Natural diamonds and their inclusions provide unique glimpses of mantle processes from as deep as ~800 km and dating back to 3.5 G.y. Once formed, diamonds are commonly interpreted to travel upward, either slowly within mantle upwellings or rapidly within explosive, carbonate-rich magmas erupting at the surface. Although global tectonics induce subduction of material from shallow depths into the deep mantle, mineralogical evidence for downward movements of diamonds has never been reported. We report the finding of an unusual composite inclusion consisting of ringwoodite (the second finding to date), tetragonal zirconia, and coesite within an alluvial super-deep diamond from the Central African Republic. We interpret zirconia + coesite and ringwoodite as prograde transformation products after zircon or reidite (ZrSiO4) and olivine or wadsleyite, respectively. This inclusion assemblage can be explained if the diamond traveled downward after entrapping olivine/wadsleyite + zircon/reidite, dragged down by a subducting slab, before being delivered to the surface. This indicates that the commonly assumed view that diamonds form at, and capture material from, a specific mantle level and then travel upward is probably too simplistic.Investigating the most inaccessible parts of Earth's mantle is a challenging task. Most of our knowledge of deep mantle composition and processes is based on indirect evidence from laboratory experiments, numerical models, and seismic tomography (Stacey and Davis, 2008). Xenoliths (i.e., mantle rocks transported to the surface by eruptions of, e.g., kimberlitic magmas) provide critical geochemical data from depths down to >300 km (Haggerty, 2017). Diamonds, which are also found in kimberlites, can incorporate material (as mineral and fluid inclusions) from the environment in which they form. Although extremely rare, sub-lithospheric diamonds from below ~300 km depths, known as super-deep diamonds, offer the unique possibility to directly investigate regions of the mantle down to 800 km depths (Shirey et al., 2013). Mineral inclusions in these diamonds commonly show evidence of retrograde transformations, such as unmixing (Walter et al., 2011) or inversion to lower pressure phases (Stachel et al., 2000). These transformations record the ascent of diamonds through the mantle, consistent with models of diamond transport in mantle upwellings and uprising magmas.Geochemical data on carbon and nitrogen isotopes suggest that the majority of super-deep diamonds precipitated during reactions of melts released by subducting slabs with the surrounding mantle (e.g., Thomson et al., 2016). Therefore, a scenario wherein super-deep diamonds travel downward, following slab-imposed dynamics, before being caught in uprising mantle plumes seems plausible. However, no mineralogical evidence of prograde transformations recording diamond descent within downwelling mantle has been found until now. It remains unknown whether the lack of preservation of prograde reactions is due to complete mineralogical resetting, to sample bias, or to diamonds only moving upward after their formation.We studied a 1.3 carat (Fig. 1), type IaAB (Fig. S1 in the Supplemental Material1), colorless alluvial diamond from the Central African Republic. Micro-Raman spectroscopy enabled identification of a tiny (~10 μm) composite inclusion of ringwoodite (γ-Mg2SiO4), tetragonal zirconia (ZrO2), and coesite (SiO2), which represents the first mineralogical evidence of the downward movement of diamonds. This finding opens new possibilities for the interpretation of information provided by super-deep diamonds.Carbon isotope (δ13CVPDB [VPDB—Vienna Peedee belemnite]), N content, and N isotope (δ15NAir) spot analysis on the diamond were performed in situ using a CAMECA 1280 (HR) large geometry–secondary ion mass spectrometer (LG-SIMS). Micro-Raman analyses were performed using a Thermo Scientific DXR Micro-Raman spectrometer equipped with 10× and 50× long working distance (LWD) objectives. A single Fourier Transform Infrared (FTIR) analysis was performed with a Thermo Scientific Nicolet Centaurμs FTIR microscope. See the Supplemental Material for details of the methods.The C isotopic composition of the diamond (δ13CVPDB ranging from -2.8‰ to -1.65‰) is homogeneous (standard deviation = 0.27‰) and shows a 13C-enriched signature with respect to average mantle (δ13CVPDB = -5 ± 2 ‰; Javoy et al., 1986). Measurements of N content returned low values (£44 ppm; Table S1). Because the N concentration is low, in situ determination of the N isotopic composition is associated with large uncertainties (see the Supplemental Material and Fig. S2 therein). However, for N contents greater than the detection limit of our instrument (24 ppm), all δ15NAir values point to 15N-enriched compositions (δ15NAir = -0.49‰ to +6.2‰) and are significantly higher than that of the average mantle (δ15NAir = -5 ± 3‰, Javoy et al., 1986; Fig. S3). These isotopic compositions are consistent with an origin from fluids or melts derived from slab materials rich in carbonates (δ13CVPDB of ~0‰) and clays (δ15NAir of ~+16‰) similar to those observed in sedimentary covers (Palot et al., 2017). The low N content and the C and N isotopes are in agreement with previously reported data for super-deep diamonds world-wide, in particular those formed in the deeper portions of the upper mantle or the transition zone (Tappert et al., 2009; Palot et al., 2012, 2014, 2017).The diamond encloses numerous inclusions measuring up to a few tens of microns (Fig. 1). Micro-Raman spectroscopy identified most of the dark-colored inclusions with irregular shape as graphite due to the characteristic Raman peak at ~1578–1593 cm–1. Three inclusions of hydrous silicic fluid were also recognized from broad peaks at 616–674 cm–1 and 755–821 cm–1 (Fig. S4), which are interpreted as trapped diamond-parent fluid (cf. Nimis et al., 2016; see the Supplemental Material). Such fluid inclusions have never been reported in super-deep diamonds. Their occurrence supports a hydrous environment of formation, possibly related to a subduction environment, as also suggested by the isotopic data. Finally, a composite inclusion measurinĝ10 μm across is observed, in which ringwoodite (γ-Mg2SiO4), tetragonal zirconia (ZrO2), and coesite (SiO2) are all in contact with one other (Fig. 1). Two Raman peaks at ~797 cm–1 and 832 cm–1 corresponding to the asymmetric (T2g) and symmetric (A1g) stretching vibrations of SiO4 tetrahedra in ringwoodite (Kleppe et al., 2002), respectively, were clearly observed (Fig. 2). Vibrational modes of zirconia are measured at ~170, 258, 330, and 648 cm–1 (Ghosh et al., 2006), while the peak at 537 cm–1 is attributed to coesite (Smith et al., 2018). The higher wavenumber of the coesite peak measured inside the diamond with respect to the reference vibrational mode position at ambient conditions (~521 cm–1) is indicative of a high residual pressure.The occurrence of ringwoodite, the high-pressure polymorph of olivine that is stable at depths between 525 and 660 km, represents only the second terrestrial finding of ringwoodite after that of Pearson et al. (2014) and the first in an African diamond. The presence of ring-woodite unequivocally confirms the sub-lithospheric nature of the specimen and indicates that, at some point, the diamond resided in the lower part of the transition zone. The presence of tetragonal ZrO2, a high-temperature, high-pressure polymorph of zirconia that is stable between ~1170 and 2370 °C (Yoshimura, 1988) and up to 20 GPa (Haines et al., 1997), is also remarkable, as a ZrO2 phase has been previously detected only by electron microprobe analysis on two polished super-deep diamonds from Juina (Thomson et al., 2014). However, the mineral structure of these zirconia inclusions (monoclinic vs. tetragonal) has never been documented. Finally, whereas coesite has been previously recognized in several super-deep diamonds (Smith et al., 2018; Zedgenizov et al. 2019), it has never been reported in contact with zirconia or high-pressure olivine polymorphs within the same diamond.Although zircon is a common accessory mineral in crustal rocks (Hoskin and Schaltegger, 2003), its occurrence in diamonds is extremely rare and limited to few lithospheric samples (Kinny and Meyer, 1994). This is probably because zircon does not normally crystallize in the mantle as its lithologies are undersaturated in Zr and Si. However, zircons are found in orogenic peridotites (Zhao et al., 2019), altered mantle xenoliths (Konzett et al., 1998; Liu et al., 2010), and ophiolites (Robinson et al., 2015), suggesting that local Zr enrichment, e.g., related to metasomatic events, can stabilize this mineral in mantle rocks.The composite inclusion of ringwoodite, tetragonal zirconia, and coesite indicates that the investigated diamond sampled one of these enriched mantle lithologies. Zircon (or reidite, the high-pressure polymorph of zircon that is stable at depths >270–330 km; Tange and Takahashi, 2004) was possibly a product of the same metasomatic event that precipitated the diamond, involving a slab-derived fluid/melt interacting with peridotites in the supra-subduction mantle (Zhao et al., 2019). Alternatively, stable and resistant zircon may have originated in a shallow environment and survived a long downward movement within the subducting slab or the immediately overlying dragged mantle before being enclosed by the diamond.Considering the association with ringwoodite, the coexistence of high-temperature, high-pressure ZrO2 and SiO2 can be interpreted as the result of the breakdown of zircon (ZrSiO4) or reidite. Within the Earth's mantle, reidite transforms into orthorhombic zirconia (cotunnite structure) + stishovite (SiO2) at conditions corresponding to a depth of ~550 km along a subduction geotherm or 610 km along a normal mantle geotherm (Tange and Takahashi, 2004; Van Westrenen et al., 2004). These conditions also correspond to depths where ringwoodite is stable. However, in our composite inclusion, we did not directly observe stishovite and orthorhombic zirconia, but we did observe coesite and tetragonal zirconia. These polymorphs likely represent the products of stishovite and orthorhombic zirconia back-transformation during the ascent of the diamond toward the surface.Experiments have demonstrated that ring-woodite and stishovite can form together in suitable chemical systems (Bolfan-Casanova et al., 2000). However, the bulk compositions of these systems are either very simplified (MgO-SiO2-H2O) or significantly SiO2-enriched with respect to mantle peridotites, in particular when they interact with slab-derived carbonatite melts (Thomson et al., 2016); i.e., the typical systems in which super-deep diamonds are formed. Therefore, ringwoodite and stishovite are not expected to form stable mineral associations in mantle rocks. In particular, experiments that reproduced deep diamond-forming conditions (Thomson et al., 2016) never produced diamond–ringwoodite–stishovite mineral assemblages. This excludes entrapment of ring-woodite and stishovite as inclusions during precipitation of the diamond in the lower part of the transition zone. Instead, the observed inclusion assemblage is consistent with the entrapment of olivine (or wadsleyite) and zircon (or reidite) by their host at shallower depths, followed by phase transformation of olivine/wadsleyite to ringwoodite and breakdown of zircon/reidite to ZrO2 + SiO2 in response to an increase in pressure. The breakdown products could thus coexist with ringwoodite and be protected from subsequent reactions. Ringwoodite and stishovite would be stable at T < 1375 °C, while at higher temperatures they would transform to akimotoite or majorite (see Fig. 3). In our case, this transformation did not occur, which suggests that this diamond was carried to the surface by rapidly ascending kimberlite magmas, as was suggested for the previously reported ringwoodite occurrence in diamond (Pearson et al., 2014).Combining the petrological considerations with the low N content of the diamond, which is typical of subduction-related, super-deep diamonds that formed at ≥300 km, a minimum depth of formation of ~300 km also can be envisaged for the investigated diamond. For a first approximation, the maximum possible depth is constrained by the stability of reidite, i.e., ~550 or 610 km for a subduction or mantle geotherm, respectively (Tange and Takahashi, 2004; Fig. 4). However, unless the diamond behaved plastically, the true reidite breakdown depth could have been even greater. In fact, the inclusion volume reduction, due to the reidite transformation, could have acted as a pressure buffer, considering the high incompressibility of diamond.Because the exact depth at which the diamond was formed is unknown, it is not possible to determine the original mineral assemblage entrapped by the diamond (i.e., olivine versus wadsleyite versus ringwoodite + zircon versus reidite). Regardless, the occurrence of dissociated SiO2 and ZrO2 suggests that the diamond traveled toward greater depths after formation, allowing its inclusion assemblage to cross the ~550 or 610 km (or slightly greater) depth at which reidite decomposes (Fig. 4). In principle, isobaric cooling of an inclusion starting from conditions close to the reidite breakdown curve, e.g., due to intrusion of “cold” slab-derived melts, could also lead to reidite decomposition (Tange and Takahashi, 2004). Nonetheless, a purely isobaric scenario seems unrealistic, as coupling of the mantle with the subducting slab would most likely drag the diamond downward in any case.The unique phase assemblage observed in this diamond indicates the downward movement of a super-deep diamond in the mantle, possibly following subducting slab dynamics, to depths reaching the lower part of the transition zone. Even though the extent of this downward movement cannot be constrained, it may have occurred over hundreds of kilometers. Considering the possibility that the original entrapped zircon had a shallower origin, our finding suggests that diamond may act as a long-route vessel for the recycling of crustal material to extreme depths within the Earth. We suggest that a comprehensive understanding of super-deep diamonds and the information contained in their inclusions may include the possibility of prograde downward movement before upwelling and final eruption.M. Alvaro and F. Nestola thank the European Research Council (grant agreements 714936 and 307322, respectively). D. Novella thanks the Rita Levi Montalcini program (Italian Ministry of University and Research) for support. LG-SIMS costs were supported by the Nancy-LG-SIMS group (Nancy, France). S.D. Jacobsen acknowledges support from U.S. National Science Foundation grant EAR-1853521. We thank Thomas Stachel, Andrea Giuliani, Win Van Westrenen, and one anonymous reviewer, whose constructive suggestions helped to improve the manuscript, and Chris Clark and Urs Schaltegger for careful editorial handling.

中文翻译：

---

Ringwoodite 和氧化锆内含物表明超深钻石向下移动

天然钻石及其内含物提供了独特的地幔过程一瞥，从深至约 800 公里，可追溯到 3.5 Gy在表面。尽管全球构造导致物质从浅层俯冲到地幔深处，但从未报道过钻石向下运动的矿物学证据。我们报告在来自中非共和国的冲积超深钻石中发现了一种不寻常的复合夹杂物，该夹杂物由菱镁矿（迄今为止的第二个发现）、四方氧化锆和柯石英组成。我们将氧化锆+柯石英和菱镁矿解释为继锆石或reidite (ZrSiO4)和橄榄石或wadsleyite之后的渐进转变产物，分别。如果钻石在被俯冲板片拖下后向下移动，然后进入地表，则可以解释这种内含物组合。这表明钻石在特定地幔层形成并从特定地幔层捕获物质然后向上传播的普遍假设的观点可能过于简单化。研究地幔最难以接近的部分是一项具有挑战性的任务。我们对深部地幔成分和过程的大部分知识都基于来自实验室实验、数值模型和地震层析成像的间接证据（Stacey 和 Davis，2008）。捕虏体（即，通过金伯利岩岩浆等喷发输送到地表的地幔岩石）提供了从深度到 > 300 公里的关键地球化学数据（哈格蒂，2017 年）。钻石，在金伯利岩中也发现了这些物质，它们可以结合它们形成的环境中的物质（如矿物和流体包裹体）。虽然极其罕见，但来自约 300 公里深度以下的亚岩石圈钻石，被称为超深钻石，为直接研究深至 800 公里深度的地幔区域提供了独特的可能性（Shirey 等人，2013 年）。这些钻石中的矿物包裹体通常显示出逆行转变的证据，例如分离（Walter 等人，2011 年）或向低压阶段反转（Stachel 等人，2000 年）。这些转变记录了钻石通过地幔的上升，与地幔上升流和上升岩浆中的钻石传输模型一致。碳和氮同位素的地球化学数据表明，大多数超深金刚石是在俯冲板片释放的熔体与周围地幔的反应过程中沉淀出来的（例如，Thomson 等人，2016 年）。因此，在被上升的地幔柱捕获之前，超深钻石在板块强加动力学之后向下移动的情况似乎是合理的。然而，到目前为止，还没有发现记录下流地幔中钻石下降的顺行转变的矿物学证据。尚不清楚是否由于矿物学完全重置、样品偏差或钻石在形成后仅向上移动而导致无法保存顺行反应。我们研究了一颗 1.3 克拉（图 1）的 IaAB 型（图 S1）补充材料1), 来自中非共和国的无色冲积钻石。显微拉曼光谱能够识别出由菱镁矿 (γ-Mg2SiO4)、四方氧化锆 (ZrO2) 和柯石英 (SiO2) 组成的微小 (~10 μm) 复合夹杂物，这是钻石向下运动的第一个矿物学证据。这一发现为解释超深钻石所提供的信息开辟了新的可能性。使用一种原位分析方法对钻石进行了碳同位素（δ13CVPDB [VPDB-Vienna Peedee belemnite]）、N 含量和 N 同位素（δ15NAir）点分析。 CAMECA 1280 (HR) 大几何-二次离子质谱仪 (LG-SIMS)。使用配备 10 倍和 50 倍长工作距离 (LWD) 物镜的 Thermo Scientific DXR 微拉曼光谱仪进行微拉曼分析。使用 Thermo Scientific Nicolet Centaurμs FTIR 显微镜进行单次傅里叶变换红外 (FTIR) 分析。有关方法的详细信息，请参阅补充材料。钻石的 C 同位素组成（δ13CVPDB 范围从 -2.8‰ 到 -1.65‰）是均质的（标准偏差 = 0.27‰），并且相对于平均地幔显示出富含 13C 的特征（δ13CVPDB = -5 ± 2 ‰；Javoy 等人，1986）。N 含量的测量值返回低值（£44 ppm；表 S1）。由于 N 浓度较低，因此 N 同位素组成的原位测定具有很大的不确定性（参见补充材料和其中的图 S2）。然而，对于大于我们仪器检测限（24 ppm）的 N 含量，所有 δ15NAir 值都指向富含 15N 的成分（δ15NAir = -0.49‰ 至 +6。2‰）并且显着高于平均地幔（δ15NAir = -5 ± 3‰，Javoy et al., 1986; Fig. S3）。这些同位素组成与源自富含碳酸盐（δ13CVPDB 约为 0‰）和粘土（δ15NAir 约为 +16‰）的板片材料的流体或熔体的来源一致，类似于在沉积盖层中观察到的那些（Palot 等，2017 ）。低 N 含量以及 C 和 N 同位素与之前报道的全球超深钻石数据一致，特别是在上地幔或过渡带较深部分形成的钻石（Tappert 等，2009； Palot et al., 2012, 2014, 2017)。钻石包裹着许多直径达几十微米的内含物（图 1）。由于在~1578-1593 cm-1 处的特征拉曼峰，显微拉曼光谱将大部分形状不规则的深色夹杂物鉴定为石墨。在 616-674 cm-1 和 755-821 cm-1 的宽峰中也发现了三个含水硅流体包裹体（图 S4），这被解释为被困金刚石母体流体（参见 Nimis 等人，2016 年） ; 见补充材料）。这种流体包裹体从未在超深钻石中报道过。它们的出现支持含水的形成环境，可能与俯冲环境有关，同位素数据也表明。最后，观察到复合夹杂物尺寸为 10 μm，其中菱镁矿 (γ-Mg2SiO4)、四方氧化锆 (ZrO2) 和柯石英 (SiO2) 都相互接触（图 1）。在~797 cm-1 和832 cm-1 处的两个拉曼峰分别对应于菱木中SiO4 四面体的不对称（T2g）和对称（A1g）伸缩振动（Kleppe et al., 2002），可以清楚地观察到（图1）。 2）。氧化锆的振动模式在 ~170、258、330 和 648 cm-1 处测量（Ghosh 等人，2006 年），而 537 cm-1 处的峰值归因于柯石英（Smith 等人，2018 年）。在环境条件下（~521 cm-1），相对于参考振动模式位置，金刚石内部测得的柯石英峰波数较高，这表明存在较高的残余压力。在 525 和 660 公里之间的深度是稳定的，这仅代表了 Pearson 等人的第二个陆地发现的菱木石。（2014 年）和第一颗非洲钻石。环木石的存在明确地证实了样品的亚岩石圈性质，并表明在某些时候，钻石位于过渡带的下部。四方 ZrO2 的存在，这是一种高温、高压氧化锆多晶型物，在 ~1170 至 2370 °C（Yoshimura，1988）和高达 20 GPa（Haines 等，1997）之间稳定，也很显着，作为 ZrO2 相，之前仅通过对来自 Juina 的两颗抛光超深钻石的电子探针分析检测到（Thomson 等人，2014 年）。然而，这些氧化锆夹杂物（单斜与四方）的矿物结构从未被记录过。最后，虽然柯石英先前已在几颗超深钻石中得到认可（Smith 等人，2018 年；Zedgenizov 等人，2019 年），从未报道过在同一颗钻石中与氧化锆或高压橄榄石多晶型物接触。虽然锆石是地壳岩石中常见的副矿物（Hoskin and Schaltegger，2003），但它在钻石中的出现极为罕见，仅限于少数岩石圈样本（Kinny 和 Meyer，1994 年）。这可能是因为锆石通常不会在地幔中结晶，因为它的岩性在 Zr 和 Si 中是不饱和的。然而，在造山带橄榄岩 (Zhao et al., 2019)、蚀变的地幔捕虏体 (Konzett et al., 1998; Liu et al., 2010) 和蛇绿岩 (Robinson et al., 2015) 中发现了锆石，这表明当地Zr 富集，例如，与交代事件有关，可以稳定地幔岩石中的这种矿物。柯石英表明，所研究的钻石对这些富集的地幔岩性之一进行了取样。锆石（或 reidite，锆石的高压多晶型物，在 >270-330 km 深度处稳定；Tange 和 Takahashi，2004 年）可能是与沉淀钻石相同的交代事件的产物，涉及板片衍生流体/熔体与超俯冲地幔中的橄榄岩相互作用（Zhao et al., 2019）。或者，稳定和耐腐蚀的锆石可能起源于浅层环境，并在俯冲板片或直接上覆的拖曳地幔中经历了长时间的向下运动，然后被金刚石包围。考虑到与菱镁矿的关联，高温、高- 压力 ZrO2 和 SiO2 可以解释为锆石 (ZrSiO4) 或 reidite 分解的结果。在地幔中，reidite 在对应于俯冲地热线约 550 公里或正常地幔地热线 610 公里深度的条件下转变为斜方晶锆石（cotunnite 结构）+ stishovite（SiO2）（Tange 和 Takahashi，2004 年；Van Westrenen等人，2004）。这些条件也对应于林伍德岩稳定的深度。然而，在我们的复合夹杂物中，我们没有直接观察到石英和斜方晶系氧化锆，但我们确实观察到了柯石英和四方晶系氧化锆。这些多晶型物很可能代表了金刚石向表面上升过程中 stishovite 和斜方晶系氧化锆反向转化的产物。实验表明，环木石和 stishovite 可以在合适的化学系统中一起形成（Bolfan-Casanova 等，2000） . 然而，这些系统的整体组成要么非常简单（MgO-SiO2-H2O），要么相对于地幔橄榄岩显着富含 SiO2，特别是当它们与板片衍生的碳酸盐岩熔体相互作用时（Thomson 等人，2016 年）；即，形成超深钻石的典型系统。因此，预计菱镁矿和石英岩不会在地幔岩石中形成稳定的矿物组合。特别是，再现深层钻石形成条件的实验（Thomson 等人，2016 年）从未产生过钻石-菱镁矿-石英矿物组合。这不包括在过渡区下部的钻石沉淀过程中作为夹杂物夹带环木石和 stishovite。反而，观察到的夹杂物组合与橄榄石（或硅钙石）和锆石（或雷长石）在较浅深度被其宿主截留一致，随后橄榄石/硅钙石相转变为菱镁石，锆石/硅镁石分解为 ZrO2 + SiO2 作为响应以增加压力。因此，分解产物可以与林伍德石共存并免受后续反应的影响。Ringwoodite 和 stishovite 在 T < 1375 °C 时会保持稳定，而在更高的温度下，它们会转变为 akimotoite 或多数石（见图 3）。在我们的案例中，这种转变没有发生，这表明这颗钻石是通过快速上升的金伯利岩岩浆带到地表的，正如先前报道的钻石中的菱镁矿出现所暗示的那样（Pearson 等人，2014 年）。将岩石学考虑与钻石的低 N 含量相结合，这是在≥300 km 处形成的与俯冲相关的超深钻石的典型特征，也可以设想所研究的钻石的最小形成深度约为 300 km。对于第一个近似值，最大可能深度受reidite 稳定性的限制，即俯冲或地幔地热分别为~550 或610 km（Tange 和Takahashi，2004；图4）。然而，除非钻石表现出塑性，否则真正的 reidite 击穿深度可能会更大。事实上，考虑到金刚石的高不可压缩性，由于reidite转变，夹杂物体积减少可能起到了压力缓冲的作用。因为金刚石形成的确切深度是未知的，无法确定被钻石包裹的原始矿物组合（即橄榄石与瓦德利石与菱镁矿 + 锆石与重橄榄石）。无论如何，解离的 SiO2 和 ZrO2 的出现表明钻石在形成后向更深处行进，使其内含物组合穿过约 550 或 610 公里（或略大）的深度，在该深度处 reidite 分解（图 4）。原则上，从接近reidite 分解曲线的条件开始的夹杂物等压冷却，例如，由于“冷”板坯衍生熔体的侵入，也可能导致reidite 分解（Tange 和Takahashi，2004 年）。尽管如此，纯粹的等压情景似乎是不现实的，因为无论如何地幔与俯冲板片的耦合很可能会将钻石拖下。在这颗钻石中观察到的独特相组合表明，地幔中的超深钻石向下运动，可能是在俯冲板片动力学之后，到达过渡带下部的深度。即使不能限制这种向下运动的程度，它可能已经发生了数百公里。考虑到原始被夹带的锆石起源较浅的可能性，我们的发现表明，钻石可以作为长程容器，将地壳物质循环到地球极深处。我们建议全面了解超深钻石及其内含物所包含的信息可能包括在上升流和最终喷发之前进行向下运动的可能性。阿尔瓦罗和 F. 雀巢感谢欧洲研究委员会（赠款协议分别为 714936 和 307322）。D. Novella 感谢 Rita Levi Montalcini 计划（意大利大学和研究部）的支持。LG-SIMS 成本由 Nancy-LG-SIMS 小组（法国南希）提供支持。SD Jacobsen 感谢美国国家科学基金会授予 EAR-1853521 的支持。我们感谢 Thomas Stachel、Andrea Giuliani、Win Van Westrenen 和一位匿名审稿人，他们的建设性建议有助于改进手稿，感谢 Chris Clark 和 Urs Schaltegger 的谨慎编辑处理。S. 国家科学基金会授予 EAR-1853521。我们感谢 Thomas Stachel、Andrea Giuliani、Win Van Westrenen 和一位匿名审稿人，他们的建设性建议有助于改进手稿，感谢 Chris Clark 和 Urs Schaltegger 的谨慎编辑处理。S. 国家科学基金会授予 EAR-1853521。我们感谢 Thomas Stachel、Andrea Giuliani、Win Van Westrenen 和一位匿名审稿人，他们的建设性建议有助于改进手稿，感谢 Chris Clark 和 Urs Schaltegger 的谨慎编辑处理。