Abstract

The mineralogical, structural, crystal-chemical, and isotope-geochronological data were obtained for the first time in two samples of globular phyllosilicates (GPS) of the glauconite–illite series collected from terrigenous rocks in two sections of the lower part of the Lower Vendian Maastakh Formation (Khorbusuonka and Ulakhan-Sololi rivers, northwestern slope of the Olenek Uplift). Simulation of experimental X-ray diffraction patterns for both samples in the air-dried and ethylene glycol-solvated states was used to determine the expandable layer contents (9, 10%), types of expandable layers (smectite- and vermiculite-type), their ratios in a three-component mixed-layer structure, parameter csinβ (9.98 Å) of mica layers, and the short-range order factor describing the alternation of different layer types (R = 2, 3). Values of the unit-cell parameter b (9.027, 9.039 Å) correspond to the dioctahedral Al, Fe-bearing micas. The mica components in the studied mixed-layer minerals are shown to be represented by Fe-illites (K_Al = ^VIAl/(^VIFe³⁺ + ^VIAl) = 0.71, 0.82) with the K₂O content of 7.77 and 8.40%. The Rb–Sr dating of the Maastakh GPS was carried out for the first time in combination with the calculation of theoretical patterns in the cation distribution in the mineral structure and comparison of the calculation results with the Mössbauer and IR spectroscopy data using the Optima software package supplemented with the new Irmes software. The Rb–Sr data obtained for two Fe-illites (Khorbusuonka and Ulakhan-Sololi rivers: 1033, 913 ± 12 Ma, respectively) are “older” relative to the Vendian Maastakh Formation (~640 ± 5), indicating a terrigenous origin of the studied grains. Globular phyllosilicates from the Maastakh Formation are similar in age and composition to the previously studied Lower Khaipakh (Middle Riphean) GPS (1172 ± 18 and 1112 ± 24 Ma, respectively). The age of GPS samples from the Maastakh Formation is younger (1033–913 Ma), probably, due to the initial cationic disordering in the GPS structure and partial loss of radiogenic elements during secondary alterations (rewashing and redeposition of Fe-illite grains in sediments of the Maastakh Formation) and, probably, during their catagenetic changes as well.

中文翻译：

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Maastakh 组陆源球状层状硅酸盐的矿物学、晶体化学和 Rb-Sr 同位素数据（下文迪安，Olenek 隆起）

摘要

首次获得了从下文德河下游两段陆源岩中采集的海绿石-伊利石系列球状页硅酸盐（GPS）的两个样品的矿物学、结构、晶体化学和同位素年代学数据。 Maastakh 组（Khorbusuonka 和 Ulakhan-Sololi 河，Olenek 隆起的西北斜坡）。对空气干燥和乙二醇溶剂化状态的两个样品的实验 X 射线衍射图进行模拟，以确定可膨胀层含量 (9, 10%)、可膨胀层类型（蒙脱石和蛭石型）、它们在三组分混合层结构中的比率、云母层的参数c sinβ (9.98 Å) 以及描述不同层类型交替的短程有序因子（R = 2, 3)。晶胞参数b (9.027, 9.039 Å) 的值对应于双八面体铝、含铁云母。所研究的混合层矿物中的云母成分以铁伊利石为代表（K _Al = ^VI Al/( ^VI Fe ³⁺ + ^VI Al) = 0.71, 0.82），K ₂O含量为7.77和8.40%。Maastakh GPS 的 Rb-Sr 测年是首次结合矿物结构中阳离子分布的理论模式计算以及计算结果与使用 Optima 软件包的穆斯堡尔和红外光谱数据进行比较补充了新的 Irmes 软件。为两条铁伊利石（Khorbusuonka 和 Ulakhan-Sololi 河：分别为 1033、913 ± 12 Ma）获得的 Rb-Sr 数据相对于 Vendian Maastakh 组（~640 ± 5）“更老”，表明研究的谷物。来自 Maastakh 组的球状页硅酸盐在年龄和成分上与先前研究的下海帕赫（中里弗亚）GPS（分别为 1172 ± 18 和 1112 ± 24 Ma）相似。