钻石证据表明磷有限度地俯冲到下地幔
加拿大阿尔伯塔大学D. Graham Pearson团队报道了钻石证据表明磷有限度地俯冲到下地幔。相关论文于2026年2月10日发表在《地质学》杂志上。
磷的循环是生命必需元素，对地球的生物地球化学系统至关重要。尽管地壳级别的磷循环已被充分约束，但地幔级别的循环，特别是磷向深部地幔运输的效率，仍然了解甚少。
研究组报道了一颗来自巴西Juína的钻石中包含的铁方镁石、方解石（退化文石）和透磷酸盐（高压磷酸盐矿物）内含物。这些内含物的地球化学特征结合热力学模型表明，其源岩是驻留在下地幔深度的俯冲改性洋壳（AOC）。这些内含物提供了矿物学证据，证明磷以透磷酸盐的形式被运输到地球的下地幔。这颗钻石及其内含物的形成要求俯冲板块遵循现代俯冲系统中已知板块地温梯度的最冷端成员。
原岩的富钙特性使这种类型的AOC能够保持在固相线以下，保留了原本会在部分熔融过程中溶解并进入浅部地幔的磷酸盐。AOC将磷运输到下地幔的条件要求极冷的板块地温梯度和富钙成分，这些严格条件有效地最小化了深部循环。在古元古代之前，这种限制效应会更加明显，当时AOC的表面温度更高，导致更强的部分熔融。因此，通过浅部地幔循环，磷主要被保留在地壳中，这在现代和尤其在古代更为显著，维持了一个对养分可得性和生命起源至关重要的可及地表磷储库。
附：英文原文
Title: Diamond evidence for limited subduction of phosphorus into the lower mantle
Author: Qiwei Zhang, Frank E. Brenker, Suzette Timmerman, Steven B. Shirey, Thomas Stachel, Robert W. Luth, Andrew J. Locock, Richard A. Stern, Ingrid L. Chinn, Laszlo Vincze, Bart Vekemans, Pieter Tack, Ella De Pauw, Miles Lindner, Antonia Ashauer, Fabrizio Nestola, D. Graham Pearson
Issue&Volume: 2026-02-10
Abstract: The cycling of phosphorus, a life-essential element, is fundamental to Earth’s biogeochemical system. While crustal-level phosphorus cycling is well constrained, mantle-level recycling, particularly the efficiency of phosphorus transport into the deep mantle, remains poorly constrained. Here, we report ferropericlase, calcite (retrogressed aragonite), and tuite (high-pressure phosphate) inclusions in a diamond from Juína, Brazil. The geochemistry of these inclusions combined with thermodynamic modeling indicates that their source rock was subducted altered oceanic crust (AOC) residing at lower-mantle depths. These inclusions provide mineralogical confirmation that phosphorus is transported into Earth’s lower mantle as tuite. Formation of this diamond and its inclusions requires the subducting slab to have followed the coldest end member of recognized slab geotherms among modern subduction systems. The Ca-rich nature of the protolith allows this type of AOC to remain subsolidus, retaining phosphate that would otherwise dissolve during partial melting and move into the shallow mantle. The requirements of both a very cold slab geotherm and a Ca-rich composition for the AOC to transport phosphorus to the lower mantle are stringent conditions that effectively minimize deep recycling. This limiting effect would have been even more pronounced prior to the Paleoproterozoic, when the surface temperatures of AOC would have been higher, leading to enhanced melting. Consequently, phosphorus is dominantly retained in the crust through shallow mantle recycling, now and especially in the ancient past, maintaining an accessible surface phosphorus reservoir critical for nutrient availability and the origin of life.
DOI: 10.1130/G54011.1
