The structural evolution of dunite and chromite ore from the Kharcheruz massif, the Polar Urals

The Kharcheruz block of the Syumkeu ultramafic massif is a southern fragment of the Khadata ophiolitic belt, which closes the ophiolites of the Polar Urals in the north. The block, striking in the latitudinal direction, is sheetlike in shape and primarily composed of dunite with nearly latitudinal zones of chromite mineralization. The dunites are subject to ductile deformation various in intensity, and this variability is displayed in their heterogeneous structure and texture. The following microstructural types are distinguished by the variety and intensity of their deformation: protogranular → mesogranular → porphyroclastic → porphyrolath → mosaic. The petrostructural patterns of olivines pertaining to the above types reflect conditions of ductile deformation. Protogranular dunite is formed as a product of pyroxene decomposition in mantle harzburgite accompanied by annealing recrystallization at a temperature above 1000°C. Mesogranular dunite is formed as a product of high-temperature plastic flow by means of translation sliding in olivine and diffuse creep at a temperature dropping from 1000 to 650°C and at a low rate (10–6 s–1). Dunite is deformed by means of syntectonic recrystallization and subordinate translation gliding. Linear zones of disseminated mineralization undergo destruction thereby, with the formation of lenticular chromitite bodies from which ductile olivine is squeezed out with the formation of densely impregnated and massive ores

New ore minerals from the Kingash ultramafic massif, Northwestern Eastern Sayan

The paper discusses earlier poorly studied mineralized rocks of the Kingash ultramafic complex in the Kan Block of the Eastern Sayan, including the large Cu–Ni–PGE deposit of the same name. Despite many researchers' increased interest in the Kingash massif, a number of questions related to the petrology, formation mechanism, and localization of Cu–Ni–PGE ore remain controversial. Along with already known ore minerals, we have identified and described a number of new mineral species: argentite, Fe-enriched sperrylite, a bismuth variety of merenskyite, gersdorffite, cobaltite, and thorianite. The ore minerals are distinguished by a higher relative amount of Fe, and this makes the Kingash deposits close to other Paleoproterozoic Cu–Ni deposits, e.g., the Jinchuan in China, Pechenga in Russia, Ungava in Canada, Mt. Scholl in Australia, etc

Plastically deformed ultramafites of the Ergaksky chromite-bearing massif (Western Sayan)

Dunites and harzburgites of Ergaksky massif constantly show signs of plastic deformation of olivine and enstatite as inhomogeneous extinction, bands of plastic fracture and sintectonic recrystallization. At level of the upper mantle dunites and harzburgites have undergone plastic deformation by translational sliding in olivine at high temperature and low speed. As a result, ultramafic with medium-grained, meso-granular texture formed. In the process of movement in the Earth's crust plastic deformation occurs mostly as sintectonic recrystallization at subordinate role of translational sliding in conditions of decreasing temperatures and growing speed of plastic flow. This has contributed to the formation of porphyroclastic textures, while translational sliding promoted the distortion of crystal structure and the emergence of non-homogeneous extinction and bands of plastic fracture. Olivinites appeared as a result of secondary recrystallization of annealing under influence of high-temperature fluids on ultramafites

Стентирование ободочной и прямой кишки у онкологических больных

Background. Malignant colonic obstruction (MCO) it is one of the most common and severe complications of colon and rectal cancer. The mechanisms underlying MCO development include impairments in motor, secretory and resorptive functions of the intestine, disorders of water-electrolyte metabolism, endotoxicosis, and compartment syndrome. All of these conditions significantly reduce patient survival.Objective: to compare the outcomes of colonic stenting in patients with primary and secondary tumors and to assess the efficacy of surgical treatment.Material and methods. This retrospective study included 149 patients with MCO caused by both primary colon tumors and secondary compression or extra-colon tumors. All patients underwent X-ray guided colonic stenting in the N.N. Blokhin National Medical Research Center of Oncology between 2013 and 2017.Results. Primary technical success was achieved in 143 (96 %) patients, whereas overall technical success (including restenting) was achieved in 144 (96.6 %) patients. A total of 121 (84 %) patients demonstrated complete clinical success, while 23 (15.98 %) patients had partial clinical success. The efficacy of stenting was significantly higher in patients with primary colorectal cancer than in patients with secondary lesions of the colon (96.7 % vs. 27.3 %; p <0.0001).Conclusion. Stenting is a safe and effective method of comprehensive treatment for patients with colon cancer and signs of MCO. It expands the scope of palliative care for disseminated cancer. However, in patients with extra-organ compression and secondary lesions of the colon, this procedure remains largely ineffective.Введение. Опухолевая обструкция толстой кишки (ТК) является одним из тяжелых и наиболее распространенных осложнений рака ободочной и прямой кишки. Звеньями патогенеза этого синдрома являются нарушения моторной и секреторно-резорбтивной функций кишечника, водно-электролитные нарушения, эндотоксикоз, компартмент-синдром, в свою очередь значительно ухудшающие прогноз выживаемости пациентов.Цель исследования – провести сравнительный анализ результатов стентирования ТК у пациентов с первичным и вторичным опухолевым поражением и определить эффективность вмешательства в каждом случае.Материалы и методы. В НИИКО ФГБУ «НМИЦ онкологии им. Н.Н. Блохина» проведено ретроспективное исследование на основе 4-летного опыта (с 2013 по 2017 г.) эндопротезирования ТК, при этом обструкция ТК была вызвана как первичным поражением кишки, так и вторичной компрессией или прорастанием извне. Стентирование ТК было выполнено у 149 пациентов. Вмешательство осуществляли под рентгенологическим контролем.Результаты. Первичный технический успех был достигнут у 143 (96 %) пациентов, общий технический успех, включая рестентирование, – у 144 (96,6 %). При этом полный клинический успех достигнут у 121 (84 %) пациента, частичный – у 23 (15,98 %). Эффективность эндопротезирования при первичном колоректальном раке оказалась значимо выше, чем в группе пациентов с вторичным поражением ТК, и составила 96,7 и 27,3 % соответственно (p <0,0001).Выводы. Стентирование является безопасным и эффективным методом комбинированного лечения онкологических пациентов с признаками опухолевой обструкции ТК, а также позволяет расширить объем паллиативной помощи у больных с диссеминированным опухолевым процессом. Но при экстраорганной компрессии и вторичном поражении ТК манипуляция пока остается неэффективной

ACCESSORY SULPHIDES AND ARSENIDES FROM CHROMYTITES OF KHARCHERUZ ULTRAMAFIC MASSIF, THE POLAR URALS

The study is focused on accessory sulfide mineralization revealed in massive chromitites of Kharcheruz ultramafic massif, which is part of the Khadatinsky ophiolite belt closing ophiolite complexes of the Polar Urals in the north. Three paragenetic associations of accessory sulfides associated with various processes of host chromitites formation and transformation are identified. Typomorphic and chemical features of ore minerals are characterized.</jats:p

Gold and silver accessory minerals in ultramafites&#x0D; of the Kyzyr-Burlyuksky ultramafic massif (Western Sayan)

The study focuses on gold and silver accessory minerals&#x0D; (native silver, cuprous gold, luanheite (Ag3Hg),&#x0D; unspecified mineral phase (Cu,Ag,Hg), first diagnosed&#x0D; in dunites and apodunite serpentinites of the Kyzyr-Burlyuksky&#x0D; ultramafic massif, which is part of the Kurtushibin&#x0D; ophiolite belt of Western Sayan. The revealed&#x0D; ore minerals are mainly observed in the form of single&#x0D; hypidiomorphic, irregular microscopic precipitates (0.5–&#x0D; 3.0 μm) mainly inside magnetite, much less often in&#x0D; grains of avaruite. Typomorphic and chemical features&#x0D; of ore minerals, their natural setting in rock-forming&#x0D; silicate matrix are characterized. Formation and concentration&#x0D; of these accessory minerals is associated with&#x0D; superimposed low-temperature transformation (hydration)&#x0D; processes affecting original ultramafic rocks. At the&#x0D; same time, the presence of luanheite and an unnamed&#x0D; phase (Cu,Ag,Hg), along with the previously identified&#x0D; potarite (PdHg), is probably evidence of low-temperature&#x0D; conditions of mineral formation during the manifestation&#x0D; of epigenetic processes of serpentinization (lowgrade&#x0D; metamorphism) due to solutions enriched in mercury.&#x0D; The source of such solutions could be gabbro intrusions&#x0D; that penetrated later into the main ultramafic body.</jats:p