U–Pb geochronological, trace‐element and Lu–Hf isotopic studies have been made on zircons from ultrahigh‐pressure (UHP) mafic eclogite from the Kumdy‐Kol area, one of the diamond‐facies domains of the Kokchetav Massif (northern Kazakhstan). The peak eclogitic assemblage equilibrated at > 900 °C, whereas the bulk sample composition displays light rare‐earth element (LREE) and Th depletion evident of partial melting. Zircons from the eclogite are represented by exclusively newly formed metamorphic grains and have U–Pb age spread over 533–459 Ma, thus ranging from the time of peak subduction burial to that of the late post‐orogenic collapse. The major zircon group with concordant age estimates have a concordia age of 508.1 ±4.4 Ma, which corresponds to exhumation of the eclogite‐bearing UHP crustal slice to granulite‐ or amphibolite‐facies depths. This may indicate potentially incoherent exhumation of different crustal blocks within a single Kumdy‐Kol UHP domain. Model Hf isotopic characteristics of zircons (ε_Hf(t) +1.5 to +7.8, Neoproterozoic model Hf ages of 1.02–0.79 Ga) closely resemble the whole‐rock values of the Kumdy‐Kol eclogites and likely reflect in situ derivation of HFSE source for newly formed grains. The ages coupled with geochemical systematics of zircons confirm that predominantly late zircon growth occurred in Th–LREE‐depleted eclogitic assemblage, that experienced incipient melting and monazite dissolution in melt at granulite‐facies depths, followed by amphibolite‐facies rehydration during late‐stage exhumation‐related retrogression.

中文翻译：

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来自库克切塔夫（Kokchetav）UHP-HP地块（哈萨克斯坦）的Kumdy-Kol的榴辉岩中普遍存在的峰后锆石：大陆俯冲环境中与掘尸相关的锆石生长和修饰的意义

U-Pb地质年代学，痕量元素和Lu-Hf同位素研究是对Kumchet-Kol地区的超高压镁铁榴辉岩中的锆石进行研究的，Kumdy-Kol地区是Kokchetav地块（哈萨克斯坦北部）的钻石相区域之一。 。峰凝结峰在> 900°C时达到平衡，而大块样品组成显示出轻稀土元素（LREE）和Th损耗，部分熔化。榴辉岩中的锆石仅以新近形成的变质晶粒为代表，其U–Pb年龄分布在533–459 Ma之间，范围从俯冲峰值埋藏时间到造山后期坍塌后期。年龄估计一致的主要锆石群的共生年龄为508.1±4.4 Ma，这对应于将榴辉岩的UHP地壳薄片挖掘成粒状或角质岩相的深度。这可能表明单个Kumdy-Kol UHP域中不同地壳块的掘出可能不连贯。锆石的Hf同位素模型特征（ε_Hf（t）+1.5至+7.8，新元古代模型Hf年龄为1.02–0.79 Ga）与Kumdy-Kol榴辉岩的全岩值非常相似，并且很可能反映了新形成颗粒的HFSE源的原位推导。年龄与锆石的地球化学系统相结合，证实锆石主要生长在贫乏Th-LREE的砾岩组合中，在粒岩相深度经历了初期熔融和独居石溶解，随后在晚期掘尸过程中闪石-岩相补水相关的倒退。