The Tisza and Dacia mega-units constitute a central part of the Alps-Carpathians-Dinarides orogenic system. Polyphase medium-grade metamorphism observed in mineral assemblages from the crystalline basement is often correlated with Variscan and pre-Variscan events. However, a mid-Cretaceous Sm–Nd garnet age (103.6 ± 1.8 Ma) from the Apuseni Mountains is at odds with this interpretation. Electron-microprobe U-Th–Pb dating of monazite in samples from the Apuseni Mountains, the Rodna Mountains, as well as the Şimleu Silvaniei, Ticău and Preluca inselbergs revealed a complex pattern of Alpine and pre-Alpine age clusters. Pre-Variscan and Variscan ages were obtained from the core of zoned monazite grains and from samples that apparently escaped Alpine overprinting. Relic monazite in the latter is often replaced by rhabdophane and/or surrounded by allanite coronas. Permian to Early Triassic monazite ages correlate with the intrusion of granitic melts and pegmatites. Early Cretaceous ages from rims of chemically zoned grains and from monazite inclusions in garnet, biotite and staurolite represent newly formed metamorphic grains that crystallized on the prograde path during Alpine metamorphism. Petrographic observations of prograde allanite breakdown reactions, Sm–Nd garnet analyses and thermobaric estimates (500–550 °C/5–8 kbar) from parts of the Tisza and Dacia mega-units constrain medium-grade conditions during Early Cretaceous times. Exclusively mid-Cretaceous monazite ages from the inselbergs and the Rebra-Unit of the Rodna Mountains, allow extending the Alpine prograde overprint across the Transylvanian basin. Together with other studies from the basement of the Pannonian basin, this implies that the Dacia Mega-Unit and parts of the Tisza Mega-Unit experienced a medium-grade metamorphic overprint and synkinematic garnet-growth during late Early Cretaceous times. The Alpine prograde medium-grade overprint is pronounced in the contact zone between the Tisza and Dacia mega-units and forms a continuous belt with the Cretaceous metamorphic imprint in the Eastern Alps, when back-rotated to its original position during the Cretaceous.

中文翻译：

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Apuseni和Rodna山（罗马尼亚）的后Variscan变质作用：Sm–Nd石榴石和U–Th–Pb独居石年代的证据

Tisza和Dacia巨型单元构成了Alps-Carpathians-Dinarides造山系统的核心部分。在晶体基底的矿物组合中观察到的多相中等等级变质作用通常与Variscan和前Variscan事件有关。然而，来自阿普塞尼山脉的白垩纪中段Sm-Nd石榴石年龄（103.6±1.8 Ma）与这种解释不一致。在Apuseni山，Rodna山以及ŞimleuSilvaniei，Ticău和Preluca inselbergs的样品中，独居石的电子探针U-Th-Pb定年显示出复杂的高山和早高山年龄群格局。前Variscan和Variscan年龄是从分区独居石颗粒的核心以及明显逃脱了高山叠印的样品中获得的。后者中的遗迹独居石经常被菱花石代替和/或被尿囊石日冕所包围。二叠纪至三叠纪早期独居石年龄与花岗岩熔体和伟晶岩的侵入有关。从化学带状颗粒的边缘以及石榴石，黑云母和星形陨石中独居石包裹体的白垩纪早期代表了新形成的变质颗粒，这些颗粒在高山变质过程中在前进路径上结晶。Tisza和Dacia巨型单元部分地区对前进的尿囊素分解反应的岩石学观察，Sm-Nd石榴石分析和热压估算（500-550°C / 5-8 kbar）限制了白垩纪早期的中等品位条件。完全来自白垩纪中期的独居石年龄，来自于罗德纳山脉的inselbergs和Rebra-Unit，允许在整个特兰西瓦尼亚盆地扩展阿尔卑斯山的叠印。连同Pannonian盆地地下室的其他研究一起，这意味着达契亚巨型单元和Tisza巨型单元的某些部分在白垩纪早期经历了中等程度的变质叠印和石榴石的运动学石榴石生长。在Tisza和Dacia大型单元之间的接触带中，高山级的中等品位叠印明显，在白垩纪回旋至原始位置时，与东部白垩纪的白垩纪变质印记形成连续带。这意味着在白垩纪晚期晚期，达契亚巨型单元和Tisza巨型单元的某些部分经历了中等程度的变质叠印和石榴石的生长。在Tisza和Dacia大型单元之间的接触带中，高山级的中等品位叠印明显，在白垩纪回旋至原始位置时，与东部白垩纪的白垩纪变质印记形成连续带。这意味着在白垩纪晚期晚期，达契亚巨型单元和Tisza巨型单元的某些部分经历了中等程度的变质叠印和石榴石的生长。在Tisza和Dacia大型单元之间的接触带中，高山级的中等品位叠印明显，在白垩纪回旋至原始位置时，与东部白垩纪的白垩纪变质印记形成连续带。