中国大陆科学钻探工程主孔及周边地区花岗质片麻岩的地球化学性质和超高压变质作用标志的识别
Geochemical characteristics and UHP metamorphism of granitic gneisses in the main drilling hole of Chinese Continental Scientific Drilling Project and its adjacent area
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摘要: 花岗质片麻岩是中国大陆科学钻探工程主孔0-2000m深度范围内出露的主要岩石类型之一,集中分布于1113.14-1596.22m之间,而在0-1113.14m和1596.22-2000m深度范围内主要以“夹层”形式赋存于副片麻岩和(退变)榴辉岩中,夹层的厚度为0.54-5.82m左右。花岗质片麻岩累计厚度430.98m,占2000m岩心的21.55％左右。地球化学研究结果表明,主孔中花岗质片麻岩SiO2含量普遍偏高,为71.55％-77.18％之间,Al2O3含量为11.54％-13.57％。TiO2、Fe2O3、FeO、MnO和MgO含量则明显偏低,其中Fe2O3 FeO总量为1.05％-2.94％,MgO=0.06％-0.59％。CaO含量为0.30％-2.65％。Na2O和K2O含量变化相对较大,分别为0.29％-4.06％和2.90％-6.67％之间,且大多数样品K2O含量高于Na2O含量。稀土元素配分模式具有右倾式的特点,轻稀土相对富集,而重稀土相对亏损,具有强烈的负Eu异常,Eu/Eu=0.21-0.26之间。在标准化蛛网图上,则显示Ta、Nb、P和Ti的明显亏损以及中等-强烈的负Ba异常,Ba/Ba=0.25-O.64之间,平均值为0.45左右。上述主元素、稀土元素和微量元素特征与中国大陆科学钻探预先导孔CCSD-PP1岩心以及东海及其邻区地表露头的花岗质片麻岩的化学成分十分相似,具有A型花岗岩的地球化学特征。采用激光拉曼技术,配备阴极发光测试,确认中国大陆科学钻Abstract: The main drilling hole CCSD-MH, Chinese Continental Scientific Drilling Project ( CCSD) , with depth of 5000 m, is located in the Donghai area in southwestern Sulu terrane. The 0 - 2000 m recovered cores in CCSD-MH are mainly comprised of fresh eclogite, retrogressive eclogite, amphibolite, paragneiss, granitic gneiss ( orthogneiss) and ultramafic rock. The granitic gneiss constitute about 21. 55 % of the 2000 m recovered lithology and as a granitic body mainly occur at the depth interval of 1113. 14 -1596.22 m, and as thin layers with thickness ranging from 0. 54 m to 5. 82 m are intercalated within paragneiss and fresh and retrogressive eclogite at the depth intervals of 0-1113. 14 m and 1596. 22 -2000 m. The SiO2 and A12O3 contents of analyzed granitic gneiss samples range from 71. 55 % to 77. 18 % , and from 11. 54 % to 13. 57 % , respectively. All the analyses show lower TiO2, Fe2O3, FeO, MnO and MgO contents; Fe2O3 FeO = 1. 05 % -2. 94 % , MgO = 0.06 % -0.59 % and CaO = 0. 30 % -2.65 %. However, the Na2 O and K2 O contents show various extents ranging from 0. 29 % to 4. 06% and from 2. 90 % to 6. 67% , respectively, with an obvious characteristic of K2 O > Na2O. The REE patterns of granitic gneiss samples are characterized by evidently negative Eu anomalies, with Eu/Eu = 0. 21 - 0. 26. Light rare earth elements are concentrated evidently and heavy rare earth elements are deficient. In the MORB normalized multi-element variation diagram, multi-element variations show the relative depletions of Ta, Nb, P and Ti, and medium-obviously negative Ba anomalies. Ba/Ba = 0. 25 - 0. 64, with an average value of 0.45. These major and trace element compositions are characterized by A-type granite, and identical to those of the typical country rock granitic gneisses at outcrops in Donghai and adjacent areas, and in the prepilot drilling hole CCSD-PP1, Chinese Continental Scientific Drilling Project. Coesite and coesite-bearing ultrahigh-pressure (UHP) minerals are identified using Raman spectroscopy as inclusions in zircons separated from granitic gneiss, amphibolite and paragneiss in the main drilling hole CCSD-MH, the prepilot drilling hole CCSD-PP1 and -PP2, and from 3800 km outcrops around Donghai area. These evidences suggest that voluminous continental materials, consisting mainly of protoliths of eclogite and its country rocks were commonly subjected to deep subduction and ultrahigh-pressure (UHP) metamorphism. Combined study of Laser Raman, cathodoluminescence ( CL) image and SHRIMP U-Pb dating reveals that zircons separated from the granitic gneiss in the main drilling hole CCSD-MH recorded complicated geochronological traces. All the analyzed zircons retain inherited magmatic crystallization cores with inherited ages of 663 -750 Ma, implying partial loss of Pb from zircon in the protolith, therefore the protolith age should be older than 750 Ma. Coesite-bearing domains of zircons recorded 226 -230 Ma for the UHP metamorphic condition, with an average age of 228 ? Ma, and quartz- and albite-bearing rims of zircons recorded 203 -214 Ma for the late amphibolite facies thermal event, with an average age of 209 ? Ma. These data indicate that UHP metamorphism in the Sulu terrane occurred in the Indosinian time. The exhumation rate of the Sulu terrane is approximately 5. 3 km/Ma calculated based on the SHRIMP data and relative P-T conditions. The large exhumation rate of the massif is in the same range as other UHP metamorphic terranes (e. g. Kokchetav massif, northern Kazakhstan) in the world, and suggests that slab decoupling may be a driving force for the exhumation of UHP metamorphic rocks from mantle depth.
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[1] ［1］Ames L, Tilton G R, Zhou G. 1993. Timing of collision of the Sino Korean and Yangtze cratons: U-Pb zircon dating of coesite-bearing eclogites. Geology, 21: 339 - 342
[2] ［2］Ames L, Zhou G, Xiong B. 1996. Geochronology and isotopic character of ultrahigh-pressure metamorphism with implications for collision of the Sino-Korean and Yangtze cratons, central China. Tectonics, 15:472 - 489
[3] ［3］Chen B, Jahn B M, Ye K, Liu J B. 2002. Cogenetic relationship of the Yangkou gabbro-to-granite unit, Su-Lu terrane, eastern China, and implications for UHP metamorphism. Journal of the Geological Society, London, 159: 457 - 467
[4] ［4］Cheng Y Q, Liu D Y, Willimas I S, Jian P, Zhuang Y X, Gao T S.2000. SHRIMP U-Pb dating of zircons of a dark eclogite and a garnet-bearing gneissic granitic rock from Bixiling, eastern Dabie area, Anhui Province: isotope chronological evidence of Neoproterozoic UHP metamorphism. Acta Geologica Sinica, 74:193-205 (in Chinese with English abstract)
[5] ［5］Chopin C. 1984. Coesite and pure pyrope in high-grade blueschists of the western Alps; a first record and some consequences. Contrib.Mineral. Petrol., 86:107-118
[6] ［6］Chopin C, Sobolev N V. 1995. Principal mineralogic indicators of UHP in crustal rocks. In: Coleman R G, Wang X (eds.). Ultrahighpressure Metamor phism, Cambridge University Press, England, 96- 133
[7] ［7］Cong B L, Zhai M, Carswell D A, Wilson R N, Wang Q, Zhao Z,Windly B F. 1995. Petrogenesis of ultrahigh-pressure rocks and their country rocks at Shuanghe in Dabieshan, central China. Eur. J.Mineral., 7:119-138刘福来等:中国大陆科学钻探工程主孔及周边地区花岗质片麻岩的地球化学性质和超高压变质作用标志的识别
[8] ［8］Cong B L, Wang Q C. 1999. A new review of Dabieshan-Sulu ultrahigh pressure belt. Chinese Science Bulletin, 44:1127 - 1141 ( in Chinese )
[9] ［9］Dong S B. 1993. Metamorphic and tectonic domains of China. J.Metamorph. Geol. , 11: 465 - 481
[10] ［10］Dong S B, Cui W Y, Zhang L F. 1996. The proterozoic glaucophane schist belt and some eclogites of North Yangtze Craton, Central China. Beijing: Science Press, 139
[11] ［11］Eby G N. 1990. The A-type granitoids: A review of their occurrence and chemical characteristics and speculations on their petrogenesis.Lithos, 26:115 - 134
[12] ［12］Eide E A, McWilliams M O, Liou J G. 1994. 40Ar/39Ar geochronology and exhumation of high-pressure to ultrahigh-pressure metamorphic rocks in east-central China. Geology, 22:601 -604
[13] ［13］Fu B, Touret J L R, Zheng Y F. 2001. Fluid inclusions in coesitebearing eclogites and jadeite quartzite at Shuanghe, Dabieshan,China. J. Metamorph. Geol., 19:529-545
[14] ［14］Fu B, Zheng Y F, Touret J L R. 2002. Petrological, isotopic and fluid inclusion studies of eclogites from Sujiahe, Dabieshan (China).Chim. Geol. , 187: 107 - 128
[15] ［15］Hacker B R, Wang Q. 1995. Ar/Ar geochronology of ultrahigh-pressure metamorphism. Tectonics, 14:994 - 1006
[16] ［16］Hacker B R, Ratschbacher L, Webb L, Ireland T, Walker D, Dong S W. 1998. U/Pb zircon ages constrain the architecture of the ultrahigh-pressure Qinling-Dabie orogen. Earth and Planetary Science Letters, 161: 215 -230
[17] ［17］Jian P, Liu D Y, Yang W R, Williams. 2000. Petrographical study of zircons and SHRIMP dating of the Caledonian Xiongdian eclogite,northwestern Dabie mountains. Acta Geologica Sinica, 74:259 -264 (in Chinese with English abstract )
[18] ［18］Kang W, Hu K, Liang W. 1996. Proterozoic High-Pressure Metamorphic Belt in Central East of China. Beijing: Geological Publishing House ( in Chinese with English abstract)
[19] ［19］Katayama I, Zayachkovsky A A, Maruyama S. 2000. Progressive P-T records from zircon in Kokchetav UHP-HP rocks, northern Kazakhstan. The Island Arc, 9: 417 - 427
[20] ［20］Kretz R. 1983. Symbols for rock-forming mineral. American Mineralogist, 68: 277 - 279
[21] ［21］Li S G, Hart S R, Zheng S G, Liu DL, ZhangGW, GuoA L. 1989. Timing of collision between north and south China blocks -The SmNd isotopic age evidence. Science in China, 32:1393 -1400
[22] ［22］Li S G, Chen Y, Ge N J, Liu D L, Zhang Z, Zhang Q D, Zhao D M.1993. U-Pb zircon ages of eclogite and gneiss from the Qingdao area: evidence for thc later Proterozoie magmatism in the Jiaonan Group. Chinese Seience Bulletin, 38:1773 -1777
[23] ［23］Li S, Wang W, Chen Y, Liu D, Qiu J, Zhou H, Zhang Z. 1994. Excess argon in phengite from eclogite: Evidence from dating of eclogite minerals by Sm-Nd, Rb-Sr and 40Ar/39 Ar methods.Chemical Geology, 112: 343 - 350
[24] ［24］Li S, Jagoutz E, Lo C, Chen Y, Li Q, Xiao Y. 2000a. Sm-Nd, Rb/Sr,and 40Ar/39 Ar isotopic systematics of the ultrahigh-pressure metamorphic rocks in the Dabie-Sulu belt, central China: A retrospective view. In: Ernst W G, Liou J G, (eds.). Ultra-High Pressure Metamorphism and Geodynamics in Collision-Type Orogenic Belts. Bellwether Publishing Ltd. , Columbia, 234 - 244
[25] ［25］Li S, Jagoutz E, Chen Y, Li Q. 2000b. Sm-Nd and Rb-Sr isotopic chronology and cooling history of ultrahigh pressure metamorphic rocks and their country rocks at Shuanghe in the Dabie Mountains,central China. Geochim. Cosmochim. Acta, 64:1077-1093
[26] ［26］Liou J G, Zhang R Y. 1996. Occurrence of intergranular coesite in Sulu ultrahigh-P rocks from China: Implications for fluid activity during exhumation. Am. Mineral. , 81: 1217 - 1221
[27] ［27］Liou J G, Zhang R Y, Bor-ming Jahn. 1997. Petrology, geochemistry and isotope data on a ultrahigh-pressure jadeite quartzite from Shuanghe, Dabie mountains, east-central China. Lithos, 41:59 -78
[28] ［28］Liou J G, Hacker B R, Zhang R Y. 2000. Into the forbidden zone.Science, 287: 1215 - 1216
[29] ［29］Liu F L, Xu Z Q, Xu H F. 1999. Petrology and genetic mechanism of granitic gneiss in Donghai ultrahigh-pressure metamorphic belt.Geological Review, 45:636 -644 (in Chinese with Englishabstract )
[30] ［30］Liu F L, Xu Z Q, Zhang Z M, Yang J S. 2001. Petrology and geochemistry of gneiss and granitic gneiss from pre-pilot drillhole ( CCSD-PP1 ), Chinese Continental Scientific Drilling Project. Acta Geologica Sinica, 75:70 -81 (in Chinese with English abstract)
[31] ［31］Liu F L, Xu Z Q, Katayama l, Yang J S, Maruyama S, Liou J G. 2001. Mineral inclusions in zircons of para- and orthogneiss from pre-pilot drillhole CCSD-PP1, Chinese Continental Scientific Drilling Project.Lithos, 59:199-215
[32] ［32］Liu F L, Xu Z Q, Liou J G, Katayama I, Masago H, Maruyama S, Yang J S. 2002. Ultrahigh-pressure mineral inclusions in zircons from gneissic core samples of the Chinese Continental Scientific Drilling site in eastern China. European Journal of Mineralogy, 14:499 -512
[33] ［33］Liu F L, Xu Z Q, Song B. 2003a. Determination of UHP and retrograde metamorphic ages of the Sulu terrane: evidence from SHRIMP U-Pb dating on zircons of gneissic rocks. Acta Geologica Siniea, 77:229-237 (in Chinese with English abstract)
[34] ［34］Liu F L, Zhang Z M, Xu Z Q. 2003b. Three-dimensional distribution of ultrahigh-pressure minerals in Sulu terrane. Acta Geologica Sinica,77:69 -84 (in Chinese with English abstract)
[35] ［35］Liu F L, Xu Z Q. 2004. Fluid inclusions hidden in coesite-bearing zircons from ultrahigh-pressure metamorphic rocks in southwestern Sulu terrane, eastern China. Chinese Science Bulletin, 49: 181 -189 (in Chinese)
[36] ［36］Liu J B, Ye K, Maruyama S, Cong B L, Fan H R. 2001. Mineral inclusions in zircon from gneisses in the ultrahigh-pressure zone of the Dabie mountains, China. J. Geol. , 109:523 -535
[37] ［37］Mattauer M, Matte P, Malavieille J, Tapponnier P, Maluski H, Qin X Z, Lun L Y, Qin T Y. 1985. Tectonics of the Qinling belt: buildup and evolution of eastern Asia. Nature, 317: 496- 500
[38] ［38］Maruyama S, Nutman A P, Morikawa T, Liou J G. 1998. SHRIMP U-Pb geochronology of ultrahigh-pressure metamorphic rocks of the Dabie mountains, central China. Continental Dynamics, 3:72 -85
[39] ［39］Okay A I, Sengor A M C. 1992. Evidence for intra-continental thrust related exhumation of the ultra-high pressure rocks in China.Geology, 20:411 -414
[40] ［40］Parkinson C D, Katayama I. 1999. Present day ultrahigh-pressure conditions of coesite inclusions in zircon and garnet: Evidence from Laser Raman microspectroscopy. Geology, 27: 979 -982
[41] ［41］Rowley D B, Xue F, Tucker R D, Peng Z X, Baker J, Davis A. 1997. Ages of ultrahigh-pressure metamorphism and protolith orthogneisses from the eastern Dabieshan: U-Pb zircon geochronology. Earth and Planetary Science Letters, 151: 191 -203
[42] ［42］Rumble D, Wang Q C, Zhang R Y. 2000. Stable isotope geochemistry of marbles from the coesite UHP terranes of Dabieshan and Su-Lu,China. Lithos, 52:79-95
[43] ［43］Rumble D, Giorgis D, Ireland T, Zhang Z, Xu H, Yui T F, Yang J, Xu Z, Liou J G. 2002. Low delta 18O zircons, U-Pb dating, and the age of the Qinglongshan oxygen and hydrogen isotope anomaly near Donghai in Jlangsu Province, China. Geochim. Cosmochim. Acta,66: 2299 - 2306
[44] ［44］Smith D C. 1984. Coesite in clinopyroxene in the Caledonides and its implications for geodynamics. Nature, 310: 641 -644
[45] ［45］Smith D C. 1988. A review of the peculiar mineralogy of the "Norwegian coesite-eclogite province", with crystal-chemical, petrological,geochemical and geodynamical notes and an extentive biblography.In: Smith D C (eds.). Eclogites and Eclogite-Facies Rocks,Amsterdam Elsevier, Holland, 1 - 126
[46] ［46］Schertl H -P, Okay A I. 1994. A coesite inclusion in dolomite in Dabie Shan, China: petrological and rheological significance. Eur. J.Mineral., 6:995-1000
[47] ［47］Song M C, Jin Z M, Wang L M, Zhang X D, Li Y Y. 2003. New discovery of the contact relation between eclogite and country rocks in Guanshan, eastern Shangdong, and its enlightenment for chronology.Acta Geologica Sinica, 77:238 -244 (in Chinese with English abstract)
[48] ［48］Tabata H, Yamauchi K, Maruyama S, Liou J G. 1998. Tracing the extent of a UHP metamorphic terrane: Mineral-inclusion study of zircons in gneisses from the Dabieshan. In: Hacker B R, Liou J G,( eds. ) When Continents Collide: Geodynamics and Geochemistry of Ultrahigh-Pressure Rocks, Kluwer Academic Publisher, London,261 - 273
[49] ［49］Wang L M, Song B, Wu H. 1994. Forming age of Shandong eclogites 207 Pb/206 Pb age of single-zircon crystals. Chinese Science Bulletin,39:1788 - 1791 (in Chinese)
[50] ［50］Wang Q, Zhao Z H, Xiong X L. 2000. The ascertainment of lateYanshanian A-type granite in Tongbai-Dabie orogenic belt. Acta Petrologica et Mineralogica, 19:297 -306 (in Chinese with English abstract )
[51] ［51］Wang X M, Liou J G, Mao H K. 1989. Coesite-bearing eclogites from the Dabie mountains in central China. Geology, 19:933 -936
[52] ［52］Wang X M, Liou J G. 1991. Regional ultrahigh-pressure coesite-bearing eclogitic terrane in central China: evidence from country-rocks,gneiss, marble, and metapelite. Geology, 19: 933 - 936
[53] ［53］Wang X M, Zhang R Y, Liou J G. 1995. Ultrahigh-pressure metamorphic terrane in eastern central China. In: Coleman R G,Wang X ( eds. ), Ultrahigh-Pressure Metamorphism. Cambridge Press, 356 - 390
[54] ［54］Whalen J B, Currie K L, Chappell B W. 1987. A-type granites:geochemcal characteristics, discrimination and petrogenesis.Contrib. Mineral. Petrol. , 95:407 -419
[55] ［55］Xu S T, Okay A I, Ji S, Sengor A M. C, Su W, Liu Y, Jiang L. 1992. Diamond from the Dabie Shan metamorphic rocks and its implication for tectonic setting. Science, 256: 8- 12
[56] ［56］Xu Z Q, Yang W C, Zhang Z M, Yang T N. 1998. Scientific significance and site-selection researches of the first Chinese Continental Scientific Deep Drillhole. Continental Dynamics, 3:1 -13
[57] ［57］Yang J J. 1991. Eclogites, garnet pyroxenites and related ultrabasics rocks in Shandong and north Jiangsu of east China. Beijing:Geological Pulishing House, 26 -52 (In Chinese)
[58] ［58］Yang J J, Jahn B-M. 2000. Deep subduction of mantle-derived garnet peridotites from the Su-lu UHP metamorphic terrane in China. J.Metamorph. Geol. , 18, 167 - 180
[59] ［59］Yang J J. 2003. Titanian clinohumite-garnet-pyroxene rock from the SuLu UHP metamorphic terrane, China: Chemical evolution and tectonic implications. Lithos, 70:359-379
[60] ［60］Yang J S, Wooden L, Wu C L, Liu F L, Xu Z Q, Shi R D, Katayama I,Liou J G, Maruyama S. 2003. SHRIMP U-Pb dating of coesitebearing zircon from the ultrahigh-pressure metamorphic rocks, Sulu terrane, east China. J. Metamorph. Geol. , 21: 551 -560
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