The gold mineralization in the Central Aldan ore district is genetically related to potassic calc-alkaline and alkaline magmatism dated at 115–150 Ma. The objective of this study is to establish the age of hydrothermal processes that accompanied the formation of Au-Te mineralization at the Samolazovsky Deposit. Based on the isotope-geochemical study of zircons from quartz-feldspar metasomatic rocks of the deposit, the granitoids and charnokites of the Nimnyr Complex (1 900–1 960 Ma) at the contact with the Yukhta monzonite-syenite massif (∼127 Ma) were studied. Zircon U-Pb dating was performed on a SHRIMP-II ion microprobe, and rare-earth and trace elements analyses of zircon were carried out in the same craters by secondary-ion mass spectrometry on a Cameca IMS-4f ion microprobe. It is revealed that the studied zircons have heterogeneous structures: dark core and lighter rim, which differ greatly in isotope-geochemical parameters. Zircon rims are cut by a network of fractures, extending into the central part of zircon grains. The rims yield a subconcordant age of 1 937±24 Ma, with an average total REE content of 550 ppm, which corresponds to the formation age of the Nimnyr Complex. All zircon cores yield a discordant age of 83±11 Ma and are characterized by a higher total REE content (∼1 812 ppm), as well as higher contents of U and non-formula elements (Ca, Sr, and Y) with respect to rims, due to the effect of fluid on zircons. Despite the limited number of zircon grains, the additional geochronological study of zircons from syenites of the ore-bearing Ryabinovy Massif has revealed the presence of two distinct age clusters: ∼125–138 and 76–83 Ma. The older ages of zircons from syenites are typical for the Central Aldan ore district. Until now, there is still no explanation for an age range (76–83 Ma) of single zircon grains from ore-bearing syenites of the Ryabinovy Massif. The obtained data suggest that the processes of activation (the effect of fluid) within the Central Aldan ore district continued until Late Mesozoic. With regards to the equivocal geotectonic position of the Mesozoic potassic magmatism in the study area and its high metallogenic potential, there exists an absolute necessity to determine the geochronological age of the rock formations. Therefore this study presents the Late Cretaceous geochronological data for the first time which can constrain the time-frame for the formation of gold-bearing magmatic and metasomatic rocks of the Aldan ore district.

中文翻译：

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锆石U-Pb年代学在俄罗斯阿尔丹希尔德的中央阿尔丹金矿区记录了晚白垩世流体活化作用：第一个数据

阿尔丹中央矿区的金矿化与钾钙碱性和碱性岩浆作用在遗传上有关，时间在115-150 Ma之间。这项研究的目的是确定伴随萨莫拉佐夫斯基矿床Au-Te矿化形成的水热过程的年龄。根据该矿床的石英-长石交代岩石中锆石的同位素地球化学研究，Nimnyr配合物（1 900– 1 960 Ma）与Yukta蒙脱石-堇青石地块（〜127 Ma）接触时的花岗岩和类斜角岩被研究了。在SHRIMP-II离子微探针上进行锆石U-Pb测年，在Cameca IMS-4f离子微探针上通过二次离子质谱法在同一陨石坑中对锆石进行稀土和痕量元素分析。结果表明，所研究的锆石具有异质结构：深色核和浅色轮缘，其同位素地球化学参数差异很大。锆石的边缘被裂缝网络切割，延伸到锆石晶粒的中央部分。轮缘产生的亚相合年龄为1 937±24 Ma，平均总REE含量为550 ppm，与Nimnyr Complex的形成年龄相对应。所有锆石岩心的年龄不一致，为83±11 Ma，并且具有较高的总REE含量（〜1 812 ppm），以及相对于U和非配方元素（Ca，Sr和Y）较高的含量由于流体对锆石的影响，轮辋到轮辋。尽管锆石数量有限，含矿石的Ryabinovy断块的正长岩中锆石的其他地质年代学研究表明，存在两个不同的年龄群：〜125–138和76–83 Ma。中部Aldan矿区的典型年龄为正长岩锆石。到现在为止，仍没有任何关于Ryabinovy地块含矿正长岩中单一锆石晶粒的年龄范围（76-83 Ma）的解释。获得的数据表明中阿尔丹矿区内部的活化过程（流体作用）一直持续到中生代晚期。关于研究区中生代钾质岩浆作用的明确构造位置及其高成矿潜力，绝对有必要确定岩层的地质年代。