Elucidating the petrological and geochemical characteristics of continental arc crustal fragments can provide unique insights into the magmatic evolutional path and physicochemical conditions (e.g., P–T–H2O) of continental magmatic arcs. This contribution provides a comprehensive set of petrological, mineralogical, geochronological, and geochemical data for the Neoproterozoic Nanba intrusive complex of the western Yangtze Block, South China, which features well-exposed middle–upper crustal sections of the Neoproterozoic continental magmatic arc, to evaluate their magmatic source and fractionation process. The Neoproterozoic Nanba intrusive complex, composed of cumulate gabbros, hornblende gabbros, gabbro-diorites, diorites, granodiorites, K-feldspar granites, and monzogranites, was emplaced at ca. 796–790 Ma. The different lithologies of the Nanba intrusive complex display relatively homogeneous Sr-Nd-Hf isotopes, which indicates a cogenetic evolutional process. The predominantly depleted isotopic characteristics, together with high values of Ba, Rb/Y, and Ba/La, demonstrate that these rocks mainly originated from a subduction fluid–metasomatized mantle source. Petrological and geochemical characteristics, as well as hornblende thermobarometric data, collectively support that the ca. 796–790 Ma Nanba intrusive complex, following the calc-alkaline trend, was dominated by the wet cogenetic fractionation of hornblende accompanied by plagioclase and accessory minerals beneath the middle–upper crustal levels (2.4–4.7 kbar). The cumulate gabbros represent the residue of accumulated hornblende + plagioclase + Fe-Ti oxides from fractionated basaltic melts. The high-SiO2 K-feldspar granites and monzogranites display complementary trace elements, which represent residual silicic cumulates and extracted interstitial liquids in the shallower crystal mush reservoir, respectively. In combination with previous studies, we propose that the middle–upper crustal sections of the Neoproterozoic continental arc of the western Yangtze Block underwent hornblende-dominated fractionation that was followed by significant crystal-liquid separation, which led to the genesis of high-SiO2 melts at the shallower crustal level. The cogenetic evolution played a significant role in molding the petrological and geochemical diversity of Neoproterozoic igneous rocks and the differentiation process of continental arc crust in the western Yangtze Block.

中文翻译：

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大陆弧中上地壳段的湿钙碱性岩浆分异：来自华南扬子地块西部新元古代南坝侵入杂岩的见解

阐明大陆弧地壳碎片的岩石学和地球化学特征可以为大陆岩浆弧的岩浆演化路径和物理化学条件（如P-T-H2O）提供独特的见解。该贡献为华南扬子地块西部新元古代南坝侵入杂岩提供了一套全面的岩石学、矿物学、年代学和地球化学数据，该杂岩具有新元古代大陆岩浆弧的中上地壳部分出露良好的特征，以评估它们的岩浆来源和分馏过程。新元古代南坝侵入杂岩由堆积辉长岩、角闪长岩、辉长闪长岩、闪长岩、花岗闪长岩、钾长石花岗岩和二长花岗岩组成，位在约 796–790 马。南坝岩体的不同岩性显示出相对均质的Sr-Nd-Hf同位素，这表明了同生演化过程。主要贫化同位素特征，加上 Ba、Rb/Y 和 Ba/La 值较高，表明这些岩石主要源自俯冲流体-交代地幔源。岩石学和地球化学特征以及角闪石温压数据共同支持大约。796~790马南巴侵入杂岩呈钙碱性趋势，以中上地壳水平（2.4~4.7 kbar）下角闪石的湿同生分异为主，伴有斜长石和副矿物。累积辉长岩代表来自分馏玄武岩熔体的累积角闪石 + 斜长石 + Fe-Ti 氧化物的残留物。高SiO2钾长石花岗岩和二长花岗岩显示出互补的微量元素，分别代表较浅的晶糊储层中残留的硅质堆积物和提取的间隙液体。结合前人研究，我们提出扬子地块西部新元古代大陆弧的中上地壳剖面经历了以角闪石为主的分馏作用，随后发生了显着的晶液分离，从而导致了高SiO2熔体的成因在较浅的地壳层面。同生演化对塑造新元古代火成岩的岩石学和地球化学多样性以及扬子地块西部陆弧地壳的分异过程发挥了重要作用。