Lithospheric mantle metasomatized by oceanic crust-derived fluids: Li and Pb isotopic evidence from potassic volcanic rocks in the southern Qiangtang terrane, central Tibet

doi:10.13745/j.esf.sf.2023.2.61

Abstract

Abstract:

Lithium (Li) isotopes show large isotopic fractionation during low-temperature processes and have been widely used to trace crust-mantle interactions. In order to identify the crust-derived components in the lithospheric mantle, this study reports new Li and Pb isotopic data for the Late Eocene (~38 Ma) lithospheric mantle-derived potassic volcanic rocks (trachydacites, rhyolites, etc.) from the southern Qiangtang terrane, central Tibet. The volcanic rocks have homogeneous Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb=18.4979-18.5772; ²⁰⁷Pb/²⁰⁴Pb=15.5940-15.6107; ²⁰⁸Pb/²⁰⁴Pb=38.6710-38.7540) and variable Li isotopic compositions, with δ⁷Li values ranging from 5.67‰ to 10.97‰ (average 8.81‰, n=11), significantly higher compared to fresh mid-ocean ridge basalts (3.4‰±1.4‰) and global subducted sediments (2.42‰±0.18‰ (GLOSS-II)) but similar to that of altered oceanic crust (6‰-14.5‰). Combined with published Sr-Nd isotopes and mixing models for Sr-Nd-Pb-Li isotopes, we suggest that mantle metasomatism occurred in the southern Qiangtang terrane by a crustal component dominated by subducted oceanic crust-derived fluids, but we do not preclude the possible contribution of subducted carbonated melts.

Key words: Li isotopes, lithospheric mantle, potassic volcanic rocks, oceanic crust-derived fluids, southern Qiangtang terrane

CLC Number:

LI Wenqiang, XU Wei, TIAN Shihong. Lithospheric mantle metasomatized by oceanic crust-derived fluids: Li and Pb isotopic evidence from potassic volcanic rocks in the southern Qiangtang terrane, central Tibet[J]. Earth Science Frontiers, 2023, 30(4): 376-388.

Figures/Tables 8

Fig.1 (a) Tectonic framework of the Qinghai-Tibet Plateau, and (b) geological sketch map of the western segment of the southern Qiangtang terrane. Modified after [25].

Fig.2 Photomicrographs of the Mendangle volcanic rocks from the southern Qiangtang terrane

Table 1 Whole rock elemental and Sr -Nd-Pb- Li isotopic data for the Mendangle volcanic rocks from the southern Qiangtang terrane

Fig.3 Geochemical analysis of the Mendangle volcanic rocks from the southern Qiangtang terrane. A modified after [56-57]; b modified after [58]; c, d adapted from [59].

Fig.4 Whole-rock Sr-Nd-Pb-Li isotopic compositions of the Mendangle volcanic rock from the southern Qiangtang terrane. A-c adapted from [13,61⇓-63]; d adapted from [8,10,13].

Fig.5 Geochemical analyses of the Mendangle volcanic rocks and Nadincuo basalts from the southern Qiangtang terrane (d adapted from [45,47,59])

Table 2 End member compositions used in modeling

地质体储层组成	w(Li)/10^-6	δ⁷Li/‰	w(Pb)/10^-6	w(Nd)/10^-6	¹⁴³Nd/¹⁴⁴Nd	²⁰⁷Pb/²⁰⁴Pb	²⁰⁸Pb/²⁰⁴Pb	w(Sr)/10^-6	⁸⁷Sr/⁸⁶Sr
海洋沉积物 (SED)	49^a	-3.0^b	30^d	34^f	0.511 95^f	15.7^b	39.9^c	330^b	0.709 0^b
蚀变洋壳 (AOC)	12^b	12.0^c	1^b	2.2^b	0.513 08^b	15.49^b	38.08^e	120^d	0.705 2^g
地幔(M)	2^b	2.0^b	0.18^b	1.2^b	0.512 88^b	15.53^b	37.75^c	18.2^b	0.702 8^b

Fig.6 Combined M (depleted mantle)-SED (sediment)-AOC (altered oceanic crust) three-component mixing models for Li and Sr-Nd-Pb isotopes

References 79

[1]	BERGER G, SCHOTT J, GUY C. Behavior of Li, Rb and Cs during basalt glass and olivine dissolution and chlorite, smectite and zeolite precipitation from seawater: experimental investigations and modelization between 50 ℃ and 300 ℃[J]. Chemical Geology, 1988, 71(4): 297-312. DOI URL
[2]	SEYFRIED JR W E, CHEN X, CHAN L H. Trace element mobility and lithium isotope exchange during hydrothermal alteration of seafloor weathered basalt: an experimental study at 350 ℃, 500 bars[J]. Geochimica et Cosmochimica Acta, 1998, 62(6): 949-960. DOI URL
[3]	FLESCH G D, ANDERSON JR A R, SVEC H J. A secondary isotopic standard for ⁶Li/⁷Li determinations[J]. International Journal of Mass Spectrometry and Ion Physics, 1973, 12(3): 265-272. DOI URL
[4]	JEFFCOATE A B, ELLIOTT T, THOMAS A, et al. Precise/small sample size determinations of lithium isotopic compositions of geological reference materials and modern seawater by MC-ICP-MS[J]. Geostandards and Geoanalytical Research, 2004, 28(1): 161-172. DOI URL
[5]	TOMASCAK P B, MAGNA T, DOHMEN R. Advances in lithium isotope geochemistry[M]. Cham, Switzerland: Springer International Publishing, 2016.
[6]	PENNISTON-DORLAND S, LIU X M, RUDNICK R L. Lithium isotope geochemistry[J]. Reviews in Mineralogy and Geochemistry, 2017, 82(1): 165-217. DOI URL
[7]	RYAN J G, LANGMUIR C H. The systematics of lithium abundances in young volcanic rocks[J]. Geochimica et Cosmochimica Acta, 1987, 51(6): 1727-1741. DOI URL
[8]	TOMASCAK P B, LANGMUIR C H, LE ROUX P J, et al. Lithium isotopes in global mid-ocean ridge basalts[J]. Geochimica et Cosmochimica Acta, 2008, 72(6): 1626-1637. DOI URL
[9]	CHAN L H, EDMOND J M, THOMPSON G, et al. Lithium isotopic composition of submarine basalts: implications for the lithium cycle in the oceans[J]. Earth and Planetary Science Letters, 1992, 108(1/2/3): 151-160. DOI URL
[10]	CHAN L H, ALT J C, TEAGLE D A H. Lithium and lithium isotope profiles through the upper oceanic crust: a study of seawater-basalt exchange at ODP Sites 504B and 896A[J]. Earth and Planetary Science Letters, 2002, 201(1): 187-201. DOI URL
[11]	CHAN L H, LEEMAN W P, PLANK T. Lithium isotopic composition of marine sediments[J]. Geochemistry, Geophysics, Geosystems, 2006, 7(6): Q06005.
[12]	BOUMAN C, ELLIOTT T, VROON P Z. Lithium inputs to subduction zones[J]. Chemical Geology, 2004, 212(1/2): 59-79. DOI URL
[13]	PLANK T. The chemical composition of subducting sediments[M]// Treatise on geochemistry. Amsterdam: Elsevier, 2014: 607-629.
[14]	AULBACH S, RUDNICK R L. Origins of non-equilibrium lithium isotopic fractionation in xenolithic peridotite minerals: examples from Tanzania[J]. Chemical Geology, 2009, 258(1/2): 17-27. DOI URL
[15]	VLASTÉLIC I, KOGA K, CHAUVEL C, et al. Survival of lithium isotopic heterogeneities in the mantle supported by HIMU-lavas from Rurutu Island, Austral Chain[J]. Earth and Planetary Science Letters, 2009, 286(3/4): 456-466. DOI URL
[16]	ZHANG H F, DELOULE E, TANG Y J, et al. Melt/rock interaction in remains of refertilized Archean lithospheric mantle in Jiaodong Peninsula, North China Craton: Li isotopic evidence[J]. Contributions to Mineralogy and Petrology, 2010, 160(2): 261-277. DOI URL
[17]	TANG M, RUDNICK R L, CHAUVEL C. Sedimentary input to the source of Lesser Antilles lavas: a Li perspective[J]. Geochimica et Cosmochimica Acta, 2014, 144: 43-58. DOI URL
[18]	MARSCHALL H R, VON STRANDMANN P A E P, SEITZ H M, et al. The lithium isotopic composition of orogenic eclogites and deep subducted slabs[J]. Earth and Planetary Science Letters, 2007, 262(3/4): 563-580. DOI URL
[19]	MARSCHALL H R, TANG M. High-temperature processes: is it time for lithium isotopes?[J]. Elements, 2020, 16(4): 247-252. DOI URL
[20]	MORIGUTI T, NAKAMURA E. Across-arc variation of Li isotopes in lavas and implications for crust/mantle recycling at subduction zones[J]. Earth and Planetary Science Letters, 1998, 163(1/2/3/4): 167-174. DOI URL
[21]	BRENS JR R, LIU X M, TURNER S, et al. Lithium isotope variations in Tonga-Kermadec arc-Lau back-arc lavas and Deep Sea Drilling Project (DSDP) Site 204 sediments[J]. Island Arc, 2019, 28(1): e12276.
[22]	HALAMA R, MCDONOUGH W F, RUDNICK R L, et al. Tracking the lithium isotopic evolution of the mantle using carbonatites[J]. Earth and Planetary Science Letters, 2008, 265(3/4): 726-742. DOI URL
[23]	WALKER J A, TEIPEL A P, RYAN J G, et al. Light elements and Li isotopes across the northern portion of the Central American subduction zone[J]. Geochemistry, Geophysics, Geosystems, 2009, 10(6): Q06S16.
[24]	TIAN S H, HOU Z Q, SU A, et al. The anomalous lithium isotopic signature of Himalayan collisional zone carbonatites in western Sichuan, SW China: enriched mantle source and petrogenesis[J]. Geochimica et Cosmochimica Acta, 2015, 159: 42-60. DOI URL
[25]	XU W, ROBERTO F W, TIAN S H, et al. K-rich adakite-like rocks in central Tibet: fractional crystallization of a hydrous, alkaline primitive melt[J]. Geophysical Research Letters, 2023, 50(10): e2022GL099887.
[26]	DING L, KAPP P, YUE Y, et al. Postcollisional calc-alkaline lavas and xenoliths from the southern Qiangtang terrane, central Tibet[J]. Earth and Planetary Science Letters, 2007, 254(1/2): 28-38. DOI URL
[27]	刘建峰, 迟效国, 赵秀羽, 等. 青藏高原北部新生代走构油茶错、纳丁错火山岩年代学、地球化学特征及其构造意义[J]. 岩石学报, 2009, 25(12): 3259-3274.
[28]	GUO Z, WILSON M. Late Oligocene-early Miocene transformation of postcollisional magmatism in Tibet[J]. Geology, 2019, 47(8): 776-780. DOI URL
[29]	QI Y, WANG Q, WEI G J, et al. Late Eocene post-collisional magmatic rocks from the southern Qiangtang terrane record the melting of pre-collisional enriched lithospheric mantle[J]. GSA Bulletin, 2021, 133(11/12): 2612-2624. DOI URL
[30]	YIN A, HARRISON T M. Geologic evolution of the Himalayan-Tibetan orogen[J]. Annual Review of Earth and Planetary Sciences, 2000, 28: 211-280. DOI URL
[31]	ZHAI Q G, ZHANG R Y, JAHN B M, et al. Triassic eclogites from central Qiangtang, northern Tibet, China: petrology, geochronology and metamorphic P-T path[J]. Lithos, 2011, 125(1/2): 173-189. DOI URL
[32]	KAPP P, DECELLES P G. Mesozoic-Cenozoic geological evolution of the Himalayan-Tibetan orogen and working tectonic hypotheses[J]. American Journal of Science, 2019, 319(3): 159-254. DOI URL
[33]	TANG X C, ZHANG K J. Lawsonite- and glaucophane-bearing blueschists from NW Qiangtang, northern Tibet, China: mineralogy, geochemistry, geochronology, and tectonic implications[J]. International Geology Review, 2014, 56(2): 150-166. DOI URL
[34]	DAN W, WANG Q, WHITE W M, et al. Rapid formation of eclogites during a nearly closed ocean: revisiting the Pianshishan eclogite in Qiangtang, central Tibetan Plateau[J]. Chemical Geology, 2018, 477: 112-122. DOI URL
[35]	ZHANG X Z, DONG Y S, WANG Q, et al. Carboniferous and Permian evolutionary records for the Paleo-Tethys Ocean constrained by newly discovered Xiangtaohu ophiolites from central Qiangtang, central Tibet[J]. Tectonics, 2016, 35(7): 1670-1686. DOI URL
[36]	ZHAI Q G, JAHN B M, WANG J, et al. Oldest paleo-Tethyan ophiolitic mélange in the Tibetan Plateau[J]. Geological Society of America Bulletin, 2016, 128(3/4): 355-373. DOI URL
[37]	李才, 程立人, 胡克, 等. 西藏龙木错-双湖古特提斯缝合带研究[M]. 北京: 地质出版社, 1995.
[38]	ZHAI Q G, JAHN B M, WANG J, et al. The Carboniferous ophiolite in the middle of the Qiangtang terrane, northern Tibet: SHRIMP U-Pb dating, geochemical and Sr-Nd-Hf isotopic characteristics[J]. Lithos, 2013, 168/169: 186-199. DOI URL
[39]	KAPP P, YIN A, MANNING C E, et al. Blueschist-bearing metamorphic core complexes in the Qiangtang block reveal deep crustal structure of northern Tibet[J]. Geology, 2000, 28(1): 19-22. DOI URL
[40]	KAPP P, YIN A, MANNING C E, et al. Tectonic evolution of the early Mesozoic blueschist-bearing Qiangtang metamorphic belt, central Tibet[J]. Tectonics, 2003, 22(4): 200TC001383.
[41]	HU P, ZHAI Q, JAHN B, et al. Early Ordovician granites from the South Qiangtang terrane, northern Tibet: implications for the Early Paleozoic tectonic evolution along the Gondwanan proto-Tethyan margin[J]. Lithos, 2015, 220/221/222/223: 318-338.
[42]	DAN W, WANG Q, ZHANG X Z, et al. Early Paleozoic S-type granites as the basement of southern Qiantang terrane, Tibet[J]. Lithos, 2020, 356/357: 105395. DOI URL
[43]	李才, 和钟铧, 李惠民. 青藏高原南羌塘基性岩墙群U-Pb和Sm-Nd同位素定年及构造意义[J]. 中国地质, 2004, 31(4): 384-389.
[44]	KAPP P, YIN A, HARRISON T M, et al. Cretaceous-Tertiary shortening, basin development, and volcanism in central Tibet[J]. Geological Society of America Bulletin, 2005, 117(7/8): 865-878. DOI URL
[45]	LIU D L, HUANG Q S, FAN S Q, et al. Subduction of the Bangong-Nujiang ocean: constraints from granites in the Bangong Co area, Tibet[J]. Geological Journal, 2014, 49(2): 188-206. DOI URL
[46]	LI S M, ZHU D C, WANG Q, et al. Northward subduction of Bangong-Nujiang Tethys: insight from Late Jurassic intrusive rocks from Bangong Tso in western Tibet[J]. Lithos, 2014, 205: 284-297. DOI URL
[47]	LI S M, ZHU D C, WANG Q, et al. Slab-derived adakites and subslab asthenosphere-derived OIB-type rocks at 156 ± 2 Ma from the north of Gerze, central Tibet: records of the Bangong-Nujiang oceanic ridge subduction during the Late Jurassic[J]. Lithos, 2016, 262: 456-469. DOI URL
[48]	HAO L L, WANG Q, WYMAN D A, et al. Underplating of basaltic magmas and crustal growth in a continental arc: evidence from Late Mesozoic intermediate-felsic intrusive rocks in southern Qiangtang, central Tibet[J]. Lithos, 2016, 245: 223-242. DOI URL
[49]	ZENG Y C, XU J F, LI M J, et al. Late Eocene two-pyroxene trachydacites from the southern Qiangtang terrane, central Tibetan Plateau: high-temperature melting of overthickened and dehydrated lower crust[J]. Journal of Petrology, 2022, 63(6): egac049. DOI URL
[50]	WANG B D, CHEN J L, XU J F, et al. Chronology and geochemistry of the Nadingcuo volcanic rocks in the southern Qiangtang region of the Tibetan Plateau: partial melting of remnant ocean crust along the Bangong-Nujiang suture[J]. Acta Geologica Sinica (English Edition), 2010, 84(6): 1461-1473. DOI URL
[51]	TIAN S H, HOU Z Q, MO X X, et al. Lithium isotopic evidence for subduction of the Indian lower crust beneath southern Tibet[J]. Gondwana Research, 2020, 77: 168-183. DOI URL
[52]	田世洪, 胡文洁, 侯增谦, 等. 拉萨地块西段中新世赛利普超钾质火山岩富集地幔源区和岩石成因: Li同位素制约[J]. 矿床地质, 2012, 31(4): 791-812.
[53]	苏嫒娜, 田世洪, 李真真, 等. MC-ICP-MS高精度测定Li同位素分析方法[J]. 地学前缘, 2011, 18(2): 835-836.
[54]	MILLOT R, GUERROT C, VIGIER N. Accurate and high-precision measurement of lithium isotopes in two reference materials by MC-ICP-MS[J]. Geostandards and Geoanalytical Research, 2004, 28(1): 153-159. DOI URL
[55]	TIAN S H, HOU Z Q, SU A N, et al. Separation and precise measurement of lithium isotopes in three reference materials using multi collector-inductively coupled plasma mass spectrometry[J]. Acta Geologica Sinica (English Edition), 2012, 86(5): 1297-1305. DOI URL
[56]	BAS M J L, MAITRE R W L, STRECKEISEN A, et al. A chemical classification of volcanic rocks based on the total alkali-silica diagram[J]. Journal of Petrology, 1986, 27(3): 745-750. DOI URL
[57]	IRVINE T N, BARAGAR W R A. A guide to the chemical classification of the common volcanic rocks[J]. Canadian Journal of Earth Sciences, 1971, 8(5): 523-548. DOI URL
[58]	PECCERILLO A, TAYLOR S R. Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, northern Turkey[J]. Contributions to Mineralogy and Petrology, 1976, 58(1): 63-81. DOI URL
[59]	SUN S S, MCDONOUGH W F. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes[J]. Geological Society, London, Special Publications, 1989, 42(1): 313-345. DOI URL
[60]	PEARCE J. Role of the sub-continental lithosphere in magma genesis at active continental margins[M]// HAWKESWORTH C J, NORRYM J. Continental basalts and mantle xenoliths. Nantwich, UK: Shiva Publishing Ltd, 1983: 230-249.
[61]	MAHONEY J J, FREI R, TEJADA M L G, et al. Tracing the Indian Ocean mantle domain through time: isotopic results from Old West Indian, East Tethyan, and South Pacific seafloor[J]. Journal of Petrology, 1998, 39(7): 1285-1306. DOI URL
[62]	ZHANG S Q, MAHONEY J J, MO X X, et al. Evidence for a widespread Tethyan upper mantle with Indian-ocean-type isotopic characteristics[J]. Journal of Petrology, 2005, 46(4): 829-858. DOI URL
[63]	XU J F, CASTILLO P R. Geochemical and Nd-Pb isotopic characteristics of the Tethyan asthenosphere: implications for the origin of the Indian Ocean mantle domain[J]. Tectonophysics, 2004, 393(1/2/3/4): 9-27. DOI URL
[64]	NESBITT H W, YOUNG G M. Early Proterozoic climates and plate motions inferred from major element chemistry of lutites[J]. Nature, 1982, 299(5885): 715-717. DOI
[65]	TOMASCAK P B, TERA F, HELZ R T, et al. The absence of lithium isotope fractionation during basalt differentiation: new measurements by multicollector sector ICP-MS[J]. Geochimica et Cosmochimica Acta, 1999, 63(6): 907-910. DOI URL
[66]	CHAN L H, FREY F A. Lithium isotope geochemistry of the Hawaiian plume: results from the Hawaii scientific drilling project and Koolau volcano[J]. Geochemistry, Geophysics, Geosystems, 2003, 4(3): 2002GC000365.
[67]	SCHUESSLER J A, SCHOENBERG R, SIGMARSSON O. Iron and lithium isotope systematics of the Hekla volcano, Iceland: evidence for Fe isotope fractionation during magma differentiation[J]. Chemical Geology, 2009, 258(1/2): 78-91. DOI URL
[68]	RICHTER F M, DAVIS A M, DEPAOLO D J, et al. Isotope fractionation by chemical diffusion between molten basalt and rhyolite[J]. Geochimica et Cosmochimica Acta, 2003, 67(20): 3905-3923. DOI URL
[69]	LUNDSTROM C C, CHAUSSIDON M, HSUI A T, et al. Observations of Li isotopic variations in the Trinity ophiolite: evidence for isotopic fractionation by diffusion during mantle melting[J]. Geochimica et Cosmochimica Acta, 2005, 69(3): 735-751. DOI URL
[70]	BECK P, CHAUSSIDON M, BARRAT J A, et al. Diffusion induced Li isotopic fractionation during the cooling of magmatic rocks: the case of pyroxene phenocrysts from nakhlite meteorites[J]. Geochimica et Cosmochimica Acta, 2006, 70(18): 4813-4825. DOI URL
[71]	TENG F Z, MCDONOUGH W F, RUDNICK R L, et al. Diffusion-driven extreme lithium isotopic fractionation in country rocks of the Tin Mountain pegmatite[J]. Earth and Planetary Science Letters, 2006, 243(3/4): 701-710. DOI URL
[72]	ARNAUD N O, VIDAL P, TAPPONNIER P, et al. The high K₂O volcanism of northwestern Tibet: geochemistry and tectonic implications[J]. Earth and Planetary Science Letters, 1992, 111(2/3/4): 351-367. DOI URL
[73]	万红琼, 孙贺, 刘海洋, 等. 俯冲带Li同位素地球化学: 回顾与展望[J]. 地学前缘, 2015, 22(5): 29-43. DOI
[74]	SIMONS K K, HARLOW G E, BRUECKNER H K, et al. Lithium isotopes in Guatemalan and Franciscan HP-LT rocks: insights into the role of sediment-derived fluids during subduction[J]. Geochimica et Cosmochimica Acta, 2010, 74(12): 3621-3641. DOI URL
[75]	LIU H, SUN H, XIAO Y, et al. Lithium isotope systematics of the Sumdo eclogite, Tibet: tracing fluid/rock interaction of subducted low-T altered oceanic crust[J]. Geochimica et Cosmochimica Acta, 2019, 246: 385-405. DOI URL
[76]	LEEMAN W P, TONARINI S, CHAN L H, et al. Boron and lithium isotopic variations in a hot subduction zone: the southern Washington Cascades[J]. Chemical Geology, 2004, 212(1/2): 101-124. DOI URL
[77]	MORIGUTI T, SHIBATA T, NAKAMURA E. Lithium, boron and lead isotope and trace element systematics of Quaternary basaltic volcanic rocks in northeastern Japan: mineralogical controls on slab-derived fluid composition[J]. Chemical Geology, 2004, 212(1/2): 81-100. DOI URL
[78]	TAYLOR R N, NESBITT R W. Isotopic characteristics of subduction fluids in an intra-oceanic setting, Izu-Bonin arc, Japan[J]. Earth and Planetary Science Letters, 1998, 164(1/2): 79-98. DOI URL
[79]	MARSCHALL H R, WANLESS V D, SHIMIZU N, et al. The boron and lithium isotopic composition of mid-ocean ridge basalts and the mantle[J]. Geochimica et Cosmochimica Acta, 2017, 207: 102-138. DOI URL