年代学-陈福坤-第七节-应用.pdf

同位素地质年代学与 放射成因同位素地球化学 同位素地质年代学与 放射成因同位素地球化学 陈福坤 固体同位素地球化学实验室固体同位素地球化学实验室 中国科学院地质与地球物理研究所 欧洲欧洲Bohemian地块西缘 华力西造山后期花岗岩 地块西缘 华力西造山后期花岗岩 Siebel et al. 2003 Int. J. Earth Sciences Chen et al. 2003 Int. J. Earth Sciences Chen et al. in press European J. Mineral. 欧洲华力西造山带欧洲华力西造山带 East European plat Black Sea Turkey Medirerranean Sea African plat Haydoutov, 1995 Atlantic Ocean V A R I S C A N B E L T A L P I N E B E L T Caledonian cores in the Alpine belt Pre-Caledonian massif in the Alpine belt Pre-Variscan massif in the Variscan belt South pole 60S Equator 30S Gondwana Siberia Laurentia Avalonia Armorica Iapetus Ocean Tornquist Sea 480 - 460 Ma435 Ma Laurentia Baltica Siberia Equator 60 30 30 Armorica Gondwana Bohemia Avalonia Baltica AvaloniaRheic ocean Saxo-ThuringiaSaxo-Thurin. Ocean Bohemia Armorican Assemblage Late Silurian Saxo-ThuringiaAvaloniaBohemiaEarly Emsian 405 Ma AvaloniaBohemiaMid-German Crystalline Moldanubian Frasnian 380 Ma Eifelian/Givetian 388 Ma Saxo-ThuringiaAvaloniaBohemiaRheno-Hercyn. Ocean After Franke 2000 Central European Variscides North Sea Armorican Massif Iberian Zone S. Portuguese Zone Ossa-Morena Zone V BF BM Alpine Front Vindel. MC Mediterranean Moravo - Silesian N. G erm an - Polish C ale doni des East European Plat Rh en o - He rcynia n Sa xo - Th urin g ian Moldanubian Coal-bearing molasse Presumed extent Flysch clastics at outcrop Caledonian deation Major thrusts and sutures Contours of Variscan massifs BM Bohemian Massif BF Black Forest MC Massif Central, France V Vosges Rheno-Hercynian Northern Phyllite Zone Saxo-Thuringian Moldanubian 欧洲华力西造山带东部岩石－构造单元欧洲华力西造山带东部岩石－构造单元 Bohemian地块 Bohemian Massif Bohemian Massif 100 km Munich RH Wroclaw Praha unmetamorphic Paleozoic volcanosedimentary rocks Variscan granites Gf l-Drosendorf metamorphic unit Cadomian basement Variscan metamorphic rocks Metamorphosed Early Palaeozoic rocks Moravo-Silesian Zone Moldanubian Zone Saxo-Thuringian Zone Erzgebirge Tepla-Barrandian N Moldanubian s. str. Bohemian地块西缘 中生代盆地 新生代火山 高温变质带 低级变质带 中压变质带 50 km Regensburg Bayreuth Passau N Moldanubian Medium-pressure metamorphites Variscan granite Saxothuringian Luhe Line Eberdorf Line Bavarian Pfahl N. Oberpfalz S. Oberpfalz Bavarian Forest 晚期热液成因石英岩墙 新生代玄武岩 Older Granites Phase Ib Younger Granites Phase II Younger Granites Phase III Redwitzites Phase Ia Tectono- metamorphic units Me so z oi c f o r e l an d KTB Mnchberg Massif Erbendorf Line MARKT- REDWITZ B鋜nau WEIDEN i.d.Opf. Luhe Line Bor Rozvadov Berlin Munich study area ZEV, M麺a, Tepl -Barrandium Saxothuringian, Moldanubian Tertiary Berlin Munich ST MO study area 0105 km F ra ncon i a n n L ie Tachov Western BOHEMIA NOP BOR WR FG 50 km Regensburg Bayreuth Passau N Moldanubian Medium-pressure metamorphites Variscan granite Saxothuringian Luhe Line Eberdorf Line Bavarian Pfahl Northern Oberpfalz 单矿物K/Ar年龄 Siebel et al. 1995 HornblendeMuscoviteBiotiteK/Ar data 2 0 4 G4 2 2 0 0 4 G3 G3 K seine 2 2 0 0 4 G2 G2 K seine 2 0 4 6 G1 2 0 2 0 0 2 0 2 0 4 Younger Granites 2 0 Zainhammer 2 0 Liebenstein 2 0 4 6 8 Falkenberg 2 0 4 Mitterteich 2 0 4 Friedenfels 2 0 4 6 Steinwald 2 0 Flossenb g 2 0 B nau 2 0 4 6 Leuchtenberg n o r t h e r n p a r t southern part Redw. W.I, R.E., BoI BoII, Bo IIIBor Crd.-bi granitoids Rozvadov Kreuzstein 290295300305310315320325Ma Older Granites Older Granites Phase Ib Younger Granites Phase II Younger Granites Phase III Redwitzites Phase Ia Tectono- metamorphic units Me so z oi c f o r e l an d KTB Mnchberg Massif Erbendorf Line MARKT- REDWITZ B nau WEIDEN i.d.Opf. Luhe Line Bor Rozvadov Berlin Munich study area ZEV, Ma, Tepl -Barrandium Saxothuringian, Moldanubian Tertiary Berlin Munich ST MO study area 0105 km F ra ncon i a n n L ie Tachov Western BOHEMIA NOP BOR WR FG 微量元素航空填图 微量元素 地球化学填图 Leuchten- berg 300 Madel 1968 Sr ppm 05 km RedwitzitesYounger Granites Older Granites Basement Paragneisses 5-10 garnet residue S-type granites Saldenburg Eberhardsreuth F黵黵stenstein Tittling Gneisses Diorites Fine grained granites Medium grained granites Coarse grained granites Younger cover N 50 km Regensburg Bayreuth Passau N Moldanubian Medium-pressure metamorphites Variscan granite Saxothuringian Luhe Line Eberdorf Line BP BP Bavarian Pfahl 2 km Diorite Granitc dyke Mafic dyke in granite AP Q After LeMaitre 1989 Quartz-rich Granitoid Grano- diorite Monzo- granite Syeno- granite Quartz syenite Quartz monzonite Quartz monzodiorite Tonalite Quarzt diorite Zircons from diorites 锆石晶型与CL特征 Diorite 207Pb/235U 206Pb/238U T2 T1 T145 /-33 Ma T2334.1 0.2/-0.1 Ma MSWD1.5 Grain 3 Grain 2 Grain 1 0.0520 100 0 200 300 332.0 /-2.3 Ma 0.0530 0.0540 207206 Pb* / Pb* Number of ratios 207235 Pb/U 206238 Pb/U Titanite from diorites 340 320 300 0.047 0.049 0.051 0.053 0.055 0.340.360.38 0.40 t 321 4 Ma MSWD 4.5 S/I-type granites 锆石晶型与CL特征 Medium-grained granites 207Pb/235U 206Pb/238U 2.3 /- 0.6 Ga 3.1 /- 0.4 Ga T2 T1 T10 5/-5 Ma forced T2322.0 0.7/-0.7 Ma MSWD2.5 Medium-grained granites 0.0520 321.2 /-0.5 Ma 0.05300.0540 Grain 3 Grain 2 Grain 4 Grain 1 0.0520 100 200 300 320.1 /-0.5 Ma 0.05300.0540 Grain 3 Grain 2 Grain 4 Grain 1 0 207206 Pb* / Pb* 400 Number of ratios Coarse-grained granites T1Sr NdSm La Lu LaLu La Lu RbLu After partial melt extraction Melts extracted from the mantle rise to the crust, carrying with them their “enrichment” in incompatible elements – Continental crust becomes “incompatible element enriched” – Mantle becomes “incompatible element depleted” 11、地壳和地幔Nd 和Sr 同位素体系特征 Higher Rb/Sr and 87Sr/86Sr ratio Lower Sm/Nd and 143Nd/144Nd ratio Lower Rb/Sr and 87Sr/86Sr ratio Lower Sm/Nd and 143Nd/144Nd ratio Lower Rb/Sr and 87Sr/86Sr ratio Higher Sm/Nd and 143Nd/144Nd ratio Low Rb/Sr and 87Sr/86Sr ratio High Sm/Nd and 143Nd/144Nd ratio Sm-Nd and Rb-Sr Isotope Systematics Upper Crust Lower Crust Upper Mantle Lower Mantle Lithosphere EnrichedDepletedPrimitive Asthenosphere 12 、放射成因同位素地球化 学在岩石成因研究的应用 Magma differentiationMagma differentiation Fractional CrystallizationFractional Crystallization Assimilation, fractional crystallizationAssimilation, fractional crystallization SiO2wt. 87Sr/86Sr 50607080 .704 .706 .708 Fractionation trend Contamination trend Magma mixing 87Sr/86Sr 0.7040.7060.7080.710 -4 0 4 Mixing trend εNd End member 1 End member 2 e.g. depleted mantle e.g. crustal material 13、等时线原理、类型和基本要求 Y ＝ c mX Slope of this line m eλt- 1 c initial isotopic ratio eλt 1 λt λt2 2 λt3 3 ... eλt1 λt when λt 800 OC Monazite 650-740 OC Sphene titanite 500-670 OC Rutile420-380 OC Apatite 350 OC 200 300 400 500 600 700 800 800850900950100010501100 Time Ma Temperature C O Mezger 1990 石榴石 U-Pb 独居石 U-Pb 榍石 U-Pb 角闪石 Ar-Ar 金红石 U-Pb 黑云母 Ar-Ar Cooling history 3oC/Ma 1oC/Ma Adirondack Highlands 南大别超高压变质带的两次快速抬升 来自李曙光等 2 0 、Fr e e T a l k 结合研究生期间专业方向，放射 成因同位素地球化学在今后的研 究领域的应用前景