We present comprehensive geochemical and isotopic (Sr-Nd-Hf) datasets for two suites of ultramafic rock in Vietnam, namely xenoliths of spinel lherzolite entrained in late Cenozoic alkali basalts, and Paleozoic ultramafic massifs that occur along the Tam Ky-Phuoc Son suture zone in central and southern Vietnam. The ultramafic massifs are the products of high degrees of melt extraction (up to 40%), and have relatively low equilibrium temperatures of 603 to 778 °C. The lherzolites are residues of relatively low degrees of fractional melting (< 1% up to 20%). The compositions of minerals in the xenoliths reveal that the late Cenozoic lithospheric mantle beneath central and southern Vietnam was hotter (825–1058 °C) than during the Paleozoic. The calculated trace element patterns of metasomatic melts that equilibrated with clinopyroxenes in the LREE-enriched xenoliths show enrichments in Th, U, and LREEs, and depletions in Nb. These data, together with the elevated Ti/Eu ratios of the clinopyroxenes, reflect the role of hydrous silicate melts as the main agents of metasomatism. The ultramafic rocks of the Paleozoic massifs contain spinel with TiO₂ contents higher than expected for residual spinel, which suggests the influence of boninitic melt(s). In the lherzolite xenoliths, the clinopyroxenes have MORB-like depleted Sr-Nd-Hf isotopic compositions (⁸⁷Sr/⁸⁶Sr = 0.70241–0.70416; ε_Nd = +6.6 to 12.3; ε_Hf = +13.1 to 25.1), suggesting metasomatic melts/fluids from upwelling asthenosphere. We suggest that subduction of the (Paleo-)Pacific Plate and continental collision during the Permian–Triassic played key roles in lithospheric replacement and thinning beneath central and southern Vietnam.

我们为越南的两套超镁铁质岩石提供了全面的地球化学和同位素（Sr-Nd-Hf）数据集，即在新生代碱性玄武岩中夹带的尖晶石锂铁矿的异岩和沿Tam Ky-Phuoc Son缝合带出现的古生代超镁铁质断层在越南中部和南部。超镁铁质断层是高熔体提取度（高达40％）的产物，并且具有603至778°C的较低平衡温度。锂铁矿是分数熔融度相对较低的残余物（<1％至20％）。新生代岩石中的矿物成分表明，越南中部和南部下方新生代岩石圈地幔比古生代更热（825-1058°C）。计算得出的富含LREE的异种岩中与次生环戊烷平衡的交代熔体的痕量元素模式显示出Th，U和LREEs富集，Nb耗竭。这些数据，再加上斜基吡咯的较高的Ti / Eu比，反映了水合硅酸盐熔体作为交代作用的主要作用。古生代地块的超镁铁质岩石含有尖晶石和TiO_2的含量高于残余尖晶石的预期含量，这表明了贝氏体熔体的影响。在包体橄榄岩，单斜辉石的具有MORB状耗尽锶的Nd-Hf同位素组合物（⁸⁷ SR / ⁸⁶ SR = 0.70241-0.70416;ε_的Nd = 6.6至12.3;ε_的Hf = 13.1至25.1），表明交代熔体/来自软流圈上升的流体。我们认为，（古-）太平洋板块的俯冲和二叠纪－三叠纪期间的大陆碰撞在越南中南部的岩石圈置换和变薄中起着关键作用。