Cenozoic mantle-derived magmas are widespread on the Tibetan Plateau, and provide evidence for the evolution of deep mantle and its influence on the Plateau development. Miocene basalts in the Maguan area on the southeastern Plateau have high MgO (9.13–13.10 wt%) and Mg (0.60–0.70) with high Ce/Pb (10.6–32.5) and Nb/U (43.7–52.9) ratios, similar to those of oceanic basalts. Distinct from Eocene-Oligocene mantle-derived potassic magmas in Western Yunnan and Cenozoic basic volcanic rocks in Tengchong, these Maguan basalts are characterized by high large ion lithophile elements (LILEs) concentrations, positive anomaly in high field strength elements (HFSEs) and depleted SrNd isotopes, consistent with the melt of an asthenospheric mantle origin. The high Ce/Pb and Nb/Y (1.80–2.68) ratios together with low Ba/Y and Ba/Th ratios indicate a significant input of slab-derived melt into the asthenospheric source. Besides, Hf/Hf* and Ti/Ti* ratios are significantly lower than those of ocean island basalt (OIB), which are proportional to the lighter δMg (-0.6‰ to -0.4‰) values. Based on the results of experimental petrology, the SrMg isotope mixing model suggests that the asthenospheric mantle beneath the Maguan area had undergone the significant metasomatism of recycled carbonates prior to the late Miocene. The above petrological and geochemical understanding, together with the geophysical data, allows us to propose that the mantle metasomatism is most probably associated with the Neo-Tethys seafloor subduction, which is further testified by the decoupling between depleted SrNd isotopes and elevated LILE concentrations.

中文翻译：

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通过青藏高原东南部马关地区中新世玄武岩识别深层再生碳酸盐

新生代地幔岩浆在青藏高原广泛分布，为深部地幔演化及其对青藏高原发展的影响提供了证据。高原东南部马关地区的中新世玄武岩具有较高的 MgO（9.13-13.10 wt%）和 Mg（0.60-0.70），以及较高的 Ce/Pb（10.6-32.5）和 Nb/U（43.7-52.9）比值，与那些海洋玄武岩。与滇西始新世-渐新世幔源钾岩浆和腾冲新生代基性火山岩不同，马关玄武岩具有高大离子亲石元素（LILE）浓度、高场强元素（HFSE）正异常和贫SrNd的特点。同位素，与软流圈地幔起源的熔化一致。高 Ce/Pb 和 Nb/Y (1.80–2.68) 比率以及低 Ba/Y 和 Ba/Th 比率表明来自板片的熔体大量输入软流圈源。此外，Hf/Hf* 和 Ti/Ti* 比值显着低于海岛玄武岩 (OIB)，这与较轻的 δMg（-0.6‰ 至 -0.4‰）值成正比。根据实验岩石学结果，SrMg同位素混合模型表明，马关地区软流圈地幔在晚中新世之前就经历了明显的再生碳酸盐交代作用。上述岩石学和地球化学认识，加上地球物理数据，使我们能够提出地幔交代作用很可能与新特提斯洋海底俯冲有关，贫SrNd同位素与升高的LILE浓度之间的脱钩进一步证明了这一点。