ABSTRACT

Cadomian magmatic activity is represented by a mafic – intermediate dyke suits in the Karacahisar dome (West – Central Taurides) formed by the southward subduction of the Proto-Tethyan ocean beneath North Gondwana. These dyke suites are classified as diabase, andesite and dacite. They display calc-alkali, high-K calc-alkali and shoshonitic character, and intruded into the siliciclastic rocks deposited in a back-arc rift setting. In this study, we present new zircon U-Pb ages, Sr-Nd isotopic and geochemical data to better understand the petrological evolution of the Cadomian magmatism. Zircon U-Pb concordia ages of 551.3 ± 3.5 Ma, 557.9 ± 3.7 Ma and 569 ± 7.2 Ma were obtained for these dykes. On the N-MORB normalized spider diagrams, mafic – intermediate dykes exhibit enrichment in large ion lithophile elements (LILE: Sr, K, Rb, Ba, Th), relatively less enrichment in light rare earth elements (LREE: La, Ce and Nd) and depletion in high field strength (HFS: Tb, Ti, Y and Yb) elements. Dyke samples have significant depletions of Ta and Nb relative to neighbouring LILE and LREE and display a significant subduction component. On the chondrite normalized REE diagrams, a weak Eu anomalies are observed, and this indicates some plagioclase accumulation. Dyke samples fall into the volcanic arc (island arc and/or continental arc), and back-arc fields on tectonic setting discrimination diagrams. The εNd_(i) values of dykes range from −1.47 to 1.76, and Nd depleted-mantle model (T_DM) ages vary between 1.32 and 1.81 Ga, and show enriched mantle or metasomatized subcontinental lithospheric mantle source signatures. The primary magmas of the dykes were derived from amphibole- and garnet-bearing mantle, and were affected by fractional crystallization, mixing and assimilation processes during ascent through the upper crust. All available data show that this magmatic activity developed in a back-arc rift setting subsequent to Cadomian arc magmatism in the West-Central Taurides.

摘要

卡多姆岩浆活动的代表是由北冈瓦纳下方的原始特提斯洋向南俯冲形成的 Karacahisar 圆顶（西 - 中 Taurides）中的镁铁质 - 中间岩脉套装。这些堤坝套件分为辉绿岩、安山岩和英安岩。它们表现出钙碱、高钾钙碱和钾玄质特征，并侵入弧后裂谷环境中沉积的硅质碎屑岩中。在这项研究中，我们提供了新的锆石 U-Pb 年龄、Sr-Nd 同位素和地球化学数据，以更好地了解卡多姆岩浆作用的岩石学演化。这些堤坝的锆石 U-Pb concordia 年龄分别为 551.3 ± 3.5 Ma、557.9 ± 3.7 Ma 和 569 ± 7.2 Ma。在 N-MORB 归一化蛛网图上，镁铁质-中间岩脉富含大离子亲石元素（LILE：Sr、K、Rb、Ba、Th），轻稀土元素（LREE：La、Ce 和 Nd）的富集相对较少，而高场强元素（HFS：Tb、Ti、Y 和 Yb）的贫化。与邻近的 LILE 和 LREE 相比，堤坝样品的 Ta 和 Nb 显着减少，并显示出显着的俯冲成分。在球粒陨石归一化 REE 图上，观察到较弱的 Eu 异常，这表明有一些斜长石堆积。岩脉样品属于火山弧（岛弧和/或大陆弧），以及构造背景判别图上的弧后场。εNd 在球粒陨石归一化 REE 图上，观察到较弱的 Eu 异常，这表明有一些斜长石堆积。岩脉样品属于火山弧（岛弧和/或大陆弧），以及构造背景判别图上的弧后场。εNd 在球粒陨石归一化 REE 图上，观察到较弱的 Eu 异常，这表明有一些斜长石堆积。岩脉样品属于火山弧（岛弧和/或大陆弧），以及构造背景判别图上的弧后场。εNd_(i)岩脉值范围从-1.47 到 1.76，Nd 贫化地幔模型 (T _DM ) 年龄在 1.32 到 1.81 Ga 之间变化，显示出富集的地幔或交代的次大陆岩石圈地幔源特征。岩脉的原生岩浆来源于含闪石和石榴石的地幔，并在通过上地壳上升过程中受到分级结晶、混合和同化过程的影响。所有可用数据表明，这种岩浆活动是在中西金牛座卡多姆弧岩浆作用之后的弧后裂谷环境中发展的。