Decoupling between Oxygen and Radiogenic Isotopes: Evidence for Generation of Juvenile Continental Crust by Partial Melting of Subducted Oceanic Crust

Abstract

There is increasing evidence indicating that melts derived from subducted oceanic crust and sediments may have played a key role in building continental crust. This mechanism predicts that juvenile arc crust should have oxygen isotope characteristics ranging from mantle-like to supracrustal, but consistent mantle-like radiogenic (Nd-Hf) isotopic signatures. Here we present in-situ zircon U-Pb dating, Hf-O isotope analyses, and whole rock major-trace element and Nd isotope analyses of a granitoid from NW India. In-situ secondary ion mass spectrometry (SIMS) zircon U-Pb dating yields a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 873±6 Ma for the granitoid. It displays mantle-like zircon ε _Hf(ε _{Hf(873 Ma)}=+9.3 to +10.9) and whole-rock Nd (ε _{Nd(873 Ma)}=+3.5) values but supracrustal δ¹⁸O values, the latter mostly varying between 9‰ and 10‰. The calculated whole-rock δ¹⁸O value of 11.3‰±0.6‰ matches well with those of hydrothermally-altered pillow lavas and sheeted dykes from ophiolites. The major and trace element composition of the granitoid is similar to petrological experimental melts derived from a mixture of MORB+sediments. Thus, the granitoid most likely represents the product of partial melting of the uppermost oceanic crust (MORB+sediments). We propose that the decoupling between Hf-Nd and O isotopes as observed in this granitoid can be used as a powerful tool for the identification of slab melting contributing to juvenile continental crustal growth. Such isotopic decoupling can also account for high δ¹⁸O values observed in ancient juvenile continental crust, such as Archean tonalite-trondhjemite-granodiorite suites.

Keywords

zircon / Hf-Nd and O isotopes / decoupling / slab melting / Neoproterozoic continental crustal growth

References

[1] Solanki A M. A Petrographic, Geochemical and Geochronological Investigation of Deformed Granitoids from SW Rajasthan: Neoproterozoic Age of Formation and Evidence of Pan-African Imprint: [Dissertation], 2011, Johannesburg: University of the Witwatersrand

[2] Ashwal L D, Solanki A M, Pandit M K, . Geochronology and Geochemistry of Neoproterozoic Mt. Abu Granitoids, NW India: Regional Correlation and Implications for Rodinia Paleogeography. Precambrian Research, 2013, 236: 265-281.

[3] Behn M D, Kelemen P B, Hirth G, . Diapirs as the Source of the Sediment Signature in Arc Lavas. Nature Geoscience, 2011, 4(9): 641-646.

[4] Bindeman I N, Eiler J M, Yogodzinski G M, . Oxygen Isotope Evidence for Slab Melting in Modern and Ancient Subduction Zones. Earth and Planetary Science Letters, 2005, 235(3/4): 480-496.

[5] Bouvier A, Vervoort J D, Patchett P J. The Lu-Hf and Sm-Nd Isotopic Composition of CHUR: Constraints from Unequilibrated Chondrites and Implications for the Bulk Composition of Terrestrial Planets. Earth and Planetary Science Letters, 2008, 273(1/2): 48-57.

[6] Buick I S, Clark C, Rubatto D, . Constraints on the Proterozoic Evolution of the Aravalli-Delhi Orogenic Belt (NW India) from Monazite Geochronology and Mineral Trace Element Geochemistry. Lithos, 2010, 120(3/4): 511-528.

[7] Castro A, Gerya T, Garcia-Casco A, . Melting Relations of MORB-Sediment Melanges in Underplated Mantle Wedge Plumes; Implications for the Origin of Cordilleran-Type Batholiths. Journal of Petrology, 2010, 51(6): 1267-1295.

[8] Castro A, Vogt K, Gerya T. Generation of New Continental Crust by Sublithospheric Silicic-Magma Relamination in Arcs: A Test of Taylor’s Andesite Model. Gondwana Research, 2013, 23(4): 1554-1566.

[9] Chappell B W. Compositional Variation within Granite Suites of the Lachlan Fold Belt: Its Causes and Implications for the Physical State of Granite Magma. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 1996, 87(1/2): 159-170.

[10] Choudhary A K, Gopalan K, Sastry C A. Present Status of the Geochronology of the Precambrian Rocks of Rajasthan. Tectonophysics, 1984, 105(1/2/3/4): 131-140.

[11] Condie K C, Baragar W R A. Rare-Earth Element Distributions in Volcanic Rocks from Archean Greenstone Belts. Contributions to Mineralogy and Petrology, 1974, 45(3): 237-246.

[12] Deb M, Thorpe R I, Krstic D, . Zircon U-Pb and Galena Pb Isotope Evidence for an Approximate 1.0 Ga Terrane Constituting the Western Margin of the Aravalli-Delhi Orogenic Belt, Northwestern India. Precambrian Research, 2001, 108(3/4): 195-213.

[13] Dhuime B, Hawkesworth C, Cawood P. When Continents Formed. Science, 2011, 331(6014): 154-155.

[14] Eiler J M. Oxygen Isotope Variations of Basaltic Lavas and Upper Mantle Rocks. Reviews in Mineralogy and Geochemistry, 2001, 43(1): 319-364.

[15] Eiler J M, McInnes B, Valley J W, . Oxygen Isotope Evidence for Slab-Derived Fluids in the Sub-Arc Mantle. Nature, 1998, 393(6687): 777-781.

[16] Eiler J M, Schiano P, Valley J W, . Oxygen-Isotope and Trace Element Constraints on the Origins of Silica-Rich Melts in the Subarc Mantle. Geochemistry, Geophysics, Geosystems, 2007, 8 9 Q09012

[17] Foley S, Tiepolo M, Vannucci R. Growth of Early Continental Crust Controlled by Melting of Amphibolite in Subduction Zones. Nature, 2002, 417(6891): 837-840.

[18] Gómez-Tuena A, Mori L, Rincón-Herrera N E, . The Origin of a Primitive Trondhjemite from the Trans-Mexican Volcanic Belt and Its Implications for the Construction of a Modern Continental Arc. Geology, 2008, 36(6): 471-474.

[19] Griffin W L, Pearson N J, Belousova E, . The Hf Isotope Composition of Cratonic Mantle: LAM-MC-ICPMS Analysis of Zircon Megacrysts in Kimberlites. Geochimica et Cosmochimica Acta, 2000, 64(1): 133-147.

[20] Griffin W L, Wang X, Jackson S E, . Zircon Chemistry and Magma Mixing, SE China: In-situ Analysis of Hf Isotopes, Tonglu and Pingtan Igneous Complexes. Lithos, 2002, 61(3/4): 237-269.

[21] Hacker B R, Kelemen P B, Behn M D. Differentiation of the Continental Crust by Relamination. Earth and Planetary Science Letters, 2011, 307(3/4): 501-516.

[22] Jagoutz O, Schmidt M W. The Formation and Bulk Composition of Modern Juvenile Continental Crust: The Kohistan Arc. Chemical Geology, 2012, 298/299: 79-96.

[23] Just J, Schulz B, de Wall H, . Monazite CHIME/EPMA Dating of Erinpura Granitoid Deformation: Implications for Neoproterozoic Tectono-Thermal Evolution of NW India. Gondwana Research, 2011, 19(2): 402-412.

[24] Jweda J, Bolge L, Class C, . High Precision Sr-Nd-Hf-Pb Isotopic Compositions of USGS Reference Material BCR-2. Geostandards and Geoanalytical Research, 2015, 40(1): 101-115.

[25] Kelemen P B. Genesis of High Mg# Andesites and the Continental Crust. Contributions to Mineralogy and Petrology, 1995, 120(1): 1-19.

[26] Kemp A I S, Hawkesworth C J, Foster G L, . Magmatic and Crustal Differentiation History of Granitic Rocks from Hf-O Isotopes in Zircon. Science, 2007, 315(5814): 980-983.

[27] Klein E M. Heinrich D H, Karl K T. Geochemistry of the Igneous Oceanic Crust. Treatise on Geochemistry, 2003, Oxford: Pergamon, 433-463

[28] Kröner A, Windley B F, Badarch G, . Accretionary Growth and Crust Formation in the Central Asian Orogenic Belt and Comparison with the Arabian-Nubian Shield. Memoirs-Geological Society of America, 2007, 200 181

[29] Li Q L, Li X H, Liu Y, . Precise U-Pb and Pb-Pb Dating of Phanerozoic Baddeleyite by SIMS with Oxygen Flooding Technique. Journal of Analytical Atomic Spectrometry, 2010, 25 7 1107

[30] Liu C Z, Wu F Y, Chung S L, . A ‘Hidden’ ¹⁸O-Enriched Reservoir in the Sub-Arc Mantle. Scientific Reports, 2014, 4 1 4232

[31] Ludwig K. User’s Manual for Isoplot 3.00: A Geochronological Toolkit for Microsoft Excel. Barkeley Geochronology Center Special Publication, 2003, 4: 1-71.

[32] Lyu P L, Li W X, Wang X-C, . Initial Breakup of Supercontinent Rodinia as Recorded by ca. 860–840 Ma Bimodal Volcanism along the Southeastern Margin of the Yangtze Block, South China. Precambrian Research, 2017, 296: 148-167.

[33] Martin H, Smithies R H, Rapp R, . An Overview of Adakite, Tonalite-Trondhjemite-Granodiorite (TTG), and Sanukitoid: Relationships and Some Implications for Crustal Evolution. Lithos, 2005, 79(1/2): 1-24.

[34] Mattey D, Lowry D, Macpherson C. Oxygen Isotope Composition of Mantle Peridotite. Earth and Planetary Science Letters, 1994, 128(3/4): 231-241.

[35] Miller J A, Cartwright I, Buick I S, . An O-Isotope Profile through the HP-LT Corsican Ophiolite, France and Its Implications for Fluid Flow during Subduction. Chemical Geology, 2001, 178(1/2/3/4): 43-69.

[36] Moyen J F, Martin H. Forty Years of TTG Research. Lithos, 2012, 148: 312-336.

[37] Naik M S. The Geochemistry and Genesis of the Granitoids of Sirohi, Rajasthan, India. Journal of Southeast Asian Earth Sciences, 1993, 8(1/2/3/4): 111-115.

[38] Niu Y L, Zhao Z D, Zhu D C, . Continental Collision Zones are Primary Sites for Net Continental Crust Growth—A Testable Hypothesis. Earth-Science Reviews, 2013, 127: 96-110.

[39] Pandit M K, Carter L M, Ashwal L D, . Age, Petrogenesis and Significance of 1 Ga Granitoids and Related Rocks from the Sendra Area, Aravalli Craton, NW India. Journal of Asian Earth Sciences, 2003, 22(4): 363-381.

[40] Pandit M K, Shekhawat L S, Ferreira V P, . Trondhjemite and Granodiorite Assemblages from West of Barmer: Probable Basement for Malani Magmatism in Western India. Journal-Geological Society of India, 1999, 53: 89-96.

[41] Pradhan V R, Meert J G, Pandit M K, . India’s Changing Place in Global Proterozoic Reconstructions: A Review of Geochronologic Constraints and Paleomagnetic Poles from the Dharwar, Bundelkhand and Marwar Cratons. Journal of Geodynamics, 2010, 50(3/4): 224-242.

[42] Rapp R P, Shimizu N, Norman M D. Growth of Early Continental Crust by Partial Melting of Eclogite. Nature, 2003, 425(6958): 605-609.

[43] Reagan M K, Hanan B B, Heizler M T, . Petrogenesis of Volcanic Rocks from Saipan and Rota, Mariana Islands, and Implications for the Evolution of Nascent Island Arcs. Journal of Petrology, 2008, 49(3): 441-464.

[44] Roy A B, Jakhar S R. Geology of Rajasthan (Northwest India)-Precambrian to Recent, 2002, Jodhpur: Scientific Publishers (India), xii+421.

[45] Smith P M, Asimow P D. Adiabat_1ph: A New Public Front-End to the MELTS, PMELTS, and PHMELTS Models. Geochemistry, Geophysics, Geosystems, 2005, 6 2 Q02004

[46] Solanki A M. A Petrographic, Geochemical, and Geochronological Investigation of Deformed Granitoids from SW Rajasthan: Neoproterozoic Age of Formation and Evidence of Pan-African Imprint: [Dissertation], 2011, Johannesburg: University of the Witwatersrand, 216.

[47] Söderlund U, Patchett P J, Vervoort J D, . The ¹⁷⁶Lu Decay Constant Determined by Lu-Hf and U-Pb Isotope Systematics of Precambrian Mafic Intrusions. Earth and Planetary Science Letters, 2004, 219(3/4): 311-324.

[48] Spandler C, Pirard C. Element Recycling from Subducting Slabs to Arc Crust: A Review. Lithos, 2013, 170/171: 208-223.

[49] Sun S S, McDonough W F. Chemical and Isotopic Systematics of Oceanic Basalts: Implications for Mantle Composition and Processes. Geological Society, London, Special Publications, 1989, 42(1): 313-345.

[50] Valley J W, Bindeman I N, Peck W H. Empirical Calibration of Oxygen Isotope Fractionation in Zircon. Geochimica et Cosmochimica Acta, 2003, 67(17): 3257-3266.

[51] Valley J W, Kinny P D, Schulze D J, . Zircon Megacrysts from Kimberlite: Oxygen Isotope Variability among Mantle Melts. Contributions to Mineralogy and Petrology, 1998, 133(1/2): 1-11.

[52] Valley J W, Lackey J S, Cavosie A J, . 4.4 Billion Years of Crustal Maturation: Oxygen Isotope Ratios of Magmatic Zircon. Contributions to Mineralogy and Petrology, 2005, 150(6): 561-580.

[53] Van Lente B, Ashwal L D, Pandit M K, . Neoproterozoic Hydrothermally Altered Basaltic Rocks from Rajasthan, Northwest India: Implications for Late Precambrian Tectonic Evolution of the Aravalli Craton. Precambrian Research, 2009, 170(3/4): 202-222.

[54] Vervoort J D, Plank T, Prytulak J. The Hf-Nd Isotopic Composition of Marine Sediments. Geochimica et Cosmochimica Acta, 2011, 75(20): 5903-5926.

[55] Volpe A M, Macdougall J D. Geochemistry and Isotopic Characteristics of Mafic (Phulad Ophiolite) and Related Rocks in the Delhi Supergroup, Rajasthan, India: Implications for Rifting in the Proterozoic. Precambrian Research, 1990, 48(1/2): 167-191.

[56] Wang X-C, Li Z-X, Li X-H, . Nonglacial Origin for Low-¹⁸O Neoproterozoic Magmas in the South China Block: Evidence from New in-situ Oxygen Isotope Analyses Using SIMS. Geology, 2011, 39(8): 735-738.

[57] Wang X-C, Wilde S A, Xu B, . Origin of Arc-Like Continental Basalts: Implications for Deep-Earth Fluid Cycling and Tectonic Discrimination. Lithos, 2016, 261: 5-45.

[58] White L T, Ireland T R. High-Uranium Matrix Effect in Zircon and Its Implications for SHRIMP U-Pb Age Determinations. Chemical Geology, 2012, 306/307: 78-91.

[59] Wu T, Zhou J-X, Wang X-C, . Identification of Ca. 850 Ma High-Temperature Strongly Peraluminous Granitoids in Southeastern Guizhou Province, South China: A Result of Early Extension along the Southern Margin of the Yangtze Block. Precambrian Research, 2018, 308: 18-34.

[60] Yamaoka K, Ishikawa T, Matsubaya O, . Boron and Oxygen Isotope Systematics for a Complete Section of Oceanic Crustal Rocks in the Oman Ophiolite. Geochimica et Cosmochimica Acta, 2012, 84: 543-559.

[61] Zhu G Z, Gerya T V, Tackley P J, . Four-Dimensional Numerical Modeling of Crustal Growth at Active Continental Margins. Journal of Geophysical Research: Solid Earth, 2013, 118(9): 4682-4698.