Microcontinents are globally recognized as continental regions partially or entirely surrounded by oceanic lithosphere. Due to their positioning, they may become entangled in subduction zones and undergo either accretion or subduction. High-pressure metamorphism in subducted continental rocks supports the idea that microcontinents can be subducted, regardless of their low densities. In this study, we used 2D numerical models to simulate collision of microcontinents with different lengths located at various distances from the upper plate in a subduction system characterized by different convergence velocities, in order to examine their effects on the thermo-mechanical evolution of subduction systems. Specifically, we analyzed the conditions that favor subduction or accretion of microcontinents and investigated how their presence affects the thermal state within the mantle wedge. Our results reveal that the presence of microcontinents can lead to four styles of subduction: (a) continuous subduction; (b) continuous subduction with jump of the subduction channel; (c) interruption and reinitiation of the subduction; (d) continental collision. We discovered that longer microcontinents and higher velocities of the subducting plate contrast a continuous subduction favoring accretion, whereas farther initial locations from the upper plate and higher velocities of the upper plate favor the subduction of the microcontinent. In addition, we observed that the subduction style has direct effects on the thermal state, with important implications for the potential metamorphic conditions recorded by the subducted continental rocks. In particular, models characterized by parameters that favor the subduction of a larger amount of continental material from the microcontinent exhibit warm mantle wedges.

中文翻译：

---

微大陆碰撞对海洋-大陆俯冲系统的热机械效应


微大陆是全球公认的部分或全部被海洋岩石圈包围的大陆区域。由于它们的位置，它们可能会纠缠在俯冲带中，并经历吸积或俯冲。俯冲大陆岩石中的高压变质作用支持了微大陆可以俯冲的观点，无论其密度如何。在这项研究中，我们使用二维数值模型模拟了在具有不同收敛速度的俯冲系统中位于距上板块不同距离处的不同长度的微大陆的碰撞，以研究它们对俯冲系统热机械演化的影响。具体来说，我们分析了有利于微大陆俯冲或吸积的条件，并研究了它们的存在如何影响地幔楔内的热状态。我们的结果表明，微大陆的存在会导致四种类型的俯冲：（a） 连续俯冲;（b） 俯冲通道跳跃的连续俯冲;（c） 俯冲的中断和重新开始;（d） 大陆碰撞。我们发现，较长的微大陆和较高的俯冲板块速度与有利于吸积的连续俯冲形成鲜明对比，而距离上板块较远的初始位置和较高板块的速度有利于微大陆的俯冲。此外，我们观察到俯冲类型对热状态有直接影响，对俯冲大陆岩石记录的潜在变质条件具有重要意义。 特别是，以有利于从微大陆俯冲大量大陆物质的参数为特征的模型表现出温暖的地幔楔形。