Serpentinized peridotites (lherzolite to harzburgite) with relict coarse-grained protogranular and porphyroclastic matrix and locally developed fine-grained spinel–pyroxene microstructures were sampled from a previously unknown tectonic exposure of the Mid-Atlantic Ridge (17°04′–17°10′ N). The mineral composition of the coarse-grained relics is typical of abyssal residual peridotites and corresponds to 13–14% fractional melting. Fine-grained spinel-pyroxene (spinel–orthopyroxene and spinel–two-pyroxene) intergrowths are regarded as traces left by peridotite interaction with an interstitial melt during the transition to the lithospheric conductive cooling at temperature of 1100–1000°C. The peridotite–melt interaction resulted in the partial orthopyroxene dissolution, local crystallization of spinel ± clinopyroxene, and uneven decrease of Al and Cr contents in both pyroxenes and Cr/Al ratio in spinel. An additional signature of the reaction melt is an overall trend of enrichment in magmatic components: clinopyroxene in REE and spinel in Zn. The inferred interstitial reaction melt was significantly depleted in incompatible elements compared to MORB-type melts. Further lithospheric cooling favored “freezing” of mineral assemblages and small-scale reactional features.

中文翻译：

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大西洋中脊17°04′至17°10′N深海橄榄岩的小规模反应特征

蛇纹岩橄榄岩（蛇纹岩至哈兹伯格岩）具有残留的粗粒原生颗粒和卟啉碎屑基质，以及局部发育的细晶尖晶石-structure微结构，该样品取自大西洋中脊（17°04'–17°10'）以前未知的构造暴露N）。深渊遗迹橄榄岩的典型特征是粗粒文物的矿物成分，对应于13-14％的分数熔融。细晶尖晶石-辉石（尖晶石-邻苯二甲醚和尖晶石-二-辉石）的共生被认为是在温度为1100-1000°C的岩石圈传导冷却过渡过程中，橄榄岩与间隙熔体相互作用而留下的痕迹。橄榄岩与熔体的相互作用导致邻位邻苯二甲醚部分溶解，尖晶石±邻苯二甲酚的局部结晶，辉石中Al和Cr含量的降低以及尖晶石中Cr / Al比的不均匀降低。反应熔体的另一个特征是岩浆成分富集的总体趋势：稀土元素中的次生辉石和锌中的尖晶石。与MORB型熔体相比，推断的间隙反应熔体的不相容元素明显减少。进一步的岩石圈冷却有利于矿物组合物的“冻结”和小规模的反应特征。