Petrology of hydrothermal metasomatism into intra-ore dolerite dikes of mesothermal gold deposits. P. 2. Zun-Kholba (East Sayan)
The relevance of the research is caused by the necessity of working up the geology-genetic theory of hydrothermal gold deposits formation instead of the four hypotheses granitogene, basaltogene, metamorphogene, polygene excepting one another. The main aim of the study is to substantiate the gold-iso...
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| Format: | Article |
| Language: | Russian |
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Tomsk Polytechnic University
2019-05-01
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| Series: | Известия Томского политехнического университета: Инжиниринг георесурсов |
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| Online Access: | http://izvestiya-tpu.ru/archive/article/view/1515 |
| Summary: | The relevance of the research is caused by the necessity of working up the geology-genetic theory of hydrothermal gold deposits formation instead of the four hypotheses granitogene, basaltogene, metamorphogene, polygene excepting one another. The main aim of the study is to substantiate the gold-isolating faculty of basaltic magmatism - the geologic process causing and ensuring ore-formation. The methods used in the study: petrologic investigation of magmatism and accompanying metasomatism fractions by means of empiric observations in gold-ore deposits of the spatially-temporary correlations of magmatic, metasomatic rocks and ore-mineral complexes, minerals diagnostics applying electronic microscope with roentgen-spectrum analysis, balance petro-chemical calculations of total chemical silicate analysis of rocks for estimation of petrogene elements and metals migration in metasomatic processes of ore-forming stages. The results. It was established that after-granitic intra-ore dikes, discovered in Zun-Kholba deposit, - the thermal fluid-conductors of the moderate alkaline dolerites, as in Kedrovskoye deposit, bed in the middle of weakly alternated granitoids of Ambartogol massif and other rocks but they were transformed into metasomatites formed by biotite (to 60 vol. per cent) accompanied by Mg-Fe-common hornblende, antigorite, chlorite, sericite, quartz, carbonates, rutile, leucoxene, pyrite in various ratio. The author distinguished biotite of early generation partially substituted for enumerated minerals and fresh biotite of the late generation, its scales edge completely the substituted crystals of former augite. Formation of late biotite after deposit of comparatively low-temperature chlorite and other metasomatic minerals is evaluated as the argument of pulsation regime of metal-bearing fluids entrance peculiar to ore-mineral complexes deposition in ore bodies. By means of balance calculations the potassium-sulphureously-carbon dioxide type of the within-dike metasomatism succeeded by the near-ore metasomatism was determined on the ways of the metal-bearing fluids hoisting with introducing and fixation in metasomatites of potassium, magnesium (to 50 wt. per cent), oxygenated carbon (to 500 wt. per cent), reduced sulfur (to 160 wt. per cent), in other deposits - titanium, phosphorus, calcium, manganese, gold, silver. So long as dolerite dikes can realize the fluid-conducting function according to the well-known physical effect only in hot condition among cold rocks, the metal-bearing fluids ascended within dikes following basaltic melts on those deep faults in the period when dikes remained hot. Similar intra-ore dikes-fluid-conductors of the moderate alkaline dolerites, transformed in metasomatites, are known in other mesothermal gold deposits located in crystalline substratum and black-shales series - Sukhoi Log, Chertovo Koryto, Kedrovskoe, Uryahskoe, Berikulskoe, Beriozovskoe, Kochkarskoe. In combination with granitoid solids and more late dioritoids they form the magmatic complexes, repeating in time and space. On the strength of all the evidences the author proved mesothermal gold mineralization formation in crystalline substratum and black-shale series at the final basaltoid stage of formation of antidromic granite-diorite-doleritic magmatic complexes, acquiring the status gold-isolating fluid-ore-magmatic complexes. |
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| ISSN: | 2500-1019 2413-1830 |