Halogen enrichment in the North American lithospheric mantle from the dehydration of the Farallon plate
Halogen enrichment in the North American lithospheric mantle from the dehydration of the Farallon plate
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法拉隆板块脱水导致北美岩石圈地幔中卤素富集
DOI：
10.1016/j.gca.2023.03.014
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发表时间：
2023
影响因子：
5
通讯作者：
John, Timm
中科院分区：
文献类型：
--
作者：
Segee-Wright, George;Barnes, Jaime D.;Lassiter, John C.;Holmes, Duncan J.;Beaudoin, Grace M.;Chatterjee, Rudra;Stockli, Daniel F.;Hoffmann, J. Elis;John, Timm
卤素（F、Cl、Br和I）在全球范围内的俯冲量似乎比在岩浆弧上的喷发量要大，这要么需要随着时间的推移增加地幔卤素预算，要么需要额外的输出通道或储层。次大陆岩石圈地幔（SCLM）就是这样一个储层。经大洋俯冲岩石圈的流体或熔体交代后，可富集挥发性元素。我们分析了纳瓦霍火山场（NVF; Colorado Plateau Central） 28个不同变质尖晶石和石榴石橄榄岩捕虏体的总体卤素含量（F, Cl， Br和I），以约束Farallon板块衍生的俯冲变质作用对北美西部SCLM卤素含量的影响。我们还分析了来自科罗拉多高原及其周围不同地区的33块无水尖晶石橄榄岩，以及来自夏威夷瓦胡岛和德国艾菲尔的捕虏体，以将它们与模态水合NVF捕虏体进行比较。Cl、Br和I在NVF捕虏体中相对于贫地幔富集，与橄榄石氧同位素值和交代指标相关。F富集程度较低，说明在板坯渣中优先保留。Br/Cl和I/Cl与部分脱水蛇纹岩相似，表明这些流体的来源与Farallon板块的蛇纹岩化海洋岩石圈一致。美国西南部无水捕虏体的Cl和F含量较低，但Br含量与NVF捕虏体相似，富集程度较高。与NVF捕虏体相似，无水捕虏体的Br/Cl和I/Cl提示Farallon衍生蛇纹岩富集卤素。这些结果表明，法拉龙板块在科罗拉多高原中南部和里约热内卢大裂谷南部的北美陆地上隔离了卤素。因此，sclc中的卤素封存可能是全球卤素循环的关键组成部分。
A greater quantity of halogens (F, Cl, Br, and I) appear to be subducted globally than are erupted at magmatic arcs, requiring either an increase in the mantle halogen budget through time or an additional output pathway or reservoir. The sub-continental lithospheric mantle (SCLM) is one such reservoir. SCLM can be enriched in volatile elements after metasomatism by fluids or melts from subducting oceanic lithosphere. We analyzed the bulk halogen content (F, Cl, Br, and I) of 28 variably metasomatized spinel and garnet peridotite xenoliths from the Navajo Volcanic Field (NVF; Central Colorado Plateau) to constrain the effects of the subducting Farallon plate-derived metasomatism on the halogen content of the western North American SCLM. We also analyzed 33 anhydrous spinel peridotites from various localities on and around the Colorado Plateau, as well as xenoliths from Oahu, Hawaii, and Eifel, Germany to compare them to the modally hydrated NVF xenoliths. Cl, Br, and I are enriched in NVF xenoliths relative to the depleted mantle, correlating with olivine oxygen isotope values and indices of metasomatism. F is less enriched, indicating preferential retention in the slab residue. Br/Cl and I/Cl are similar to partially dehydrated serpentinite, indicating that the source of these fluids is consistent with serpentinized oceanic lithosphere of the Farallon plate. Anhydrous xenoliths from the southwestern United States have more depleted mantle-like Cl and F contents but have highly enriched Br contents similar to the NVF xenoliths. Similar to NVF xenoliths, anhydrous xenolith Br/Cl and I/Cl suggest a Farallon derived serpentinite source of halogen enrichment. These results indicate that the Farallon slab sequestered halogens in the North American SCLM of the central and south Colorado Plateau and the southern Rio Grande Rift. Therefore, halogen sequestration in the SCLM may be a critical component in the global halogen cycle.
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DOI：
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发表时间：
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