Abstract Although often speculated, the link between the Middle Triassic shoshonitic magmatism at the NE margin of the Adria plate and the subduction-related metasomatism of the Southern Alps Sub-Continental Lithospheric Mantle (SCLM) has never been constrained. In this paper, a detailed geochemical and petrological characterization of the lavas, dykes and ultramafic cumulates belonging to the shoshonitic magmatic event that shaped the Dolomites (Southern Alps) was used to model the composition and evolution of the underlying SCLM in the time comprised between the Variscan subduction and the opening of the Alpine Tethys. Geochemical models and numerical simulations enabled us to define that 5–7% partial melting of an amphibole + phlogopite-bearing spinel lherzolite, similar to the Finero phlogopite peridotite, can account for the composition of the primitive Mid-Triassic SiO2-saturated to -undersaturated melts with shoshonitic affinity (87Sr/86Sri = 0.7032–0.7058; 143Nd/144Ndi = 0.51219–0.51235; Mg # ~ 70; ~1.1 wt% H2O). By taking into account the H2O content documented in mineral phases from the Finero phlogopite peridotite, it is suggested that the Mid-Triassic SCLM source was able to preserve a significant enrichment and volatile content (600–800 ppm H2O) for more than 50 Ma, i.e. since the slab-related metasomatism connected to the Variscan subduction. The partial melting of a Finero-like SCLM represents the exhaustion of the subduction-related signature in the Southern Alps lithosphere that predated the Late Triassic-Early Jurassic asthenospheric upwelling related to the opening of the Alpine Tethys.

中文翻译：

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南阿尔卑斯山次大陆岩石圈地幔中的 Variscan 俯冲继承：来自中三叠世白云岩（意大利东北部）的橄榄岩岩浆作用的线索

摘要 虽然经常被推测，但亚德里亚板块东北缘的中三叠世橄榄岩岩浆作用与南阿尔卑斯山次大陆岩石圈地幔 (SCLM) 的俯冲相关交代作用之间的联系从未受到限制。在本文中，对属于形成白云岩（南阿尔卑斯山）的橄榄岩岩浆事件的熔岩、岩脉和超镁铁质堆积物的详细地球化学和岩石学特征，用于模拟下伏 SCLM 的组成和演化。 Variscan 俯冲和高山特提斯的开放。地球化学模型和数值模拟使我们能够确定角闪石 + 含金云母尖晶石二长橄榄岩的 5-7% 部分熔化，类似于 Finero 金云母橄榄岩，可以解释原始中三叠纪 SiO2 饱和至欠饱和熔体的组成，具有钾离子亲和力（87Sr/86Sri = 0.7032–0.7058；143Nd/144Ndi = 0.51219–0.51235；% Mg ~1O）。考虑到 Finero 金云母橄榄岩矿物相中记录的 H2O 含量，表明中三叠世 SCLM 源能够在超过 50 Ma 的时间内保持显着的富集和挥发物含量（600-800 ppm H2O），即因为与板片相关的交代作用与 Variscan 俯冲有关。类似 Finero 的 SCLM 的部分熔化代表了南阿尔卑斯山岩石圈中与俯冲相关的特征的枯竭，该特征早于与高山特提斯山脉的开放相关的晚三叠世-早侏罗世软流圈上升流。