Abstract A unique scapolite-rich gabbro has been found in the Cho Don complex (north-eastern Vietnam) and investigated using cathodoluminescence microscopy and spectroscopy, electron-microscopic observations, and Raman micro-spectroscopy. The scapolite, occupying up to ca. 30 vol% of rock matrix, displays distinctive brownish to greenish (S2_activated) luminescence, while its chemical composition is marked by the enrichment in Ca (~Me73–80) and CO2 (~4.60 wt%). Meionitic scapolite is accompanied by such magmatic phases as: clinopyroxenes (partially altered to uralite), oligoclase-andesine, K-feldspars, biotite, as well as fluorapatite and titanite. On the basis of micro-textural observations and phase-relations including interstitial form of scapolite, the high Ca content relative to adjacent Na-rich plagioclase and high-angle contacts between pyroxenes and scapolites, it may be inferred that the investigated Me-scapolite represents a high-temperature igneous phase. The presence of wollastonite, vesuvianite and calcite within the rock matrix gives a clue to the interaction between parental melt and country rocks that could act as a source for the formation of a specific CO2-enriched magma. Furthermore, scapolite breaks down into: (1) intergrowths of Ca-rich plagioclase with worm-like calcite that may reflect isobaric cooling following the high-temperature stage of rock evolution, and (2) prehnite-vuagnatite clusters, which in turn correspond to the late-stage low-temperature hydrothermal alteration. The formation of the latter could be induced by alteration of primary clinopyroxenes due to the release of Ca2+ and Ti4+. According to major and trace element data of whole-rock samples, the scapolite-rich gabbro originated from slightly evolved alkaline melt, but also shows enrichment in LREE relative to HREE ([La/Yb]CN ~ 10.24), as well as strong depletion in Nb-Ta-Ti relative to U and Th content. These geochemical signatures point to the enriched lithospheric mantle source of parental magma, which is likely to have been imprinted by subduction components (possibly sediment-derived melts) and/or crustal contamination.

中文翻译：

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越南东北部碱性 Cho Don 杂岩中富含方柱石的辉长岩的岩石成因——矿物学和地球化学意义

摘要 在 Cho Don 复合体（越南东北部）中发现了一种独特的富含方柱石的辉长岩，​​并使用阴极发光显微镜和光谱、电子显微镜观察和拉曼显微光谱进行了研究。方柱石，占据约约。30 vol% 的岩石基质，显示出独特的褐色到绿色 (S2_activated) 发光，而其化学成分以富含 Ca (~Me73-80) 和 CO2 (~4.60 wt%) 为标志。Meionic 方柱石伴随着这样的岩浆相，如：单斜辉石（部分改变为 uralite）、长石长石、钾长石、黑云母以及氟磷灰石和钛白石。根据微观结构观察和相关系，包括方柱石的间隙形式，相对于相邻的富钠斜长石的高 Ca 含量以及辉石和方柱石之间的高角度接触，可以推断出所研究的 Me-方柱石代表了高温火成相。硅灰石、硅灰石和方解石在岩石基质中的存在为母体熔体和围岩之间的相互作用提供了线索，这可能是形成特定富含 CO2 的岩浆的来源。此外，方柱石分解为：（1）富含钙的斜长石与蠕虫状方解石的共生，这可能反映了岩石演化的高温阶段后的等压冷却，以及（2）早长岩-布瓦格纳长石簇，这反过来对应于后期低温热液蚀变。后者的形成可能是由于 Ca2+ 和 Ti4+ 的释放导致初级单斜辉石的改变而诱导的。根据全岩样品的主量和微量元素数据，富含方柱石的辉长岩起源于轻微演化的碱性熔体，但相对于重稀土（[La/Yb]CN~10.24），LREE富集，并具有强烈​​的耗损Nb-Ta-Ti 相对于 U 和 Th 含量。这些地球化学特征表明母岩浆富含岩石圈地幔源，这很可能被俯冲成分（可能是沉积物衍生的熔体）和/或地壳污染所印记。24)，以及相对于 U 和 Th 含量的 Nb-Ta-Ti 的强烈消耗。这些地球化学特征表明母岩浆富含岩石圈地幔源，这很可能被俯冲成分（可能是沉积物衍生的熔体）和/或地壳污染所印记。24)，以及相对于 U 和 Th 含量的 Nb-Ta-Ti 的强烈消耗。这些地球化学特征表明母岩浆富含岩石圈地幔源，这很可能被俯冲成分（可能是沉积物衍生的熔体）和/或地壳污染所印记。