Petrology of Eclogite at Huwan, Western Dabie and Implications for Phase Equilibrium Modeling on LT-HP/UHP Eclogite

Abstract

Phase equilibrium modeling using internally consistent thermodynamic dataset and associated activity-composition (a-x) models are very helpful for quantifying P-T evolution for eclogite, which is the basis for deciphering the geodynamic processes in subduction zones. In this study, we apply different versions of datasets (ds55 and ds62) and associated a-x relations to a well-established LT-HP eclogite at Huwan in the classic western Dabie orogen to constrain its P-T evolution. The eclogite comprises garnet + omphacite + amphibole + white mica + epidote + quartz + chlorite + rutile/ilmenite/sphene. Garnet porphyroblasts show mono-variation in the end members (spessartine from 17 mol% to 0, pyrope from 2 mol% to 18 mol%, almandine from 47 mol% to 64 mol% and grossular from 35 mol% to 18 mol%) from core to rim. Phase diagrams combined with compositional isopleth thermobarometry show that dataset ds62 and associated a-x relations yield P _max of ∼33 kbar at ∼560 °C, conflicting with our petrological observations and previous studies. On the other hand, phase equilibrium modeling using dataset ds62 and a revised symmetric garnet a-x model irrespective of Fe³⁺ (O) gives P _max of ∼27 kbar at ∼560 °C, consistent with the results using dataset ds55 and associated a-x relations. Therefore, we recommend a symmetric model for garnet involving py, alm, gr and spss, without Fe³⁺ components, instead of the asymmetric garnet a-x relations involving py, alm, gr, spss and kho by White et al. (2014), for calculating phase diagrams for LT-(U)HP eclogite when using dataset ds62. In this study, the defined P-T path is characterized by a segment of the prograde evolution showing a first moderate slope, followed by gentle then steep slopes, representing the thermal structure evolution recorded by slab surface during continental subduction. Our work combined with previous studies conclude that in western Dabie, the Huwan HP eclogite belt to the north and the Hong’an HP eclogite belt to the south belong to the same HP slice overlying the Xinxian UHP slice.

Keywords

phase equilibrium modeling / LT-HP eclogite / continental subduction / western Dabie / garnets / petrology

References

[1] AgardP, Vitale-BrovaroneA. Thermal Regime of Continental Subduction: The Record from Exhumed HP-LT Terranes (New Caledonia, Oman, Corsica). Tectonophysics, 2013, 601: 206-215

[2] BaderT, ZhangL F, LiX W. Is the Songshugou Complex, Qinling Belt, China, an Eclogite Facies Neoproterozoic Ophiolite?. Journal of Earth Science, 2019, 30(3): 460-475

[3] BovayT, LanariP, RubattoD, et al.. Pressure-Temperature-Time Evolution of Subducted Crust Revealed by Complex Garnet Zoning (Theodul Glacier Unit, Switzerland). Journal of Metamorphic Geology, 2022, 40(2): 175-206

[4] BrouwerF M, GroenM, NebelO, et al.. Coherence of the Dabie Shan UHPM Terrane Investigated by Lu-Hf and ⁴⁰Ar/³⁹Ar Dating of Eclogites. Ultrahigh-Pressure Metamorphism, 2011 Amsterdam Elsevier 325-357

[5] CarswellD A Eclogite Facies Rocks, 1990 New York Blackie 396

[6] ChengH, DuFraneS A, VervoortJ D, et al.. The Triassic Age for Oceanic Eclogites in the Dabie Orogen: Entrainment of Oceanic Fragments in the Continental Subduction. Lithos, 2010, 117(1–4): 82-98

[7] ChengH, KingR L, NakamuraE, et al.. Transitional Time of Oceanic to Continental Subduction in the Dabie Orogen: Constraints from U-Pb, Lu-Hf, Sm-Nd and Ar-Ar Multichronometric Dating. Lithos, 2009, 110(1–4): 327-342

[8] ChengH, VervoortJ D, DragovicB, et al.. Coupled Lu-Hf and Sm-Nd Geochronology on a Single Eclogitic Garnet from the Huwan Shear Zone, China. Chemical Geology, 2018, 476: 208-222

[9] CoggonR, HollandT J B. Mixing Properties of Phengitic Micas and Revised Garnet-Phengite Thermobarometers. Journal of Metamorphic Geology, 2002, 20(7): 683-696

[10] DienerJ F A, PowellR. Revised Activity-Composition Models for Clinopyroxene and Amphibole. Journal of Metamorphic Geology, 2012, 30(2): 131-142

[11] EvansT P. A Method for Calculating Effective Bulk Composition Modification due to Crystal Fractionation in Garnet-Bearing Schist: Implications for Isopleth Thermobarometry. Journal of Metamorphic Geology, 2004, 22(6): 547-557

[12] FuB, ZhengY F, TouretJ L R. Petrological, Isotopic and Fluid Inclusion Studies of Eclogites from Sujiahe, NW Dabie Shan (China). Chemical Geology, 2002, 187(1/2): 107-128

[13] GaoS, QiuY M, LingW L, et al.. SHRIMP Single Zircon U-Pb Geochronology of Eclogite from Yingshan and Xiongdian. Earth Science, 2002, 27(5): 558-564 (in Chinese with English Abstract)

[14] GreenE C R, WhiteR W, DienerJ F A, et al.. Activity-Composition Relations for the Calculation of Partial Melting Equilibria in Metabasic Rocks. Journal of Metamorphic Geology, 2016, 34(9): 845-869

[15] HackerB R, RatschbacherL, WebbL, et al.. Exhumation of Ultrahigh-Pressure Continental Crust in East Central China: Late Triassic–Early Jurassic Tectonic Unroofing. Journal of Geophysical Research, 2000, 105(B6): 13339-13364

[16] HamelinC, BradyJ B, CheneyJ T, et al.. Pseudomorphs after Lawsonite from Syros, Greece. Journal of Petrology, 2018, 59(12): 2353-2384

[17] HollandT J B, PowellR. An Improved and Extended Internally Consistent Thermodynamic Dataset for Phases of Petrological Interest, Involving a New Equation of State for Solids. Journal of Metamorphic Geology, 2011, 29(3): 333-383

[18] HollandT, PowellR. Activity-Composition Relations for Phases in Petrological Calculations: An Asymmetric Multicomponent Formulation. Contributions to Mineralogy and Petrology, 2003, 145(4): 492-501

[19] HollandT J B, PowellR. An Internally Consistent Thermodynamic Data Set for Phases of Petrological Interest. Journal of Metamorphic Geology, 1998, 16(3): 309-343

[20] HouX G, YuZ Q, ChenS F, et al.. Trace Element Mobility in Subducted Marble and Associated Eclogite: Constraints from UHP Rocks in the Shuanghe Area, Central-East China. Journal of Earth Science, 2024, 35(1): 1-15

[21] JahnB M, LiuX C, YuiT F, et al.. High-Pressure/Ultrahigh-Pressure Eclogites from the Hong’an Block, East-Central China: Geochemical Characterization, Isotope Disequilibrium and Geochronological Controversy. Contributions to Mineralogy and Petrology, 2005, 149(5): 499-526

[22] LiX, LiuL, LiaoX Y, et al.. Metamorphic Evolution of Garnet Amphibolite from the Yaganbuyang Area in the South Altyn Orogen, West China: Insights from Phase Equilibria Modeling and Geochronology. Journal of Earth Science, 2023, 34(3): 640-657

[23] LiY, ZhangC, LiuX Y, et al.. Metamorphism and Oceanic Crust Exhumation—Constrained by the Jilang Eclogite and Meta-Quartzite from the Sumdo (U)HP Metamorphic Belt. Journal of Earth Science, 2019, 30(3): 510-524

[24] LinS W, ZhangQ Q, GaoX Y, et al.. Metamorphic Evolution of Garnet Amphibolite at Songshugou in the North Qinling Orogen: Evidence from Garnet Geochemistry and Zircon Geochronology. Earth Science, 2024, 49(8): 2714-2735 (in Chinese with English Abstract)

[25] LiuP L, JinZ M. Metamorphic Evolution of a Tremolite Marble from the Dabie UHP Terrane, China: A Focus on Zircon. Journal of Earth Science, 2022, 33(2): 493-506

[26] LiuX C, JahnB M, LiuD Y, et al.. SHRIMP U-Pb Zircon Dating of a Metagabbro and Eclogites from Western Dabieshan (Hong’an Block), China, and Its Tectonic Implications. Tectonophysics, 2004, 394(3/4): 171-192

[27] LiuX C, WeiC J, LiS Z, et al.. Thermobaric Structure of a Traverse across Western Dabieshan: Implications for Collision Tectonics between the Sino-Korean and Yangtze Cratons. Journal of Metamorphic Geology, 2004, 22(4): 361-379

[28] LouY X, WeiC J, LiuX C, et al.. Metamorphic Evolution of Garnet Amphibolite in the Western Dabieshan Eclogite Belt, Central China: Evidence from Petrography and Phase Equilibria Modeling. Journal of Asian Earth Sciences, 2013, 63: 130-138

[29] LouY X, WeiC J, ChuH, et al.. Metamorphic Evolution of High-Pressure Eclogite from Hong’an, Western Dabie Orogen, Central China: Evidence from Petrography and Calculated Phase Equilibria in System Na₂O-CaO-K₂O-FeO-MgO-Al₂O₃-SiO₂-H₂O-(Fe₂O₃). Acta Petrologica Sinica, 2009, 25: 124-138 (in Chinese with English Abstract)

[30] MaharE M, BakerJ M, PowellR, et al.. The Effect of Mn on Mineral Stability in Metapelites. Journal of Metamorphic Geology, 1997, 15(2): 223-238

[31] PowellR, HollandT. Relating Formulations of the Thermodynamics of Mineral Solid Solutions; Activity Modeling of Pyroxenes, Amphiboles, and Micas. American Mineralogist, 1999, 84(1/2): 1-14

[32] PowellR, HollandT J B. On Thermobarometry. Journal of Metamorphic Geology, 2008, 26(2): 155-179

[33] RatschbacherL, FranzL, EnkelmannE, et al. HackerB R, McClellandW C, LiouJ G, et al.. The Sino-Korean-Yangtze Suture, the Huwan Detachment, and the Paleozoic - Tertiary Exhumation of (Ultra)High-Pressure Rocks along the Tongbai-Xinxian-Dabie Mountains. Ultrahigh-Pressure Metamorphism: Deep Continental Subduction, 2006

[34] SpearF S Metamorphic Phase Equilibria and Pressure-Temperature-Time Paths, 1993 Washington, D.C. Mineralogical Society of America 799

[35] StarrP G, BroadwellK S, DragovicB, et al.. The Subduction and Exhumation History of the Voltri Ophiolite, Italy: Evaluating Exhumation Mechanisms for High-Pressure Metamorphic Massifs. Lithos, 2020, 376: 105767

[36] SuoS T, ZhongZ Q, ZhouH W. Late-Stage Ductile Deformation in Xiongdian-Suhe HP Metamorphic Unit, North-Western Dabie Shan, Central China. Journal of Earth Science, 2004, 15(3): 262-274

[37] SyracuseE M, van KekenP E, AbersG A, et al.. The Global Range of Subduction Zone Thermal Models. Physics of the Earth and Planetary Interiors, 2010, 183(1/2): 73-90

[38] TrappS, JanákM, FassmerK, et al.. Variscan Ultra-High-Pressure Eclogite in the Upper Allochthon of the Rhodope Metamorphic Complex (Bulgaria). Terra Nova, 2021, 33(2): 174-183

[39] van KekenP E, KieferB, PeacockS M. High-Resolution Models of Subduction Zones: Implications for Mineral Dehydration Reactions and the Transport of Water into the Deep Mantle. Geochemistry, Geophysics, Geosystems, 2002, 3(10): 20

[40] WeiC J, LiY J, YuY, et al.. Phase Equilibria and Metamorphic Evolution of Glaucophane-Bearing UHP Eclogites from the Western Dabieshan Terrane, Central China. Journal of Metamorphic Geology, 2010, 28(6): 647-666

[41] WeiC J, SuX L, LouY X, et al.. A New Interpretation of the Conventional Thermobarometry in Eclogite: Evidence from the Calculated P-T Pseudosections. Acta Petrologica Sinica, 2009, 25(9): 2078-2088 (in Chinese with English Abstract)

[42] WhiteR W, PomroyN E, PowellR. An in situ Metatexite-Diatexite Transition in Upper Amphibolite Facies Rocks from Broken Hill, Australia. Journal of Metamorphic Geology, 2005, 23(7): 579-602

[43] WhiteR W, PowellR, HollandT J B, et al.. New Mineral Activity-Composition Relations for Thermodynamic Calculations in Metapelitic Systems. Journal of Metamorphic Geology, 2014, 32(3): 261-286

[44] WuY B, ZhengY F. Tectonic Evolution of a Composite Collision Orogen: An Overview on the Qinling-Tongbai-Hong’an-Dabie-Sulu Orogenic Belt in Central China. Gondwana Research, 2013, 23(4): 1402-1428

[45] WuY B, HancharJ M, GaoS, et al.. Age and Nature of Eclogites in the Huwan Shear Zone, and the Multi-Stage Evolution of the Qinling-Dabie-Sulu Orogen, Central China. Earth and Planetary Science Letters, 2009, 277(3/4): 345-354

[46] XiaB, BrownM, ZhangL F. P-T Evolution and Tectonic Significance of Lawsonite-Bearing Schists from the Eastern Segment of the Southwestern Tianshan, China. Journal of Metamorphic Geology, 2020, 38(9): 935-962

[47] XiaB, BrownM, WangL, et al.. Phase Equilibrium Modeling of MT-UHP Eclogite: A Case Study of Coesite Eclogite at Yangkou Bay, Sulu Belt, Eastern China. Journal of Petrology, 2018, 59(7): 1253-1280

[48] XiaB, YangQ, ChenN S, et al.. Phase Equilibrium Modeling of Retrograded Eclogite at the Kekesu Valley, Eastern Segment of SW Tianshan Orogen and Tectonic Implications. Journal of Earth Science, 2018, 29(5): 1060-1073

[49] ZhouG S, ZhangJ X, LiY S, et al.. Metamorphic Evolution and Tectonic Implications of the Granulitized Eclogites from the Luliangshan Terrane in the North Qaidam Ultrahigh Pressure Metamorphic Belt, NW China: New Constraints from Phase Equilibrium Modeling. Journal of Earth Science, 2019, 30(3): 585-602

[50] ZhouL G, XiaQ X, ZhengY F, et al.. Polyphase Growth of Garnet in Eclogite from the Hong’an Orogen: Constraints from Garnet Zoning and Phase Equilibrium. Lithos, 2014, 206/207: 79-99

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