, slab thickness and density to connect the influx of slab material into the mantle with the timing of kimberlite eruptions. We find that subduction angles combined with peaks in slab flux predict pulses of kimberlite eruptions. High rates of subducting slab material trigger mantle return flow that stimulates fertile reservoirs in the mantle. These convective instabilities transport slab-influenced melt to the surface at a distance inbound from the trench corresponding to the subduction angle. Our deep-time slab dip formulation has numerous potential applications including modelling the deep carbon and water cycles, and an improved understanding of subduction-related mineral deposits.
金伯利岩起源于热化学上升流，可将钻石运移到地壳表面。保存在地球表面的大多数金伯利岩是在 2.5 亿至 5000 万年前喷发的，这与板块速度变化或地幔柱有关。然而，这些机制无法解释在一些白垩纪金伯利岩中观察到的强烈俯冲特征。这就提出了一个问题，是否存在一种俯冲过程，可以统一我们对金伯利岩喷发时间的理解。我们开发了一种新的俯冲角计算方法，该方法基于海沟迁移、汇聚速度、板块厚度和密度，将板块物质的涌入与金伯利岩喷发的时间联系起来。我们发现，俯冲角度与板块通量峰值相结合，可以预测金伯利岩喷发的脉冲。大量俯冲板块物质会引发地幔返回流，从而刺激地幔中的肥沃储层。这些对流不稳定性将受板块影响的熔体输送到表面，距离海沟的距离与俯冲角相对应。我们的深时板块倾角公式具有许多潜在的应用，包括模拟深部碳和水循环，以及更好地理解与俯冲有关的矿床。
