Alteration of abyssal peridotites is a major sink in the W geochemical cycle
Alteration of abyssal peridotites is a major sink in the W geochemical cycle
复制标题
深海橄榄岩的蚀变是 W 地球化学循环中的主要汇
DOI：
10.1016/j.gca.2021.12.030
复制
发表时间：
2022
影响因子：
5
通讯作者：
Scheibner
中科院分区：
文献类型：
--
作者：
Reifenröther;Münker;Paulick;Scheibner
相对于类似的不相容元素，弧熔岩和大陆地壳表现出 W 的选择性富集，表明俯冲带环境是 W 从俯冲板片中动员出来的构造环境。在这里，我们提供了证据表明，蚀变海洋岩石圈的超镁铁质部分是 W 的主要汇，并评估了如何将其 W 预算纳入限制 W 的全球地球化学循环。我们报告了通过同位素稀释获得的高精度 W、HFSE 和 U-Th 数据，这些数据是在 ODP 209 段（北纬 14° 至 16°N 之间）沿大西洋中脊超慢扩散速度形成的蚀变基底。海洋基底由深海橄榄岩和在岩浆匮乏的环境中挖掘出的相关辉长岩组成。样本集中涵盖的热液蚀变类型包括蛇纹石化、滑石质蚀变和低T海水蚀变。钻探的岩石部分是迄今为止研究过的 HFSE 含量最贫乏的部分之一。钨浓度范围从蚀变最小的方辉橄榄岩中的 4 ppb 到强烈蛇纹石化沙丘岩中的 500 ppb。在局部，与典型地幔值相比，W 相对于 U、Th 和 Ta 显着富集高达 100 倍，远高于蚀变洋壳的镁铁质部分，如 1256D 孔（高达 10）。来自 ODP Leg 209 的样品显示在渐进蛇纹石化过程中（孔 1268A、孔 1270 和 1271）和晚期氧化海水蚀变过程中（孔 1270D 和 1272A），W 强烈富集。相反，与滑石蚀变相关的二氧化硅交代作用（孔1268A）与相对于Th和Ta的选择性W消耗相关。微量元素模型表明，通过重新分布引起的钨的热液富集是比海水衍生的钨更有可能的来源。总的来说，我们的数据表明，蚀变的超镁铁质岩石可能构成钨的全球地球化学循环中的重要地球化学储库，有助于弧熔岩中发现的钨的富集以及将钨再循环到地幔中。
Arc lavas and the continental crust exhibit a selective enrichment of W relative to similarly incompatible elements, indicating that subduction zone environments are a tectonic setting where W is mobilized from the subducting slab. Here we present evidence that ultramafic portions of altered oceanic lithosphere are a major sink for W and evaluate how its W budget needs to be included in constraining the global geochemical cycle of W. We report high precision W, HFSE and U-Th data obtained by isotope dilution for altered basement formed at super-slow spreading rates along the Mid-Atlantic Ridge drilled during ODP Leg 209 (between 14°N and 16°N). The oceanic basement consists of abyssal peridotites and associated gabbroic rocks exhumed in a magma starved setting. Hydrothermal alteration styles covered in the sample set are serpentinization, talc alteration, and low-T seawater alteration. The drilled rock portions are among the most depleted in HFSE that have ever been studied.Tungsten concentrations range from 4 ppb in the least altered harzburgites to 500 ppb in strongly serpentinized dunites. Locally, W is significantly enriched relative to U, Th and Ta by factors of up to 100 compared to canonical mantle values, much higher than in mafic portions of altered oceanic crust such as hole 1256D (up to 10). The samples from ODP Leg 209 show strong W enrichment during progressive serpentinization (holes 1268A, 1270 and 1271) and during late-stage oxidative seawater alteration (hole 1270D and 1272A). In contrast, silica metasomatism associated with talc alteration (hole 1268A) is associated with selective W depletion relative to Th and Ta. Trace element modelling indicates that hydrothermal enrichment of W by redistribution is a more likely source than seawater-derived W. Collectively, our data show that altered ultramafic rocks likely constitute an important geochemical reservoir in the global geochemical cycle of W contributing to the enrichment of W found in arc lavas and to the recycling of W into the Earth’s mantle.
登录
查看更多内容
沿大西洋中脊初始热液海水混合过程中形成的喷口流体颗粒的地球化学
影响因子：
3.7
作者：
Klevenz V;Bach W;Schmidt K;Hentscher M;Koschinsky A;Petersen S
通讯作者：
Petersen S
富钾熔岩成岩过程中扩展 HFSE 族（Nb、Ta、Zr、Hf、W、Mo）的行为：东地中海案例
影响因子：
5
作者：
Kirchenbaur;Münker
通讯作者：
Münker
影响因子：
5.3
作者：
Kishida, K;Sohrin, Y;Ishibachi, J
通讯作者：
Ishibachi, J
影响因子：
5.3
作者：
Fonseca, Raul O. C.;Mallmann, Guilherme;Blanchard, Henrik
通讯作者：
Blanchard, Henrik
DOI：
10.2204/iodp.proc.309312.204.2009
发表时间：
2009
期刊：
--
影响因子：
--
作者：
N. Neo;S. Yamazaki;S. Miyashita
通讯作者：
N. Neo;S. Yamazaki;S. Miyashita