ROCK FRACTURES NEAR FAULTS: SPECIFIC FEATURES OF STRUCTURAL‐PARAGENETIC ANALYSIS

The new approach to structural‐paragenetic analysis of near‐fault fractures [Seminsky, 2014, 2015] and specific features of its application are discussed. This approach was tested in studies of fracturing in West Pribaikalie and Central Mongolia. We give some recommendations concerning collection, selection and initial processing of the data on fractures and faults. The analysis technique is briefly described, and its distinctive details are specified. Under the new approach, we compare systems of natural fractures with the standard joint sets. By analysing the mass measurements of the orientations of joint sets in a fault zone, it becomes possible to reveal the characteristics of this fault zone, such as its structure, morphogenetic type, etc. The comparative analysis is based on the identification of the main fracture paragenesis near the faults. This paragenesis is represented by a triplet of mutually perpendicular joint sets. The technique uses the qualitative approach to establish the rank hierarchy of fractures and stress fields on the basis of genetic subordination. We collect and analyse the data on tectonic fractures identified from a number of indicators, the main of which are the geometric structure of the (systematic or chaotic) fracture system, and shear type of fractures. The new technique can be applied to analyse other genetic types of fractures (primary, hypergenic), provided that tectonic stresses were significantly involved in fracturing, which is evidenced by the corresponding indicators. Methods for conducting geological and structural observations are uniform for all sites and points, and increasing the number of observation points provides for a more effective use of the new technique. In our paper, we give specific parameters for constructing circle fracture diagrams. All the maximums in the diagram are involved in the analysis for comparison with the standard patterns. Errors caused by random coincidence are minimized by using special criteria to estimate the diagrams, and the reliability of the solutions is thus ensured. This paper considers various problems related to interpretations of natural fracture systems, concerning the angles between the conjugate joint sets, the presence of non‐standard fracture parageneses, fault zones of mixed types, and structural‐material inhomogeneities. The recommendations based on our experience of selection and processing of input field data can be viewed as a sup‐ plement to the method of analysis used for specialized mapping of faults zones and detection of stress fields [Seminsky, 2014, 2015]. The discussed information can be useful for those who are willing to successfully use this new approach to investigate the fault systems in the upper crust and solve applied and fundamental problems in the studies of faulting.

joint, joint system, fault zone, fracture paragenesis, tectonic jointing, conjugate fractures, triplet of joint sets, stress field

1. Burzunova Yu.P., 2009. Near-fault fracture systems: using the new opportunities of the paragenetic analysis (West Pribaikalie). In: Faulting and seismicity in lithosphere: Tectonophysical Concepts and Results. Proceedings of the All-Russia Conference (Irkutsk, August 18–21, 2009). Vol. 1. IEC SB RAS, Irkutsk, p. 20–22 (in Russian) [Бурзунова Ю.П. Приразломные трещинные сети: применение новых возможностей парагенетического анализа (на одном из участков Западного Прибайкалья) // Разломообразование и сейсмичность в литосфере: тектонофизические концепции и следствия: Материалы Всероссийского совещания (г. Иркутск, 18–21 августа 2009 г.). Иркутск: Институт земной коры СО РАН, 2009. Т. 1. С. 20–22].

2. Burzunova Yu.P., 2011. The angles between conjugate tectonic fracture sets in standard and natural paragenesis forming in different dynamic conditions. Litosfera (Lithosphere) (2), 94–110 (in Russian) [Бурзунова Ю.П. Углы между сопряженными системами приразломных трещин в идеализированных и природных парагенезисах, формирующихся в различных динамических обстановках // Литосфера. 2011. № 2. С. 94–110].

3. Burzunova Yu.P., 2013. Possibilities of structural-paragenetic analysis of fractures: local and regional stress fields in the Olkhon area, West Pribaikalie. In: Modern tectonophysics. Methods and results. Proceedings of the 3rd Youth Workshop (Moscow, 14–18 October 2013). Vol. 1. IEP, Moscow, p. 58–66 (in Russian) [Бурзунова Ю.П. Возможности структурно-парагенетического анализа трещин: локальные и региональные поля напряжений Приольхонья (Западное Прибайкалье) // Современная тектонофизика. Методы и результаты: Материалы третьей молодежной школы-семинара (г. Москва, 14–18 октября 2013 г.). М.: ИФЗ, 2013. Т. 1. С. 58–66].

4. Burzunova Yu.P., 2014. Joint systems in rocks of active tectonic regions: irregularity degree estimation. Bulletin of Irkutsk State Technical University (4), 45–49 (in Russian) [Бурзунова Ю.П. Трещинные сети в породах тектонически активных регионов: оценка степени хаотичности // Вестник Иркутского государственного технического университета. 2014. № 4. С. 45–49].

5. Burzunova Yu.P., 2015. Tazheran syenite massif fault zones (West Pribaikalie) by the results of structural paragenetic analysis of meso-fracturing. Proceedings of Siberian Department of the Section of Earth Sciences Russian Academy of Natural Sciences. Geology, Exploration and Development of Mineral Deposits (1), 58–67 (in Russian) [Бурзунова Ю.П. Разломные зоны Тажеранского массива сиенитов (Западное Прибайкалье) по результатам структурно-парагенетического анализа трещиноватости // Известия Сибирского отделения Секции наук о Земле РАЕН. Геология, разведка и разработка месторождений полезных ископаемых. 2015. № 1. С. 58–67].

6. Chernyshev S.N., 1983. Rock Fractures. Nauka, Moscow. 240 p. (in Russian) [Чернышев С.Н. Трещины горных пород. М.: Наука, 1983. 240 с.].

7. Danilovich V.N., 1961. Method of Belts in Study of Fracturing Related to the Fault Displacements. Irkutsk Polytechnic Institute, Irkutsk, 47 p. (in Russian) [Данилович В.Н. Метод поясов в исследовании трещиноватости, связанной с разрывными смещениями. Иркутск: Иркутский политехнический институт, 1961. 47 с.].

8. Dodin A.L. (Ed.), 1986. State Geological Map of Russia. Sheet N (47) 48. Scale 1:1000000. VSEGEI, Leningrad (in Russian)

9. [Государственная геологическая карта России. Лист N (47) 48. Масштаб 1: 1000000 / Ред. А.Л. Додин. Л.: ВСЕГЕИ, 1986. Available from: http: //www.geolkarta.ru/list_200.php?idlist=N(47)48&idlist_d=G&gen=1&g=1 (last accessed: March 10, 2017).

10. Gladkov A.S., Seminskii K.Z., 1999. Nontraditional analysis of fracturing belts on mapping of subhorizontal fault structures (exemplified by the vicinities of Irkutsk). Geologiya i Geofizika (Russian Geology and Geophysics) 40 (2), 213–220.

11. Goncharov M.A., Talitsky V.G., Frolova N.S., 2005. Introduction to Tectonophysics. Knizhnyj Dom “Universitet”, Moscow, 496 p. (in Russian) [Гончаров М.А., Талицкий В.Г., Фролова Н.С. Введение в тектонофизику. М.: Книжный дом «Университет», 2005. 496 с.].

12. Gzovsky M.V., 1963. The Main Issues of Tectonophysics and Tectonics of Baydzhansaysky Anticlinorium. Parts III and IV. Publishing House of the USSR Academy of Sciences, Moscow, 544 p. (in Russian) [Гзовский М.В. Основные вопросы тектонофизики и тектоника Байджансайского антиклинория. Ч. III, IV. М.: Изд-во АН СССР, 1963. 544 с.].

13. Gzovsky М.V., 1975. Fundamentals of Tectonophysics. Nauka, Moscow, 536 p. (in Russian) [Гзовский М.В. Основы тектонофизики. М.: Наука, 1975. 536 с].

14. Hancock P.L., 1985. Brittle microtectonics principles and practice. Journal of Structural Geology 7 (3–4), 437–457. https://doi.org/10.1016/0191-8141(85)90048-3.

15. Lobatskaya R.M., 1987. Structural Zonation of Faults. Nedra, Moscow, 128 p. (in Russian) [Лобацкая Р.М. Структурная зональность разломов. М.: Недра, 1987. 128 c.].

16. Mikhailov A.E., 1984. Structural Geology and Geological Mapping. Textbook. Nedra, Moscow, 464 p. (in Russian) [Михайлов А.Е. Структурная геология и геологическое картирование. Учебное пособие для вузов. М.: Недра, 1984. 464 с.].

17. Nevsky V.A., 1979. Fracture Tectonics of Ore Fields and Deposits. Nedra, Moscow, 224 p. (in Russian) [Невский В.А. Трещинная тектоника рудных полей и месторождений. М.: Недра, 1979. 224 с.].

18. Nikolaev P.N., 1992. Tectonodynamic Analysis Technique. Nedra, Moscow, 295 p. (in Russian) [Николаев П.Н. Методика тектонодинамического анализа. М.: Недра, 1992. 295 с.].

19. Nikolaevsky V.N., 2010. Collection of Works. Geomechanics. Volume 2. Earth's crust. Nonlinear Seismics. Whirlwinds and Hurricanes. Institute for Computer Research, Moscow–Izhevsk, 560 p. (in Russian) [Николаевский В.Н. Собрание трудов. Геомеханика. Том 2. Земная кора. Нелинейная сейсмика. Вихри и ураганы. Москва–Ижевск: Институт компьютерных исследований, 2010. 560 с.].

20. Pluijm B.A., 2004. Earth Structure: An Introduction to Structural Geology and Tectonics. W.W. Norton & Company, New York, 656 p.

21. Ramsey J.M., Chester F.M., 2004. Hybrid fracture and the transition from extension fracture to shear fracture. Nature 428 (6978), 63–66. https://doi.org/10.1038/nature02333.

22. Rastsvetaev L.M., 1987. Paragenetic method for the structural analysis of faults. In: A.V. Peive, A.V. Luk’yanov (Eds.), Problems of structural geology and physics of tectonic processes. Part 2. GIN AN SSSR, Moscow, p. 173–235 (in Russian) [Расцветаев Л.М. Парагенетический метод структурного анализа дизъюнктивных тектонических нарушений // Проблемы структурной геологии и физики тектонических процессов. Ч. 2 / Ред. А.В. Пейве, А.В. Лукьянов. М.: ГИН АН СССР, 1987. С. 173–235].

23. Seminskii K.Zh., 1997. Angle relationships between conjugate joint systems near strike-slip, normal, and thrust fault planes. Transactions (Doklady) of the Russian Academy of Sciences: Earth Science Sections 345 (4), 531–533.

24. Seminskii K.Zh., Gladkov A.S., Lunina O.V., 2001a. Tectonophysics of the Angara fault zone (southern Siberian platform). Geologiya i Geofizika (Russian Geology and Geophysics) 42 (8), 1252–1262.

25. Seminskii K.Zh., Karabanov E.B., Kuz'min M.I., 2001b. Faulting in Baikal bottom sediments (studies of drilling core BDP-98). Geologiya i Geofizika (Russian Geology and Geophysics) 42 (1–2), 306–316.

26. Seminskii K.Zh., Kozhevnikov N.O., Cheremnykh A.V., Pospeeva E.V., Bobrov A.A., Olenchenko V.V., Tugarina M.A., Potapov V.V., Burzunova Yu.P., 2012. Interblock zones of the northwestern Baikal rift: results of geological and geophysical studies along the Bayandai Village – Cape Krestovskii profile. Russian Geology and Geophysics 53 (2), 194–208. https://doi.org/10.1016/j.rgg.2011.12.016.

27. Seminsky K.Zh., 2003. The Internal Structure of Continental Fault Zones. Tectonophysical Aspect. GEO Branch, Publishing House of SB RAS, Novosibirsk, 243 p. (in Russian) [Семинский К.Ж. Внутренняя структура континентальных разломных зон. Тектонофизический аспект. Новосибирск: Изд-во СО РАН, филиал «Гео», 2003. 243 с.].

28. Seminsky K.Zh., 2014. Specialized mapping of crustal fault zones. Part 1: Basic theoretical concepts and principles. Geodynamics & Tectonophysics 5 (2), 445–467 (in Russian) [Семинский К.Ж. Спецкартирование разломных зон земной коры. Статья 1: Теоретические основы и принципы // Геодинамика и тектонофизика. 2014. Т. 5. № 2. С. 445–467]. https://doi.org/10.5800/GT-2014-5-2-0136.

29. Seminsky K.Zh., 2015. Specialized mapping of crustal fault zones. Part 2: Main stages and prospects. Geodynamics & Tectonophysics 6 (1), 1–43 (in Russian) [Семинский К.Ж. Спецкартирование разломных зон земной коры. Статья 2: Основные этапы и перспективы // Геодинамика и тектонофизика. 2015. Т. 6. № 1. С. 1–43]. https://doi.org/10.5800/GT-2015-6-1-0170.

30. Seminsky K.Zh., Burzunova Yu.P., 2007. Interpretation of chaotic jointing near fault planes: a new approach. Russian Geology and Geophysics 48 (3), 257–266. https://doi.org/10.1016/j.rgg.2007.02.009.

31. Seminsky K.Zh., Cheremnykh A.V., 2011. Jointing patterns and stress tensors in Cenozoic sediments of the Baikal rift: development of the structural-genetic approach. Russian Geology and Geophysics 52 (3), 353–367. https://doi.org/10.1016/j.rgg.2011.02.008.

32. Seminsky K.Zh., Gladkov A.S., 1991. The new approach to studies of tectonic fracturing in fault zones. Geologiya i Geofizika (Russian Geology and Geophysics) 32 (5), 130–140 (in Russian) [Семинский К.Ж., Гладков А.С. Новый подход к изучению тектонической трещиноватости в разрывных зонах // Геология и геофизика. 1991. Т. 32. № 5. С. 130–140].

33. Sherman S.I., 2002. Methodology for Studying and Analyzing Quantitative Parameters of Lithospheric Faults. ISTU Publishing House, Irkutsk, 60 p. (in Russian) [Шерман С.И. Методика изучения и анализа количественных параметров разломов литосферы. Изд-во ИрГТУ, Иркутск, 2002. 60 с.].

34. Sherman S.I., Bornyakov S.A., Buddo V.Yu., 1983. Areas of Dynamic Influence of Faults (Modelling Results). Nauka, Novosibirsk, 110 p. (in Russian) [Шерман С.И., Борняков С.А., Буддо В.Ю. Области динамического влияния разломов (результаты моделирования). Новосибирск: Наука. СО АН СССР, 1983. 110 с.].

35. Sherman S.I., Seminsky K.Zh., Bornyakov S.A., Adamovich A.N., Lobatskaya R.M., Lysak S.V., Levi K.G., 1992. Faulting in the Lithosphere. Extension Zones. Nauka, Siberian Branch, Novosibirsk, 228 p. (in Russian) [Шерман С.И., Семинский К.Ж., Борняков С.А., Адамович А.Н., Лобацкая Р.М., Лысак С.В., Леви К.Г. Разломообразование в литосфере. Зоны растяжения. Новосибирск: Наука. СО, 1992. 228 с.].

36. Sibson R.N., 1998. Brittle failure mode plots for compressional and extensional tectonic regimes. Journal of Structure Geology 20 (5), 655–660. https://doi.org/10.1016/S0191-8141(98)00116-3.

37. Tevelev A.L., 2011. Structural Geology and Geological Mapping. Lectures. Teaching Manual. GERS Publishing House, Tver, 292 p. (in Russian) [Тевелев А.В. Структурная геология и геологическое картирование. Курс лекций. Учебно-методическое пособие. Тверь: Издательство ГЕРС, 2011. 292 с.].

38. Twiss R.J., 1992. Structural Geology. W.H. Freeman & Company, New York, 532 p.

39. Yanshin A.L. (Ed.), 1989. Map of Geological Formations of the Mongolian People's Republic. Scale 1:1500000. The USSR Academy of Sciences. Academy of Sciences of the Mongolian People's Republic. Joint Soviet-Mongolian Scientific Research Geological Expedition of the USSR Academy of Sciences and the Academy of Sciences of the Mongolian People's Republic. Main Department of Geodesy and Cartography (The USSR Council of Ministers), Moscow (in Russian) [Карта геологических формаций Монгольской Народной Республики. Масштаб: 1:1500000 / Ред. А.Л. Яншин. Академия наук СССР. Академия наук МНР. Совместная советско-монгольская научно-исследовательская геологическая экспедиция АН СССР и АН МНР. М.: Главное управление геодезии и картографии при Совете Министров СССР, 1989. Available from: http://neotec.ginras.ru/neomaps/M015_Mongolia_1989_Tectonics_Karta-geologicheskih-formaciy-mongolskoy-narodnoy-respubliki.html (last accessed: March 10, 2017).