On mechanisms of the accessory chromian spinel formation in plastic deformed crystals of enstatite from kraka massifs (Urals ophiolite belt)

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Abstract

Tiny chromian spinel precipitations associated with plastic deformed enstatite crystals from spinel peridotite were studied. It is defined that there are several localizations of the precipitations: 1) in recrystallization zones where they coexist with olivine and enstatite neoblasts, 2) in the volume of polygonized primary enstatite crystals as lamellae and holly leaf grains, 3) in lamellae and neoblasts of diopside and pargasite which were formed during a plastic deformation of primary orthopyroxene. In the first two cases, we suggest the solid-state mechanism of their formation. First, it is a result of an impurities segregation on the structure defects (dislocation → subgrain boundary → grain boundary). Second, it is a result of the nucleation and growth of the new-formed mineral phases (spinel, forsterite, enstatite II) in most distorted places of porphyroclasts. In the third case, it is possible that chromian spinel were appears either as a result of the solid-state crystallization or as a cumulate of «diopside» or «pargasite» melts formed by frictional melting of orthopyroxene porphyroclasts in micro-chambers.

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About the authors

D. E. Saveliev

Institute of Geology, Ufimian Federal Research Centre RAS

Author for correspondence.
Email: savl71@mail.ru
Russian Federation, Ufa

I. I. Musabirov

Institute for Metals Superplasticity Problems RAS

Email: irekmusabirov@mail.ru
Russian Federation, Ufa

References

  1. Boland J. N. Lamellar structures in low calcium orthopyroxenes. Contrib. Miner. Petrol. 1974. Vol. 47. P. 215-222.
  2. Bunin K. P., Baranov A. A. Metallography. Moscow: Metallurgiya, 1970. 312 p. (in Russian).
  3. Carter N. L. Steady state flow of rocks. Rev. Geophys. Space Phys. 1976. Vol. 14. P. 301-360.
  4. Coe R. S., Kirby S. H. The orthoenstatite to clinoenstatite transformation by shearing and reversion by annealing: mechanism and potential applications. Contrib. Miner. Petrol. 1975. Vol. 52. P. 20-55.
  5. Gorelik S. S. Recrystallization of metals and alloys. Moscow: Metallurgiya, 1978. 568 p. (in Russian).
  6. Johnson C. Podiform chromite at Voskhod, Kazakhstan. Ph. D. thesis. Cardiff University, 2012. 468 p.
  7. Kirby S. H., Etheridge M. A. Exsolution of Ca pyroxene from orthopyroxene aided by deformation. Phys. Chem. Miner. 1981. Vol. 7. P. 105-109.
  8. Kohlstedt D. L., Van der Sande J. B. Transmission electron microscopy investigation of the defect structure of four natural orthopyroxenes. Contrib. Miner. Petrol. 1973. Vol. 42. P. 169-180.
  9. Manthilake M. A. G. M., Miyajima N., Heidelbach F., Soustelle V., Frost D. J. The effect of aluminum and water on the development of deformation fabrics of orthopyroxene. Contrib. Miner. Petrol. 2013.Vol. 165. P. 495-505.
  10. McLaren A. C., Etheridge M. A. A transmission electron microscope study of naturally deformed orthopyroxene. I. Slip mechanisms. Contrib. Miner. Petrol. 1976. Vol. 57. P. 163-177.
  11. Mercier J-C. C. Nicolas A. Textures and fabrics of upper-mantle peridotites as illustrated by xenoliths from basalts. J. Petrol. 1975. Vol. 16. P .454-487.
  12. Nicolas A. Principles of Rock Deformation. Dordrecht: Reidel, 1987. 208 p.
  13. Nicolas A., Poirier J. P. Crystalline plasticity and solid state flow in metamorphic rocks. London: Wiley - Interscience, 1976. 444 p.
  14. Ohuchi T., Karato S. I., Fujino K. Strength of single-crystal orthopyroxene under lithospheric conditions. Contrib. Miner. Petrol. 2010. Vol. 161. P. 961-975.
  15. Raimbourg H., Kogure T., Toyoshima T. Crystal bending, subgrain boundary development, and recrystallization in orthopyroxene during granulite-facies deformation. Contrib. Miner. Petrol. 2011. Vol. 162. P. 1093-1111.
  16. Saranchina G. M., Kozhevnikov V. N. Fedorov’s method (mineral definition, microstructural analysis). Leningrad: Nedra, 1985. 208 p. (in Russian).
  17. Saveliev D. E., Belogub E. V., Blinov I. A., Kozhevnikov D. A., Kotlyarov V. A. Petrological evidences of syndeformation matter segregation during a dunite formation process (for example Kraka ophiolite, the Southern Urals). Mineralogy. 2016. N 2 (4). P. 56-77 (in Russian).
  18. Saveliev D. E., Kozhevnikov D. A. Textural and petrographic features of ultramaflc rocks within area of «Deposit 33», eastern part of the Sredniy Kraka massif (South Urals). Herald Perm University. Geology. 2015. N l (26). P. 60-84 (in Russian).
  19. Saveliev D. E., Puchkov V. N., Sergeev S. N., Musabirov I. I. Deformation-induced decomposition of enstatite in mantle peridotite and its role in partial melting and chromite ore formation. Doklady EarthSci. 2017. Vol. 476. Part 1. P. 1058-1061.
  20. Saveliev D. E., Sergeev S. N. Enstatite from ophiolite ultramafic rocks: plastic deformation and related chemical changes. Mineralogy. 2018. N 1 (6). P. 68-81 (in Russian).
  21. Skrotzki W. Defect structure and deformation mechanisms in naturally deformed augite and enstatite. Tectonophysics. 1994. Vol. 229 (1-2/15). P. 43-68.
  22. Spray J. G. Generation and crystallization of an amphibolite shear melt: an investigation using radial friction welding apparatus. Contrib. Miner. Petrol. 1988. Vol. 99. P. 464-475.
  23. Spray J. G. A physical basis for the frictional melting of some rock-forming minerals. Tectonophysics. 1992. Vol. 204. P. 205-221.
  24. Suzuki A. M., Yasuda A., Ozawa K. Cr and Al diffusion in chromite spinel: experimental determination and its implication for diffusion creep. Phys. Chem. Miner. 2008. Vol. 35. P. 433-445.
  25. Van Duysen J. C., Doukhan N., Doukhan J. C. Transmission electron microscope study of dislocations in orthopyroxene (Mg,Fe)2Si2O6. Phys. Chem. Miner. 1985. Vol. 12. P. 39-44.

Supplementary files

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2. Fig. 1. Sketch geological map of Kraka massifs (a) and locations of studied samples in the deposits No 33 in eastern part of the Middle Kraka massif (б) and in the Menzhinsky deposit, the Southern Kraka massif (в).

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3. Fig. 2. Plastic deformed enstatite crystals from Kraka peridotites (а—в) and theoretical outline of bended crystal (г) after (Nicolas, Poirier, 1976; Nicolas, 1987). Thin sections, transmitted cross-polarized light. RZ are recrystallization zones localized at places where the lattice is highly distorted.

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4. Fig. 3. Different morphologies of chromian spinel at places, consisting of neoblasts of olivine and pyroxenes near to large deformed orthopyroxene crystals. BSE images.

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5. Fig. 4. Formation of chromian spinel, diopside and pargasite precipitations in the large deformed orthopyroxene crystal. а — thin section, transmitted cross-polarized light, б—г — BSE images.

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6. Fig. 5. General view of СК-85/2 sample and an outline of the thin section oriented parallel to the (110) plane of a large deformed orthopyroxene crystal. On the lower left there is the upper hemisphere of the Wulf’s stereographic projection showing the orientation of points indicated on the right.

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7. Fig. 6. Crystal of enstatite from СК-85/2 sample with lamellae and grains of chromian spinels, diopside, and pargasite. а—г — thin sections (а, г — cross-polarized light, б, в — parallel-polarised light); д—к — BSE images.

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8. Fig. 7. Deformed crystal of orthopyroxene with lamellae and neoblasts of diopside. ЮК-1991-2 sample. а, б — thin section, transmitted cross-polarized light, в, г — BSE images.

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9. Fig. 8. Dependencies between chemical compositions and grain morphologies of pyroxenes and amphiboles. Fields: П — porphyroclasts, Н — neoblasts, Л — lamellae.

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10. Fig. 9. Chromian spinel compositional variations depending on the size of grains and their morphology. Cr# = Cr/(Cr + Fe), Mg# = Mg/(Mg + Fe).

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11. Fig. 10. Relationship between а joint of large crystals and tiny precipitations of chromian spinel inside silicates. СК-103-6 sample. BSE-images.

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12. Fig. 11. Precipitations of chromian spinels in different silicate phases. СК-103-6 sample. BSE-images.

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