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首页> 外文期刊>Ofioliti >REACTIVE MELT MIGRATION CONTROLS THE TRACE ELEMENT BUDGET OF THE LOWER OCEANIC CRUST: INSIGHTS FROM THE TROCTOLITE-OLIVINE GABBRO ASSOCIATION OF THE PINETO OPHIOLITE (CORSICA, FRANCE)
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REACTIVE MELT MIGRATION CONTROLS THE TRACE ELEMENT BUDGET OF THE LOWER OCEANIC CRUST: INSIGHTS FROM THE TROCTOLITE-OLIVINE GABBRO ASSOCIATION OF THE PINETO OPHIOLITE (CORSICA, FRANCE)

机译：活性熔体迁移控制着低洋地壳的痕量元素预算：斜长石-斜长石的滑石-橄榄石长链协会的见解（法国科西嘉）

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The Pineto gabbroic sequence is a ～ 1.5 km-thick crustal section similar to those forming the oceanic core complexes at modern slow-spreading ridges. The sequence is subdivided into two sectors displaying different bulk compositions. The deeper sector consists of troctolites, with minor olivine gabbros and sparse olivine-rich troctolite intercalations. We carried out a thorough chemical characterization, including minerals and bulk rocks, of the troctolite/olivine gabbro association. Although the whole-rock compositions are mainly controlled by mineral proportions, the whole-rock variability of some minor (e.g., Cr, Ni) and trace (e.g., Y, REE) elements reveals formation by open-system crystallization processes. This interpretation is supported by the trace element mineral compositions. The incompatible trace element signature of clinopyroxene in the different rock types is nearly undistinguishable, whereas olivine and plagioclase show substantial variability of trace element compositions. In particular, olivine and plagioclase from the Ol-gabbros are typically depleted in incompatible elements compared to olivine and plagioclase from the troctolites. This chemical variability attests that fractional crystallization alone cannot have determined the compositions of these rocks, but requires an open system process where melts migrate and chemically interact with pre-existing crystal mushes leading to the redistribution of major and trace elements throughout the cumulate pile.
机译：Pineto辉长岩层序是一个约1.5 km厚的地壳断面，类似于那些在现代缓慢扩张的山脊上形成海洋核心复合体的断层。该序列被细分为两个显示不同总体组成的扇区。较深的部分由闪长石，少量的橄榄石辉长岩和稀疏的富含橄榄石的滑石层夹层组成。我们对滑石/橄榄石辉长岩协会进行了全面的化学表征，包括矿物和大块岩石。尽管整个岩石的组成主要受矿物比例的控制，但某些微量元素（例如Cr，Ni）和痕量元素（例如Y，REE）的整个岩石变异性却表明是通过开放系统结晶过程形成的。微量元素矿物成分支持了这种解释。斜柏在不同岩石类型中的不相容痕量元素特征几乎无法区分，而橄榄石和斜长石显示出痕量元素组成的显着变化。特别地，与来自闪石的橄榄石和斜长石相比，来自Ol-gabbros的橄榄石和斜长石通常被贫化不相容的元素。这种化学变异性证明，仅靠分步结晶尚不能确定这些岩石的成分，而是需要一个开放的系统过程，在该过程中，熔体迁移并与预先存在的水晶糊状化学相互作用，从而导致主要和微量元素在整个堆积堆中重新分布。

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