Here we report the first investigation of spinel-bearing mantle xenoliths from Los Gemelos volcano, Canquel Plateau, Patagonia. They are highly-depleted Mesoproterozoic (ReOs model ages of 1.3–0.9 Ga) harzburgites and clinopyroxene-poor lherzolites characterized by typical indicators of partial melt extraction, such as low whole-rock Al2O3 and CaO contents (<1.5 wt%), high Mg# of silicate phases (90–95), and Cr-rich spinel (Cr# 0.20–0.42). Depletion of incompatible highly siderophile elements (Re, Ru, Pd) relative to the primitive upper mantle supports high degrees of melt extraction. The occurrence of phlogopite and K-rich alkaline glass veins with high- and low-SiO2 compositions is clear evidence of modal metasomatism. The light rare earth element (LREE) enrichment in clinopyroxene, as well as the whole-rock U-shaped REE pattern, confirms cryptic metasomatism. This melt-rock interaction is corroborated by major (i.e., Mg# vs. basaltic elements) and trace (i.e., La/YbN vs. Sr/Y and Ti/Eu; and Sr vs. Ti/Eu) element contents of pyroxenes. The calculated compositions of melts in equilibrium with clinopyroxene coexisting with phlogopite suggest interaction with slab-derived materials. This metasomatism has been generated by a chromatographic fractionation-reaction process, from deep to shallow mantle domains. The percolation of a high-K hydrous magma probably is associated with the upwelling of asthenospheric material through a slab-window, which caused partial melting of oceanic crust and overlying sediments during the Paleocene. The varying intensities of metasomatic imprints recorded by mantle xenoliths from Los Gemelos provide valuable insights into the interaction of slab-derived materials near the lithosphere-asthenosphere boundary, at a distance of ∼600 km from the Andean volcanic arc.

中文翻译：

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巴塔哥尼亚弧后高钾水熔体交代中元古代贫化尖晶石橄榄岩


在这里，我们报告了对来自巴塔哥尼亚坎奎尔高原洛斯杰梅洛斯火山的含尖晶石地幔捕虏体的首次调查。它们是高度贫化的中元古代（ReOs 模型年龄为 1.3–0.9 Ga）方辉橄榄岩和贫单斜辉石二辉橄榄岩，其特征是部分熔融提取的典型指标，例如全岩 Al2O3 和 CaO 含量较低（<1.5 wt%），高 Mg# 硅酸盐相 (90–95) 和富铬尖晶石 (Cr# 0.20–0.42)。相对于原始上地幔，不相容的高亲铁元素（Re、Ru、Pd）的消耗支持了高程度的熔体萃取。具有高和低 SiO2 成分的金云母和富钾碱性玻璃脉的出现是模式交代作用的明确证据。单斜辉石中轻稀土元素 (LREE) 的富集以及全岩 U 形 REE 模式证实了神秘的交代作用。这种熔岩相互作用得到了辉石中主要（即 Mg# 与玄武岩元素）和微量（即 La/YbN 与 Sr/Y 和 Ti/Eu；以及 Sr 与 Ti/Eu）元素含量的证实。与金云母共存的单斜辉石处于平衡状态的熔体的计算组成表明与板衍生材料的相互作用。这种交代作用是由从深地幔域到浅地幔域的色谱分馏反应过程产生的。高 K 含水岩浆的渗滤可能与软流圈物质通过板窗的上涌有关，这导致古新世期间洋壳和上覆沉积物部分融化。 Los Gemelos 地幔捕虏体记录的不同强度的交代印记为了解距安第斯火山弧约 600 公里的岩石圈-软流圈边界附近板片衍生物质的相互作用提供了宝贵的见解。