Hybrid troctolites from mid-ocean ridges: inherited mantle in the lower crust
Hybrid troctolites from mid-ocean ridges: inherited mantle in the lower crust
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DOI：
10.1016/j.lithos.2015.06.025
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发表时间：
2015-09
期刊：
影响因子：
3.5
通讯作者：
A. Sanfilippo;T. Morishita;H. Kumagai;Kentaro Nakamura;K. Okino;K. Hara;A. Tamura;S. Arai
中科院分区：
文献类型：
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作者：
A. Sanfilippo;T. Morishita;H. Kumagai;Kentaro Nakamura;K. Okino;K. Hara;A. Tamura;S. Arai
对大洋中脊富含橄榄石的长角闪岩的研究表明，混杂地幔岩可能局部地构成下洋壳的一小部分。它们起源的确切反应过程仍有争议，它们的混合性质也有争议。我们发现，纹理和化学继承的预先存在的地幔保存在富含橄榄石troctolites最近在中印度洋脊采样。一个大的斜方辉石的可能的地幔起源的发生表明，这些岩石通过地幔橄榄岩的反应叠印形成。结合我们的数据与世界各地的橄榄石丰富的troctolites，我们表明，从这些岩石的单斜辉石遵循的化学趋势略有不同的大洋辉长岩。这些化学趋势可以归因于从熔融同化地幔橄榄岩结晶，这表明“地幔味”可以在这些混合岩石中局部保留。目前的分布的奥尔富troctolites表明，熔融地幔反应过程，这些岩石起源可能是更分散在较慢的传播环境，广泛的熔融岩石反应在一个厚的热边界层内增强转换的浅洋地幔混合地壳岩石。
Studies on olivine-rich troctolites from oceanic ridges propose that hybridized mantle rocks may locally constitute small portions of the lower oceanic crust. The exact reaction process by which they originate is still debated and their hybrid nature is controversial. We show that textural and chemical inheritances of the pre-existing mantle are preserved in olivine-rich troctolites recently sampled at the Central Indian Ridge. The occurrence of a large orthopyroxene of a probable mantle origin suggests that these rocks formed through the reactive overprint of a mantle peridotite. Combining our data with those of olivine-rich troctolites worldwide, we show that the clinopyroxenes from these rocks follow chemical trends slightly distinct to those of the oceanic gabbros. These chemical trends can be ascribed to crystallization from melts assimilating mantle peridotites, suggesting that a “mantle flavor” can be locally retained in these hybrid rocks. The present distribution of Ol-rich troctolites suggests that melt-mantle reaction processes by which these rocks originate is likely to be more diffuse at slower spreading environments, where extensive melt-rock reactions within a thick thermal boundary layer enhances the conversion of the shallow oceanic mantle into hybrid crustal rocks.