Impact of Fluorine on Crystal-Melt Separation in High-Silica Magma: Insights from Muscovite in the Ramba Leucogranite of Tethyan Himalaya

Abstract

The process of crystal-melt separation in the high-silica magmatic mush is still a subject of debate. To explore the process, we conducted a detailed study of Late Miocene leucogranites (SiO₂ > 70 wt.%) in the Ramba dome of the Tethyan Himalaya, focusing on the genesis and fluorine content of muscovite. The Ramba leucogranites consist of two-mica granite with minor garnet-bearing granite. Large and euhedral muscovites are found in both types of granite exhibiting different geochemical features. The muscovites from the two-mica granites exhibit lower F (mean value: ∼0.41 wt.%–0.43 wt.%), FeO (mean value: ∼1.75 wt.%–1.81 wt.%), but higher TiO₂ (mean value: ∼0.61 wt.%–0.73 wt.%) contents compared to those from the garnet-bearing granites (mean F value: ∼0.72 wt.%; mean FeO value: 2.48 wt.%; mean TiO₂ value ∼0.23 wt.%). According to geochemical criteria, we categorized the muscovites from the two-mica granite as two groups: (1) crystallized from the early magma, and (2) formed from interstitial residual melt. In comparison, the muscovite from the garnet-bearing granite was likely crystallized from residual melt extracted from the same magmatic reservoir which underwent a higher degree of evolution. Accordingly, the two-mica granite represents the residual crystal mush consisting of early crystals crystallized from magma and trapped interstitial residual melt, while the garnet-bearing granite represents the aggregation of extracted residual melt. We examined the possibility of crystal-melt separation by estimating the variation of fluorine content and viscosity between the early magma and residual melt. Our results indicate a notable disparity in fluorine content between the residual melt (mean value: ∼4 364 ppm) and the early magma (mean value: ∼2 033 ppm). As a result, the estimated viscosity experiences a reduction from 10^6.52 Pa·s for the early magma to 10^5.87 Pa·s for the residual melt. The fluorine enrichment could have played a critical role in decreasing melt viscosity and initiating crystal-melt separation. Our result supports the crystal-melt separation process during the evolution of the Ramba leucogranitic magma. This study underscores the significance of investigating the genesis and fluorine content of muscovite in granite as a crucial constraint for understanding the process of crystal-melt separation in the high-silica magmatic mush.

Keywords

fluorine / crystal-melt separation / muscovite / granite / Ramba dome / Himalaya

References

[1] Anderson J L, Rowley M C. Synkinematic Intrusion of Peraluminous and Associated Metaluminous Granitic Magmas, Whipple Mountains, California. The Canadian Mineralogist, 1981, 19(1): 83-101

[2] Bachmann O, Miller C F, de Silva S L. The Volcanic-Plutonic Connection as a Stage for Understanding Crustal Magmatism. Journal of Volcanology and Geothermal Research, 2007, 167(1/2/3/4): 1-23

[3] Borodina N S, Fershtater G B. Composition and Nature of Muscovite in Granites. International Geology Review, 1988, 30(4): 375-381

[4] Brophy J G. Composition Gaps, Critical Crystallinity, and Fractional Crystallization in Orogenic (Calc-Alkaline) Magmatic Systems. Contributions to Mineralogy and Petrology, 1991, 109(2): 173-182

[5] Carroll M R, Webster J D. Sulfur, Noble Gases, and Halogens: Solubility Relations of the Less Abundant Volatile Species in Magmas. Reviews in Mineralogy, 1994, 30: 331-371

[6] Chen C, Ding X, Li R, et al.. Crystal Fractionation of Granitic Magma during Its Non-Transport Processes: A Physics-Based Perspective. Science China Earth Sciences, 2018, 61(2): 190-204

[7] Creaser R A, Price R C, Wormald R J. A-Type Granites Revisited: Assessment of a Residual-Source Model. Geology, 1991, 19(2): 163

[8] Davis R H, Acrivos A. Sedimentation of Noncolloidal Particles at Low Reynolds Numbers. Annual Review of Fluid Mechanics, 1985, 17: 91-118

[9] Ding X, Su K L, Yan H B, et al.. Effect of F-Rich Fluids on the A-Type Magmatism and Related Metal Mobilization: New Insights from the Fogang-Nankunshan-Yajishan Igneous Rocks in Southeast China. Journal of Earth Science, 2022, 33(3): 591-608

[10] Gao L E, Zeng L S, Asimow P D. Contrasting Geochemical Signatures of Fluid-Absent versus Fluid-Fluxed Melting of Muscovite in Metasedimentary Sources: The Himalayan Leucogranites. Geology, 2017, 45(1): 39-42

[11] Giordano D, Russell J K, Dingwell D B. Viscosity of Magmatic Liquids: A Model. Earth and Planetary Science Letters, 2008, 271(1/2/3/4): 123-134

[12] Gou Z B, Zhang Z M, Dong X, et al.. Petrogenesis and Tectonic Implications of the Yadong Leucogranites, Southern Himalaya. Lithos, 2016, 256: 300-310

[13] Gualda G A R, Ghiorso M S, Lemons R V, et al.. Rhyolite-MELTS: A Modified Calibration of MELTS Optimized for Silica-Rich, Fluid-Bearing Magmatic Systems. Journal of Petrology, 2012, 53(5): 875-890

[14] Guo L, Zhang J J, Zhang B. Structures, Kinematics, Thermochronology and Tectonic Evolution of the Ramba Gneiss Dome in the Northern Himalaya. Progress in Natural Science, 2008, 18(7): 851-860

[15] Holtz F, Dingwell D B, Behrens H. Effects of F, B₂O₃ and P₂O₅ on the Solubility of Water in Haplogranite Melts Compared to Natural Silicate Melts. Contributions to Mineralogy and Petrology, 1993, 113(4): 492-501

[16] Hu G Y, Zeng L S, Gao L E, et al.. Diverse Magma Sources for the Himalayan Leucogranites: Evidence from B-Sr-Nd Isotopes. Lithos, 2018, 314: 88-99

[17] Icenhower J, London D. An Experimental Study of Element Partitioning among Biotite, Muscovite, and Coexisting Peraluminous Silicic Melt at 200 MPa (H₂O). American Mineralogist, 1995, 80(11/12): 1229-1251

[18] Kaeter D, Barros R, Menuge J F, et al.. The Magmatic-Hydrothermal Transition in Rare-Element Pegmatites from Southeast Ireland: LA-ICP-MS Chemical Mapping of Muscovite and Columbite-Tantalite. Geochimica et Cosmochimica Acta, 2018, 240: 98-130

[19] Keppler H. Influence of Fluorine on the Enrichment of High Field Strength Trace Elements in Granitic Rocks. Contributions to Mineralogy and Petrology, 1993, 114(4): 479-488

[20] Li J, Huang X L, He P L, et al.. In Situ Analyses of Micas in the Yashan Granite, South China: Constraints on Magmatic and Hydrothermal Evolutions of W and Ta-Nb Bearing Granites. Ore Geology Reviews, 2015, 65: 793-810

[21] Li X Y, Zhang C, Wang L X, et al.. Experiments on the Saturation of Fluorite in Magmatic Systems: Implications for Maximum F Concentration and Fluorine-Cation Bonding in Silicate Melt. Journal of Earth Science, 2020, 31(3): 456-467

[22] Liu Z C, Wu F Y, Liu X C, et al.. The Mechanisms of Fractional Crystallization for the Himalayan Leucogranites. Acta Petrologica Sinica, 2020, 36(12): 3551-3571 in Chinese with English Abstract)

[23] Liu Z C, Wang J G, Liu X C, et al.. Middle Miocene Ultrapotassic Magmatism in the Himalaya: a Response to Mantle Unrooting Process beneath the Orogen. Terra Nova, 2021, 33(3): 240-251

[24] Liu Z C, Wu F Y, Ji W Q, et al.. Petrogenesis of the Ramba Leucogranite in the Tethyan Himalaya and Constraints on the Channel Flow Model. Lithos, 2014, 208: 118-136

[25] Liu Z C, Wu F Y, Liu X C, et al.. Mineralogical Evidence for Fractionation Processes in the Himalayan Leucogranites of the Ramba Dome, Southern Tibet. Lithos, 2019, 340/341: 71-86

[26] Miller C F, Stoddard E F, Bradfish L J, et al.. Composition of Plutonic Muscovite: Genetic Implications. The Canadian Mineralogist, 1981, 19(1): 25-34

[27] Monier G, Mergoil-Daniel J, Labernadière H. Générations Successives de Muscovites et Feldspaths Potassiques Dans Les Leucogranites Du Massif de Millevaches (Massif Central Français). Bulletin de Minéralogie, 1984, 107(1): 55-68

[28] Nishimura S, Matsumoto S, Terashima K. Variation of Silicon Melt Viscosity with Boron Addition. Journal of Crystal Growth, 2002, 237: 1667-1670

[29] Pérez-Soba C, Villaseca C. Li-Na-Metasomatism Related to I-Type Granite Magmatism: A Case Study of the Highly Fractionated La Pedriza Pluton (Iberian Variscan Belt). Lithos, 2019, 344/345: 159-174

[30] Pichavant M, Villaros A, Deveaud S, et al.. The Influence of Redox State on Mica Crystallization in Leucogranitic and Pegmatitic Liquids. The Canadian Mineralogist, 2016, 54(3): 559-581

[31] Ren C M, Zheng Y C, Li X, et al.. Characteristics and Geological Significance of Late Miocene Skarn-Type Tungsten Mineralization in Ramba, Southern Tibet. Earth Science, 2024, 49(10): 3610-3628(in Chinese with English Abstract)

[32] Reid J B, Murray D PJr., Hermes O D, et al.. Fractional Crystallization in Granites of the Sierra Nevada: How Important Is It?. Geology, 1993, 21(7): 587-590

[33] Scaillet B, Pêcher A, Rochette P, et al.. The Gangotri Granite (Garhwal Himalaya): Laccolithic Emplacement in an Extending Collisional Belt. Journal of Geophysical Research: Solid Earth, 1995, 100(B1): 585-607

[34] Sparks R S J, Folkes C B, Humphreys M C S, et al.. Uturuncu Volcano, Bolivia: Volcanic Unrest Due to Mid-Crustal Magma Intrusion. American Journal of Science, 2008, 308(6): 727-769

[35] Speer J A, Becker S W. Evolution of Magmatic and Subsolidus AFM Mineral Assemblages in Granitoid Rocks: Biotite, Muscovite, and Garnet in the Cuffytown Creek Pluton, South Carolina. American Mineralogist, 1992, 77(7/8): 821-833

[36] Teiber H, Marks M A W, Wenzel T, et al.. The Distribution of Halogens (F, Cl, Br) in Granitoid Rocks. Chemical Geology, 2014, 374: 92-109

[37] Tischendorf G, Gottesmann B, Förster H J, et al.. On Li-Bearing Micas: Estimating Li from Electron Microprobe Analyses and an Improved Diagram for Graphical Representation. Mineralogical Magazine, 1997, 61(409): 809-834

[38] Wang L X, Ma C Q, Zhang C, et al.. Halogen Geochemistry of I- and A-Type Granites from Jiuhuashan Region (South China): Insights into the Elevated Fluorine in AType Granite. Chemical Geology, 2018, 478: 164-182

[39] Wu F Y, Liu X C, Ji W Q, et al.. Highly Fractionated Granites: Recognition and Research. Science China Earth Sciences, 2017, 60(7): 1201-1219

[40] Wu F Y, Liu X C, Liu Z C, et al.. Highly Fractionated Himalayan Leucogranites and Associated Rare-Metal Mineralization. Lithos, 2020, 352/353: 105319

[41] Wu J, Tian S H, Li G M, et al.. Petrogenesis of Lalong leucogranites in estern Himalayan orogenic belt and relationship with South Tibetan Detachment System. Earth Science, 2025, 50(7): 2593-2612(in Chinese with English Abstract)

[42] Wyllie P J, Tuttle O F. Experimental Investigation of Silicate Systems Containing Two Volatile Components; Part 2, the Effects of NH₃ and HF, in Addition to H₂O on the Melting Temperatures of Albite and Granite. American Journal of Science, 1961, 259(2): 128-143

[43] Yang S Y, Jiang S-Y, Mao Q, et al.. Electron Probe Microanalysis in Geosciences: Analytical Procedures and Recent Advances. Atomic Spectroscopy, 2022, 43(1): 186-200

[44] Yin A. Cenozoic Tectonic Evolution of the Himalayan Orogen as Constrained by Along-Strike Variation of Structural Geometry, Exhumation History, and Foreland Sedimentation. Earth-Science Reviews, 2006, 76(1/2): 1-131

[45] Young E J, Myers A T, Munson E L, et al.. Mineralogy and Geochemistry of Fluorapatite from Cerro de Mercado, Durango, Mexico. US Geological Survey: Chapter D, 1969, Washington, D.C., United States Government Printing Office, 84-93

[46] Zhang B T, Wu J Q, Ling H F, et al.. Petrological Discrimination between Primary and Secondary Muscovites and Its Geological Implications: A Case Study of Fucheng Peraluminous Granite Pluton in Southern Jiangxi. Acta Petrologica et Mineralogica, 2010, 29(3): 225-234(in Chinese with English Abstract)

[47] Zhang C, Koepke J, Wang L X, et al.. A Practical Method for Accurate Measurement of Trace Level Fluorine in Mg- and Fe-Bearing Minerals and Glasses Using Electron Probe Microanalysis. Geostandards and Geoanalytical Research, 2016, 40(3): 351-363

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