福建明溪麻粒岩包体的年代学和矿物学特征:地温曲线及其华南中生代壳-幔相互作用意义
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摘要
明溪新生代玄武岩中的麻粒岩包体将为探讨华南地区中生代壳-幔相互作用过程提供线索。锆石U-Pb定年表明麻粒岩包体的原岩曾经历多期次岩浆活动,并以最后的晚侏罗世-早白垩世岩浆活动最强,其锆石εHf(t)值普遍较低(-16.1～-6.3),应以再循环地壳物质为主。根据矿物成分估算麻粒岩包体的平衡温度(756～826℃)、压力(0.55～0.78GPa),结合橄榄岩包体的平衡温压资料,重建了明溪地区地温曲线,由此推得的岩石学壳幔边界深度(～25km)明显浅于地震莫霍面深度(～31km),表明该区存在明显的壳幔过渡带。华南内陆地区曾经历中生代岩浆底侵作用过程,可能是华南中生代广泛岩浆活动的重要原因。
The granulite xenoliths in the Mingxi Cenozoic basalts provide a clue to understand the Mesozoic crustal-mantle interaction in South China.Zircon U-Pb dating of the Mingxi granulite xenolith reveals that the protolith were formed by multi-episodes of magmatisms.The dominant and the last magmatisms,which have negative zircon εHf(t) values(-16.1~-6.3),occurred in the Late Jurassic and the Early Cretaceous,respectively.These all suggest that the protolith of the Mingxi granulite xenolith was dominantly derived from the recycled crustal materials.In combination with P-T data of the Mingxi peridotite xenoliths,the lower crust-upper mantle geotherm beneath the Mingxi area are reconstructed according to the equilibrium t-p of the granulite xenoliths(756-826℃ and 0.55~0.78 GPa) calculated by the mineral compositions.The depth of petrologic crust-mantle boundary(~ 25 km) calculated from the Mingxi new geotherm is much lower than the seismic Moho depth(~ 31 km),suggesting a distinct crust-mantle transition zone in the area.Thus,the Mesozoic underplating may have occurred in the lower crust beneath the inland of South China,which may be an important mechanism of generating the Mesozoic felsic magmatism in South China.
The granulite xenoliths in the Mingxi Cenozoic basalts provide a clue to understand the Mesozoic crustal-mantle interaction in South China.Zircon U-Pb dating of the Mingxi granulite xenolith reveals that the protolith were formed by multi-episodes of magmatisms.The dominant and the last magmatisms,which have negative zircon εHf(t) values(-16.1~-6.3),occurred in the Late Jurassic and the Early Cretaceous,respectively.These all suggest that the protolith of the Mingxi granulite xenolith was dominantly derived from the recycled crustal materials.In combination with P-T data of the Mingxi peridotite xenoliths,the lower crust-upper mantle geotherm beneath the Mingxi area are reconstructed according to the equilibrium t-p of the granulite xenoliths(756-826℃ and 0.55~0.78 GPa) calculated by the mineral compositions.The depth of petrologic crust-mantle boundary(~ 25 km) calculated from the Mingxi new geotherm is much lower than the seismic Moho depth(~ 31 km),suggesting a distinct crust-mantle transition zone in the area.Thus,the Mesozoic underplating may have occurred in the lower crust beneath the inland of South China,which may be an important mechanism of generating the Mesozoic felsic magmatism in South China.
引文
[1]Zhou X M,Li W X.Origin of Late Mesozoic igneous rocks of southeastem China:Implications for lithosphere subduction and underplating of mafic magma[J].Tectonophysics,2000,326:269—287.
[2]Zhou X M,Sun T,Shen W Z,Shu L S,Niu Y L.Petrogene-sis of Mesozoic granitoids and volcanic rocks in South China:A response to tectonic evolution[J].Episodes,2006,29:26—33.
[3]Furlong K P,Fountain D M.Continental crustal underplating:thermal considerations and seismic-petrological consquences[J].J.Geophys.Res.,1986,91(B8):8285—8294.
[4]Rudnick R L.Nd and Sr isotopic compositions of lower crustal xenoliths from North Queensland,Australia:Implications for Nd model ages and crustal growth processes[J].Chem.Geol.,1990,83:195—208.
[5]Rudnick R L.Xenoliths-samples of the lower continental crust[A].Fountain D M,Arculus R,Kay R W.Continental Low-er Crust[C].Amsterdam:Elsevier,1992:269—316.
[6]Zhou X M,Yu J H,Xu X S.Discovery and significance of granulite xenoliths in the Nushan basalt,East China[J].Chi-nese Sci.Bull.,1992,37:1730—1734.
[7]Fan Q C,Liu R X,Li H M,Sui J L,Lin Z R.Zircon chronol-ogy and REE geochemistry of granulite xenoliths at Hannuoba[J].Chinese Sci.Bull.,1998,43:1510—1515.
[8]Chen S H,O’Reilly S Y,Zhou X H,Griffin W L,Zhang G H,Sun M,Feng J L,Zhang M.Thermal and petrological structure of the lithosphere beneath Hannuoba,Sino—Korean Craton,China:Evidence from xenolith[J].Lithos,2001,56:267—301.
[9]Liu Y S,Gao S,Jin S Y,Hu S H,Zhao Z B,Feng J L.Geo-chemistry of lower crustal xenoliths from Neogene Hannuoba basalt,north China Craton:Implication for petrogenesis and lower crustal composition[J].Geochim.Cosmochim.Acta,2001,65:2589—2604.
[10]Huang X L,Xu Y G,Liu D Y.Geochronology,petrology and geochemistry of the granulite xenoliths from Nushan,east China:Implication for a heterogeneous lower crust be-neath the Sino—Korean craton[J].Geochim.Cosmochim.Acta,2004,68:127—149.
[11]Ying J F,Zhang H F,Tang Y J.Lower crustal xenoliths from Junan,Shandong province and their bearing on the na-ture of the lower crust beneath the North China Craton[J].Lithos,2010119:363—376.
[12]徐夕生,周新民,O’Reilly S Y,唐红峰.中国东南部下地壳物质与花岗岩成因探索[J].岩石学报,1999,15:217—223.
[13]于津海,赵蕾,徐夕生.中国东南新生代玄武岩中麻粒岩相捕虏体的新发现及其意义[J].高校地质学报,2002,8:280—292.
[14]Yu J H,Fang Z,Zhou X M,Lai M Y,Xu X S,Zhou X M.Garnet granulite facies xenoliths from Yingfengling Cenozoic basalt in Leizhou,Guangdong Province[J].Chinese Sci.Bull.,1998,43:2013—2018.
[15]Yu J H,O’Reilly S Y,Griffin W L,Xu X S,Zhang M,Zhou X M.The thermal state and composition of lithospheric mantle beneath Leizhou Peninsula,south China[J].Journal of Volcanology and Geothermal Research,2003,122:165—189.
[16]刘若新,陈文寄,孙建中,李大明.中国新生代火山岩的K-Ar年代与构造环境[A].刘若新.中国新生代火山岩年代学与地球化学[C].北京:地震出版社,1992:1—43.
[17]孙伟汉,赖志敏.福建省新生代火山岩岩石化学特征及与构造地质关系的讨论[J].地球化学,1980,9(2):134—147.
[18]张俊成,卢清地.福建新生代玄武岩的特征、起源及其成因探讨[J].福建地质,1997,16(1):1—9.
[19]陈道公,张剑波.福建龙海明溪两区玄武质火山岩钾-氩年龄和Nd,Sr,Pb同位素[J].岩石学报,1992,8(4):326—331.
[20]Li X H,Liu Y,Li Q L,Guo C H,Chamberlain K R.Pre-cise determination of Phanerozoic zircon Pb/Pb age by multi-collector SIMS without external standardization[J].Geo-chem.Geophys.Geosyst.2009,10,Q04010,doi:10.1029/2009GC002400.
[21]Wiedenbeck M,Alle P,Corfu F,Griffin W L,Meier M,Oberli F,Vonquadt A,Roddick J C,Speigel W.Three nat-ural zircon standards for U-Th-Pb,Lu-Hf,trace-element and REE analyses[J].Geostandards Newsl.,1995,19:1—23.
[22]Ludwig K R.Isopot:A geochronological toolkit for Mi-crosoft Excel[D].Berkeley Geochronology Centre Special Publication No.4,2003.
[23]Wu F Y,Yang Y H,Xie L W,Yang J H,Xu P.Hf isotopic compositions of the standard zircons and baddeleyites used in U–Pb geochronology[J].Chem.Geol.,2006,234:105—126.
[24]Sderlund U,Patchett P J,Vervoort J D,Isachsen C E.The 176 Lu decay constant determined by Lu-Hf and U-Pb isotope systematics of Precambrian mafic intrusions[J].Earth Plan-et.Sci.Lett.,2004,219:311—324.
[25]Bouvier A,Vervoort J D,Patchett P J.The Lu-Hf and Sm-Nd isotopic composition of CHUR:Constraints from unequil-ibrated chondrites and implications for the bulk composition of terrestrial planets[J].Earth Planet.Sci.Lett.,2008,273:48—57.
[26]Griffin W L,Pearson N J,Belousova E,Jackson S E,O'Reil-ly S Y,van Achterberg E,Shee S R.The Hf isotope compo-sition of cratonic mantle:LAM-MC-ICPMS analysis of zircon megacrysts in kimberlites[J].Geochim.Cosmochim.Acta,2000,64:133—147.
[27]Bhattacharyya C.An evaluation of the chemical distinctions between igneous and metamorphic orthopyroxenes[J].A-merican Mineralogist,1971,56:499—506.
[28]Brey G P,Khler T.Geothermobarometry in four-phase lherzolites II.New thermobarometers,and practical assess-ment of existing thermobarometers[J].J.Petrol.,1990,31:1353—1378.
[29]Witt-Eickschen G,Seck H A.Solubility of Ca and Al in or-thopyroxene from spinel peridotite:An improved version of an empirical geothermometer[J].Contrib.Mineral.Petrol.,1991,106:431—439.
[30]Wells P R A.Pyroxene thermometry in simple and complex systems[J].Contrib.Mineral.Petrol.,1977,62:129—139.
[31]Wood B J,Banno S.Garnet-orthopyroxene and orthopyrox-ene-clinopyroxene relationships in simple and complex sys-tems[J].Contrib.Mineral.Petrol.,1973,46:1—15.
[32]McCarthy T C,Patiňo Douce A E.Empirical calibration of the silica-Ca-tschermak’s-anorthite(SCAn)geobarometer[J].Journal of Metamorphic Geology,1998,16:675—686.
[33]林传勇,史兰斌,陈孝德,韩秀玲.福建明溪上地幔热结构及流变学特征[J].地质论评,1999,45:352—360.
[34]O’Reilly S Y,Griffin W L.A xenoliths-derived geotherm for southeastern Australia and its geological implications[J].Tectonophysics,1985,111:41—63.
[35]Qi Q,Taylor L A,Zhou X M.Petrology and geochemistry of mantle peridotite xenoliths from SE China[J].J.Petrol.,1995,36:55—79.
[36]O’Neill H S C.The transition between spinel lherzolite and garnet lherzolite,and its use as a geobarometer[J].Contrib.Mineral.Petrol.,1981,77:185—194.
[37]Herzberg C.Pyroxene geothermometry and geobarometry:experimental and thermodynamic evaluation of some subsoli-dus phases relations involving clinopyroxenes in the system CaO-MgO-Al 2 O 3-SiO 2[J].Geochim.Cosmochim.Acta,1978,42:945—957
[38]Huang X L,Xu Y G.Thermal state and structure of the lith-osphere beneath eastern China:A synthesis on basalt-borne xenoliths[J].Journal of Earth Science,2010,21(5):711—730.
[39]王培宗,陈耀安,曹宝庭,潘金滇,王长炎.福建省地壳-上地幔结构及深部构造背景的研究[J].福建地质,1993,12:79—158.
[40]O’Reilly S Y,Griffin W L.4-D Lithosphere Mapping:Methodology and Examples[J].Tectonophysics,1996,262:3—18.
[41]孙涛.新编华南花岗岩分布图及其说明[J].地质通报,2006,25(3):332—335.
[2]Zhou X M,Sun T,Shen W Z,Shu L S,Niu Y L.Petrogene-sis of Mesozoic granitoids and volcanic rocks in South China:A response to tectonic evolution[J].Episodes,2006,29:26—33.
[3]Furlong K P,Fountain D M.Continental crustal underplating:thermal considerations and seismic-petrological consquences[J].J.Geophys.Res.,1986,91(B8):8285—8294.
[4]Rudnick R L.Nd and Sr isotopic compositions of lower crustal xenoliths from North Queensland,Australia:Implications for Nd model ages and crustal growth processes[J].Chem.Geol.,1990,83:195—208.
[5]Rudnick R L.Xenoliths-samples of the lower continental crust[A].Fountain D M,Arculus R,Kay R W.Continental Low-er Crust[C].Amsterdam:Elsevier,1992:269—316.
[6]Zhou X M,Yu J H,Xu X S.Discovery and significance of granulite xenoliths in the Nushan basalt,East China[J].Chi-nese Sci.Bull.,1992,37:1730—1734.
[7]Fan Q C,Liu R X,Li H M,Sui J L,Lin Z R.Zircon chronol-ogy and REE geochemistry of granulite xenoliths at Hannuoba[J].Chinese Sci.Bull.,1998,43:1510—1515.
[8]Chen S H,O’Reilly S Y,Zhou X H,Griffin W L,Zhang G H,Sun M,Feng J L,Zhang M.Thermal and petrological structure of the lithosphere beneath Hannuoba,Sino—Korean Craton,China:Evidence from xenolith[J].Lithos,2001,56:267—301.
[9]Liu Y S,Gao S,Jin S Y,Hu S H,Zhao Z B,Feng J L.Geo-chemistry of lower crustal xenoliths from Neogene Hannuoba basalt,north China Craton:Implication for petrogenesis and lower crustal composition[J].Geochim.Cosmochim.Acta,2001,65:2589—2604.
[10]Huang X L,Xu Y G,Liu D Y.Geochronology,petrology and geochemistry of the granulite xenoliths from Nushan,east China:Implication for a heterogeneous lower crust be-neath the Sino—Korean craton[J].Geochim.Cosmochim.Acta,2004,68:127—149.
[11]Ying J F,Zhang H F,Tang Y J.Lower crustal xenoliths from Junan,Shandong province and their bearing on the na-ture of the lower crust beneath the North China Craton[J].Lithos,2010119:363—376.
[12]徐夕生,周新民,O’Reilly S Y,唐红峰.中国东南部下地壳物质与花岗岩成因探索[J].岩石学报,1999,15:217—223.
[13]于津海,赵蕾,徐夕生.中国东南新生代玄武岩中麻粒岩相捕虏体的新发现及其意义[J].高校地质学报,2002,8:280—292.
[14]Yu J H,Fang Z,Zhou X M,Lai M Y,Xu X S,Zhou X M.Garnet granulite facies xenoliths from Yingfengling Cenozoic basalt in Leizhou,Guangdong Province[J].Chinese Sci.Bull.,1998,43:2013—2018.
[15]Yu J H,O’Reilly S Y,Griffin W L,Xu X S,Zhang M,Zhou X M.The thermal state and composition of lithospheric mantle beneath Leizhou Peninsula,south China[J].Journal of Volcanology and Geothermal Research,2003,122:165—189.
[16]刘若新,陈文寄,孙建中,李大明.中国新生代火山岩的K-Ar年代与构造环境[A].刘若新.中国新生代火山岩年代学与地球化学[C].北京:地震出版社,1992:1—43.
[17]孙伟汉,赖志敏.福建省新生代火山岩岩石化学特征及与构造地质关系的讨论[J].地球化学,1980,9(2):134—147.
[18]张俊成,卢清地.福建新生代玄武岩的特征、起源及其成因探讨[J].福建地质,1997,16(1):1—9.
[19]陈道公,张剑波.福建龙海明溪两区玄武质火山岩钾-氩年龄和Nd,Sr,Pb同位素[J].岩石学报,1992,8(4):326—331.
[20]Li X H,Liu Y,Li Q L,Guo C H,Chamberlain K R.Pre-cise determination of Phanerozoic zircon Pb/Pb age by multi-collector SIMS without external standardization[J].Geo-chem.Geophys.Geosyst.2009,10,Q04010,doi:10.1029/2009GC002400.
[21]Wiedenbeck M,Alle P,Corfu F,Griffin W L,Meier M,Oberli F,Vonquadt A,Roddick J C,Speigel W.Three nat-ural zircon standards for U-Th-Pb,Lu-Hf,trace-element and REE analyses[J].Geostandards Newsl.,1995,19:1—23.
[22]Ludwig K R.Isopot:A geochronological toolkit for Mi-crosoft Excel[D].Berkeley Geochronology Centre Special Publication No.4,2003.
[23]Wu F Y,Yang Y H,Xie L W,Yang J H,Xu P.Hf isotopic compositions of the standard zircons and baddeleyites used in U–Pb geochronology[J].Chem.Geol.,2006,234:105—126.
[24]Sderlund U,Patchett P J,Vervoort J D,Isachsen C E.The 176 Lu decay constant determined by Lu-Hf and U-Pb isotope systematics of Precambrian mafic intrusions[J].Earth Plan-et.Sci.Lett.,2004,219:311—324.
[25]Bouvier A,Vervoort J D,Patchett P J.The Lu-Hf and Sm-Nd isotopic composition of CHUR:Constraints from unequil-ibrated chondrites and implications for the bulk composition of terrestrial planets[J].Earth Planet.Sci.Lett.,2008,273:48—57.
[26]Griffin W L,Pearson N J,Belousova E,Jackson S E,O'Reil-ly S Y,van Achterberg E,Shee S R.The Hf isotope compo-sition of cratonic mantle:LAM-MC-ICPMS analysis of zircon megacrysts in kimberlites[J].Geochim.Cosmochim.Acta,2000,64:133—147.
[27]Bhattacharyya C.An evaluation of the chemical distinctions between igneous and metamorphic orthopyroxenes[J].A-merican Mineralogist,1971,56:499—506.
[28]Brey G P,Khler T.Geothermobarometry in four-phase lherzolites II.New thermobarometers,and practical assess-ment of existing thermobarometers[J].J.Petrol.,1990,31:1353—1378.
[29]Witt-Eickschen G,Seck H A.Solubility of Ca and Al in or-thopyroxene from spinel peridotite:An improved version of an empirical geothermometer[J].Contrib.Mineral.Petrol.,1991,106:431—439.
[30]Wells P R A.Pyroxene thermometry in simple and complex systems[J].Contrib.Mineral.Petrol.,1977,62:129—139.
[31]Wood B J,Banno S.Garnet-orthopyroxene and orthopyrox-ene-clinopyroxene relationships in simple and complex sys-tems[J].Contrib.Mineral.Petrol.,1973,46:1—15.
[32]McCarthy T C,Patiňo Douce A E.Empirical calibration of the silica-Ca-tschermak’s-anorthite(SCAn)geobarometer[J].Journal of Metamorphic Geology,1998,16:675—686.
[33]林传勇,史兰斌,陈孝德,韩秀玲.福建明溪上地幔热结构及流变学特征[J].地质论评,1999,45:352—360.
[34]O’Reilly S Y,Griffin W L.A xenoliths-derived geotherm for southeastern Australia and its geological implications[J].Tectonophysics,1985,111:41—63.
[35]Qi Q,Taylor L A,Zhou X M.Petrology and geochemistry of mantle peridotite xenoliths from SE China[J].J.Petrol.,1995,36:55—79.
[36]O’Neill H S C.The transition between spinel lherzolite and garnet lherzolite,and its use as a geobarometer[J].Contrib.Mineral.Petrol.,1981,77:185—194.
[37]Herzberg C.Pyroxene geothermometry and geobarometry:experimental and thermodynamic evaluation of some subsoli-dus phases relations involving clinopyroxenes in the system CaO-MgO-Al 2 O 3-SiO 2[J].Geochim.Cosmochim.Acta,1978,42:945—957
[38]Huang X L,Xu Y G.Thermal state and structure of the lith-osphere beneath eastern China:A synthesis on basalt-borne xenoliths[J].Journal of Earth Science,2010,21(5):711—730.
[39]王培宗,陈耀安,曹宝庭,潘金滇,王长炎.福建省地壳-上地幔结构及深部构造背景的研究[J].福建地质,1993,12:79—158.
[40]O’Reilly S Y,Griffin W L.4-D Lithosphere Mapping:Methodology and Examples[J].Tectonophysics,1996,262:3—18.
[41]孙涛.新编华南花岗岩分布图及其说明[J].地质通报,2006,25(3):332—335.
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