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Composition and Structure of Zircon from Harzburgite Inclusion Hosted in Granulites of the Bug Complex, Ukrainian Shield
Geology of Ore Deposits ( IF 0.7 ) Pub Date : 2020-02-05 , DOI: 10.1134/s1075701519080075
S. B. Lobach-Zhuchenko , S. G. Skublov , Yu. S. Egorova , D. V. Prishchepenko , O. L. Galankina

Abstract

The comprehensive study (electron microscopy, mass-spectrometry of secondary ions, Raman spectroscopy) of zircon from harzburgite inclusion in granulites of the Bug complex (Ukrainian Shield) is carried out. Based on a number of features, the studied zircons are subdivided into three groups. Zircon from the first group is of igneous genesis and crystallized 2.8 Ga ago at the temperature of about 650°C from a melt of orthopyroxenite composition. Zircon from the second group underwent hydrothermal alteration ca. 2.75 Ga ago at the temperature of about 750°C. Zircon from the third group is distinctive in several geochemical characteristics (higher Lu/Hf ratio, etc.) and formed before the hydrothermal process, but their compositions were altered by the fluid. Conditions of the igneous zircon (first group) crystallization were characterized by the higher \({{f}_{{{{{\text{O}}}_{{\text{2}}}}}}}\) value, compared to the later hydrothermal alteration. The hydrothermal process has provided the distortion of zircon crystal lattice, which is reflected in the Raman spectra, and the formation of amorphous structure in the uranium-rich zircon from the third group. In terms of trace element contents, the first and second zircon groups indicate different initial melts (from which they originated) from the third zircon group; the melt of the third group was more mafic. The obtained results support the idea about the hybrid character of the melt and that the rock formed in two main stages, namely, a magmatic one and fluid alteration, separated in time and having different oxidation-reduction conditions.


中文翻译:

乌克兰盾构Bug复合体颗粒物中的含Harzburgite夹杂物的锆石的组成和结构

摘要

对Bug配合物(乌克兰盾牌公司)的粒状颗粒中的钙锌矿包裹体中的锆石进行了综合研究(电子显微镜,二次离子质谱,拉曼光谱)。基于许多特征,所研究的锆石可分为三组。第一组中的锆石具有火成因,并在约650°C的温度下由正辉石组成的熔体结晶形成2.8 Ga。第二组锆石经历了水热蚀变。2.75 Ga之前,温度约为750°C。第三组锆石具有多种地球化学特征(较高的Lu / Hf比等),并且在水热过程之前就形成了,但其组成因流体而改变。与后来的水热蚀变相比,\({{f} _ {{{{\ text {O}}} _ {{\ text {2}}}}}} \)值。水热过程提供了拉曼光谱中反映的锆石晶格畸变,以及第三组富铀锆石中非晶态结构的形成。就痕量元素含量而言,第一和第二锆石组表示与第三锆石组不同的初始熔体(它们起源于此)。第三组的熔体更黑手党。所获得的结果支持了关于熔体的混合特性的思想,以及在两个主要阶段形成的岩石,即岩浆形成和流体蚀变,它们在时间上分开并且具有不同的氧化还原条件。
更新日期:2020-02-05
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