Abstract
Late-Pan-African granitic pegmatites in Malawi host gem mineralization (tourmaline, beryl/aquamarine/heliodor). We use major and trace element chemistry of mica and tourmaline as proxies to describe the geochemical characteristics and to analyze the evolution of the pegmatite-forming melts. Trace element contents and ratios of pegmatitic micas and tourmalines show characteristic fractionation trends. Mica from highly fractionated pegmatite typically shows high Rb, Cs, Zn, Nb, Ta, F, and Li concentrations but low Ni, Co, V, Ti and Sc concentrations. In their less fractionated counterparts, these compositional patterns are largely reversed. Exceptions in these element patterns are related to the presence or absence of other phases that may fractionate specific elements more strongly than mica. Tourmaline shows similar fractionation trends in major and trace elements. The observed patterns indicate fractional crystallization as the dominant process of melt evolution. A near exponential decrease of alkali element ratios, such as K/Rb and K/Cs, and an increase in Rb, Cs and Li in white mica from the less to the more strongly differentiated zones suggest Rayleigh fractional crystallization. The modelling of these element ratios shows that in different pegmatite bodies the least differentiated zone formed at a fractionation coefficient of F = 0.35–0.5. Zones of intermediate fractionation show F = 0.85–0.9. Gem mineralization is associated with the most highly fractionated pegmatites or pegmatite zones (F = ~ 0.99). These highly fractionated pegmatites show strong enrichment of Li, Rb and Cs in mica and tourmaline forming from melts rich in incompatible elements. The crystallization of gem phases depended on this highly enriched environment.
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19 December 2023
A Correction to this paper has been published: https://doi.org/10.1007/s00126-023-01241-4
References
Adam J, Green T (2006) Trace element partitioning between mica-and amphibole-bearing garnet lherzolite and hydrous basanitic melt: 1. Experimental results and the investigation of controls on partitioning behaviour. Contrib Mineral Petrol 152:1–17
Andreoli MAG (1984) Petrochemistry, tectonic evolution and metasomatic mineralisations of Mozambique belt granulites from S Malawi and Tete (Mozambique). Precambrian Res 25:161–186. https://doi.org/10.1016/0301-9268(84)90031-7
Ashwal LD, Armstrong RA, Roberts RJ et al (2007) Geochronology of zircon megacrysts from nepheline-bearing gneisses as constraints on tectonic setting: Implications for resetting of the U-Pb and Lu-Hf isotopic systems. Contrib Mineral Petrol 153:389–403. https://doi.org/10.1007/s00410-006-0153-9
Ashworth L, Kinnaird JA, Nex PAM et al (2020) Origin of rare-element-mineralized Damara Belt pegmatites: A geochemical and light stable isotope study. Lithos 372–373:105655. https://doi.org/10.1016/J.LITHOS.2020.105655
Bea F, Pereira MD, Corretgé LG, Fershtater GB (1994) Differentiation of strongly peraluminous, perphosphorus granites: the Pedrobernardo pluton, central Spain. Geochim Cosmochim Acta 58:2609–2627
Bloomfield K (1968) Pre-Karroo Geology of Malawi. Malawi Geol Surv Dept-Memoir 5:166
Büttner SH (2012) Rock Maker: An MS Excel™ spreadsheet for the calculation of rock compositions from proportional whole rock analyses, mineral compositions, and modal abundance. Mineral Petrol 104:129–135. https://doi.org/10.1007/S00710-011-0181-7/TABLES/1
Cameron EN, Jahns RH, McNair AH, Page L (1949) Internal structure of granitic pegmatites. Econ Geol Monograph 2, p 115
Canosa F, Martin-Izard A, Fuertes-Fuente M (2012) Evolved granitic systems as a source of rare-element deposits: The Ponte Segade case (Galicia, NW Spain). Lithos 153:165–176. https://doi.org/10.1016/J.LITHOS.2012.06.029
Carter, GS; Bennet JD (1973) The geology and mineral resources of Malawi. Geol Surv Malawi Bull 6
Černý P (1991) Rare-element granitic pegmatites. Part II: regional to global environments and petrogenesis. Geosci Canada 18:68–81
Černý P, Ercit TS (2005) The classification of granitic pegmatites revisited. Can Mineral 43:2005–2026. https://doi.org/10.2113/GSCANMIN.43.6.2005
Černý P, Meintzer RE, Anderson AJ (1985) Extreme fractionation in rare-element granitic pegmatites; selected examples of data and mechanisms. Can Mineral 23:381–421
Černý P, London D, Novák M (2012) Granitic pegmatites as reflections of their sources. Elements 8:289–294. https://doi.org/10.2113/GSELEMENTS.8.4.289
Černý P, Trueman DL, Ziehlke DV, Goad BE, Paul BJ (1981) The Cat Lake-Winnipeg River and the Weskusko Lake pegmatite fields, Manitoba. Manitoba Department of Energy and Mines, Mineral Resources Division, Economic Geology Report ER80–1, p 234
Chakraborty T, Upadhyay D (2020) The geochemical differentiation of S-type pegmatites: constraints from major–trace element and Li–B isotopic composition of muscovite and tourmaline. Contrib Mineral Petrol 175:1–25. https://doi.org/10.1007/s00410-020-01697-x
Chakraborty T, Kankuzi CF, Glodny J et al (2023) The timing and tectonic context of Pan-African gem bearing pegmatites in Malawi: Evidence from Rb–Sr and U-Pb geochronology. J African Earth Sci 197:104750. https://doi.org/10.1016/j.jafrearsci.2022.104750
Chappell BW, White AJR (1992) I-and S-type granites in the Lachlan Fold Belt. Earth Environ Sci Trans R Soc Edinb 83:1–26
Cooper W, Bloomfield K (1961) The geology of the Tambani-Salambidwe area (with accompanying geological map, scale 1:100,000). Geol Surv Nyasal Bull 13:63
Dill HG (2007) A review of mineral resources in Malawi: With special reference to aluminium variation in mineral deposits. JAfES 47:153–173. https://doi.org/10.1016/J.JAFREARSCI.2006.12.006
Eby GN, Woolley AR, Platt VDG (1998) Geochemistry and petrogenesis of nepheline syenites: Kasungu-Chipala, Ilomba, and Ulindi nepheline syenite intrusions, North Nyasa Alkaline Province, Malawi. J Petrol 39:1405–1424. https://doi.org/10.1093/petroj/39.8.1405
Fritz H, Abdelsalam M, Ali KA et al (2013) Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution. J African Earth Sci 86:65–106. https://doi.org/10.1016/j.jafrearsci.2013.06.004
Garate-Olave I, Roda-Robles E, Gil-Crespo PP, Pesquera A (2018) Mica and feldspar as indicators of the evolution of a highly evolved granite-pegmatite system in the Tres Arroyos area (Central Iberian Zone, Spain). J Iber Geol 44:375–403. https://doi.org/10.1007/s41513-018-0077-z
Grantham GH, Maboko M, Eglington BM (2003) A review of the evolution of the Mozambique Belt and implications for the amalgamation and dispersal of Rodinia and Gondwana. Geol Soc Spec Publ 206:401–425. https://doi.org/10.1144/GSL.SP.2003.206.01.19
Grantham GH, Macey PH, Horie K et al (2013) Comparison of the metamorphic history of the Monapo Complex, northern Mozambique and Balchenfjella and Austhameren areas, Sør Rondane, Antarctica: Implications for the Kuunga Orogeny and the amalgamation of N and S. Gondwana. Precambrian Res 234:85–135. https://doi.org/10.1016/J.PRECAMRES.2012.11.012
Greenland LP (1970) An equation for trace element distribution during magmatic crystallization. Am Mineral J Earth Planet Mater 55:455–465
Hanson RE (2003) Proterozoic geochronology and tectonic evolution of southern Africa. Geol Soc Spec Publ 206:427–463. https://doi.org/10.1144/GSL.SP.2003.206.01.20
Henry DJ, Novák M, Hawthorne FC et al (2011) Nomenclature of the tourmaline-supergroup minerals. Am Mineral 96:895–913. https://doi.org/10.2138/am.2011.3636
Hertogen J, Gijbels R (1976) Calculation of trace element fractionation during partial melting. Geochim Cosmochim Acta 40:313–322. https://doi.org/10.1016/0016-7037(76)90209-X
Higuchi H, Nagasawa H (1969) Partition of trace elements between rock-forming minerals and the host volcanic rocks. Earth Planet Sci Lett 7:281–287
Hulsbosch N, Hertogen J, Dewaele S et al (2014) Alkali metal and rare earth element evolution of rock-forming minerals from the Gatumba area pegmatites (Rwanda): Quantitative assessment of crystal-melt fractionation in the regional zonation of pegmatite groups. Geochim Cosmochim Acta 132:349–374. https://doi.org/10.1016/j.gca.2014.02.006
Icenhower J, London D (1995) An experimental study of element partitioning among biotite, muscovite, and coexisting peraluminous silicic melt at 200 MPa (H2O). Am Mineral 80:1229–1251
Jahns RH, Burnham CW (1969) Experimental studies of pegmatite genesis: I. A model for the derivation and crystallization of granitic pegmatites. Econ Geol 64:843–864. https://doi.org/10.2113/gsecongeo.64.8.843
Johnson SP, Rivers T, De Waele B (2005) A review of the Mesoproterozoic to early Palaeozoic magmatic and tectonothermal history of south-central Africa: Implications for Rodinia and Gondwana. J Geol Soc London 162:433–450. https://doi.org/10.1144/0016-764904-028
Jolliff BL, Papike JJ, Shearer CK (1987) Fractionation trends in mica and tourmaline as indicators of pegmatite internal evolution: Bob Ingersoll pegmatite, Black Hills, South Dakota. Geochim Cosmochim Acta 51:519–534. https://doi.org/10.1016/0016-7037(87)90066-4
Jolliff BL, Papike JJ, Shearer CK (1992) Petrogenetic relationships between pegmatite and granite based on geochemistry of muscovite in pegmatite wall zones, Black Hills, South Dakota, USA. Geochim Cosmochim Acta 56:1915–1939. https://doi.org/10.1016/0016-7037(92)90320-I
Kankuzi CF (2019) Gem-bearing granitic pegmatites in Malawi: their mineralogy, geochemistry, age, and fluid compositional variations. PhD thesis, Rhodes University (South Africa)
Kravuchuk IK, Chernysheva I, Urosov S (1981) Element distribution between plagioclase and groundmass as an indicator for crystallization conditions of the basalts in the southern vent of Tolbachik. Geochem Int 17:18–24
Kröner A, Willner AP, Hegner E et al (2001) Single zircon ages, PT evolution and Nd isotopic systematics of high-grade gneisses in southern Malawi and their bearing on the evolution of the Mozambique Belt in southeastern Africa. Precambrian Res 109:257–291. https://doi.org/10.1016/S0301-9268(01)00150-4
Lenoir JL, Liégeois J-P, Theunissen K, Klerkx J (1994) The Palaeoproterozoic Ubendian shear belt in Tanzania: geochronology and structure. J African Earth Sci 19:169–184. https://doi.org/10.1016/0899-5362(94)90059-0
London D (2005a) Granitic pegmatites: An assessment of current concepts and directions for the future. Lithos 80:281–303. https://doi.org/10.1016/j.lithos.2004.02.009
London D (2005b) Geochemistry of alkalis and alkali earths in ore-forming granites, pegmatites, and rhyolites. In: Linnen R and Samson I (eds) Rare element geochemistry of ore deposits. Geol Assoc Can, Short Course Handbook 17:17–43
London D (2008) Pegmatites. Can Mineral Special Publ 10:347
London D (2009) Volume 47 August 2009 Part 4 The origin of primary textures in granitic pegmatites. Mineral Can 47:697–724
London D (2014) A petrologic assessment of internal zonation in granitic pegmatites. Lithos 184–187:74–104. https://doi.org/10.1016/j.lithos.2013.10.025
London D (2015) Reply to Thomas and Davidson on “A petrologic assessment of internal zonation in granitic pegmatites” (London 2014a). Lithos 212–215:469–484. https://doi.org/10.1016/j.lithos.2014.11.025
London D (2018) Ore-forming processes within granitic pegmatites. Ore Geol Rev 101:349–383. https://doi.org/10.1016/j.oregeorev.2018.04.020
London D (2022) Rayleigh model of cesium fractionation in granite-pegmatite systems. Am Mineral 107:82–91
London D, Morgan GB (2012) The pegmatite puzzle. Elements 8:263–268. https://doi.org/10.2113/gselements.8.4.263
Long PE (1978) Experimental determination of partition coefficients for Rb, Sr and Ba between alkali feldspar and silicate liquid. Geochim Cosmochim Acta 42:833–846. https://doi.org/10.1016/0016-7037(78)90096-0
Maneta V, Baker DR, Minarik W (2015) Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts. Contrib Mineral Petrol 170:4. https://doi.org/10.1007/s00410-015-1158-z
Matsui Y, Onuma N, Nagasawa H, Higuchi H, Banno S (1977) Crystal structure control in trace element partition between crystal and magma. Tectonics 100:315–324
Meert JG (2003) A synopsis of events related to the assembly of the eastern Gondwana. Tectonophysics 362(1–4):1–40
Morgan GB (2016) A spreadsheet for calculating normative mole fractions of end-member species for Na-Ca-Li-Fe2+-Mg-Al tourmalines from electron microprobe data. Am Mineral 101:111–119. https://doi.org/10.2138/am-2016-5392
Müller A, Simmons W, Beurlen H et al (2022) A proposed new mineralogical classification system for granitic pegmatites - Part I: History and the need for a new classification. Can Mineral 60:203–227. https://doi.org/10.3749/canmin.1700088
Nash WP, Crecraft HR (1985) Partition coefficients for trace elements in silicic magmas. Geochim Cosmochim Acta 49:2309–2322
Nielsen RL, Ustunisik G, Weinsteiger AB, Tepley FJ, Johnston AD, Kent AJR (2017) Trace element partitioning between plagioclase and melt: An investigation of the impact of experimental and analytical procedures. Geochem Geophys Geosyst 18:3359–3384. https://doi.org/10.1002/2017GC007080
Niggli P (1920) Die leichtflüchtigen Bestandteile im Magma. B. G. Teubner, Leipzig
Novák M, Henry DJ, Hawthorne FC et al (2009) Nomenclature of the tourmaline-group minerals. Report of the Subcommittee on Tourmaline Nomenclature to the International Mineralogical Association’s Commission on New Minerals, Nomenclature and Classification (CNMMN), as approved by the CNMMN at July 8th, 2009
Oriolo S, Oyhantçabal P, Wemmer K, Siegesmund S (2017) Contemporaneous assembly of Western Gondwana and final Rodinia break-up: Implications for the supercontinent cycle. Geosci Front 8:1431–1445. https://doi.org/10.1016/j.gsf.2017.01.009
Philpotts JA, Schnetzler CC (1970) Phenocryst-matrix partition coefficients for K, Rb, Sr and Ba, with applications to anorthosite and basalt genesis. Geochim Cosmochim Acta 34:307–322
Ray GE (1974) The structural and metamorphic geology of northern Malawi. J Geol Soc London 130:427–440. https://doi.org/10.1144/GSJGS.130.5.0427
Roda Robles E, Pesquera Perez A, Velasco Roldan F, Fontan F (1999) The granitic pegmatites of the Fregeneda area (Salamanca, Spain); characteristics and petrogenesis | Mineralogical Magazine | GeoScienceWorld. Mineral Mag 63:535–558
Roda-Robles E, Pesquera A, Gil-Crespo P, Torres-Ruiz J (2012) From granite to highly evolved pegmatite: A case study of the Pinilla de Fermoselle granite-pegmatite system (Zamora, Spain). Lithos 153:192–207. https://doi.org/10.1016/j.lithos.2012.04.027
Simmons WBS, Webber KL (2008) Pegmatite genesis: state of the art. Eur J Mineral 20:421–438. https://doi.org/10.1127/0935-1221/2008/0020-1833
Smeds S-A (1992) Trace elements in potassium-feldspar and muscovite as a guide in the prospecting for lithium- and tin-bearing pegmatites in Sweden. J Geochem Explor 42:351–369
Thomas R, Davidson P (2016) Origin of miarolitic pegmatites in the Königshain granite/Lusatia. Lithos 260:225–241. https://doi.org/10.1016/j.lithos.2016.05.015
Thomas R, Davidson P, Beurlen H (2012) The competing models for the origin and internal evolution of granitic pegmatites in the light of melt and fluid inclusion research. Mineral Petrol: 55–73. https://doi.org/10.1007/s00710-012-0212-z
Tindle AG, Breaks FW, Selway B (2002) Tourmaline in petalite-subtype granitic pegmatites: evidence of fractionation and contamination from the Pakeagama Lake areas of northwestern Ontario, Canada. Can Mineral 40:753–788
Tischendorf G, Förster H-J, Gottesmann B, Rieder M (2007) True and brittle micas: composition and solid-solution series. Mineral Mag 71:285–320. https://doi.org/10.1180/MINMAG.2007.071.3.285
Trueman DL, Černý P (1982) Exploration for rare-element granitic pegmatites. In: Černý, P. (Ed.), Granitic Pegmatites in Science and Industry. Mineralogical Association of Canada Short Course Handbook
Tsunogae T, Uthup S, Nyirongo MW et al (2021) Neoproterozoic crustal growth in southern Malawi: New insights from petrology, geochemistry, and U-Pb zircon geochronology, and implications for the Kalahari Craton-Congo Craton amalgamation. Precambrian Res 352:106007. https://doi.org/10.1016/j.precamres.2020.106007
van Hinsberg VJ (2011) Preliminary experimental data on trace-element partitioning between tourmaline and silicate melt. Can Mineral 49:153–163
Vereshchagin OS, Wunder B, Britvin SN, Frank-Kamenetskaya OV, Wilke FDH, Vlasenko NS, Shilovskikh VV (2020) Synthesis and crystal structure of Pb-dominant tourmaline. Amer Mineral 105(10):1589–1592. https://doi.org/10.2138/am-2020-7457
Wise MA, Müller A, Simmons WB (2022) A proposed new mineralogical classification system for granitic pegmatites. Can Mineral 60:229–248. https://doi.org/10.3749/canmin.1800006
Whitney DL, Evans BW (2010) Abbreviations for names of rock-forming minerals. Am Mineral 95(1):185–187. https://doi.org/10.2138/am.2010.3371
Acknowledgements
Reviews by Alessandra Altieri and David London helped us to improve the manuscript. We thank Celestine Mercer and Karen Kelley for their editorial handling of this paper and for comprehensive and very detailed editorial recommendations and instructions.
Funding
Glencore-Xstrata funded a post-doctoral fellowship for TC. The DST-NRF Centre of Excellence (CoE) for Integrated Mineral and Energy Resource Analysis (CIMERA) supported funding for analytical costs and provided a partial bursary for CFK’s PhD studies. Opinions expressed and conclusions arrived at, are those of the author(s) and are not necessarily to be attributed to the CoE. The Rhodes University EPMA laboratory was funded by a grant from the NRF National Equipment Programme (UID: 74464).
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Chakraborty, T., Büttner, S.H., Costin, G. et al. The petrogenesis of highly fractionated gem-bearing pegmatites of Malawi: evidence from mica and tourmaline chemistry and finite step trace element modelling. Miner Deposita 59, 837–857 (2024). https://doi.org/10.1007/s00126-023-01236-1
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DOI: https://doi.org/10.1007/s00126-023-01236-1