Basalts exposed in the Platta and Tasna nappes (SE Switzerland) derive from the Alpine‐Tethys ocean–continent transitions (OCT) and overlie subcontinental lithospheric mantle (SCLM). We show that the trace element signatures of these basalts differ from mid‐ocean ridge basalts (MORB). Two types of basalts occur in the OCT: a type‐1 showing a ‘garnet signature’ that can be modelled by the partial melting of the SCLM in the spinel stability field and a type‐2 characterized by an enrichment in incompatible elements that can be explained by the mixing between garnet‐pyroxenite‐derived melts and the melting of either a depleted MORB mantle or a refertilized SCLM. Based on the geological and geochemical observations, we propose that the basalts from the Alpine‐Tethys OCTs result from a poly‐phase magmatic system that carries an inherited SCLM signature. These basalts should therefore be referred to as OCT‐basalts rather than as MOR‐basalts.

中文翻译：

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与初期海洋化有关的玄武岩的地球化学特征：以高山特提OCT为例

Platta和Tasna尿布（瑞士东南部）中暴露的玄武岩来源于高山特提斯海陆过渡（OCT），并覆盖了陆下岩石圈地幔（SCLM）。我们表明，这些玄武岩的痕量元素特征与中海脊玄武岩（MORB）不同。OCT中有两种类型的玄武岩：一种具有“石榴石特征”的1型可以通过尖晶石稳定性场中SCLM的部分融化来建模，另一种类型2的特征在于可以增加不相容元素的含量。石榴石-辉绿岩衍生的熔体与耗尽的MORB地幔或经精炼的SCLM的熔体之间的混合解释了这一现象。根据地质和地球化学的观测结果，我们认为高山特提OCT的玄武岩是由具有继承的SCLM特征的多相岩浆系统产生的。