玄武岩斑晶中熔体包裹体 岩石学研究和实验测试 报告人：张春来 导 师：刘勇胜 2010年05月06日 第85期ODM Email：chlzh_01 电 话：15972066299 Henry Clifton Sorby The first to document microscopic melt inclusions in crystals in 1858 提纲 n为什么选择熔体包裹体作为研究对象 n什么是熔体包裹体及其形成机制和后期变 化 n熔体包裹体的（P、T、x）测试技术及存在 问题 n熔体包裹体在地幔熔体研究中的应用 Why melt inclusion？ 1）形成于高压环境下斑晶中的熔体包裹体 不受浅处减压去气作用影响而保存了脱气 前熔体中的挥发份元素组成； 2）熔体包裹体保存了比寄主岩石和基质玻 璃更多样的熔体组成和更原始的岩浆组成 ； 3）熔体包裹体不受寄主岩石被风化、热液 侵蚀或低温变质作用影响，提供了唯一直 接测定熔体组成的介质。 （Norman et al.2002） 能够捕获比 全岩更可观 的多样性熔 体，为研究 岩浆过程提 供高分辨率 证据 (Kamenetsky V.S. et.al., 2002) 保存最原始 岩浆信息 n为什么选择熔体包裹体作为研究对象 n什么是熔体包裹体及其形成机制和后期变 化 n熔体包裹体的（P、T、x）测试技术及存在 问题 n熔体包裹体在地幔熔体研究中的应用 What are melt inclusions to 1600C; Baker, 2004; Moore et al, 2008); to 1600C; Baker, 2004; Moore et al, 2008) BasaltBasalt RhyoliteRhyolite Ni-NiO H2O-CO2 fluid Moore et al, 2008 Analytical techniques for H2O and CO2 measurement Determining Determining glassglass H H 2 2 O-COO-CO 2 2 contents (see contents (see IhingerIhinger et al, 1994): et al, 1994): Bulk techniques (Bulk techniques (primaryprimary): ): 1. 1. High T vacuum High T vacuum manometrymanometry (H (H 2 2 O and COO and CO 2 2 ) ) 2. 2. Karl-Fischer titration (HKarl-Fischer titration (H 2 2 O only)O only) 3. 3. Elemental Analyzer (COElemental Analyzer (CO 2 2 only) only) MicrobeamMicrobeam techniques for both H techniques for both H 2 2 O and COO and CO 2 2 ( (secondarysecondary): ): 1. 1. Fourier-transform Infra-red spectroscopy (FTIR)Fourier-transform Infra-red spectroscopy (FTIR) Secondary ion mass spectrometry (SIMS)Secondary ion mass spectrometry (SIMS) 1. 1. Raman spectroscopyRaman spectroscopy Determining Determining fluidfluid composition (H composition (H 2 2 O-COO-CO 2 2 fluids only) : fluids only) : 1. 1. Mass balance/Mass balance/gravimetrygravimetry 1. 1. Simple, but error related to fluid mass and scale precision (20-100% error Simple, but error related to fluid mass and scale precision (20-100% error reported).reported). 2. 2. Low T vacuum Low T vacuum manometrymanometry Requires a vacuum line, precise to 10 micromoles of fluid (5-10% relative error).Requires a vacuum line, precise to 10 micromoles of fluid (5-10% relative error). Two critical measurements: HTwo critical measurements: H 2 2 O-COO-CO 2 2 content of melt content of melt ANDAND fluid composition fluid composition Summary of solubility data for pure H2O and CO2 in natural melts Pure HPure H 2 2 O (Table 1):O (Table 1): Greater than 30 different melt compositionsGreater than 30 different melt compositions 44-78 wt% SiO44-78 wt% SiO 2 2 ; ; peralkalineperalkaline to to peraluminousperaluminous Broad range in P and TBroad range in P and T 0.1 to 500 0.1 to 500 MPaMPa; 800-1250C; good coverage for most compositions; 800-1250C; good coverage for most compositions Pure COPure CO 2 2 (Table 1): (Table 1): Only 7 compositionsOnly 7 compositions mostly mafic compositions (32-55 wt% SiOmostly mafic compositions (32-55 wt% SiO 2 2 ); ); rhyolitesrhyolites studied earlier studied earlier Dominated by high P ( 1000 Dominated by high P ( 1000 MPaMPa) and T ( 1200C) and T ( 1200C) Due to low solubility of CODue to low solubility of CO 2 2 and increased and increased solidussolidus T; not extremely useful for T; not extremely useful for understanding melt inclusion measurementsunderstanding melt inclusion measurements General H2O solubility behavior Relatively large dissolved HRelatively large dissolved H 2 2 O contents (1-8 O contents (1-8 wt%; to 20-25 mol%) at magmatic P-T wt%; to 20-25 mol%) at magmatic P-T conditions.conditions. Strong Strong postivepostive P dependence, with weaker P dependence, with weaker negative T dependence.negative T dependence. Total HTotal H 2 2 O solubility has a significant O solubility has a significant compositional dependence (e.g. Moore et al, compositional dependence (e.g. Moore et al, 1998; Behrens Behrens King et al, (Behrens et al, 2004; King et al, 2002).2002). DaciteDaciteAndesiteAndesite Solubility data for mixed H2O + CO2 fluids in natural melts Most important for melt inclusion interpretation, yet only 8 new studies Most important for melt inclusion interpretation, yet only 8 new studies (see (see Table 2)Table 2). . Good coverage for calc-alkaline Good coverage for calc-alkaline rhyoliterhyolite melts, but mafic and intermediate melts, but mafic and intermediate studies are sparse, as are alkaline compositions.studies are sparse, as are alkaline compositions. SilicicSilicic: : 20-500 20-500 MPaMPa, 800-1100C (e.g. , 800-1100C (e.g. TamicTamic et al, 2001) et al, 2001) Mafic and intermediate:Mafic and intermediate: 20-700 20-700 MPaMPa, up to 1400C (e.g. Dixon et al, 1995; , up to 1400C (e.g. Dixon et al, 1995; BotcharnikovBotcharnikov et al, 2005, 2006, 2007). et al, 2005, 2006, 2007). Difficult experimental solubility measurements:Difficult experimental solubility measurements: Fluid composition measurement (low T Fluid composition measurement (low T manometrymanometry or weig