Depletion ages and factors of MORB mantle sources
Depletion ages and factors of MORB mantle sources
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MORB地幔源区的枯竭年龄及影响因素
DOI：
10.1016/j.epsl.2019.115926
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发表时间：
2020
影响因子：
5.3
通讯作者：
Zhang, Youxue
Gan
中科院分区：
文献类型：
--
作者：
Zhang, Youxue
Gan
摘要Sr-Nd-Hf-Pb同位素表明亏损MORB地幔（DMM）是不均一的。这种不均匀性是由于DMM的不同年龄的耗尽和/或不同程度的耗尽对于一个给定的域，以及多个耗尽事件，交代作用，DMM和其他地幔成分之间的混合。大洋中脊玄武岩，原则上，应该包含有关其地幔源的耗尽历史的信息。在这里，我们开发了一个模型，提取模型耗尽年龄和组成的MORB地幔源MORB生产之前，使用Sr-Nd同位素或Sr-Hf同位素在MORB。在这篇文章中，没有讨论多重贫化事件、混合、交代和富集的复杂性。该模型基于两个假设：（1）MORB地幔的同位素演化遵循两阶段演化模型，第一阶段是从太阳系形成之初到Td年地幔亏损时的原始地幔，第二阶段是从Td年至今的亏损地幔。也就是说，只有一个单一的耗尽事件。要确定某一地幔源的亏损年龄和亏损程度。(ii)对应于给定MORB的亏损地幔源的微量元素组成可以通过与相容性指数CoI的对数线性关系与参考DMM相关（Zhang，2014）。将这两个假设应用于可用的大型MORB数据库（Gale等人，2013年），我们计算了全球亚脊地幔年龄和组成的分布。结果表明：（1）Salters和Stracke（2004）的平均或参考MORB地幔成分接近于平均亏损MORB地幔成分，而Workman和哈特（2005）的平均或参考MORB地幔成分明显比平均亏损MORB地幔成分亏损。(ii)海脊下地幔亏损的模式年龄大多在0.8 ~ 3.0Ga之间。(iii)亚洋脊地幔区存在大尺度的亏损年龄模式。例如，在中大西洋海岭下，30° N以北的地幔亏损年龄较年轻（0.8 ~ 2.1 Ga），25° N ~ 35° S之间的地幔亏损年龄较老（1.6 ~ 4.5 Ga），35° S以南的地幔亏损年龄为混合型（0.6-4.4 Ga）。太平洋次洋脊地幔的模式亏损年龄范围很窄，为1.6 ~ 3.0Ga，平均为2.3Ga。印度次洋脊地幔的平均亏损年龄为1.7Ga。这些大规模的模式揭示了地幔亏损，地幔对流的历史，并可能混合之间的老和年轻的亏损地幔。
Abstract Sr-Nd-Hf-Pb isotopes show that the depleted MORB mantle (DMM) is not homogeneous. The heterogeneity is attributed to different ages of depletion and/or various degrees of depletion for a given domain of DMM, as well as multiple depletion events, metasomatism, and mixing between DMM and other mantle components. A mid-ocean ridge basalt, in principle, should contain information about the depletion history of its mantle sources. Here we develop a model to extract the model depletion age and the composition of a MORB mantle source prior to MORB production using Sr-Nd isotopes or Sr-Hf isotopes in a MORB. The complexities of multiple depletion events, mixing, metasomatism, and enrichment are not addressed in this contribution. The model is based on two assumptions:(i) Isotope evolution in a MORB mantle follows a two-stage evolution model, the first stage in the primitive mantle from the beginning of the solar system to the time of mantle depletion at age T d, and the second stage in the depleted mantle from age T d to the present day. That is, there is only one single depletion event. The depletion age and degree of depletion of a given mantle source are to be determined.(ii) The trace element composition of a depleted mantle source corresponding to the given MORB can be related to a reference DMM by a log-linear relation with the compatibility index CoI (Zhang, 2014). Applying the two assumptions to the available and large MORB database (Gale et al., 2013), we calculate the global distribution of sub-ridge mantle age and composition. The results show:(i) Mean or reference MORB mantle composition of Salters and Stracke (2004) is close to the average depleted MORB mantle composition, whereas that of Workman and Hart (2005) is significantly more depleted than the average depleted MORB mantle.(ii) Model ages for sub-ridge mantle depletion are mostly between 0.8 to 3.0 Ga.(iii) There are large-scale patterns in depletion ages for sub-ridge mantle regions. For example, beneath Mid-Atlantic Ridge, mantle depletion ages are young (0.8 to 2.1 Ga) north of 30° N, older (1.6 to 4.5 Ga) between 25° N to 35° S), and mixed (0.6-4.4 Ga) south of 35° S. The Pacific sub-ridge mantle has a narrow range of model depletion ages of 1.6 to 3.0 Ga, with a mean of 2.3 Ga. Indian sub-ridge mantle has a younger mean depletion age of 1.7 Ga. These large-scale patterns reveal history of mantle depletion, mantle convection, and possible mixing between older and younger depleted mantles.
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影响因子：
5
作者：
Villa, I. M.;De Bievre, P.;Renne, P. R.
通讯作者：
Renne, P. R.
阿尔汉格尔斯克-塞拉利昂断裂带（大西洋中部）大西洋中脊玄武岩的新同位素数据
影响因子：
0.9
作者：
S. Skolotnev
通讯作者：
S. Skolotnev
东北太平洋探险家海脊富集的洋中脊玄武岩中的放射性同位素
影响因子：
5
作者：
B. Cousens;D. Weis;M. Constantin;S. Scott
通讯作者：
S. Scott
DOI：
--
发表时间：
1973
期刊：
影响因子：
--
作者：
C. M. Gray;D. Papanastassiou;G. Wasserburg
通讯作者：
G. Wasserburg