Abstract
When supercontinent Rodinia began to break up at ~ 800 Ma, wide rifts formed evolving into a passive margin of the Mozambique Ocean. At one stage, organic-rich pelites with gypsum/anhydrite (the later host rock of tsavorites) were interbedded with siliciclastics, carbonates, and bimodal volcanic rocks. Later, ocean closure, subduction, collision, and welding of various microcontinents and volcanic arcs formed the Mozambique Belt and at ~ 550 Ma, ended with the assembly of supercontinent Gondwana. In East Africa, deformation and metamorphism climaxed at 615–600 Ma. At peak metamorphic conditions, anatexis of siliciclastic metasediments produced abundant metamorphic mobilizates such as pegmatites and quartz veins. In the graphite schist hosting tsavorites, however, partial melting only produced small fractions of a supercritical hydrous liquid, the peculiar corrosive nature of which was due to the reduction of Ca-sulfate by reaction with organic C. Most of this melt/fluid phase remained within the host but migrated over short distances into structural traps of different origin; turbid green grossular crystallized from the melt and transparent tsavorite from residual fluids.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Feneyrol J, Giuliani G, Demaiffe D, Ohnenstetter D, Fallick AE, Dubessy J, Martelat JE, Rakotondrazafy AFM, Omito E, Ichang’i D, Nyamai C, Wamunyu AW (2017) Age and origin of the tsavorite and tanzanite mineralizing fluids in the Neoproterozoic Mozambique Metamorphic Belt. Can Mineral 55:763–786
Feneyrol J, Giuliani G, Ohnenstetter D, Fallick AE, Martelat JE, Monié P, Dubessy J, Rollion-Bard C, le Goff E, Malisa E, Rakotondrazafy AFM, Pardieu V, Kahn T, Ichang'i D, Venance E, Voarintsoa NR, Ranatsenho MM, Simonet C, Omito E, Nyamai C, Saul M (2013) Worldwide tsavorite deposits: new aspects and perspectives. Ore Geol Rev 53:1–25
Frisch W, Pohl WL (1986) Petrochemistry of some mafic and ultramafic rocks from the Mozambique Belt, SE Kenya. Mitt Oesterr Geol Ges (Austrian J Earth Sciences) 78:97–114
Fritz H, Abdelsalam M, Ali KA, Bingen B, Collins AS, Fowler AR, Ghebreab W, Hauzenberger CA, Johnson PR, Kusky TM, Macey P, Muhongo S, Stern RJ, Viola G (2013) Orogen styles in the East African Orogen: a review of the Neoproterozoic to Cambrian tectonic evolution. J Afr Earth Sci 86:65–106
Giuliani G, Dubessy J, Ohnenstetter D, Banks D, Branquet Y, Feneyrol J, Fallick AE, Martelat JE (2018) The role of evaporites in the formation of gems during metamorphism of carbonate platforms: a review. Mineral Deposita 53:1–20
Giuliani G, Dubessy J, Ohnenstetter D, Banks D, Feneyrol J, Branquet Y, Fallick AE (2015) Le fluide, l’Arlésienne du métamorphisme. Géochronique 136:65–69
Gorbaty YE, Bondarenko GV (1998) The physical state of supercritical fluids. J Supercrit Fluids 14:1–8
Hagemann SG, Lisitsin VA, Huston DL (2016) Mineral system analysis: quo vadis. Ore Geol Rev 76:504–522
Hunt JM (1996) Petroleum geochemistry and geology. Freeman, New York
Jacob J-B, Martelat J-E, Goncalves P, Giuliani G et al (2018) New P-T-X conditions for the formation of gem tsavorite garnet in the Voi area (southwestern Kenya). Lithos 320–321:250–264
Martelat J-E, Paquette J-L, Bosse V, Giuliani G, Monié P, Omito E, Simonet C, Ohnenstetter D, Ichang'i D, Nyamai C, Wamunyu A (2017) Chronological constraints on tsavorite mineralizations and related metamorphic episodes in Southeast Kenya. Can Mineral 55:845–865
Neuendorf KKE, Mehl JP, Jackson JA (eds) (2005) Glossary of Geology. 5th edn. 779 pp. American Geological Institute, Alexandria, Virginia
Pohl WL (2019) Economic geology, principles and practice: metals, minerals, coal and hydrocarbons – an introduction to formation and sustainable exploitation of mineral deposits, 2nd edn. Schweizerbart Science Publishers, Stuttgart
Pohl WL (1985) Contributions on the origin of the Mangari gem corundum (ruby) deposits (SE Kenya). In: Tole MP (ed) Proceed. 1st Conf. Geol. Soc. Kenya (1984) GSK no. 2, Nairobi, pp 58–65
Pohl WL, Horkel A (1980) Notes on the geology and mineral resources of the Mtito Andei-Taita area (Southern Kenya). Mitt Oesterr Geol Ges 73:135–152
Pohl WL, Nauta WJ, Niedermayr G (1979) Geology of the Mwatate quadrangle and the vanadium grossular deposits of the area (with geological map 1:50,000). Kenya Geol Survey Report 101:1–55
Sorokina ES, Roesel D, Haeger T et al (2017) LA-ICP-MS U–Pb dating of rutile inclusions within corundum (ruby and sapphire): new constraints on the formation of corundum deposits along the Mozambique belt. Mineral Deposita 52:641–649. https://doi.org/10.1007/s00126-017-0732-x
Suwa K, Suzuki K, Miyakawa K, Agata T (1996) Vanadium grossular from the Mozambique metamorphic rocks, South Kenya. J SE Asian Earth Sci 14(3/4):299–308. https://doi.org/10.1016/s0743-9547(96)00066-9
Thomas R, Rericha A, Pohl WL, Davidson P (2018) Genetic significance of the 867 cm-1 out-of-plane Raman mode in graphite associated with V-bearing green grossular. Mineral Petrol 72:1088–1101. https://doi.org/10.1007/s00710-018-0563-1
Thomas R, Davidson P (2016) Revisiting complete miscibility between silicate melts and hydrous fluids, and the extreme enrichment of some elements in the supercritical state—consequences for the formation of pegmatites and ore deposits. Ore Geol Rev 72:1088–1101
Tomkins AG, Pattison DRM, Zaleski E (2004) The Hemlo gold deposit, Ontario: an example of melting and mobilization of a precious metal-sulfosalt assemblage during amphibolite facies metamorphism and deformation. Econ Geol 99:1063–1084
USGS DSL7 (2017) Digital spectral library 7. URL https://speclab.cr.usgs.gov/spectral-lib.html accessed April 2019
Warren JK (2006) Sabkhas, saline mudflats and pans. Chapter 3:139–220 In: Warren JK (ed) Evaporites: sediments, resources and hydrocarbons. 1035 pp. Springer Berlin–Heidelberg
Acknowledgments
I am grateful to the The Evaluation and Publication Committee of CAJG-2018 Tunisia (www.cajg.org), who invited me to submit this paper; my paper no. 81 having been selected by Springer Editors as one of the best contributions to the 1st Conference of the Arabian Journal of Geosciences, Tunisia 2018 (CAJG-2018).
Author information
Authors and Affiliations
Corresponding author
Additional information
Responsible Editor: François Roure
This paper was selected from the 1st Conference of the Arabian Journal of Geosciences (CAJG), Tunisia 2018
Rights and permissions
About this article
Cite this article
Pohl, W.L. The tsavorite (gem quality green vanadium grossular) minerogenetic system in East Africa: a case of metamorphic partial melting and lateral secretion. Arab J Geosci 12, 612 (2019). https://doi.org/10.1007/s12517-019-4744-y
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s12517-019-4744-y