Partial melting time of the Sulu UHP terrane: Constraints from zircon U-Pb age, trace element and Lu-Hf isotope composition of leucosome in Rongcheng granitic gneiss
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摘要:
威海-荣成地区混合岩化花岗质片麻岩为研究超高压地体折返过程中的部分熔融提供了理想的窗口。本文通过对荣成地区鲍村花岗质片麻岩中浅色条带野外观察、岩相学以及锆石的CL图像、U-Pb定年、微量元素和Lu-Hf同位素的系统研究表明，鲍村花岗质片麻岩中的浅色条带为部分熔融的产物，其主要矿物组成为石英+斜长石+钾长石+黑云母。锆石CL图像显示清楚的核-边结构：继承岩浆核和新生岩浆边。继承核的206Pb/238U协和年龄为620±8~784±7Ma (Mean=701±33Ma)；具有典型的岩浆锆石的微量元素特征，如重稀土(HREE) 和Y富集，强烈的正Ce异常和负Eu异常，以及极低的(Gd/Lu)N和Hf/Y比值；εHf(t=700Ma) 值为-13.0~-8.0 (Mean=-10.9±0.8)，相应的tDM2为2120~2429Ma (Mean=2303±51Ma)。新生边的206Pb/238U协和年龄为211±6~244±5Ma (226±10Ma)；虽然微量元素的整体含量低于继承核，但也具有岩浆锆石的微量元素特征，如稀土元素配分模式显示HREE明显上翘的特征，正Ce异常和负Eu异常，以及极低的(Gd/Lu)N比值；εHf(t=225Ma) 值为-17.3~-14.2 (Mean=-15.2±0.6)，相应的tDM2为2152~2347Ma (Mean=2214±33Ma)。上述特征表明，部分熔融的原岩是由古元古代(2.2~2.3Ga) 的地壳物质在新元古代(701±33Ma) 重熔而成，部分熔融可能发生在超高压地体折返早期的热折返阶段(榴辉岩相-高压麻粒岩相条件下)，时代应为226±10Ma。威海-荣成混合岩化片麻岩内广泛发育的富含钾长石和石英的酸性岩脉(约220~210Ma)，可能为折返晚期的角闪岩相冷凝阶段，部分熔融形成的熔体经历了结晶分异作用的产物。
Abstract:In order to decipher the partial melting time of the Sulu ultrahigh pressure (UHP) terrane during exhumation, we carried out a combined study of zircon internal structure, U-Pb age, trace element and Lu-Hf isotopic compositions coupled with fieldwork on leucosome of the Baocun grantic gneiss in Rongcheng region. Our works suggest that the leucosome, mainly composed of quartz, plagioclase, K-feldspar, and biotite, was the product of partial melting. Zircon from the leucosome display core-rim structure in cathodoluminescence (CL) images: inherited magmatic core and new growth magmatic rim. Most age data of the inherited cores are concordant with apparent 206Pb/238U ages ranging from 620±8Ma to 784±7Ma with a weighted mean age of 701±33Ma. The inherited cores have the characteristics of typical magmatic zircons, e.g., high HREE and Y contents, strong HREE enrichment on chondrite-normalized REE plot, very large positive Ce and negative Eu anomalies, and very low (Gd/Lu)N and Hf/Y ratios. The inherited cores have εHf(t=700Ma) values of -13.0 to -8.0 (mean=-10.9±0.8) and tDM2 of 2120Ma to 2429Ma (mean=2303±51Ma). The new growth rims have concordant 206Pb/238U ages ranging from 211±6Ma to 244±5Ma with a weighted mean age of 226±10Ma. Although the new growth rims are greatly different from the inherited cores in trace element compositions, they still display features of the magmatic zircon, e.g., strong HREE enrichment on chondrite-normalized REE plot, large positive Ce and negative Eu anomalies, and very low (Gd/Lu)N and Hf/Y ratios. The new growth rims have εHf(t=225Ma) values of -17.3 to -14.2 (mean=-15.2±0.6) and tDM2 between 2152Ma and 2347Ma (mean=2214±33Ma). These results suggest that protolith of the leucosome are Mid-Neoproterozoic (701±33Ma) magmatic rocks which were from Paleoproterozoic (2.2~2.3Ga) continental crust. The partial melting is expected under eclogite-facies to granulite-facies conditions during the early stage hot exhumation of the Rongcheng UHP felsic gneisses, and the partial melting time might be 226±10Ma. The K-feldspar-and quartz-rich pegmatitic veins (ca. 220~210Ma) in the Weihai-Rongcheng region might be from fractional crystallization of the partial melts during late stage cool exhumation under amphibolite facies conditions
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Key words:
- Partial melting /
- Granitic gneiss /
- Rongcheng /
- Sulu UHP terrane
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图 1
苏鲁地区地质简图(据Ye et al., 2000b资料修改)
Figure 1.
Geological sketch map of Sulu ultra-high pressure (UHP) metamorphic terrane in eastern China (modified after Ye et al., 2000b)
图 3
鲍村花岗质片麻岩中浅色条带(05BC) 锆石的阴极发光图像(CL) 和部分锆石相应的LA-ICPMS U-Pb定年和Hf同位素结果
Figure 3.
Cathodoluminescence (CL) images of representative zircon grains with 206Pb/238U age (Ma) and εHf(t) values for the leucosome of the Baocun grantic gneiss
图 4
鲍村花岗质片麻岩中浅色条带(05BC) 锆石的206Pb/238U-207Pb/235U年龄关系图解及206Pb/238U年龄加权平均结果
Figure 4.
Zircon U-Pb concordia diagrams for the leucosome layer of the Baocun grantic gneiss The level of uncertainty plotted is 2σ
图 5
鲍村花岗质片麻岩中浅色条带的锆石REE球粒陨石标准化图解
Figure 5.
Chondrite-normalized REE patterns of zircon from the leucosome in Baocun ganitic gneiss
图 6
鲍村花岗质片麻岩中浅色条带(05BC) 的锆石微区(Gd/Lu)N-Eu/Eu* (a)、Y-Eu/Eu* (b) 和Y-Hf/Y (c) 图解
Figure 6.
Selected trace element plots of zircons from the leucosome (005BC) in Baocun ganitic gneiss
图 7
鲍村花岗质片麻岩中浅色条带(05BC) 的锆石微区εHf(t) (a、c) 和tDM2(Ma) (b、d)
Figure 7.
Integration of the εHf(t) value (a, c) and tDM2 age (Ma) (b, d) of zircon from the leucosome in Baocun ganitic gneiss
图 8
鲍村花岗质片麻岩中浅色条带(05BC) 的锆石微区Lu-Hf同位素组成演化图
Figure 8.
Schematic giagram for zircon Lu-Hf isotopic evolution of the leucosome in Baocun ganitic gneiss
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Ames L, Zhou GZ and Xiong BC. 1996. Geochronology and isotopic character of ultrahigh-pressure metamorphism with implications for collision on the Sino- Korean and Yangtze cratons, central China. Tectonics, 15(2): 472-489
Banno S, Enami M, Hirajima T, Ishiwatari A and Wang QC. 2000. Decompression P-T path of coesite eclogite to granulite from Weihai, eastern China. Lithos, 52(1-4): 97-108
Blichert-Toft J, Chauvel C and Albarède F. 1997. Separation of Hf and Lu for high-precision isotope analysis of rock samples by magnetic sector-multiple collector ICP-MS. Contributions to Mineralogy and Petrology, 127(3): 248-260
Chen JF, Xie Z, Li HM, Zhang XD, Zhou TX, Park YS, Ahn KS, Chen DG and Zhang X. 2003. U-Pb zircon ages for a collision-related K-rich complex at Shidao in the Sulu ultrahigh pressure terrane, China. Geochemical Journal, 37(1): 35-46
Cherniak DJ and Watson EB. 2003. Diffusion in zircon. Reviews in Mineralogy and Geochemistry, 53(1): 113-143
Cong BL, Wang QC, Zhai MG et al. 1994. Ultra-high pressure metamorphic rocks in the Dabie-Sulu region, China: Their formation and exhumation. Island Arc, 3(3): 135-150
Cong BL and Wang QC. 1999. The Dabie-Sulu UHP rocks belt: Review and prospect. Chinese Science Bulletin, 44(12): 1074-1086
Guo JH, Chen FK, Zhang XM, Siebel W and Zhai MG. 2005. Evolution of syn- to post-collisional magmatism from north Sulu UHP belt, eastern China: Zircon U-Pb geochronology. Acta Petrologica Sinica, 21(4): 1281-1301 (in Chinese with English abstract)
Hacker B, Ratschbacher L, Webb L, Ireland T, Walker D and Dong SW. 1998. U/Pb zircon ages constrain the architecture of the ultrahigh-pressure Qinling-Dabie Orogen, China. Earth and Planetary Science Letters, 161(1-4): 215-230
Hu ZC, Gao S, Liu YS, Hu SH, Chen HH and Yuan HL. 2008. Signal enhancement in laser ablation ICP-MS by addition of nitrogen in the central channel gas. Journal of Analytical Atomic Spectrometry, 23(8): 1093-1101
Hu ZC, Liu YS, Gao S, Xiao SQ, Zhao LS, Günther D, Li M, Zhang W and Zong KQ. 2012. A 'wire' signal smoothing device for laser ablation inductively coupled plasma mass spectrometry analysis. Spectrochimica Acta Part B: Atomic Spectroscopy, 78: 50-57
Huang J, Zheng YF, Zhao ZF, Wu YB, Zhou JB and Liu XM. 2006. Melting of subducted continent: Element and isotopic evidence for a genetic relationship between Neoproterozoic and Mesozoic granitoids in the Sulu orogen. Chemical Geology, 229(4): 227-256
Li XH, Chen FK, Li CF, Guo JH and Yang YH. 2007. Zircon ages and Hf isotopic composition of gneisses from the Rongcheng ultrahigh-pressure terrain in the Sulu orogenic belt. Acta Petrologica Sinica, 23(2): 351-368 (in Chinese with English abstract)
Liou JG, Ernst WG, Zhang RY, Tsujimori T and Jahn BM. 2009. Ultrahigh-pressure minerals and metamorphic terranes: The view from China. Journal of Asian Earth Sciences, 35 (3-4): 199-231
Liu FL, Xu ZQ and Xue HM. 2004a. Tracing the protolith, UHP metamorphism, and exhumation ages of orthogneiss from the SW Sulu terrane (eastern China): SHRIMP U-Pb dating of mineral inclusion-bearing zircons. Lithos, 78(4): 411-429
Liu FL, Xu ZQ, Liou JG and Song B. 2004b. SHRIMP U-Pb ages of ultrahigh-pressure and retrograde metamorphism of gneisses, south-western Sulu terrane, eastern China. Journal of Metamorphic Geology, 22(4): 315-326
Liu FL, Gerdes A, Zeng LS and Xue HM. 2008. SHRIMP U-Pb dating, trace elements and the Lu-Hf isotope system of coesite-bearing zircon from amphibolite in the SW Sulu UHP terrane, eastern China. Geochimica et Cosmochimica Acta, 72(12): 2973-3000
Liu FL, Xue HM and Liu PH. 2009. Partial melting time of ultrahigh-pressure metamorphic rocks in the Sulu UHP terrane: Constrained by zircon U-Pb ages, trace elements and Lu-Hf isotope compositions of biotite-bearing granite. Acta Petrologica Sinica, 25(5): 1039-1055 (in Chinese with English abstract)
Liu FL, Robinson PT, Gerdes A, Xue HM, Liu PH and Liou JG. 2010a. Zircon U-Pb ages, REE concentrations and Hf isotope compositions of granitic leucosome and pegmatite from the north Sulu UHP terrane in China: Constraints on the timing and nature of partial melting. Lithos, 117(1-4): 247-268
Liu FL, Robinson PT and Liu PH. 2012. Multiple partial melting events in the Sulu UHP terrane: Zircon U-Pb dating of granitic leucosomes within amphibolite and gneiss. Journal of Metamorphic Geology, 30(8): 887-906
Liu YS, Gao S, Hu ZC, Gao CG, Zong KQ and Wang DB. 2010b. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen: U-Pb dating, Hf isotopes and trace elements in zircons from mantle xenoliths. Journal of Petrology, 51(1-2): 537-571
Ludwig KR. 2003. ISOPLOT 3.00: A Geochronological Toolkit for Microsoft Excel. California, Berkeley: Berkeley Geochronology Center, 39
Nakamura D and Hirajima T. 2000. Granulite-facies overprinting of ultrahigh-pressure metamorphic rocks, noertheastern Sulu region, eastern China. Journal of Petrology, 41(4): 563-582
Rubatto D. 2002. Zircon trace element geochemistry: Partitioning with garnet and the link between U-Pb ages and metamorphism. Chemical Geology, 184(1-2): 123-138
Segal I, Halicz L and Platzner IT. 2003. Accurate isotope ratio measurements of ytterbium by multiple collection inductively coupled plasma mass spectrometry applying erbium and hafnium in an improved double external normalization procedure. Journal of Analytical Atomic Spectrometry, 18(10): 1217-1223
Tang J, Zheng YF, Wu YB, Gong B, Zha XP and Liu XM. 2008. Zircon U-Pb age and geochemical constraints on the tectonic affinity of the Jiaodong terrane in the Sulu orogen, China. Precambrian Research, 161(3-4): 389-418
Vervoort JD and Blichert-Toft J. 1999. Evolution of the depleted mantle: Hf isotope evidence from juvenile rocks through time. Geochimica et Cosmochimica Acta, 63(3-4): 533-556
Wallis S, Tsuboi M, Suzuki K, Fanning M, Jiang LL and Tanaka T. 2005. Role of partial melting in the evolution of the Sulu (eastern China) ultrahigh-pressure terrane. Geology, 33(2): 129-132
Wang QC, Ishiwatari A, Zhao ZY, Hirajima T, Hiramatsu N, Enami M, Zhai MG, Li J and Cong BL. 1993. Coesite-bearing granulite retrograded from eclogite in Weihai, eastern China. European Journal of Mineralogy, 5(1): 141-151
Wang XM, Liou JG and Mao HK. 1989. Coesite-bearing eclogite from the Dabie Mountains in central China. Geology, 17(12): 1085-1088
Wang XM and Liou JG. 1991. Regional ultrahigh-pressure coesite-bearing eclogitic terrane in central China: Evidence from country rocks, gneiss, marble, and metapelite. Geology, 19(9): 933-936
Wiedenbeck M, Allé P, Corfu F, Griffin WL, Meier M, Oberli F, Quadt AV, Roddick JC and Spiegel W. 1995. Three natural zircon standards for U-Th-Pb, Lu-Hf, trace element and REE analyses. Geostandards and Geoanalytical Research, 19(1): 1-23
Xu HF, Yang TN, Liu FL and Liou JG. 2001. Multi age-time evolution of granite gneisses-granite in the southern Sulu HP-UHP metamorphic belt. Acta Geologica Sinica, 75(3): 371-378 (in Chinese with English abstract)
Xu HJ, Ye K and Zhang JF. 2012a. Temperature of prograde metamorphism, decompressional partial melting and subsequent melt fractional crystallization in the Weihai migmatitic gneisses, Sulu UHP terrane: Constraints from Ti-in-zircon thermometer. Journal of Earth Science, 23(6): 813-827
Xu HJ, Song YR, Ye K, Zhang JF and Wang HR. 2012b. Petrogenesis of mafic dykes and high-Mg adakitic enclaves in the Late Mesozoic Fangshan low-Mg adakitic pluton, North China Craton. Journal of Asian Earth Sciences, 54-55: 143-161
Xu HJ, Ye K, Song YR, Chen Y, Zhang JF, Liu Q and Guo S. 2013. Prograde metamorphism, decompressional partial melting and subsequent melt crystallization in the Weihai migmatitic gneisses, Sulu UHPM Terrane, eastern China. Chemical Geology, 341: 16-37
Yang JH, Chung SL, Wilde SA, Wu FY, Chu MF, Lo CH and Fan HR. 2005. Petrogenesis of post-orogenic syenites in the Sulu Orogenic Belt, East China: Geochronological, geochemical and Nd-Sr isotopic evidence. Chemical Geology, 214(1-2): 99-125
Yang JS, Wooden JL, Wu CL, Liu FL, Xu ZQ, Shi RD, Katayama I, Liou JG and Maruyama S. 2003. SHRIMP U-Pb dating of coesite-bearing zircon from the ultrahigh-pressure metamorphic rocks, Sulu terrane, East China. Journal of Metamorphic Geology, 21(6): 551-560
Yao YP, Ye K, Liu JB, Cong BL and Wang QC. 2000. A transitional eclogite- to high pressure granulite-facies overprint on coesite-eclogite at Taohang in the Sulu ultrahigh-pressure terrane, eastern China. Lithos, 52(1-4): 109-120
Ye K, Cong BL and Ye DN. 2000a. The possible subduction of continental material to depths greater than 200km. Nature, 407(6805): 734-736
Ye K, Yao YP, Katayama I, Cong BL, Wang QC and Maruyama S. 2000b. Large areal extent of ultrahigh-pressure metamorphism in the Sulu ultrahigh-pressure terrane of East China: New implications from coesite and omphacite inclusions in zircon of granitic gneiss. Lithos, 52(1-4): 157-164
Zhang ZM, Shen K, Wang JL and Dong HL. 2009. Petrological and geochronological constraints on the formation, subduction and exhumation of the continental crust in the southern Sulu orogen, eastern-central China. Tectonophysics, 475(2): 291-307
Zhao ZF, Zheng YF, Zhang J, Dai LQ, Li QL and Liu XM. 2012. Syn-exhumation magmatism during continental collision: Evidence from alkaline intrusives of Triassic age in the Sulu orogen. Chemical Geology, 328: 70-88
Zheng YF, Fu B, Gong B and Li L. 2003. Stable isotope geochemistry of ultrahigh pressure metamorphic rocks from the Dabie-Sulu Orogen in China: Implications for geodynamics and fluid regime. Earth-Science Reviews, 62(1-2): 105-161
Zheng YF, Wu YB, Chen FK, Gong B and Zhao ZF. 2004. Zircon U-Pb and oxygen isotope evidence for a large-scale 18O depletion event in igneous rocks during the Neoproterozoic. Geochimica et Cosmochimica Acta, 68(20): 4145-4165
Zheng YF, Wu YB, Zhao ZF, Zhang SB, Xu P and Wu FY. 2005. Metamorphic effect on zircon Lu-Hf and U-Pb isotope systems in ultrahigh-pressure eclogite-facies metagranite and metabasite. Earth and Planetary Science Letters, 240: 378-400
Zheng YF. 2008. A perspective view on ultrahigh-pressure metamorphism and continental collision in the Dabie-Sulu orogenic belt. Chinese Science Bulletin, 53(20): 3081-3104
Zheng YF. 2012. Metamorphic chemical geodynamics in continental subduction zones. Chemical Geology, 328: 5-48
Zong KQ, Liu YS, Hu ZC, Kusky T, Wang DB, Gao CG, Gao S and Wang JQ. 2010. Melting-induced fluid flow during exhumation of gneisses of the Sulu ultrahigh-pressure terrane. Lithos, 120(3-4): 490-510
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