Contributions to Mineralogy and Petrology ( IF 3.5 ) Pub Date : 2022-07-21 , DOI: 10.1007/s00410-022-01940-7 Leon Gläser , Anna Grosche , Panagiotis C. Voudouris , Karsten M. Haase
Genetic models for the formation of K-rich magmas in subduction-related settings range from partial melting of subduction-affected mantle sources to melting of crustal rocks depending on the local tectonic framework. The Miocene high-K calc-alkaline to shoshonitic rocks of Limnos Island reflect the magmatic activity in the northern Aegean, which migrated southwards in response to trench retreat and the collision of continental terranes in the Hellenic subduction system. New whole rock and mineral data of basaltic andesites, dacites and monzonites from Limnos indicate that the magmas underwent fractional crystallization of olivine, clinopyroxene, amphibole, apatite, and Fe-Ti oxides at 1100 to 700 °C and 0.5 to 0.1 GPa without significant assimilation of crustal rocks during the magma evolution. The strong enrichment of large ion lithophile elements and light rare-earth elements relative to depleted heavy rare earth and high-field strength elements points towards a mantle source that has been extensively hybridized by subducted sedimentary material. New Sr–Nd-Pb isotope data reveal a distinct isotopic composition of the Limnos rocks with high 207Pb/204Pb at low 206Pb/204Pb and 143Nd/144Nd ratios that is likely related to the subduction of the continental crustal succession of the Apulian block which was subducted prior to the onset of magmatism on Limnos. Partial melting models assuming a hybridized mantle source suggest that the primary melts of Limnos formed by melting of a phlogopite pyroxenite at melting degrees of 5 to 10%. Compositional differences between high-K calc-alkaline and shoshonitic magmas are explained by variable melting degrees and varying amounts of sediment supply to the mantle. The magmatic and tectonic evolution of Limnos island is typical for the Oligocene and Miocene volcanic centres of the migrating western Aegean arc front.
中文翻译:
希腊利姆诺斯的高钾钙碱性到玄武岩火山活动:对爱琴海北部地球动力学演化的影响
俯冲相关背景下富钾岩浆形成的成因模型范围从受俯冲影响的地幔源的部分熔融到取决于当地构造框架的地壳岩石的熔融。利姆诺斯岛中新世高钾钙碱性到钾玄质岩反映了爱琴海北部的岩浆活动,在希腊俯冲系统中,随着海沟退缩和大陆地体的碰撞,岩浆向南迁移。来自 Limnos 的玄武岩安山岩、英安岩和二长岩的新全岩和矿物数据表明,岩浆在 1100 至 700 °C 和 0.5 至 0.1 GPa 的温度下经历了橄榄石、单斜辉石、闪石、磷灰石和铁钛氧化物的分级结晶,没有显着同化岩浆演化过程中的地壳岩石。大离子亲石元素和轻稀土元素相对于贫化重稀土和高场强元素的强富集指向了一个被俯冲沉积物质广泛杂化的地幔源。新的 Sr-Nd-Pb 同位素数据揭示了 Limnos 岩石的独特同位素组成207 Pb/ 204 Pb 低206 Pb/ 204 Pb 和143 Nd/ 144Nd 比率可能与 Apulian 地块的大陆地壳序列的俯冲有关,该地块在 Limnos 岩浆作用开始之前俯冲。假设杂化地幔源的部分熔融模型表明,Limnos 的主要熔体是由熔融度为 5% 至 10% 的金云母辉石岩熔融形成的。高钾钙碱性岩浆和钾玄质岩浆之间的成分差异可以通过不同的熔融程度和不同数量的地幔沉积物供应来解释。利姆诺斯岛的岩浆和构造演化是爱琴海西部弧锋迁移的渐新世和中新世火山中心的典型特征。