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Volume 31 Issue 5
Oct.  2020
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Mingde Lang, Zhiguo Cheng, Zhaochong Zhang, Fangyue Wang, Qian Mao, M. Santosh. Hisingerite in Trachydacite from Tarim: Implications for Voluminous Felsic Rocks in Transitional Large Igneous Province. Journal of Earth Science, 2020, 31(5): 875-883. doi: 10.1007/s12583-020-1330-x
Citation: Mingde Lang, Zhiguo Cheng, Zhaochong Zhang, Fangyue Wang, Qian Mao, M. Santosh. Hisingerite in Trachydacite from Tarim: Implications for Voluminous Felsic Rocks in Transitional Large Igneous Province. Journal of Earth Science, 2020, 31(5): 875-883. doi: 10.1007/s12583-020-1330-x

Hisingerite in Trachydacite from Tarim: Implications for Voluminous Felsic Rocks in Transitional Large Igneous Province

doi: 10.1007/s12583-020-1330-x
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  • Unlike the typical large igneous provinces (LIPs) that are dominated by mafic-ultramafic rocks,the Tarim large igneous province (TLIP) is characterized by a high proportion of felsic rocks,based on which the TLIP is classified as a transitional LIP. In this study,we focus on the trachydacite from the TLIP in which we report the characteristics of hisingerite employing a variety of techniques such as EMPA,LA-ICPMS,CCD single crystal diffraction,and bulk-rock oxygen isotopes. The hisingerite in this rock is associated with plagioclase,amphibole,apatite and ilmenite. These minerals occur as aggregates of fine curled fibers in micron-scale and display heavy rare earth elements (HREE) enriched signature with significant negative Eu anomalies. In the primitive mantle-normalized trace element spider diagrams,they show pronounced Th and U spikes and Nb,Zr,Hf troughs. Petrological observation and mineralogical study reveal a closely genetic relationship between hisingerite and amphibole,indicating that the hisingerite might have been derived from the breakdown of amphibole during the magma ascent. The formation of hisingerite requires excess water from the surrounding melts,suggesting a hydrous parental magma. The hisingerite and amphibole assign a hydrous crustal source for the rock,and extensive crustal melting accounts for the voluminous felsic rocks in the TLIP.
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  • Ayalew, D., Gibson, S. A., 2009. Head-to-Tail Transition of the Afar Mantle Plume: Geochemical Evidence from a Miocene Bimodal Basalt-Rhyolite Succession in the Ethiopian Large Igneous Province. Lithos, 112(3/4): 461-476. https://doi.org/10.1016/j.lithos.2009.04.005 doi:  10.1016/j.lithos.2009.04.005
    Boutilier, R. R., Keen, C. E., 1999. Small-Scale Convection and Divergent Plate Boundaries. Journal of Geophysical Research: Solid Earth, 104(B4): 7389-7403. https://doi.org/10.1029/1998jb900076 doi:  10.1029/1998jb900076
    Bryan, S. E., 2007. Silicic Large Igneous Provinces. Episodes, 30: 20-31 doi:  10.18814/epiiugs/2007/v30i1/004
    Bryan, S. E., Ernst, R. E., 2008. Revised Definition of Large Igneous Provinces (LIPs). Earth-Science Reviews, 86: 175-202. https://doi.org/10.1016/j.earscirev.2007.08.008 doi:  10.1016/j.earscirev.2007.08.008
    Bryan, S. E., Riley, T. R., Jerram, D. A., et al., 2002. Silicic Volcanism: An Undervalued Component of Large Igneous Provinces and Volcanic Rifted Margins. Geological Society of America Special Paper, 362: 97-118. https://doi.org/10.1130/0-8137-2362-0.97 doi:  10.1130/0-8137-2362-0.97
    Cheng, Z. G., Zhang, Z. C., Xie, Q. H., et al., 2018. Subducted Slab-Plume Interaction Traced by Magnesium Isotopes in the Northern Margin of the Tarim Large Igneous Province. Earth and Planetary Science Letters, 489: 100-110. https://doi.org/10.1016/j.epsl.2018.02.039 doi:  10.1016/j.epsl.2018.02.039
    Eggleton, R. A., Tilley, D. B., 1998. Hisingerite: A Ferric Kaolin Mineral with Curved Morphology. Clays and Clay Minerals, 46(4): 400-413. https://doi.org/10.1346/ccmn.1998.0460404 doi:  10.1346/ccmn.1998.0460404
    Ewart, A., Milner, S. C., Armstrong, R. A., et al., 1998. Etendeka Volcanism of the Goboboseb Mountains and Messum Igneous Complex, Namibia. Part II: Voluminous Quartz Latite Volcanism of the Awahab Magma System. Journal of Petrology, 39(2): 227-253. https://doi.org/10.1093/petroj/39.2.227 doi:  10.1093/petroj/39.2.227
    Gaspar, M., Knaack, C., Meinert, L. D., et al., 2008. REE in Skarn Systems: A LA-ICP-MS Study of Garnets from the Crown Jewel Gold Deposit. Geochimica et Cosmochimica Acta, 72(1): 185-205. https://doi.org/10.1016/j.gca.2007.09.033 doi:  10.1016/j.gca.2007.09.033
    He, X. H., Zhong, H., Zhao, Z. F., et al., 2018. U-Pb Geochronology, Elemental and Sr-Nd Isotopic Geochemistry of the Houyaoyu Granite Porphyries: Implication for the Genesis of Early Cretaceous Felsic Intrusions in East Qinling. Journal of Earth Science, 29(4): 920-938. https://doi.org/10.1007/s12583-018-0788-2 doi:  10.1007/s12583-018-0788-2
    Herzberg, C., Gazel, E., 2009. Petrological Evidence for Secular Cooling in Mantle Plumes. Nature, 458(7238): 619-622. https://doi.org/10.1038/nature07857 doi:  10.1038/nature07857
    Hu, A. Q., Jahn, B. M., Zhang, G. X., et al., 2000. Crustal Evolution and Phanerozoic Crustal Growth in Northern Xinjiang: Nd Isotopic Evidence. Part I. Isotopic Characterization of Basement Rocks. Tectonophysics, 328(1/2): 15-51. https://doi.org/10.1016/s0040-1951(00)00176-1 doi:  10.1016/s0040-1951(00)00176-1
    James, D. E., 1981. The Combined Use of Oxygen and Radiogenic Isotopes as Indicators of Crustal Contamination. Annual Review of Earth and Planetary Sciences, 9(1): 311-344. https://doi.org/10.1146/annurev.ea.09.050181.001523 doi:  10.1146/annurev.ea.09.050181.001523
    Jones, A. P., 2005. Meteorite Impacts as Triggers to Large Igneous Provinces. Elements, 1(5): 277-281. https://doi.org/10.2113/gselements.1.5.277 doi:  10.2113/gselements.1.5.277
    Kohyama, N., Sudo, T., 1975. Hisingerite Occurring as a Weathering Product of Iron-Rich Saponite. Clays and Clay Minerals, 23(3): 215-218. https://doi.org/10.1346/ccmn.1975.0230309 doi:  10.1346/ccmn.1975.0230309
    Leake, B. E., Woolley, A. R., Arps, C. E. S., et al., 1997. Nomenclature of Amphiboles Report of the Subcommittee on Amphiboles of the International Mineralogical Association Commission on New Minerals and Mineral Names. European Journal of Mineralogy, 9(3): 623-651. https://doi.org/10.1127/ejm/9/3/0623 doi:  10.1127/ejm/9/3/0623
    Lin, C. S., Li, H., Liu, J. Y., 2012. Major Unconformities, Tectonostratigraphic Frameword, and Evolution of the Superimposed Tarim Basin, Northwest China. Journal of Earth Science, 23(4): 395-407. https://doi.org/10.1007/s12583-012-0263-4 doi:  10.1007/s12583-012-0263-4
    Liu, Y. S., Hu, Z. C., Zong, K. Q., et al., 2010. Reappraisement and Refinement of Zircon U-Pb Isotope and Trace Element Analyses by LA-ICP-MS. Chinese Science Bulletin, 55(15): 1535-1546. https://doi.org/10.1007/s11434-010-3052-4 doi:  10.1007/s11434-010-3052-4
    Liu, H. Q., Xu, Y. G., Tian, W., et al., 2014. Origin of Two Types of Rhyolites in the Tarim Large Igneous Province: Consequences of Incubation and Melting of a Mantle Plume. Lithos, 204: 59-72. https://doi.org/10.1016/j.lithos.2014.02.007 doi:  10.1016/j.lithos.2014.02.007
    Liu, H. Q., Xu, Y. G., Zhong, Y. T., et al., 2019. Crustal Melting above a Mantle Plume: Insights from the Permian Tarim Large Igneous Province, NW China. Lithos, 326-327: 370-383. https://doi.org/10.1016/j.lithos.2018.12.031 doi:  10.1016/j.lithos.2018.12.031
    Liu, S. X., Xu, H. J., 2019. Geochemistry, Zircon U-Pb Age and Hf Isotope of the Huilanshan Granitoids in the North Dabie Terrane: Implications for Syn-Collapse Magmatism of Orogen. Journal of Earth Science, 30(3): 636-646. https://doi.org/10.1007/s12583-019-0892-y doi:  10.1007/s12583-019-0892-y
    Long, X. P., Yuan, C., Sun, M., et al., 2010. Archean Crustal Evolution of the Northern Tarim Craton, NW China: Zircon U-Pb and Hf Isotopic Constraints. Precambrian Research, 180(3/4): 272-284. https://doi.org/10.1016/j.precamres.2010.05.001 doi:  10.1016/j.precamres.2010.05.001
    Mahoney, J. J., Saunders, A. D., Storey, M., et al., 2008. Geochemistry of the Volcan de L'Androy Basalt-Rhyolite Complex, Madagascar Cretaceous Igneous Province. Journal of Petrology, 49(6): 1069-1096. https://doi.org/10.1093/petrology/egn018 doi:  10.1093/petrology/egn018
    Meyer, R., Nicoll, G. R., Hertogen, J., et al., 2009. Trace Element and Isotope Constraints on Crustal Anatexis by Upwelling Mantle Melts in the North Atlantic Igneous Province: An Example from the Isle of Rum, NW Scotland. Geological Magazine, 146(3): 382-399. https://doi.org/10.1017/s0016756809006244 doi:  10.1017/s0016756809006244
    McDonough, W. F., Sun, S. S., 1995. The Composition of the Earth. Chemical Geology, 120(3/4): 223-253. https://doi.org/10.1016/0009-2541(94)00140-4 doi:  10.1016/0009-2541(94)00140-4
    McIntire, W. L., 1963. Trace Element Partition Coefficients—A Review of Theory and Applications to Geology. Geochimica et Cosmochimica Acta, 27(12): 1209-1264. https://doi.org/10.1016/0016-7037(63)90049-8 doi:  10.1016/0016-7037(63)90049-8
    Milner, S. C., Duncan, A. R., Ewart, A., 1992. Quartz Latite Rheoignimbrite Flows of the Etendeka Formation, North-Western Namibia. Bulletin of Volcanology, 54(3): 200-219. https://doi.org/10.1007/bf00278389 doi:  10.1007/bf00278389
    Milner, S. C., Duncan, A. R., Whittingham, A. M., et al., 1995. Trans-Atlantic Correlation of Eruptive Sequences and Individual Silicic Volcanic Units within the Paraná-Etendeka Igneous Province. Journal of Volcanology and Geothermal Research, 69(3/4): 137-157. https://doi.org/10.1016/0377-0273(95)00040-2 doi:  10.1016/0377-0273(95)00040-2
    Ngia, N. R., Hu, M. Y., Gao, D., et al., 2019. Application of Stable Strontium Isotope Geochemistry and Fluid Inclusion Microthermometry to Studies of Dolomitization of the Deeply Buried Cambrian Carbonate Successions in the West-Central Tarim Basin, NW China. Journal of Earth Science, 30(1): 176-193. https://doi.org/10.1007/s12583-017-0954-y doi:  10.1007/s12583-017-0954-y
    Pan, Y., Pan, M., Tian, W., et al., 2013. Redefined Distribution of the Permian Basalt in the Central Tarim Area: A New Approach Based on Down Hole Logging Data Explanation. Acta Geologica Sinica, 87(10): 1542-1550 (in Chinese with English Abstract) http://en.cnki.com.cn/Article_en/ http://search.cnki.net/down/default.aspx?filename=DZXE201310005&dbcode=CJFD&year=2013&dflag=pdfdown
    Pankhurst, M. J., Schaefer, B. F., Betts, P. G., 2011. Geodynamics of Rapid Voluminous Felsic Magmatism through Time. Lithos, 123(1/2/3/4): 92-101. https://doi.org/10.1016/j.lithos.2010.11.014 doi:  10.1016/j.lithos.2010.11.014
    Putirka, K., 2016. Amphibole Thermometers and Barometers for Igneous Systems and Some Implications for Eruption Mechanisms of Felsic Magmas at Arc Volcanoes. American Mineralogist, 101(4): 841-858. https://doi.org/10.2138/am-2016-5506 doi:  10.2138/am-2016-5506
    Shangguan, S. M., Peate, I. U., Tian, W., et al., 2016. Re-Evaluating the Geochronology of the Permian Tarim Magmatic Province: Implications for Temporal Evolution of Magmatism. Journal of the Geological Society, 173(1): 228-239. https://doi.org/10.1144/jgs2014-114 doi:  10.1144/jgs2014-114
    Shayan, A., 1984. Hisingerite Material from a Basalt Quarry Near Geelong, Victoria, Australia. Clays and Clay Minerals, 32(4): 272-278. https://doi.org/10.1346/ccmn.1984.0320404 doi:  10.1346/ccmn.1984.0320404
    Sobolev, A. V., Hofmann, A. W., Kuzmin, D. V., et al., 2007. The Amount of Recycled Crust in Sources of Mantle-Derived Melts. Science, 316: 412-417. https://doi.org/ 10.1126/science. 1138113 doi:  10.1126/science.1138113
    Stern, R. J., Li, S. M., Keller, G. R., 2018. Continental Crust of China: A Brief Guide for the Perplexed. Earth-Science Reviews, 179: 72-94. https://doi.org/10.1016/j.earscirev.2018.01.020 doi:  10.1016/j.earscirev.2018.01.020
    Sun, S. S., McDonough, W. F., 1989. Chemical and Isotopic Systematic of Oceanic Basalts: Implications for Mantle Composition and Process. In: Saunders, A. D., Norry, M. J., eds., Magmatism in Ocean Basins. Geological Society London Special Publications, 42: 313-345. https://doi.org/10.1144/gsl.sp.1989.042.01.19
    Tang, L. J., Huang, T. Z., Qiu, H. J., et al., 2014. Fault Systems and Their Mechanisms of the Formation and Distribution of the Tarim Basin, NW China. Journal of Earth Science, 25(1): 169-182. https://doi.org/10.1007/s12583-014-0410-1 doi:  10.1007/s12583-014-0410-1
    Tian, W., Campbell, I. H., Allen, C. M., et al., 2010. The Tarim Picrite-Basalt-Rhyolite Suite, a Permian Flood Basalt from Northwest China with Contrasting Rhyolites Produced by Fractional Crystallization and Anatexis. Contributions to Mineralogy and Petrology, 160(3): 407-425. https://doi.org/10.1007/s00410-009-0485-3 doi:  10.1007/s00410-009-0485-3
    Turner, S., Rushmer, T., 2009. Similarities between Mantle-Derived A-Type Granites and Voluminous Rhyolites in Continental Flood Basalt Provinces. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 100(1/2): 51-60. https://doi.org/10.1017/s1755691009016181 doi:  10.1017/s1755691009016181
    Wang, F. Y., Ge, C., Ning, S. Y., et al., 2017. A New Approach to LA-ICP-MS Mapping and Application in Geology. Acta Petrologica Sinica, 33(11): 3422-3436 (in Chinese with English Abstract) http://www.zhangqiaokeyan.com/academic-journal-cn_acta-petrologica-sinica_thesis/0201252013664.html
    Whelan, J. A., Goldich, S. S., 1961. New Data for Hisingerite and Neotocite. The American Mineralogist, 46: 1412-1423 http://ci.nii.ac.jp/naid/10008768203
    White, R. S., 1992. Magmatism during and after Continental Break-Up. In: Storey, B. C., Alabaster, T., Pankhurst, R. J., eds., Magmatism and the Causes of Continental Break-Up. Geological Society London Special Publication, 68: 1-16. https://doi.org/10.1144/gsl.sp.1992.068.01.01
    Xiao, X., Zhou, T. F., White, N. C., et al., 2018. The Formation and Trace Elements of Garnet in the Skarn Zone from the Xinqiao Cu-S-Fe-Au Deposit, Tongling Ore District, Anhui Province, Eastern China. Lithos, 302-303: 467-479. https://doi.org/10.1016/j.lithos.2018.01.023 doi:  10.1016/j.lithos.2018.01.023
    Xu, Y. G., Wei, X., Luo, Z. Y., et al., 2014. The Early Permian Tarim Large Igneous Province: Main Characteristics and a Plume Incubation Model. Lithos, 204: 20-35. https://doi.org/10.1016/j.lithos.2014.02.015 doi:  10.1016/j.lithos.2014.02.015
    Yang, S. F., Chen, H. L., Li, Z. L., et al., 2013. Early Permian Tarim Large Igneous Province in Northwest China. Science China Earth Sciences, 56(12): 2015-2026. https://doi.org/10.1007/s11430-013-4653-y doi:  10.1007/s11430-013-4653-y
    Yang, Z. Y., Luo, P., Liu, B., et al., 2019. Depositional Characteristics of Early Cambrian Hydrothermal Fluid: A Case Study of Siliceous Rocks from Yurtus Formation in Aksu Area of Tarim Basin, Northwest China. Earth Science, 44(11): 3845-3870 (in Chinese with English Abstract) http://en.cnki.com.cn/Article_en/CJFDTotal-DQKX201911022.htm
    Yu, J. C., Mo, X. X., Dong, G. C., et al., 2011. Felsic Volcanic Rocks from Northern Tarim, NW China: Zircon U-Pb Dating and Geochemical Characteristics. Acta Petrologica Sinia, 27(7): 2184-2194. https://doi.org/10.1016/j.sedgeo.2011.06.007 doi:  10.1016/j.sedgeo.2011.06.007
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Hisingerite in Trachydacite from Tarim: Implications for Voluminous Felsic Rocks in Transitional Large Igneous Province

doi: 10.1007/s12583-020-1330-x

Abstract: Unlike the typical large igneous provinces (LIPs) that are dominated by mafic-ultramafic rocks,the Tarim large igneous province (TLIP) is characterized by a high proportion of felsic rocks,based on which the TLIP is classified as a transitional LIP. In this study,we focus on the trachydacite from the TLIP in which we report the characteristics of hisingerite employing a variety of techniques such as EMPA,LA-ICPMS,CCD single crystal diffraction,and bulk-rock oxygen isotopes. The hisingerite in this rock is associated with plagioclase,amphibole,apatite and ilmenite. These minerals occur as aggregates of fine curled fibers in micron-scale and display heavy rare earth elements (HREE) enriched signature with significant negative Eu anomalies. In the primitive mantle-normalized trace element spider diagrams,they show pronounced Th and U spikes and Nb,Zr,Hf troughs. Petrological observation and mineralogical study reveal a closely genetic relationship between hisingerite and amphibole,indicating that the hisingerite might have been derived from the breakdown of amphibole during the magma ascent. The formation of hisingerite requires excess water from the surrounding melts,suggesting a hydrous parental magma. The hisingerite and amphibole assign a hydrous crustal source for the rock,and extensive crustal melting accounts for the voluminous felsic rocks in the TLIP.

Mingde Lang, Zhiguo Cheng, Zhaochong Zhang, Fangyue Wang, Qian Mao, M. Santosh. Hisingerite in Trachydacite from Tarim: Implications for Voluminous Felsic Rocks in Transitional Large Igneous Province. Journal of Earth Science, 2020, 31(5): 875-883. doi: 10.1007/s12583-020-1330-x
Citation: Mingde Lang, Zhiguo Cheng, Zhaochong Zhang, Fangyue Wang, Qian Mao, M. Santosh. Hisingerite in Trachydacite from Tarim: Implications for Voluminous Felsic Rocks in Transitional Large Igneous Province. Journal of Earth Science, 2020, 31(5): 875-883. doi: 10.1007/s12583-020-1330-x
  • Large igneous provinces (LIPs) are characterized by the massive eruption of basaltic rocks (area > 105 km2, volume > 105 km3) within a short period of time (1-5 Ma; Bryan and Ernst, 2008). Although diverse models were proposed for the origin of these rocks such as strong convection at plate edges (Boutilier and Keen, 1999), fertilized mantle (Sobolev et al., 2007) and asteroid impact (Jone, 2005), the origin of LIPs are commonly attributed to thermally buoyant, deep-sourced mantle plume (Putirka, 2016; Herzberg and Gazel, 2009). Unlike the typical LIPs (e.g., Deccan, Emeishan and Siberian LIP) that are dominated by the mafic-ultramafic rocks, the Tarim large igneous province (TLIP) is characterized by a high proportion of felsic rocks with 265 000 km2 basaltic rocks and 48 000 km2 felsic rocks. Previous studies suggested that crustal anataxis, assimilation and fractional crystallization (AFC) were responsible for the generation of the felsic rocks (Liu H Q et al., 2019a, 2014; Tian et al., 2010). However, these processes could not explain the occurrence of a high proportion of felsic rocks in the TLIP as compared with a minor volume (< 10%) in the other mafic LIPs (Bryan, 2007; Bryan et al., 2002). Bryan et al. (2002) proposed that the properties of the crust might play a crucial role in the production of large volume of felsic rocks, particularly hydrous crust that would readily melt as against a refractory dry crust, and the low proportion of the felsic rocks in mafic LIPs is ascribed to the anhydrous crust. However, there is still no robust evidence for hydrous felsic rocks in LIPs due to the highly evolved nature and anhydrous mineralogy (Pankhurst et al., 2011).

    Our recent studies recognized the occurrence of hisingerite, a hydrous mineral, in the trachydacite from Northern Tarim depression (NTU) in the TLIP. We report results from detailed mineralogical and oxygen isotopic study on the trachydacite, and our results provide insights into the role of hydrous crustal anatexis in the generation of felsic rocks in LIPs.

  • Located in the northwestern part of China, the Tarim Craton (TC) is surrounded by the Tianshan orogenic belt to the north and the Kunlun-Altun orogenic belt to the south. Together with the North China and Yangtze cratons, the TC constitutes the main tectonic architecture of China. The TC is dominantly

    composed of a Precambrian basement and thick Phanerozoic cover. The Precambrian basement mainly consists of Paleoproterozoic and Mesoproterozoic metamorphic rocks, with minor Neoarchean to Early Paleoproterozoic tonalite-trondhjemite-granodiorite suite (Ngia et al., 2019; Yang et al., 2019; Stern et al., 2018; Tang et al., 2014; Lin et al., 2012; Long et al., 2010; Hu et al., 2000). The Phanerozoic cover is composed of Ordovician to Neogene strata. Cenozoic India-Eurasia collision induced large-scale folds and faults with several E-W trending uplifts and depressions within the TC called as Kuche depression (KD), NTU, Northern Tarim depression (NTD), Central Tarim uplift (CTU) and Southwestern depression (SWD) from north to south (Fig. 1; Tian et al., 2010).

    Figure 1.  (a) Location of TC together with North China Craton and Yangtze craton; (b) geological map of the TLIP and where HT1 were located (Liu et al., 2014; Xu et al., 2014; Pan et al., 2013); (c) litholo-stratigraphic sections of drill-hole HT1. The red star represents the location of the samples in this study.

    The TLIP was developed within the Permian strata. Drill-hole data and seismic profiles recognized ~265 000 km2 mafic and 48 000 km2 felsic volcanic rocks (Fig. 1; Liu et al., 2014; Xu et al., 2014; Pan et al., 2013). Compared to the other typical large igneous provinces of the world, the TLIP is characterized by a relatively long duration, complex lithology, voluminous ferrobasalts and also the presence of bimodal volcanic rocks (Cheng et al., 2018; Xu et al., 2014; Yang et al., 2014). Felsic rocks of the TLIP mainly occur in the NTU, and are composed of rhyolite, trachydacite, andesite, dacite and ignimbrite. Previous zircon geochronological studies revealed that the felsic magmatism had a long duration from 291-272 Ma (Shangguan et al., 2016; Liu et al., 2014; Yu et al., 2011; Tian et al., 2010). Based on the geochemical composition, the felsic rocks in TLIP can be classified as two groups: Group 1 with crust-like signatures and Group 2 with mantle-like features, which were attributed to the crustal anatexis and AFC process, respectively (Liu H Q et al., 2019, 2014; Liu and Xu, 2019; He et al., 2018; Tian et al., 2010). The trachydacite of Group 1 in this study was taken from the drill-hole of HT1 with a depth of 4 844-4 849 m (Table 1), which is located in NTU (Fig. 1b). Based on the log records, the Permian volcanic sequence overlie Carboniferous mudstone and are covered by Triassic sandstone. The volcanic rocks are bimodal and composed of trachydacite (4 844-4 970 m) and basanite (4 970-5 004 m) (Fig. 1c).

    Borehole Sample Hight (m) Rock type Rock texture Mineral (%)
    Ph Kfs Q Pl Hgt Ilm Am
    HT1 HT1-7 4 844.39 Trachydacite Porphyritic 15 40 25 33 - 2 -
    HT1 HT1-14 4 845.37 Trachydacite Porphyritic 17 35 26 35 - 2 4
    HT1 HT1-15 4 845.45 Trachydacite Porphyritic 17 35 26 35 - 2 4
    HT1 HT1-19 4 846.21 Trachydacite Porphyritic 15 40 26 30 - 2 2
    HT1 HT1-22 4 846.35 Trachydacite Porphyritic 20 33 25 35 - 2 5
    HT1 HT1-29 4 847.47 Trachydacite Porphyritic 19 38 20 35 2 2 3
    HT1 HT1-31 4 847.75 Trachydacite Porphyritic 18 33 25 35 3 2 2
    HT1 HT1-33 4 848.03 Trachydacite Porphyritic 20 30 25 35 5 2 3
    Latitude and longitude of Borehole HT1 is X=4569068, Y=15231951. Am. Amphibole; Pl. plagioclase; Q. quartz; Kfs. K-feldspar; Ilm. ilmenite; Hgt. hisingerite; Ph. phenocrysts.

    Table 1.  Locations and detailed sample descriptions of the trachydacite in TLIP

  • The trachydacite displays porphyritic texture with typically 10% to 20% phenocrysts comprising 30%-35% alkali-feldspar, 20%-30% plagioclase, 25%-30% quartz, 2%-5% hisingerite, 2%-5% amphibole and 2%-3% ilmenite (Fig. 2a). Among these, some of the alkali-feldspar, quartz and plagioclase phenocrysts are present as megacrysts. The diameter of alkali-feldspar ranges from 0.3 mm×0.4 mm to 1 mm×2 mm for phenocrysts and from 2 mm×3 mm to 3 mm×5 mm for megacrysts. They commonly occur as subhedral-euhedral tabular crystals. Carlsbad twin crystals are well developed in some alkali-feldspar grains. The granular quartz with erosion texture ranges in size from 0.4 mm×0.3 mm to 4 mm×4.5 mm (Fig. 2b). BSE images reveal several types of melt inclusions (partly or completely crystalline) in quartz, which are 50 μm×60 μm to 80 μm×100 μm across and composed of hisingerite+apatite+ilmenite+melt (Fig. 2c) and calcite +allanite+apatite+alkali-feldspar (Fig. 2d). Plagioclase occurs as subhedral to euhedral tabular crystals and the size is from 0.5 mm×1 mm to 1 mm×2 mm. Hisingerite is prismatic with cracks, subhedral to euhedral, and is generally associated with plagioclase, amphibole, apatite and ilmenite (Figs. 2e, 2g). Some hisingerite contains apatite with zoned textures, and diameter ranging from 0.7 mm×0.8 mm to 1 mm×1.5 mm. Ilmenite shows a size range of 0.1 mm×0.1 mm to 0.4 mm×0.5 mm in diameter. Most of amphibole grains are surrounded by irregular-shaped opaque minerals and the grains size varies from 0.4 mm×0.4 mm to 2 mm×4 mm (Fig. 2f). Occasionally, amphibole is associated with apatite. The groundmass is cryptocrystalline and dominated by the crystallite of alkali-feldspar, quartz and plagioclase.

    Figure 2.  Photomicrographs and BSE images of trachydacite. (a) Trachydacite displaying porphyritic texture with phenocrysts of alkali-feldspar, quartz and plagioclase, crossed-porlarized light; (b) quartz occurring as rounded grain, plane-polarized light; (c) BSE image showing melt inclusion consisting of ilmenite, hisingerite and apatite, the host mineral is quartz of Fig. 2b; (d) BSE image showing melt inclusion consisting of calcite+allanite+apatite+ilmenite+melt. The host mineral is quartz of Fig. 2b; (e) prismatic hisingerite with cracks, subhedral to euhedral, plane-polarized light; (f) amphibole associated with the apatite, and are surrounded by irregular-shaped opaque minerals, plane-polarized light; (g) hisingerite closely related to plagioclase, crossed-porlarized light; (h) BSE image showing the sharp contact between the amphibole and hisingerite; (i) BSE image revealing compositional variation in fibrous micron-scale of the hisingerite. Am. Amphibole; Pl. plagioclase; Q. quartz; Kfs. K-feldspar; Ilm. ilmenite; Hgt. hisingerite; Ap. apatite; Cal. calcite; Aln. allanite.

  • The electron microprobe analyses (EMPA) was conducted on polished sections using JXA-8230 electron microprobes and a CAMECA SXFiveFE electron microprobe. The JXA-8230 is housed at the Institute of Mineral Resources, Chinese Academy of Geological Sciences, and State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing, respectively. The CAMECA SXFiveFE electron microprobe is at the State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, respectively. For JXA-8230, the analyses were performed with 15 kv acceleration voltage, 20 nA beam current and 1-5 μm beam width using wavelength dispersive technique. For CAMECA SXFiveFE, quantitative analysis was performed under 15 kV, 20 nA and a defocused beam (dia.5 micron). The crystal TAP (for Si, Al, Mg, Na), large crystal LPET (K, Ca, Ti, Cl), LLIF (Cr, Mn, Fe, Ni) and LPCO (F) were adopted in four WDS, with peak counting time of 10-30 s. Calibration standards include natural minerals and synthetic oxides. Matrix corrections were done with X-PHI model. The detection limit for F is about 800 ppm, for Na, Mg, Al, Si, K, Ca, Ti and Cl less than 100 ppm, for Cr, Mn, Fe and Ni less than 200 ppm.

  • Trace elements in hisingerite were measured by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) at the National Research Centre for Geoanalysis, Beijing. The equipment is an Element 2 Plasma Mass Spectrometer (Thermoscientific, Germany) with a UP 213 laser ablation system (New Wave Research, USA). We adopted a beam diameter of 30 μm, at 10 Hz with a pulse energy of 2 mJ per pulse. A total of 43 ms dwell time was used and ion signals were collected over a period of 70 s. Calibration was made by NIST 612 (synthetic silicate melt glass). Standards were run for every 7 spots. The data were calibrated by the ICPMSdataCal program (Liu et al., 2010). It is worth to note that the analysis spots here were almost located at the cores of hisingerite.

    Element mapping of hisingerite was conducted at the Ore Deposit and Exploration Centre (ODEC), School of Resources and Environmental Engineering, Hefei University of Technology, using a laser ablation system (PhotonMachines Analyte HE with 193-nm ArF Excimer), coupled to a quadrupole-based ICP-MS (Agilent 7900). Detailed description of procedure was published by Wang et al. (2017). The element maps were generated via ablating sets of parallel line rasters in a grid across the sample. A 15 μm beam size and 15 μm/s scan speed was employed in our study. GSD-1G is standard material for data calibration. Data were compiled into 2-D images by the LIMS program.

  • Whole-rock oxygen isotopes were analyzed at the Beijing Createch Testing Technology Company by the standard BrF5 method. A few micrograms powder of samples was put into a nickel reaction tube, which then was placed in the metal vacuum and evacuated until to 10-3 Pa. The samples reacted with BrF5 at 500-680 oC for about 14 h, producing O2, SiF4 and BrF3. SiF4 and BrF3 were removed by a freezing method, and then O2 was converted to CO2 in a graphite reactor at 700 oC with the presence of Pt catalyst. The CO2 was collected and analyzed using mass spectrometer MAT-253. The oxygen isotope ratios were converted to values relative to SMOW (Standard Mean Ocean Water). Two Chinese national quartz standards (GBW04409 and GBW04410) were adopted to monitor the accuracy, and the analytical precision is better than ±0.2‰.

  • Amphibole is the dominant water-rich mineral in trachydacite from the TLIP. As shown in Table 2, the mineral contains 42.04 wt.%-44.71 wt.% SiO2, and 21.69 wt.%-22.98 wt.% FeO, 10.12 wt.%-11.41 wt.% CaO, 7.27 wt.%-8.55 wt% MgO and 5.66 wt.%-6.52 wt.% Al2O3, with minor TiO2 (0.67 wt.%-1.5 wt%), K2O (0.65 wt.%-1.57 wt.%) and Na2O (1.79 wt.%-2.01 wt.%; Table 2). The Mg# [atomic Mg/(Mg+Fe2+) ranges from 0.57 to 0.69. According to the nomenclature of Leake et al. (1997), the amphiboles in TLIP are plotted into the field of edenitic amphiboles (Fig. 3).

    Samples 1-32 1-32 1-32 1-32 1-32-2 1-32-2 1-32-2 1-32-2 1-33-2 1-33-3 1-33-2 1-33-3
    SiO2 43.49 43.65 44.11 43.28 43.30 44.71 43.68 43.48 43.66 44.44 42.04 42.80
    TiO2 1.27 1.41 1.10 1.47 0.67 1.22 1.41 1.39 1.50 1.39 1.50 1.39
    Al2O3 6.06 6.27 5.66 6.37 5.76 6.23 6.30 6.22 6.51 6.25 6.52 6.26
    FeO 21.83 21.89 22.98 22.37 22.23 22.44 22.01 22.00 22.56 22.16 22.08 21.69
    MnO 0.28 0.29 0.31 0.26 0.28 0.28 0.27 0.31 0.26 0.26 0.26 0.26
    MgO 8.36 8.29 8.29 8.05 8.24 8.55 8.43 8.50 7.27 7.91 7.28 7.91
    CaO 11.17 11.25 10.12 11.30 11.06 11.35 11.29 11.33 11.41 11.15 11.41 11.15
    Na2O 1.85 1.99 1.79 1.98 1.91 1.79 2.00 2.01 1.86 1.88 1.86 1.88
    K2O 1.45 1.43 1.27 0.71 1.31 1.47 0.65 1.40 1.57 1.44 1.57 1.43
    F 2.05 2.61 2.44 2.65 2.39 2.60 2.37 2.65 2.09 2.59 2.09 2.59
    Cl 0.44 0.45 0.33 0.46 0.40 0.48 0.43 0.40 0.54 0.47 0.54 0.47
    Si 6.72 6.66 6.80 6.64 6.75 6.70 6.68 6.63 6.70 6.74 6.61 6.65
    Al 1.10 1.13 1.03 1.15 1.06 1.10 1.14 1.12 1.18 1.12 1.21 1.15
    Al 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    Ti 0.15 0.16 0.13 0.17 0.08 0.14 0.16 0.16 0.17 0.16 0.18 0.16
    Fe3+ 0.56 0.64 0.68 0.72 0.58 0.67 0.68 0.60 0.61 0.72 0.55 0.66
    Fe2+ 2.26 2.16 2.28 2.15 2.32 2.15 2.14 2.20 2.28 2.09 2.36 2.16
    Mn 0.04 0.04 0.04 0.03 0.04 0.04 0.04 0.04 0.03 0.03 0.03 0.03
    Mg 1.93 1.88 1.90 1.84 1.92 1.91 1.92 1.93 1.66 1.79 1.71 1.83
    Ca 1.85 1.84 1.67 1.86 1.85 1.82 1.85 1.85 1.88 1.81 1.92 1.85
    Na 0.55 0.59 0.54 0.59 0.58 0.52 0.59 0.59 0.55 0.55 0.57 0.57
    K 0.29 0.28 0.25 0.14 0.26 0.28 0.13 0.27 0.31 0.28 0.31 0.28

    Table 2.  EMPA data of amphibole (wt.%) and cations calculated by EMPA data

    Figure 3.  The classification diagram of amphibole (after Leake et al., 1997).

  • Hisingerite contains 30.77 wt.%-45.96 wt.% SiO2, and 30.49 wt.%-39.96 wt.% FeO, 3.26 wt.%-8.87 wt.% Al2O3 and 1.79 wt.%-5.91 wt.% MgO, with minor CaO (0.32 wt.%-1.83 wt.%), MnO (0.17 wt.%-1.07 wt.%) and Na2O (0.05 wt.%-1.40 wt.%; Table S1). In addition, the Cl shows moderate abundance of up to 1.29 wt.%. Two EMPA profiles reveal oscillatory zones. The total rare earth elements (REEs) range from 109 ppm to 323 ppm, with extremely low Eu abundance (0-0.5 ppm; Table S2). The chondrite-normalized REE patterns display heavy rare earth element (HREE) enrichment with significant negative Eu anomalies (Fig. 4a). In the primitive mantle-normalized trace element spider diagrams, the hisingerite is characterized by pronounced Th and U spikes and Nb, Zr, Hf troughs (Fig. 4b). As shown in Fig. 5, element mapping reveals clear zoning for hisingerite, with increasing Si, Mg, Na, Ca, Al, Ce, Pr, Nd, Rb, Sr and decreasing in Fe, Mn, V, Pb, Nb, Er, Dy, Yb, Lu, from core to rim.

    Figure 4.  (a) Chondrite-normalized REE patterns and (b) primitive mantle-normalized trace element spider diagrams of hisingerite. Primitive mantle and chondrite values are from McDonough and Sun (1995) and Sun and McDonough (1989), respectively.

    Figure 5.  Element mapping by LA-ICP-MS which reveals distinct compositional difference between the core and rim of hisingerite from Tarim. The compositional variation within the micron-scale fibrous hisingerite is also revealed.

  • The EMPA data of apatite are given in Table 3. Apatite in the trachydacite is F-rich with F contents ranging from 3.07 wt.% to 6.55 wt.%, whereas P2O5 and CaO contents vary from 39.41 wt.% to 42.81 wt.% and 50.66 wt.% to 54.61 wt.%, respectively. The apatite enclosed by hisingerite is also zoned as revealed by BSE images, and the composition ranges from 3.13 wt.%, 3.41 wt.%, 3.73 wt.% to 3.37 wt.% for F, 54.56 wt.%, 50.98 wt.%, 53.3 wt.% 3 to 53.51 wt.% for CaO and 42.92 wt.%, 43.81 wt.%, 42.58 wt.% to 42.80 wt.% for P2O5, from core to rim.

    Comment SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 F Total
    HT1-29-6 0.24 0.16 0.00 0.43 0.04 0.03 54.04 0.09 0.01 41.26 3.43 98.34
    HT1-29-7 0.14 0.00 0.01 0.34 0.02 0.01 53.27 0.07 0.00 40.96 4.67 97.59
    HT1-29-8 0.21 0.04 0.01 0.25 0.03 0.04 54.61 0.08 0.00 41.16 3.23 98.33
    HT1-29-11 1.21 0.03 0.00 0.27 0.05 0.00 52.25 0.02 0.00 41.45 3.73 97.51
    HT1-31-3 0.10 0.00 0.00 0.30 0.06 0.03 53.11 0.07 0.00 39.41 5.35 96.23
    HT1-25-6 0.20 0.00 0.00 0.18 0.07 0.03 54.12 0.05 0.02 42.81 3.57 99.60
    HT1-25-2 0.43 0.01 0.03 0.24 0.07 0.02 53.48 0.11 0.00 42.36 3.07 98.58
    HT1-17-8 0.28 0.00 0.01 0.33 0.01 0.03 54.04 0.08 0.01 42.45 4.17 99.69
    HT1-13-5 0.59 0.00 0.01 0.21 0.06 0.02 52.46 0.05 0.00 42.47 4.23 98.36
    HT1-32-1 0.64 0.11 0.01 0.57 0.03 0.00 52.29 0.11 0.01 40.83 4.59 99.23
    HT1-32-2 0.26 0.00 0.00 0.51 0.01 0.04 52.12 0.09 0.01 41.32 6.26 100.60
    HT1-32-3 0.91 0.00 0.01 0.70 0.00 0.04 50.66 0.09 0.01 40.18 6.55 99.20
    HT1-17 EMPA profile from core to rim
    HT1-17-3 0.18 0.06 0.00 0.20 0.09 0.01 54.56 0.09 0.00 42.92 3.13 99.99
    HT1-17-4 1.74 0.00 0.02 0.26 0.01 0.02 50.98 0.00 0.01 43.81 3.41 98.86
    HT1-17-5 0.64 0.11 0.03 0.28 0.00 0.02 53.33 0.04 0.00 42.58 3.73 99.20
    HT1-17-6 0.90 0.06 0.01 0.22 0.00 0.02 53.51 0.02 0.00 42.80 3.37 99.54

    Table 3.  Major elements (wt.%) of the apatite in the trachydacite in TLIP analyzed by EMPA

  • All the Fe-Ti oxides in trachydacite are ilmenite and contains 51.70 wt.%-52.94 wt.% TiO2 and 45.32 wt.%-46.06 wt.% FeO with minor MgO (0.39 wt.%-0.53 wt.%) and V2O3 (0.55 wt.%-0.61 wt.%; Table 4). The ilmenite enveloped by the hisingerite contains 47.91 wt.% TiO2 and 44.12 wt.% FeO. No magnetite has been identified in the trachydacite.

    Comment FeO TiO2 SiO2 Al2O3 MgO MnO V2O3 Cr2O3 NiO Total
    HT1-13-5-1 45.32 52.37 0.00 0.01 0.52 0.62 0.61 0.06 0.04 99.54
    HT1-32-1-3 46.06 51.70 0.06 0.06 0.39 0.61 0.55 0.06 0.00 99.60
    HT1-29-11-1 45.85 52.94 0.02 0.02 0.53 0.48 0.58 0.02 0.00 100.49
    HT1-27 inclusion 44.12 47.91 0.11 0.05 0.37 0.54

    Table 4.  Major elements (wt.%) of the Fe-Ti oxides in the trachydacite and rhyolite in TLIP

  • The bulk-rock oxygen isotope data are listed in Table 5, and the results yield δ18OV-SMOW values of 11.18‰ to 13.55‰ for the trachydacite.

    Sample δ18OV-SMOW Sample δ18OV-SMOW
    HT1-7 12.39 HT1-26 12.47
    HT1-10 13.55 HT1-29 11.33
    HT1-13 13.06 HT1-31 11.80
    HT1-14 11.32 HT1-32 12.33
    HT1-15 11.18 HT1-33 11.70
    HT1-17 13.02

    Table 5.  Bulk-rock oxygen isotopic compositions of thetrachydacite in TLIP

  • Hisingerite is a hydrous iron silicate with variable compositions (Kohyama and Sudo, 1975), and has been reported from a variety of occurrences, including sulphide ore deposits such as copper, iron, lead, zinc and manganese (Eggleton and Tilley, 1998; Shayan, 1984; Whelan and Goldich, 1961). They commonly occur as aggregates of fine curled fibers with an amorphous to poorly crystalline state (Eggleton and Tilley, 1998; Whelan and Goldich, 1961). Unlike previously reports, the hisingerite grains in the Tarim trachydacite exhibit subhedral to euhedral prismatic crystal morphology, and are closely associated with plagioclase, ilmenite and apatite. The EMPA data reveal clear oscillatory zones in the mineral (Fig. 6). However, LA-ICP-MS elemental mapping does not bring out the oscillatory zones, although distinct compositional difference is between the cores and rims, suggesting reaction between the mineral and surrounding melts (Fig. 5). Moreover, within the grain, elemental mapping could reveal the compositional variation as fibrous in micron-scale, which is also observed under the BSE image in Fig. 2i. Therefore, although the hisingerite occurs as subhedral to euhedral prismatic grains, they are actually aggregates of micron-scale curled fibers.

    Figure 6.  Two EMPA profiles of hisingerite which reveal oscillatory zones for the hisingerite, the position of arrows A to B in (b)-(c) are shown in (a) while the the position of arrows A to B in (e)-(f) are shown in (d).

  • Hisingerite has long been regarded as a secondary mineral produced by weathering of ferromagnesian minerals such as olivine, pyroxene, garnet and iron-amphiboles or a product of late-stage deuteric or hydrothermal alteration (Eggleton and Tilley, 1998; Whelan and Goldich, 1961). The hisingerite in the trachydacite is closely associated with amphiboles, together with plagioclase+apatite+ilmenite (Figs. 2e, 2g). Moreover, the amphibole in TLIP trachydacite is also ferroedenite in composition as shown in Fig. 3, which belongs to the ferrotschermakite group according to the classification of Leake et al. (1997), indicating that the hisingerite might have originated from the amphibole. Our observations do not favor the origin of this mineral in our rocks by weathering or through hydrothermal alteration. Firstly, the samples studied are fresh and also the associated minerals such as plagioclase are remarkably fresh with no alteration. Secondly, the hisingerite has a sharp contact with the amphibole as revealed by BSE images instead of any metasomatic textures or secondary alteration features (Fig. 2h). Thirdly, hisingerite is also recognized as inclusions in quartz and plagioclase (Fig. 2c), where the host minerals shielded these grains from hydrothermal alteration or weathering.

    We therefore infer that the hisingerite was derived from amphibole decomposition. During magma ascent and decrease in pressure, the amphibole became unstable and broke down, leading to the formation of hisingerite. This assumption is consistent with the close petrogenetic relationship between hisingerite and amphibole, where the hisingerite occurs around amphibole grains as rims (Fig. 2f). Clearly, the transformation from amphibole to hisingerite requires excess water from the surrounding melts, which indicates a hydrous parental magma for the trachydacite. The chemical interaction (e.g., diffusion metasomatism) between the hydrous melts and amphibole might be responsible for the compositional change such as the gain in Fe and depletion of Mg, Ca, Na and K, and also the zones as revealed by the EMPA profiles and LA-ICP-MS imaging (Xiao et al., 2018; Gaspar et al., 2008; McIntire, 1963).

  • The felsic rocks in LIPs were traditionally regarded as "A-type granitoids" characterized by anhydrous minerals and high temperature (Pankhurst et al., 2011; Ayalew and Gibson, 2009; Turner and Rushmer, 2009), and they show relatively in minor proportion compared to the mafic rocks (< 10%). This scenario has been attributed to the poor preservation due to the significant denudation following kilometer-scale uplift in other LIPs, as the felsic rocks tend to occur in the middle and upper parts of the volcanic piles (Bryan et al., 2002). It has also been assumed that the viscosity barrier may prevent the ascent of felsic magmas and that the formation of rhyolite is likely to be inhibited by the basaltic component (Mahoney et al., 2008; White, 1992). This assumption was challenged by the occurrence of voluminous quartz latites (eruptive volumes of > 8 000 km3) in the Paraná-Etendeka LIP that have low magma viscosities as indicated by the spatter and globule textures (Bryan et al., 2002; Milner et al., 1995, 1992). Moreover, geochronological data and stratigraphic information from some of the LIPs illustrate that felsic magmas could also precede (e.g., Ferrar, North Atlantic Igneous Province, Yellowstone) or be coeval (e.g., Paraná-Etendeka, Tarim) with the peak of flood basalts (Xu et al., 2014; Meyer et al., 2009; Bryan et al., 2002; Ewart et al., 1998).

    As the silicic LIPs (SLIPs) are generally restricted to the margin of cratons, Bryan et al. (2002) proposed that hydrous crust may play an important role in the formation of the felsic rocks in SLIP. The hydrous crust was suggested to be formed by ancient subduction events. Water is critical for partial melting process, which makes the crust more fusible producing large volume felsic rocks. In crustal melting, the solidus curve could be significantly affected by increasing H2O contents. Moreover, phenocrysts of the felsic rocks in SLIP are dominated by plagioclase and quartz with minor mafic minerals such as pyroxene and amphibole, but very few alkaline feldspar. Compared to the SLIP, the felsic rocks in the mafic LIPs are characterized by anhydrous minerals (e.g., alkaline feldspar and quartz), indicating the role of anhydrous melts (Pankhurst et al., 2011; Ayalew and Gibson, 2009; Turner and Rushmer, 2009). Oxygen isotope is an efficient tool to trace the origin of the felsic rocks. Previous studies reveal that the normal mantle (δ18OV-SMOW=5.7‰±0.3‰) exhibit distinct isotopic compositions from the crustal rocks with much higher δ18OV-SMOW values (James, 1981). In this study, oxygen isotopic compositions with δ18OV-SMOW values of 11.18‰ to 13.55‰ suggest a crust-dominated source for the Tarim trachydacite and they should belong to Group 1 felsic rocks in TLIP, rather than derived from the basaltic rocks by extensive fractional crystallization. The occurrence and nature of hisingerite and amphibole in the trachydacite indicate that the parental magma was hydrous. As the trachydacite is less differentiated and close to the primary magma, the hydrous character is expected to reflect the water-enriched nature of the source region. The mineralogy of the trachydacite from TLIP is between the silicic LIPs and mafic LIPs, with the presence of the alkali-feldspar, plagioclase, quartz and also the amphibole. Moreover, the high proportion of the felsic rocks in TLIP also suggests that the water contents of the felsic rocks were between that of silicic and mafic LIPs. Our findings thus provided important implications that hydrous crustal melting contributed to the voluminous felsic rocks in the TLIP.

  • Based in integrated petrological, mineral chemical and isotope data, we show that the hisingerite in trachydacite from the Tarim large igneous province was derived from amphibole decomposition, rather than from secondary alteration. The finding of hisingerite and amphibole suggests that the felsic rocks in this LIP were derived from a hydrous source, and that hydrous crustal anataxis might have contributed to the large volume of felsic rocks in the TLIP.

  • We thank Tarim Oil Company for provide the drill core samples of the trachydacite. This work is supported by the National Natural Science Foundation of China (Nos. 41772057, 41702064) and the Fundamental Research Funds for the Central Universities (Nos. 2652018118, PA2018GDQT0020). The final publication is available at Springer via https://doi.org/10.1007/s12583-020-1330-x.

    Electronic Supplementary Materials: Supplementary materials (Tables S1, S2) are available in the online version of this article at https://doi.org/10.1007/s12583-020-1330-x.

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