The paper describes disseminated tabular, podiform massive, and transitional chromitite deposits from a mantle section of the Kraka ophiolite massif, South Urals, Russia. The chromitite is hosted by dunite with no correlation between their size and quality and the size of the dunite bodies. Thick dunite bodies mostly host disseminated fine-grained banded chromitite; massive ores are composed of coarse-grained chromitite typically with a thin dunite envelope. The chromitite and host ultramafic rocks exhibit plastic deformation of silicates and chromite, which is expressed in microstructural features, preferred orientation of rock-forming olivine, and folding of the chromitite bodies. The ultramafic rocks are also characterized by deformation-induced textures leading to the formation of the small-size chromite grains on structural defects of plastically deformed rock-forming olivine and orthopyroxene. The formation of dunite bodies and associated chromitite is related to the localization of deformation of rising mantle flows under decompression conditions. Dunite was the most rheologically weak zone exhibiting a focused solid state flow and effective separation of mineral phases (olivine and chromite). The higher amount of the latter in dunite is a result of deformation-induced breakdown of enstatite and removal of trace elements from olivine. The structural features of massive chromitite aggregates indicate that they are a product of concentration and aggregation of grains under the influence of tectonic stresses at high temperatures and pressures, similar to pressure sintering.

该论文描述了来自俄罗斯南乌拉尔山脉Kraka蛇绿岩断块地幔部分的散布的板状，豆状块状和过渡性铬铁矿矿床。铬铁矿是由辉光岩包裹的，它们的尺寸和质量与辉光岩体的尺寸之间没有关联。厚厚的榴辉岩体大部分都带有散布的细粒带状铬铁矿。块状矿石是由粗粒铬铁矿组成的，通常带有薄薄的褐铁矿包膜。铬铁矿和基质超镁铁质岩表现出硅酸盐和铬铁矿的塑性变形，这表现为微观结构特征，成岩橄榄石的优选取向以及铬铁矿体的折叠。超镁铁质岩的特征还在于变形引起的织构，导致在塑性变形的成岩橄榄石和邻二甲苯的结构缺陷上形成小尺寸的铬铁矿晶粒。榴辉岩体和伴生的铬铁矿的形成与减压条件下上升的地幔流变形的局部化有关。榴石是流变最弱的区域，表现出集中的固态流动和有效分离矿物相（橄榄石和亚铬铁矿）。褐铁矿中后者的含量较高是由于变形引起的顽辉石分解和从橄榄石中除去微量元素的结果。