Transient mobilization of subcrustal carbon coincident with Palaeocene-Eocene Thermal Maximum
Transient mobilization of subcrustal carbon coincident with Palaeocene-Eocene Thermal Maximum
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DOI：
10.1038/s41561-022-00967-6
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发表时间：
2022-06-23
影响因子：
18.3
通讯作者：
Palmer, Martin R.
中科院分区：
文献类型：
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作者：
Gernon, Thomas M.;Barr, Ryan;Palmer, Martin R.
在全球温暖的新生代早期，地幔柱岩浆活动和大陆裂解导致东北大西洋打开。这种温暖在一次短暂的（17万年，吉尔）高温事件中达到顶峰，该事件与5600万年前（Ma）的古新世-始新世最高热期（PETM）的大量碳排放（如果约束不善）有关。来自同时期北大西洋火成岩省（NAIP）热液喷口的甲烷被认为是触发因素，尽管来自深海沉积物的同位素限制反而暗示了火山二氧化碳（CO2）的直接排放。在这里，我们计算出来自大洋中脊和大型火成岩省的火山放气背景水平仅产生触发高温所需碳的五分之一。然而，对跨越 NAIP 裂谷到漂移阶段的火山序列的地球化学分析表明，与 PETM 一致的岩浆活动突然增强了 220 kyr 长。这可能是由于次大陆岩石圈地幔变薄和减压熔融增强所致，其中关键含有高比例的富碳交代碳酸盐。融化模型和耦合的构造-地球化学模拟表明，超过 10(4) 十亿吨的地壳下碳足够快地转移到海洋和大气中，足以解释 PETM 的规模和速度。
Plume magmatism and continental breakup led to the opening of the northeast Atlantic Ocean during the globally warm early Cenozoic. This warmth culminated in a transient (170 thousand year, kyr) hyperthermal event associated with a large, if poorly constrained, emission of carbon called the Palaeocene-Eocene Thermal Maximum (PETM) 56 million years ago (Ma). Methane from hydrothermal vents in the coeval North Atlantic Igneous Province (NAIP) has been proposed as the trigger, though isotopic constraints from deep sea sediments have instead implicated direct volcanic carbon dioxide (CO2) emissions. Here we calculate that background levels of volcanic outgassing from mid-ocean ridges and large igneous provinces yield only one-fifth of the carbon required to trigger the hyperthermal. However, geochemical analyses of volcanic sequences spanning the rift-to-drift phase of the NAIP indicate a sudden similar to 220 kyr-long intensification of magmatic activity coincident with the PETM. This was likely driven by thinning and enhanced decompression melting of the sub-continental lithospheric mantle, which critically contained a high proportion of carbon-rich metasomatic carbonates. Melting models and coupled tectonic-geochemical simulations indicate that >10(4) gigatons of subcrustal carbon was mobilized into the ocean and atmosphere sufficiently rapidly to explain the scale and pace of the PETM.