Abstract

The paper presents data on sulfide globules in picrodolerites from a bottom apophysis of the Yoko-Dovyren massif, northern Transbaikalia. Textural features of the rocks indicate that they crystallized at rapid magma cooling. Their composition is similar to that of chilled olivine gabbronorites from the lower contact of the massif. Many droplet-shaped sulfides, which range from 2 to 15 mm, were identified in one of the samples using X-ray computed tomography. The largest of these globules was drilled out and studied in detail to clarify its inner structure, which consists of the main spheroid and a surrounding halo of disseminated sulfides. The main globule and surrounding halo significantly differ in composition (the halo is richer in Cu), as was calculated using the average compositions of the dominant sulfide phases and their relative proportions. The weighted mean (with regard for halo) composition can be assumed as an approximation of the composition of the initial sulfide liquid that was formed near the chill zone of the gabbronorite apophysis from the main intrusive chamber. The Cu content in the initial sulfide corresponds to the results of thermodynamic modeling (with the COMAGMAT-5 program package) of the geochemistry of primitive sulfides in ultramafite rocks from the basal zone of the massif. The differences in the composition of the halo and the main globule indicate the possibility of local migration (within a few millimeters) of the residual sulfide liquids enriched in Cu when the protosulfide melt differentiated. As a physical mechanism that produced the halo, we assumed that the latest sulfide fraction was pressed off into the pore space of rapidly crystallizing olivine orthocumulates.

中文翻译：

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Yoko-Dovyren层状侵入体近底部的垂体形成的吡咯石中硫化物液滴的形态，矿物学和组成

摘要

该论文提供了横贯北贝科利亚北部Yoko-Dovyren断层的底部隆突的亚闪闪石中硫化球的数据。岩石的质地特征表明它们在岩浆快速冷却下结晶。从地块下部的接触来看，它们的成分类似于冷冻的橄榄石辉长岩。使用X射线计算机断层扫描在其中一个样品中鉴定出许多液滴状的硫化物，范围从2到15 mm。这些球中最大的球被钻出并进行了详细研究以阐明其内部结构，该结构由主要球体和周围弥散的硫化物组成。主要小球和周围的晕在成分上有明显的不同（晕富含铜），如使用主要硫化物相的平均组成及其相对比例所计算的。加权平均值（相对于卤素而言）的组成可以假定为初始硫化物液体的组成的近似值，该初始硫化物液体是从主侵入室在辉长岩隆突的冷却区附近形成的。初始硫化物中的Cu含量对应于来自地块基底带的超黑铁矿岩石中原始硫化物的地球化学热力学模拟结果（使用COMAGMAT-5程序包）。晕圈和主要小球的成分差异表明，当原硫化物熔体分化时，富集在铜中的残留硫化物液体有可能局部迁移（几毫米之内）。作为产生光环的物理机制，