Abstract The geodynamic environment of the 407–392 Ma Altai-Sayan Rift System is characterized using previously published and new original data on whole rock, trace and Sr Nd isotopic compositions, along with U Pb zircon ages. Five magmatic associations are present: basalt (basalts and basaltic trachyandesites), continuous (basalts, andesites, dacite-rhyolites), alkaline (basalts, nephelinite, tephrite, phonotephrite, phonolite, teralite, ijolite-urthite, foyaite, nepheline and alkaline syenite), bimodal (trachybasalts, trachyrhyolites-pantellerites and peralkaline granites) and ultramafic-mafic (picrites and picrodolerites). Mafic rocks of basalt, continuous, alkaline, and bimodal associations exhibit a wide variation of TiO2 (from 1.05 to 4.05 wt%) and are compositionally intermediate between intraplate basalts of OIB type and basalts of active continental margins IAB type. The TiO2 content in these mafic rocks correlates directly with the content of large ion lithophile elements (LILE), rare-earth elements (REE), high field strength elements (HSFE), and particularly with Nb and Ta. The basaltic samples have positive eNd(395) values (+3.4 to +7.7) and a large range of eSr(395) values (−13.6 to +12.6). eSr(395) decreases with increasing TiO2 abundance. Pantellerites and alkaline granites have ore-level concentrations of Nb, Ta, Zr, Hf, REE; and they have similar Sr and Nd isotope parameters to those of the high-Ti basalts. This indicates their origin via fractionation of mantle magmas. Rhyolite samples are depleted in rare incompatible elements, but have low positive eNd(395) values (+1.5 to +1.8), and eSr(395) values (+16.6 to +20.6), and they compositionally resemble the rocks produced from anatectic magmas of crustal origin. Whole-rock elemental and isotopic data suggest that the mafic rocks were likely derived from lithospheric mantle that was metasomatized during the prior Caledonian accretion/subduction event. In combination with the field relationship and regional geology, our study suggests that the rock associations from the Devonian Altai-Sayan Rift System were derived by the activity of mantle plumes.

中文翻译：

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泥盆纪阿尔泰-萨彦裂谷系统的岩浆作用：各种羽流-岩石圈相互作用的地质和地球化学证据

摘要 407-392 马阿尔泰-萨彦裂谷系统的地球动力学环境使用先前发表的和新的原始数据来表征，包括全岩、痕量和 Sr Nd 同位素组成，以及 U Pb 锆石年龄。存在五种岩浆组合：玄武岩（玄武岩和玄武质粗安岩）、连续岩（玄武岩、安山岩、英安岩-流纹岩）、碱性岩浆（玄武岩、霞石、软长岩、音长岩、响长岩、辉长岩、菱沸石-尿长岩、菱长石） 、双峰（粗玄武岩、粗流纹岩-斑纹岩和过碱性花岗岩）和超镁铁质-镁铁质（苦麻岩和细长岩）。玄武岩、连续、碱性和双峰组合的基性岩表现出 TiO2 的广泛变化（从 1.05 到 4. 05 wt%) 并且在成分上介于 OIB 型板内玄武岩和活动大陆边缘 IAB 型玄武岩之间。这些基性岩中的 TiO2 含量与大离子亲石元素 (LILE)、稀土元素 (REE)、高场强元素 (HSFE) 的含量直接相关，尤其是与 Nb 和 Ta 的含量相关。玄武岩样品具有正 eNd(395) 值（+3.4 至 +7.7）和大范围的 eSr(395) 值（-13.6 至 +12.6）。eSr(395) 随着 TiO2 丰度的增加而降低。Pantellites 和碱性花岗岩具有矿石级浓度的 Nb、Ta、Zr、Hf、REE；它们具有与高钛玄武岩相似的 Sr 和 Nd 同位素参数。这表明它们的起源是通过地幔岩浆的分馏。流纹岩样品耗尽了稀有的不相容元素，但它们的正 eNd(395) 值较低（+1.5 至 +1.8）和 eSr(395) 值（+16.6 至 +20.6），并且它们在成分上类似于地壳起源的深熔岩浆产生的岩石。全岩元素和同位素数据表明，基性岩可能来自在先前的加里东期吸积/俯冲事件期间交代的岩石圈地幔。结合现场关系和区域地质，我们的研究表明泥盆纪阿尔泰-萨彦裂谷系统的岩石组合是由地幔柱的活动产生的。全岩元素和同位素数据表明，基性岩可能来自在先前的加里东期吸积/俯冲事件期间交代的岩石圈地幔。结合现场关系和区域地质，我们的研究表明泥盆纪阿尔泰-萨彦裂谷系统的岩石组合是由地幔柱的活动产生的。全岩元素和同位素数据表明，基性岩可能来自在先前的加里东期吸积/俯冲事件期间交代的岩石圈地幔。结合现场关系和区域地质，我们的研究表明泥盆纪阿尔泰-萨彦裂谷系统的岩石组合是由地幔柱的活动产生的。