Metamorphic evolution of glaucophane eclogites from Sumdo, Lhasa block of Tibetan Plateau：Phase equilibria and metamorphic P-T path
-
摘要: 青藏高原拉萨地块松多蓝闪石榴辉岩主要矿物组合为石榴石、绿辉石、蓝闪石、绿帘石/斜黝帘石，及少量的金红石、石英、多硅白云母和普通角闪石。石榴石具有成分环带，从核到边Xpy升高，Xgr降低，部分石榴石外边缘受退变质改造影响，形成富Xgr的成分带。利用NCKMnFMASHTO体系中的P-T视剖面图，结合石榴石边部最大Xpy等值线和多硅白云母最大Si-含量值确定了松多榴辉岩的峰期变质条件为30±0.6kbar和610±6℃。石榴石核部到幔部成分环带记录的相对平缓的P-T轨迹反应了岩石早期经历了以加热升温为主、轻微加压的缓慢俯冲过程，地温梯度为7~8℃/km。石榴石幔部到边部成分环带，结合多硅白云母最大Si含量等值线模拟了以缓慢升温、快速增压为特征的P-T轨迹，反应了岩石由早期的缓慢俯冲进入到后期的快速俯冲阶段，地温梯度由7~8℃/km减小到5~6℃/km。峰期之后的榴辉岩经历了早期近等温减压的变质过程，以硬柱石和少量滑石的脱水反应生成蓝闪石和绿帘石（约22~23kbar）为主要特征。其后的晚期退变质阶段以硬柱石消失后局部成分域内由富余流体的消耗形成冻蓝闪石（约16kbar）以及蓝闪石和绿辉石边部发育后成合晶为特征（11~12kbar），石榴石边部的韭闪石冠状体和金红石边部生成的榍石退变边也大致发生在该阶段。榴辉岩近等温减压的变质过程可能代表了早期的构造快速抬升过程。松多榴辉岩带可能代表了青藏高原拉萨地块内一条新的大洋型高压-超高压变质带，大约266Ma的榴辉岩相变质时代说明在拉萨地块内部可能存在过一个二叠纪的古特提斯洋盆。Abstract: The general mineral assemblage of glaucophane eclogite from Sumdo, Lhasa block of Tibetan Plateau is garnet+omphacite+glaucophane+epidote/clinozoisite, with minor rutile, phengite, hornblende and quaretz. Garnet porphyroblasts show compositional zonation with Xpy increase and Xgr decease from the core to the rim. Part of garnet has an Xgr rich outer rim due to retrogression. We calculated the P-T pseudosection in the system of NCKMnFMASHTO, and estimated a peak metamorphic condition of 30±0.6kbar and 610±6℃ based on the isopleths of the maximum Xpy of garnet and maximum Si content of phengite. The moderate slope of the P-T path recorded by the composition of garnet from the core to the mantle indicate that the rock experienced heating with less pressure increasing in the early stage of slow subduction. The geothermal gradient is about 7~8℃/km. However, the composition of garnet from the mantle to the rim, combined with the Si content of phengite give out a slow heating but fast increasing pressure P-T path, which means it went into a fast subduction stage, and the geothermal gradient decreased to 5~6℃/km. After peak metamorphism, the eclogite went into an early isothermal decompressional process, characterized by lawsonite + minor talc dehydrated to produce glaucophane and epidote (at about 22~23kbar). In the late retrogression period, lawsonite completely disappear and barrosite formed due to the enrichment in fluids in some area (about 16kbar). Symplectite generally occur at the rim of glaucophane and omphacite (about 11~12kbar), and pargasite corona in the rim of garnet, titanite overgrowing rutile also formed at such stage. The isothermal decompression of eclogite probably represent a fast tectonic exhumation. Above all, Sumdo eclogite maybe represent a new oceanic HP-UHP metamorphic belt in Lhasa block of Tibetan Plateau, and the metamorphic age of the eclogite which is about 266Ma suggest that there might be a palaeo-ocean in Permian in the central part of Lhasa block.
-
Key words:
- Eclogite /
- Phase equilibrium /
- P-T path /
- Lhasa block /
- Tibetan Plateau
-
-
[1] Bureau of Geology and Mineral Resources of Xizang Autonomous Region. 1994. Regional Geological Survey Report of the People’s Republic of China, 1200000 Chin Tang (Voca) Picture. Beijing: Geological Publishing House (in Chinese)
[2] Carson CJ, Powell R and Clarke GL. 1999. Calculated mineral equilibria for eclogites in CaO-Na2O-FeO-MgO-Al2O3-SiO2-H2O: Application to the Pou bo Terrane, Pam Peninsula, New Caledonia. Journal of Metamorphic Geology, 17: 9-24
[3] Carswell DA, O’Brien PJ, Wilson RN and Zhai M. 1997. Thermobarometry of phengite-bearing eclogites in the Dabie Mountains of central China. Journal of Metamorphic Geology, 15(2): 239-252
[4] Chen SY, Yang JS, Luo LQ, Li ZL, Xu XZ, Li TF, Ren YF and Li HQ. 2007. MORB-type eclogites in the Lhasa block, Tibet, China: Petrochemical evidence. Geological Bulletin of China, 26(10): 1327-1339 (in Chinese with English abstract)
[5] Chen SY, Yang JS, Li Y and Xu XZ. 2009. Ultramafic blocks in Sumdo region, Lhasa Block, Eastern Tibet Plateau: An ophiolite unit. Journal of Earth Science, 20(2): 332-347
[6] Chen SY. 2010. The development of Sumdo suture in the Lhasa Block, Tibet. Ph. D. Dissertation. Beijing: Chinese Academy of Geological Science, 1-199 (in Chinese with English summary)
[7] Chengdu Institute of Geology and Mineral Resources, China Geological Survey. 2004. Geological Map of Tibetan Plateau, 11500000. Chengdu: Chengdu Cartographic Publishing House (in Chinese)
[8] Cheng H, Zhang C, Vervoot JD, Lu HH, Wang C and Cao DD. 2012. Zircon U-Pb and garnet Lu-Hf geochronology of eclogites from the Lhasa Block, Tibet. Lithos, 155: 341-359
[9] Clarke GL, Powell R and Fitzherbert JA. 2006. The lawsonite paradox: A comparison of field evidence and mineral equilibria modelling. Journal of Metamorphic Geology, 24(8): 715-725
[10] Coggon R and Holland TJB. 2002. Mixing properties of phengitic micas and revised garnet phengite thermobarometers. Journal of Metamorphic Geology, 20(7): 683-696
[11] Diener JFA, Powell R, White RW and Holland TJB. 2007. A new thermodynamic model for clino- and ortho-amphiboles in the system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O-O. Journal of Metamorphic, 25(6): 631-656
[12] Du JX, Zhang LF, Chen ZY and Lü Z. 2011a. Lawsonite-bearing eclogite from HP-UHP metamorphic belt in SW Tianshan, China. Abstracts of 9th International Eclogite Conference
[13] Du JX, Zhang LF, Lü Z and Chu X. 2011b. Lawsonite-bearing chloritoid-glaucophane schist from SW Tianshan, China: Phase equilibria and P-T path. J. Asian Earth Sci., 42(4): 684-693
[14] Ernst WG. 2006. Preservation/exhumation of ultrahigh-pressure subduction complexes. Lithos, 92(3-4): 321-335
[15] Green DH and Hellman PL. 1982. Fe-Mg partitioning between coexisting garnet and phengite at high pressures, and comments on a garnetphengite geothermometer. Lithos, 15(4): 253-266
[16] Green ECR, Holland TJB and Powell R. 2007. An order-disorder model for omphacitic pyroxenes in the system jadeite-diopside-hedenbergite-acmite, with applications to eclogitic rocks. American Mineralogist, 92(7): 1181-1189
[17] Guiraud M, Powell R and Rebay G. 2001. H2O in metamorphism and unexpected behaviour in the preservation of metamorphic mineral assemblages. Journal of Metamorphic Geology, 19(4): 445-454
[18] Holland TJB and Powell R. 1998. An internally consistent themodynamic data set for phase of petrological interest. Journal of Metamorphic Geology, 16(3): 309-343
[19] Holland TJB, Baker J and Powell R. 1998. Mixing properties and activity-composition relationships of chlorites in the system MgO-FeO-Al2O3-SiO2-H2O. European Journal of Mineralogy, 10(3): 395-406
[20] Holland TJB and Powell R. 2003. Activity-composition relations for phases in petrological calculations: An asymmetric multicomponent formulation. Contributions to Mineralogy and Petrology, 145(4): 492-501
[21] Hu DG, Wu ZH, Jiang W, Shi YR, Ye PS and Liu QS. 2005. SHRIMP zircon U-Pb age and Nd isotopic study on the Nyainqentanglha Group in Tibet. Science in China (Series D), 48(9): 1377-1386
[22] Krogh EJ. 1988. The garnet-clinopyroxene Fe-Mg geothermometer: A reinterpretation of existing experimental data. Contributions to Mineralogy and Petrology, 99(1): 44-48
[23] Krogh Ravna EJ. 2000. The garnet-clinopyroxene Fe2+ -Mg geothermometer: An updated calibration. Journal of Metamorphic Geology, 18(2): 211-219
[24] Krogh Ravna EJ and Terry MP. 2001. Geothermobarometry of phengite-kyanite-quartz/coesite eclogites. 11th Annual V. M. Goldschmidt Conference, Abstract: 3145
[25] Krogh Ravna EJ and Paquin J. 2004. Thermobarometric methodologite applicable to eclogites and garnet ultrabasites. EMU Notes in Mineralogy, 5(8): 229-259
[26] Krogh Ravna EJ and Terry MP. 2004. Geothermobarometry of UHP and HP eclogites and schists: An evaluation of equilibria among garner-clinopyroxene-kyanite-phengite-coesite/quartz. Journal of Metamorphic Geology, 22(6): 579-592
[27] Leake, BE, Woolley AR, Arpes CES, Birch WD, Gilbert MC, Grice JD, Hawthome FC, Kalo A, Kisch HJ, Krivovichev VG, Linthout K, Laird J, Mandarino JA, Maresch WV, Nickel EH, Rock NMS, Schumacher JC, Smith DC, Stephenson NCN, Ungaretti L, Whittaker EJW and Guo YZ. 1997. Nomenclature of amphiboles: Report of the Subcommittee on Amphiboles of the International Mineralogical Association, Commission on New Minerals and Mineral Names. American Mineralogist, 82: 1019-1037
[28] Li TF, Yang JS, Li ZL, Xu XZ, Ren YF, Wang RC and Zhang WL. 2007. Petrography and metamorphic evolution of the Sumdo eclogite, Qinghai-Tibetan Plateau. Geological Bulletin of China, 16(10): 1310-1326 (in Chinese with English abstract)
[29] Liu XC, Wei CJ, Li SZ, Dong SW and Liu JM. 2004. Thermobaric structure of a traverse across western Dabieshan: Implications for collision tectonics between the Sino-Korean and Yangtze cratons. Journal of Metamorphic Geology, 22(4): 361-379
[30] Lou YX, WEi CJ, Chu H, Wang W and Zhang JS. 2009. Metamorphic evolution of high-press eclogite from Hong’an, Western Dabie Orogen, central China: Evidence from petrography and calculated phase equilibira in system Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-O(Fe2O3). Acta Petrologica Sinica, 25(1): 124-138 (in Chinese with English abstract)
[31] Maruyama S, Liou JG and Tarabayashi M. 1996. Blueschists and eclogites of the world and their exhumation. International Geology Review, 38(6): 485-594
[32] Powell R. 1985. Regression diagnostic and robust regression in geothermometer/geobarometer calibration: The garnet-clinopyroxene geothermometer resisted. Journal of Metamorphic Geology, 3: 327-342
[33] Powell R, Holland TJB and Worley B. 1998. Calculating phase diagrams involving solid solutions via nonlinear equations, with examples using Thermocalc. Journal of Metamorphic Geology, 16(4): 577-588
[34] Song SG, Zhang LF, Niu YL, Wei CJ, Liou JG and Shu GM. 2007. Eclogite and carpholite bearing metasedimentary rocks in the North Qilian suture zone, NW China: Implications for Early Palaeozoic cold oceanic subduction and water transport into mantle. Journal of Metamorphic Geology, 25(5): 547-563
[35] Tian ZL and Wei CJ. 2013. Metamorphism of ultrahigh-pressure eclogites from the Kebuerte Valley, South Tianshan, NW China: Phase equilibria and P-T path. J. Metamorph. Geol., 31(3): 281-300
[36] Tsujimori T, Sisson VB, Liou JG, Harlow GE and Sorensen SS. 2006. Very-low-temperature record of the subduction process: A review of worldwide lawsonite eclogites. Lithos, 92(3-4): 609-624
[37] Waters DJ and Martin HN. 1993. Geobarometry of phengite-bearing eclogite. Terra Abstract, 5: 410- 411
[38] Wei CJ, Powell R and Zhang LF. 2003. Eclogites from the south Tianshan, NW China: Petrologic characteristic and calculated mineral equilibria in the Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O system. Journal of Metamorphic Geology, 21(2): 163-179
[39] Wei CJ, Powell R and Clarke GL. 2004. Calculated phase equilibria for low-and medium-pressure metapelites in the KFMASH and KMnFMASH systems. Journal of Metamorphic Geology, 22(5): 495-508
[40] Wei CJ, Su XL, Lou YX and Li YJ. 2009. A new interpretation of the conventional thermobarometry in eclogite: Evidence from the calculated PT pseudosections. Acta Petrologica Sinica, 25(9): 2078-2088(in Chinese with English abstract)
[41] Wei CJ, Li YJ, Yu Y and Zhang JS. 2010. Phase equilibria and metamorphic evolution of glaucophane-bearing UHP eclogites from the Western Dabieshan Terrane, Central China. Journal of Metamorphic Geology, 28(6): 647-666
[42] Wei CJ and Clarke GL. 2011. Calculated phase equilibria for MORB compositions: A reappraisal of the metamorphic evolution of lawsonite eclogite. Journal of Metamorphic Geology, 29(9): 939-952
[43] Wei CJ and Cui Y. 2011. Metamorphic evolution during subduction and exhumation of crust: Evidence from phase equilibria modelling for high- and ultrahigh-pressure eclogites. Acta Petrologica Sinica, 27(4): 1067-1074 (in Chinese with English abstract)
[44] Wei CJ, Qian JH and Tian ZL. 2013. Metamorphic evolution of medium-temperature ultra-high pressure (MT-UHP) eclogites from the South Dabie orogen, Central China: An insight from phase equilibria modelling. Journal of Metamorphic Geology, 31(7): 755-774
[45] Wei CJ, Tian ZL and Zhang LF. 2013. Modelling of peak mineral assemblages and P-T conditions for high-pressure and ultra high-pressure eclogites. Chinese Science Bulletin, 58(22): 2159-2164 (in Chinese)
[46] Yang JS, Xu ZQ, Geng QR, Li ZL, Xu XZ, Li TF, Ren YF, Li HQ, Cai ZH, Liang FH and Chen SY. 2006. A possible new HP-UHP (?) metamorphic belt in China: Discovery of eclogite in the Lhasa terrane Tibet. Acta Geologica Sinica, 80(12): 1787-1792(in Chinese with English abstract)
[47] Yang JS, Xu ZQ, Li ZL, Xu XZ, Li TF, Ren YF, Li HQ, Chen SY and Robinson PT. 2009. Discovery of an eclogite belt in the Lhasa Block, Tibet: A new border for Paleo-Tethys? Journal of Asian Earth Sciences, 34(1): 76-89
[48] Zeng LS, Liu J, Gao LE, Chen FY and Xie KJ. 2009. Early Mesozoic high-pressure metamorphism within the Lhasa Block, Tibet and its implications for regional tectonics. Earth Science Frontiers, 16(2):140-151 (in Chinese with English abstract)
[49] Zhang DD, Zhang LF and Zhao ZD. 2011. A study of metamorphism of Sumdo eclogite in Tibet, China. Earth Science Frontiers, 18(2): 116-126 (in Chinese with English abstract)
[50] Zhang JX, Meng FC and Wan YS. 2007. A cold Early Palaeozoic subduction zone in the North Qilian Mountains, NW China: Petrological and U-Pb geochronological constraints. Journal of Metamorphic Geology, 25(3): 285-304
[51] Zhang KJ and Tang XC. 2009. Eclogites in the interior of the Tibetan Plateau and their geodynamic implications. Chinese Science Bulletin, 54(15): 2556-2567
[52] Zhang LF, Lü Z, Zhang GB and Song SG. 2008. The geological characteristics of oceanic-type UHP metamorphic belts and their tectonic implications: Case studies from Southwest Tianshan and North Qaidam in NW China. Chinese Science Bulletin, 53(20): 3120-3130
[53] Zhang ZM, Dong X, Geng GS, Wang W, Yu F and Liu F. 2010. Precambrian metamorphism of the Northern Lhasa Terrane, South Tibet and its tectonic implications. Acta Geologica Sinica, 84(4): 449-456(in Chinese with English abstract)
[54] Zhang ZM, Dong X, Liu F, Lin YH, Yan R and Santosh M. 2012. Themaking of Gondwana: Discovery of 650Ma HP granulites from the North Lhasa, Tibet. Precambrian Research, 212-213: 107-116
[55] 陈松永, 杨经绥, 罗立强, 李兆丽, 徐向珍, 李天福, 任玉峰, 李化启. 2007. 西藏拉萨地块MORB型榴辉岩的岩石地球化学特征. 地质通报, 26(10): 1327-1339
[56] 陈松永. 2010. 西藏拉萨地块中古特提斯缝合带的厘定. 博士学位论文. 北京: 中国地质科学院, 1-199
[57] 胡道功, 吴珍汉, 江万, 石玉若, 叶培盛, 刘琦胜. 2005. 西藏念青唐古拉岩群SHRIMP锆石U-Pb年龄和Nd同位素研究. 中国科学(D辑), 35(1): 29-37
[58] 李天福, 杨经绥, 李兆丽, 徐向珍, 任玉峰, 王汝成, 张文兰. 2007. 青藏高原拉萨地块松多榴辉岩的岩相学特征和变质演化过程. 地质通报, 26(10): 1310-1326
[59] 娄玉行, 魏春景, 初航, 王伟, 张景森. 2009. 西大别造山带红安高压榴辉岩的变质演化: 岩相学与Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-O(Fe2O3)体系中相平衡关系. 岩石学报, 25(1): 124-138
[60] 魏春景, 苏香丽, 娄玉行, 李艳娟. 2009. 榴辉岩中传统地质温压计新解: 来自PT视剖面图的证据. 岩石学报, 25(9): 2078-2088
[61] 魏春景, 崔莹. 2011. 地壳俯冲与折返过程的变质作用演化: 来自高压-超高压榴辉岩相平衡模拟的证据. 岩石学报, 27(4): 1067-1074
[62] 魏春景, 田作林, 张立飞. 2013. 高压-超高压榴辉岩的峰期矿物组合与P-T条件模拟. 科学通报, 58(22): 2159-2164
[63] 西藏自治区地质矿产局. 1994. 中华人民共和国区域地质调查报告, 1200000下巴淌(沃卡)幅. 北京: 地质出版社
[64] 杨经绥, 许志琴, 耿全如, 李兆丽, 徐向珍, 李天福, 任玉峰, 李化启, 蔡志慧, 梁凤华, 陈松永. 2006. 中国境内可能存在一条新的高压/超高压(?)变质带——青藏高原拉萨地块中发现榴辉岩带. 地质学报, 80(12): 1787-1792
[65] 曾令森,刘静,高利娥,陈方远,谢克家.2009.青藏高原拉萨地块早古生代高压变质作用及其大地构造意义.地学前缘, 16(2):140-151
[66] 张丁丁, 张立飞, 赵志丹. 2011. 西藏松多榴辉岩变质作用研究. 地学前缘, 18(2): 116-126
[67] 张泽明, 董昕, 耿官升, 王伟, 于飞, 刘峰. 2010. 青藏高原拉萨地体北部的前寒武纪变质作用及构造意义. 地质学报, 84(4): 449-456
[68] 中国地质调查局成都地质矿产研究所. 2004.
-
计量
- 文章访问数: 7672
- PDF下载数: 15741
- 施引文献: 0
下载: