The Sturtian “Snowball Earth” glaciation (ca. 717–661 Ma) is regarded as the most extreme interval of icehouse climate in Earth’s history. The exact trigger and sustention mechanisms for this long-lived global glaciation remain obscure. The most widely debated causes are silicate weathering of the ca. 718 Ma Franklin large igneous province (LIP) and changes in the length and degassing of continental arcs. A new generation of two independent Neoproterozoic full-plate tectonic models now allows us to quantify the role of tectonics in initiating and sustaining the Sturtian glaciation. We find that continental arc length remains relatively constant from 850 Ma until the end of the glaciation in both models and is unlikely to play a role. The two plate motion models diverge in their predictions of the timing and progression of Rodinia break-up, ocean-basin age, ocean-basement depth, sea-level evolution, and mid-ocean ridge (MOR) carbon outflux. One model predicts MOR outflux and ocean basin volume–driven sea level lower than during the Late Cenozoic glaciation, while the other predicts outgassing and sea level exceeding those of the Late Cretaceous hothouse climate. The second model would preclude a major glaciation, while the first model implies that the trigger for the Sturtian glaciation could have been a combination of an extremely low MOR outflux (~9 Mt C/yr) and Franklin LIP weathering. Such minimal outflux could have maintained an icehouse state for 57 m.y. when silicate weathering was markedly reduced, with a gradual build-up of MOR CO2 in the atmosphere paired with terrestrial volcanism leading to its termination.The low-paleolatitude Sturtian glaciation (ca. 717–661 Ma) represents the longest and most extreme period of icehouse climate in Earth’s history, and the mainstay of the “Snowball Earth” hypothesis in which the entire global ocean surface becomes frozen via a runaway ice-albedo feedback (Hoffman et al., 2017). Various factors have been implicated in initiating the glaciation (Walzer and Hendel, 2023), including an increase in planetary albedo caused by volcanic aerosols (Macdonald and Wordsworth, 2017) and high obliquity of the ecliptic (Williams, 2008). However, enhanced continental silicate weathering and organic burial linked to the breakup of Rodinia are viewed as the main mechanisms drawing down atmospheric CO2 and driving planetary cooling (e.g., Goddéris et al., 2003; Donnadieu et al., 2004; Cox et al., 2016; Hoffman et al., 2017). The emplacement of the Franklin large igneous province (LIP; Ernst et al., 2021; Fig. 1) has been of particular interest because its rapid weathering at tropical latitudes may have triggered the Sturtian glaciation (Goddéris et al., 2003; Cox et al., 2016). Precise dating of the Franklin LIP at 718 Ma now places it immediately prior to the Sturtian glaciation (Dufour et al., 2023); however, its duration of ~2 m.y. (Pu et al., 2022; Dufour et al., 2023) likely limited the supply of fresh mafic rock surface for weathering due to regolith development (Park et al., 2021). The role of the Franklin LIP as the sole trigger of the Sturtian glaciation has been further questioned as the majority of tropical Phanerozoic LIPs did not drive icehouse climates (McKenzie et al., 2016; Park et al., 2021), and there is no significant LIP associated with the Marinoan glaciation (Ernst et al., 2021). In addition, numerical box modeling by Defliese (2021) suggests that the continental and seafloor weathering feedback mechanisms become insignificant at extremely low temperatures, rendering the drawdown of CO2 insufficient to maintain a “Snowball Earth” glaciation. Defliese (2021) hypothesized that the long duration of the Sturtian glaciation was sustained by a consistently low crustal production and mid-ocean ridge (MOR) CO2 outgassing rate. This variable provides a critical input parameter for any model designed to understand the mechanisms driving Cryogenian glaciations but is unconstrained. We are now able to place quantitative bounds on MOR outgassing rates using a new generation of two independent full-plate models (Me21 [Merdith et al., 2021] and Li23 [Li et al., 2023b]; Fig. 1) that capture Neoproterozoic plate boundary evolution. We also evaluate both plate models in terms of their compatibility with the Sturtian glaciation and show that crustal production and MOR outflux played a key role in Cryogenian cooling of Earth.We use GPlately (https://github.com/GPlates/gplately; Mather et al., 2023) to compute MOR length, mean global spreading rates, and crustal production (Figs. 2A–2C) for plate motion models Me21 (Merdith et al., 2021) and Li23, the preferred model of Li et al. (2023b). Melt beneath MORs dissolves mantle carbon, which partly degasses during seafloor spreading. The MOR carbon outflux (Fig. 2D) is computed following Keller et al. (2017). Sea level is computed by producing grids of the age-area distribution of ocean crust through time based on the plate topologies and rotations in each plate model using the method of Williams et al. (2021). The paleo-age grids are then translated to paleo-basement depth grids using the age-depth relationship of Richards et al. (2018). We disregard other processes contributing to global sea level to focus on a first-order comparison of the implication of two alternative plate models and implied oceanic paleo-depth distributions on global sea-level change (Fig. 2E).The two available full-plate models for the Neoproterozoic are based on diverse data; however, Me21 (Merdith et al., 2021) emphasizes geological data while Li23 (Li et al., 2023b) favors paleomagnetic data, resulting in starkly different plate motion and plate boundary evolution histories (Fig. 1; Table S1 and Videos S1 and S2 in the Supplemental Material1). The models are especially different in the configuration and dispersal of Rodinia, which plays a key role in understanding the causes of Cryogenian glaciations (e.g., Cox et al., 2016; Hoffman et al., 2017; Li et al., 2023b). In Me21, Rodinia excludes several continents separated by ocean basins (Fig. 1A), with an initial break up at ca. 800 Ma (Merdith et al., 2021). This results in a modest lengthening of the global MOR system from ~40,000 km to ~50,000 km at 800 Ma (Fig. 2A) and an increase in crustal production rate from ~3.5 km2/yr to ~5 km2/yr (Fig. 2C). A global plate reorganization at ca. 760 Ma (Fig. 1C) causes a shortening of the global plate boundary system, which is reflected in the subduction and/or cessation of some spreading ridges and the transition of several subduction zones to passive margins (see Merdith et al., 2021, for details). Subduction along the South China block and northern India and along much of the western side of Rodinia stops at this time (Fig. 1E). Another major tectonic reorganization occurs at 720 Ma, when both subduction and spreading systems surrounding the North China block, as well as the North and South Australian cratons, become extinct, resulting in a shortening of the Mirovia MORs (Fig. 1D) and a reduction in crustal production (Fig. 1C; Collins et al., 2021).In contrast, in Li23, all continents are assembled into Rodinia, which is encircled by the Mirovia Ocean (Figs. 1F–1H). The initiation of Rodinia’s dispersal at ca. 750 Ma (Fig. 1H) results in a doubling of the MOR length from 40,000 km to 80,000 km (Fig. 2A), as well as the crustal production rate from ~4 km2/yr at 750 Ma to ~8 km2/yr at 740 Ma (Fig. 2C). Plate reorganization, including the separation of Siberia from Laurentia at ca. 720 Ma (Li et al., 2023b), leads to a modest decrease in ridge length to ~65,000 km (Fig. 1A) and a high rate of crustal production of ~7 km2/yr (Fig. 1C) at the onset of the Sturtian glaciation. Crustal production remains relatively high at 6–7 km2/yr in Li23 throughout the Sturtian glaciation until ca. 620 Ma, while in Me21, crustal production remains low at ~2.5 km2/yr until ca. 620 Ma (Figs. 1A and 1C), when the fragmentation of plates reaches a post-Rodinia break-up maximum.The “Snowball Earth” model–driven hypothesis proposes a shutdown of the hydrological cycle during the Cryogenian glaciations (Hoffman et al., 2017). However, abundant and diverse geological evidence, such as hummocky cross-stratification generated by storm waves (Le Heron, 2015; Qi et al., 2023), complex communities of microbiota (Moczydłowska, 2008), and non-glacial sediments and sedimentary structures (Allen and Etienne, 2008) in Sturtian glacial successions, indicates the presence of open marine water and a functioning hydrological cycle (Le Heron, 2015; Spence et al., 2016; Lloyd et al., 2023). The presence of open water facilitates a slow and continuous exchange of CO2 between the ocean and the atmosphere, modulating climate and weathering reactions as part of the long-term carbon cycle (Berner, 2004). Carbon dioxide is constantly outfluxed from the solid Earth, chiefly from degassing of MORs during seafloor spreading and outgassing from volcanic arcs (Müller et al., 2022). The build-up of atmospheric CO2 is, in part, regulated by chemical weathering of silicates on continents and in seafloor basalt (Brantley et al., 2023). This temperature-dependent negative feedback mechanism draws down CO2 and buffers Earth’s climate over geological timescales (Berner, 2004). During a global glaciation, when silicate weathering becomes negligible at extremely low temperatures (Defliese, 2021) and high aridity (Brantley et al., 2023), the uptake of CO2 by weathering is severely reduced, allowing that greenhouse gas to build up in the atmosphere, leading to a warmer climate. We propose that in order for the Sturtian glaciation to be sustained for 57 m.y., the reduction in the drawdown of atmospheric CO2 must have been balanced by an exceptionally low solid Earth carbon outflux for the duration of the glaciation.The MOR outflux (Fig. 2D) mirrors the rates of crustal production (Fig. 2C), with the Me21 and Li23 models diverging significantly during the Sturtian glaciation when the rates of MOR outflux are high in Li23 and low in Me21 (Fig. 1D). The outflux in Me21 shows a step-wise decrease from a maximum of ~25 Mt C/yr at ca. 770 Ma, to ~12 Mt C/yr between 760 and 720 Ma, reaching a Neoproterozoic minimum of ~9 Mt C/yr at the onset of the Sturtian glaciation. This minimum persists for 20 m.y., with a slight increase to ~12 Mt C/yr after 700 Ma, which remains relatively constant until the end of the Sturtian glaciation, gradually increasing to a maximum of ~23 Mt C/yr at ca. 570 Ma (Fig. 1D). In contrast, the Li23 model shows a much earlier MOR outflux minimum of ~16 Mt C/yr at ca. 770 Ma. This value increases dramatically to a Neoproterozoic maximum of ~37 Mt C/yr at ca. 740, remaining very high (~32–28 Mt C/yr) throughout the duration of the Sturtian glaciation and decreasing toward a minimum of ~15 Mt C/yr at ca. 565 Ma (Fig. 1D). The peak MOR outflux in Li23 during the Sturtian far exceeds the mean of ~12 Mt C/yr computed for the Cenozoic glaciation and even the Cretaceous hothouse maximum of ~27 Mt C/yr following the break-up of Pangea (Müller et al., 2022; Fig. 1D). This comparative analysis suggests that the MOR outgassing history implied by the Li23 model is inconsistent with a Cryogenian icehouse climate and would preclude a widespread glaciation. We propose that the MOR outflux from Me21, which is lower than Cenozoic icehouse estimates, would be sufficiently small to help trigger and sustain a global glaciation.Outgassing along continental arcs is another potentially important driver of long-term climate (McKenzie et al., 2016). Continental arc CO2 emissions depend on the outflux of carbon from the subducting plate (in the lithospheric mantle, crust, and sediments) into the sub-arc mantle (Müller et al., 2022), and metamorphic decarbonation of carbon-bearing rocks (e.g., carbonate platforms) in the overriding plate (Mason et al., 2017). These components have evaded quantification for pre-Phanerozoic time because relicts of these reservoirs are rarely preserved in the geological record. McKenzie et al. (2016) suggested that Cryogenian glaciations were triggered by a major drop in CO2 fluxes from continental volcanic arcs associated with the assembly of Rodinia, with arc length and CO2 increasing during Rodinia break-up. A similar result by Mills et al. (2017) was based on total global subduction length. Neither approach considered changes in convergence rates. However, analogous to MOR outflux, we expect arc outgassing to roughly track crustal destruction rates, which are the product of the arc length and convergence rates (Fig. 3). We find that the continental arc length in both Me21 and Li23 models remains relatively constant from 850 Ma until the end of the Sturtian glaciation at 661 Ma (Fig. 3A). The maximum arc length increases post–660 Ma in both models, doubling from ~20,000 km to 40,000 km in Li23, with a transient increase from 20,000 km to 27,000 km in Me21 (Fig. 3A). However, at the same time, plate convergence and subduction rates decrease dramatically in Li23 and remain low in Me21 (Figs. 3B and 3C). This indicates that despite an increase in continental volcanic arc length, subduction-related CO2 outflux postdating 660 Ma was likely modest because crustal destruction rates are low in both models (Fig. 3C). In summary, neither the onset nor the termination of Cryogenian glaciations appear to have been induced by changing continental arc length.Our modeled sea-level curves, which are solely based on changes in mean oceanic basement depth (Fig. 2E), are starkly different between Me21 and Li23. Sea level is similar for both plate models for much of the Tonian but diverges markedly at ca. 750 Ma when it drops by ~150 m in Me21 due to a shortening of the global plate boundary system (Fig. 1) and rises by ~550 m in Li23 due to the formation of new MORs. The Sturtian glaciation is marked by a sea-level minimum in Me21 and a sea-level maximum in Li23. The sea-level curves slowly converge in the Ediacaran, following a major decrease in sea level in Li23 and a small increase in Me21 (Fig. 1E). The Sturtian sea-level peak in Li23 is ~100 m higher than the mid-Cretaceous hothouse sea level computed with the same method (Fig. 2E; Fig. S1) when solid-Earth CO2 degassing was at a maximum following Pangea break-up (Müller et al., 2022). Such a climate would be the consequence of the Li23 plate model evolution, inhibiting a global glaciation. A sea-level curve derived from the seawater 87Sr/86Sr record (van der Meer et al., 2017), largely based on pre/post glacial strata (Spence et al., 2016), is broadly similar in shape to the Me21 sea level. It lacks the Sturtian maximum evident in Li23, providing an independent, but not well-constrained, check of the models.Our computations suggest that the low solid-Earth outflux during the Sturtian glaciation based on the Me21 model would be sufficient to sustain a global glaciation in the presence of open water and significantly reduced silicate weathering. We envisage that the initial driving mechanism for the Sturtian glaciation was a combination of Franklin LIP weathering and extremely low MOR outflux. The termination of the glaciation may have been triggered by a gradual build-up of MOR CO2 in the atmosphere combined with deglacial terrestrial volcanism (Li et al., 2023a). Solid-Earth degassing alone does not explain the drivers or the termination of the Marinoan glaciation (Fig. 2); however, multiple poorly constrained carbon sinks (e.g., seafloor alteration, organic carbon flux), sources (e.g., rift volcanism; Lan et al., 2022), and climate-modulating orbital forcing (Benn et al., 2015) may also be important.We thank three anonymous reviewers for their constructive comments. Funding for this work includes Australian Research Council (ARC) Future Fellowship FT190100829 (A. Dutkiewicz), ARC DECRA Fellowship DE230101642 (A. Merdith), ARC Linkage grants LP210200822 and LP200301457 (A. Collins), ARC Discovery grant DP200100966 (B. Mather), ARC DECRA Fellowship DE210100084 (S. Zahirovic), and the National Collaborative Research Infrastructure Strategy (NCRIS) via AuScope (L. Ilano and R.D. Müller).

中文翻译：

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斯图尔特“雪球地球”冰川作用的持续时间与异常低的洋中脊排气有关

斯图尔特“雪球地球”冰川期（约717-661 Ma）被认为是地球历史上最极端的冰室气候时期。这种长期全球冰川作用的确切触发和维持机制仍然不清楚。最广泛争论的原因是约的硅酸盐风化。 718 Ma Franklin 大火成岩省 (LIP) 以及大陆弧长度和脱气的变化。新一代的两个独立的新元古代全板块构造模型现在使我们能够量化构造在引发和维持斯图尔特冰川作用中的作用。我们发现，在两个模型中，从 850 Ma 到冰川期结束，大陆弧长度保持相对恒定，不太可能发挥作用。这两个板块运动模型在对罗迪尼亚分裂的时间和进展、洋盆年龄、海底深度、海平面演化和洋中脊（MOR）碳流出的预测方面存在分歧。一种模型预测 MOR 流出和洋盆体积驱动的海平面低于新生代晚期冰川期，而另一种模型则预测排气和海平面超过晚白垩世温室气候。第二个模型将排除重大冰川作用，而第一个模型意味着斯图尔特冰川作用的触发因素可能是极低的 MOR 流出量（约 9 Mt C/年）和富兰克林 LIP 风化的结合。当硅酸盐风化显着减少时，这种最小的流出量可以维持冰室状态 57 my，大气中 MOR CO2 逐渐积累，加上陆地火山活动导致其终止。低古纬度 Sturtian 冰川作用（约 717 年） –661 Ma）代表了地球历史上最长、最极端的冰室气候时期，也是“雪球地球”假说的支柱，在该假说中，整个全球海洋表面通过失控的冰反照率反馈而被冻结（Hoffman等人， 2017）。冰川作用的引发涉及多种因素（Walzer 和 Hendel，2023），包括火山气溶胶引起的行星反照率增加（Macdonald 和 Wordsworth，2017）和黄道高倾角（Williams，2008）。然而，与罗迪尼亚分裂相关的大陆硅酸盐风化和有机埋藏增强被视为减少大气二氧化碳和驱动行星冷却的主要机制（例如，Goddéris 等，2003；Donnadieu 等，2004；Cox 等，2004）。 ，2016；霍夫曼等人，2017）。富兰克林大型火成岩省（LIP；Ernst 等人，2021；图 1）的侵位引起了特别关注，因为它在热带纬度的快速风化可能引发了 Sturtian 冰川作用（Goddéris 等人，2003 年；Cox 等人）等，2016）。对富兰克林 LIP 的精确年代确定为 718 Ma，现在将其置于斯图尔蒂安冰川作用之前（Dufour 等人，2023）；然而，其持续时间约为 2 my（Pu 等人，2022；Dufour 等人，由于风化层的发育，2023年）可能限制了用于风化的新鲜镁铁质岩石表面的供应（Park等人，2021年）。富兰克林 LIP 作为斯图尔特冰川作用唯一触发因素的作用受到进一步质疑，因为大多数热带显生宙 LIP 并未驱动冰室气候（McKenzie 等，2016；Park 等，2021），并且没有与马里诺冰川作用相关的显着 LIP（Ernst 等人，2021）。此外，Defliese（2021）的数值盒模型表明，大陆和海底的风化反馈机制在极低的温度下变得微不足道，导致二氧化碳的减少不足以维持“雪球地球”冰川作用。 Defliese (2021) 假设，斯图尔特冰川作用持续时间较长是由于地壳生产量持续较低和洋中脊 (MOR) 二氧化碳释气率持续较低。该变量为任何旨在了解冰河作用驱动机制的模型提供了关键的输入参数，但不受约束。我们现在能够使用新一代两个独立的全板模型（Me21 [Merdith et al., 2021] 和 Li23 [Li et al., 2023b]；图 1）对 MOR 脱气率进行定量限制，这些模型捕获了新元古代板块边界演化。我们还评估了这两种板块模型与 Sturtian 冰川作用的兼容性，并表明地壳生成和 MOR 流出在地球低温冷却中发挥了关键作用。我们使用 GPlately (https://github.com/GPlates/gplately; Mather等人，2023）计算板块运动模型 Me21（Merdith 等人，2021）和 Li23（Li 等人的首选模型）的 MOR 长度、平均全球扩张率和地壳产量（图 2A-2C）。 （2023b）。 MOR 下方的熔化物溶解了地幔碳，这些碳在海底扩张过程中部分脱气。 MOR 碳流出量（图 2D）是按照 Keller 等人的方法计算的。 （2017）。海平面的计算是通过使用 Williams 等人的方法，根据每个板块模型中的板块拓扑和旋转生成海洋地壳随时间变化的年龄区域分布的网格。 （2021）。然后使用理查兹等人的年龄-深度关系将古时代网格转换为古基底深度网格。 （2018）。我们忽略对全球海平面有贡献的其他过程，重点关注两个替代板块模型的含义的一阶比较以及隐含的海洋古深度分布对全球海平面变化的影响（图2E）。两个可用的全板块新元古代模型基于不同的数据；然而，Me21（Merdith等，2021）强调地质数据，而Li23（Li等，2023b）偏向古地磁数据，导致板块运动和板块边界演化历史截然不同（图1；表S1和视频S1和补充材料中的 S21)。这些模型在罗迪尼亚的配置和分散方面尤其不同，这对于理解成冰期冰川作用的成因起着关键作用（例如，Cox et al., 2016; Hoffman et al., 2017; Li et al., 2023b）。在Me21中，罗迪尼亚排除了被海洋盆地分隔的几个大陆（图1A），最初的分裂发生在大约。 800 Ma（Merdith 等人，2021）。这导致全球 MOR 系统在 800 Ma 时从约 40,000 公里适度延长至约 50,000 公里（图 2A），地壳生产率从约 3.5 平方公里/年增加到约 5 平方公里/年（图 2C） ）。大约在 2017 年进行的全球板块重组。 760Ma（图1C）导致全球板块边界系统缩短，这反映在一些扩张脊的俯冲和/或停止以及一些俯冲带向被动边缘的过渡（参见Merdith等，2021，了解详情）。沿着华南地块和印度北部以及沿着罗迪尼亚西侧大部分地区的俯冲此时停止（图1E）。另一次重大构造重组发生在720 Ma，此时华北地块周围的俯冲和扩张系统以及北澳大利亚和南澳大利亚克拉通都消失了，导致Mirovia MORs缩短（图1D）并减少地壳生产过程中（图1C；Collins等，2021）。相比之下，在Li23中，所有大陆都聚集成罗迪尼亚，被米罗维亚洋包围（图1F-1H）。罗迪尼亚的分散开始于大约。 750 Ma（图1H）导致MOR长度加倍，从40,000公里增加到80,000公里（图2A），地壳生产率从750 Ma时的约4平方公里/年增加到750 Ma的约8平方公里/年740 Ma（图2C）。板块重组，包括西伯利亚与劳伦大陆的分离。 720 Ma（Li et al., 2023b），导致山脊长度适度减少至约 65,000 km（图 1A），并且在斯图尔特冰川作用。在整个 Sturtian 冰川时期，Li23 的地壳产量仍然相对较高，为 6-7 平方公里/年，直到大约 2007 年。 620 Ma，而在 Me21，地壳产量保持在约 2.5 km2/年的低水平，直到约 200 Ma。 620 Ma（图 1A 和 1C），此时板块破碎达到罗迪尼亚分裂后的最大值。“雪球地球”模型驱动的假说提出了低温冰期期间水文循环的关闭（Hoffman 等，2016）。 ，2017）。然而，丰富多样的地质证据，例如风暴波产生的丘状交叉分层（Le Heron，2015；Qi等，2023）、复杂的微生物群落（Moczydłowska，2008）以及非冰川沉积物和沉积结构（Allen 和 Etienne，2008）在 Sturtian 冰川演替中，表明存在开放的海水和有效的水文循环（Le Heron，2015；Spence 等，2016；Lloyd 等，2023）。开放水域的存在促进了海洋和大气之间缓慢而持续的二氧化碳交换，作为长期碳循环的一部分调节气候和风化反应（Berner，2004）。二氧化碳不断从固体地球中流出，主要来自海底扩张过程中 MOR 的脱气和火山弧的脱气（Müller 等，2022）。大气中二氧化碳的积累部分受到大陆和海底玄武岩硅酸盐化学风化的调节（Brantley et al., 2023）。这种依赖于温度的负反馈机制会在地质时间尺度上减少二氧化碳并缓冲地球气候（Berner，2004）。在全球冰川作用期间，当硅酸盐风化在极低温度（Defliese，2021）和高干旱（Brantley 等，2023）下变得可以忽略不计时，风化对二氧化碳的吸收会严重减少，从而使温室气体在气氛，导致气候变暖。我们建议，为了使斯图尔蒂安冰川作用持续 57 my，大气中二氧化碳减少的减少必须通过冰川作用期间极低的固体地球碳流出来平衡。MOR 流出（图 2D） ）反映了地壳生产速率（图2C），在Sturtian冰川期，当Li23的MOR流出速率较高而Me21较低时，Me21和Li23模型显着分歧（图1D）。 Me21 的流出量显示出从约 25 Mt C/年的最大值逐步减少。 770 Ma，在 760 至 720 Ma 之间达到约 12 Mt C/年，在 Sturtian 冰川作用开始时达到约 9 Mt C/年的新元古代最小值。这个最小值持续了 20 my，在 700 Ma 后略有增加到约 12 Mt C/年，直到 Sturtian 冰川作用结束为止保持相对恒定，在约 100 Ma 时逐渐增加到最大值约 23 Mt C/年。 570 Ma（图1D）。相比之下，Li23 模型显示出更早的 MOR 流出最小值，大约在 16 Mt C/年。 770马。该值在大约 10 年后急剧增加至新元古代最大值约 37 Mt C/年。 740，在整个 Sturtian 冰川作用期间保持非常高的温度（约 32-28 Mt C/年），并在约 740 时降至最低约 15 Mt C/年。 565 Ma（图1D）。 Sturtian 时期 Li23 的 MOR 流出峰值远远超过新生代冰川期计算的平均值约 12 Mt C/年，甚至超过盘古大陆分裂后白垩纪温室最大值约 27 Mt C/年（Müller 等，2017）。 ，2022 年；图 1D）。这一比较分析表明，Li23 模型所暗示的 MOR 排气历史与成冰期冰室气候不一致，并且会排除广泛的冰川作用。我们认为，Me21 的 MOR 流出量（低于新生代冰室估计值）将足够小，足以帮助触发和维持全球冰川作用。沿着大陆弧的排气是长期气候的另一个潜在重要驱动因素（McKenzie 等人， 2016）。大陆弧二氧化碳排放量取决于碳从俯冲板块（在岩石圈地幔、地壳和沉积物中）流入弧下地幔的量（Müller et al., 2022），以及上覆板块中含碳岩石（例如碳酸盐台地）的变质脱碳作用（Mason 等，2017）。这些成分在前显生宙时期无法量化，因为这些储层的遗迹很少保存在地质记录中。麦肯齐等人。 (2016) 认为，成冰纪冰川作用是由与罗迪尼亚聚集相关的大陆火山弧二氧化碳通量大幅下降引发的，在罗迪尼亚分裂期间，弧长和二氧化碳增加。米尔斯等人也得出了类似的结果。 （2017）基于全球俯冲总长度。这两种方法都没有考虑收敛率的变化。然而，与 MOR 流出类似，我们预计电弧逸气将大致跟踪地壳破坏率，这是弧长和收敛率的乘积（图 3）。我们发现Me21和Li23模型中的大陆弧长度从850 Ma直到661 Ma的Sturtian冰川期结束都保持相对恒定（图3A）。两个模型的最大弧长在 660 Ma 后均增加，Li23 中从约 20,000 km 翻倍至 40,000 km，Me21 中从 20,000 km 瞬时增加至 27,000 km（图 3A）。然而，与此同时，Li23 中的板块收敛和俯冲速率急剧下降，而 Me21 中的板块收敛和俯冲速率仍然很低（图 3B 和 3C）。这表明，尽管大陆火山弧长度增加，但 660 Ma 后与俯冲相关的 CO2 流出量可能不大，因为两种模型中的地壳破坏率都很低（图 3C）。总之，成冰期冰川作用的开始和结束似乎都不是由大陆弧长度的变化引起的。我们模拟的海平面曲线完全基于平均海洋基底深度的变化（图2E），两者截然不同Me21 和 Li23 之间。对于托尼安河的大部分地区，两个板块模型的海平面相似，但在大约 10 处明显不同。 750 Ma，由于全球板块边界系统的缩短，Me21 中下降了约 150 m（图 1），并且由于新 MOR 的形成，Li23 中上升了约 550 m。斯图尔特冰川作用的标志是 Me21 的海平面最低点和 Li23 的海平面最高点。随着 Li23 海平面大幅下降和 Me21 小幅上升（图 1E），埃迪卡拉纪海平面曲线缓慢收敛。 Li23的斯图尔特海平面峰值比用相同方法计算的白垩纪中期温室海平面高约100米（图2E；图S1），当时盘古大陆破裂后固体地球CO2脱气达到最大值（穆勒等人，2022）。这样的气候是Li23板块模型演化的结果，抑制了全球冰川作用。从海水 87Sr/86Sr 记录得出的海平面曲线（van der Meer 等，2017）主要基于冰期前/后地层（Spence 等，2016），其形状与 Me21 海大致相似等级。它缺乏 Li23 中明显的 Sturtian 最大值，提供了一个独立的，但没有很好约束的，我们的计算表明，基于 Me21 模型的斯图尔特冰川期间的低固体地球流出量足以在开放水域存在的情况下维持全球冰川作用，并显着减少硅酸盐风化。我们设想 Sturtian 冰川作用的最初驱动机制是富兰克林 LIP 风化和极低 MOR 流出的结合。冰川作用的终止可能是由于大气中 MOR CO2 的逐渐积累以及冰消期的陆地火山作用所引发的（Li et al., 2023a）。固体地球脱气本身并不能解释马里诺冰川作用的驱动因素或终止（图 2）；然而，多个约束不良的碳汇（​​例如海底蚀变、有机碳通量）、来源（例如裂谷火山活动；Lan 等人，2022）和气候调节轨道强迫（Benn 等人，2015）也可能是重要的是。我们感谢三位匿名审稿人的建设性意见。这项工作的资助包括澳大利亚研究委员会 (ARC) 未来奖学金 FT190100829 (A. Dutkiewicz)、ARC DECRA 奖学金 DE230101642 (A. Merdith)、ARC Linkage 赠款 LP210200822 和 LP200301457 (A. Collins)、ARC Discovery 赠款 DP200100966 (B. Mather) ）、ARC DECRA 奖学金 DE210100084（S. Zahirovic）以及 AuScope 的国家合作研究基础设施战略（NCRIS）（L. Ilano 和 RD Müller）。