1、第85期ODMEmail：chlzh_電 話enry Clifton SorbyThe first to document microscopic melt inclusions in crystals in 1858（Norman et al.2002）能夠捕獲比全巖更可觀的多樣性熔體，為研究巖漿過程提供高分辨率證據(jù)(Kamenetsky V.S. et.al., 2002)保存最原始保存最原始巖漿信息巖漿信息What are melt inclusions & how do they form?熔體包裹體(又稱巖漿包裹體) 是指巖漿巖形成過程中，各種巖漿巖礦物在其

2、結(jié)晶生長過程中所捕獲的微量天然巖漿珠滴，隨著主礦物冷卻，它們或淬火凝結(jié)成玻璃，或進一步結(jié)晶析出硅酸鹽子礦物、金屬相和流體相（夏林圻，2002）。(1) 降壓和喪失揮發(fā)組分，升高了巖漿的過飽和程度，引 起晶體突然迅速生長，產(chǎn)生骸晶狀邊緣；(2) 早期晶體被部分熔蝕，在晶面上產(chǎn)生一些凹陷或熔蝕港灣(3) 溫度降低，也可以使巖漿成為過飽和，從而導致結(jié)晶成核作用發(fā)生，晶芽呈骸晶狀和樹枝狀快速生長；(4) 固體物質(zhì)被粘著于生長中晶體的晶面上，可以導致微量巖漿熔體與固體物質(zhì)一道被捕獲，形成一種“固體包裹體+ 熔體包裹體”的混合式包裹體，這種包裹體中，熔體包裹體通常位于固體包裹體向著主礦物晶體外側(cè)的那一面上

3、，該特點可幫助我們區(qū)別固體包裹體和子礦物；(5) 晶體的定向優(yōu)先生長也可以導致熔體包裹體被捕獲（夏林圻，2002，及其中參看文獻）知微而見著？100 mmExperimental and natural polyhedral olivine with melt inclusions (slow cooling)Keanakakoi Ash, Kilauea, HawaiiFaure & Schiano (2005)Experimental & natural skeletal (hopper morphology) olivine with melt inclusions (faster co

4、oling)Paricutin, Mexico500 mmKeanakakoi AshFaure & Schiano (2005)100 m mmJorullo volcano, MexicoFaure & Schiano (2005)Experiments in CMAS system.Effect of Growth Rate on Trapped Melt Compositions Rapid growth morphologies have inclusions that are moderately to strongly enriched in Al2O3. This is cau

5、sed by boundary layer enrichment due to slow diffusion of Al2O3 relative to CaO.Differences between Experimental & Natural Melt Inclusions Most natural melt inclusions show no evidence of anomalous enrichment in slowly diffusing elements, even in small inclusions and rapid growth forms like skeletal

6、 or hopper crystals. Volatile components have faster diffusivities than Al2O3 and thus should not generally be affected by boundary layer enrichment effects. Data from Johnson et al. (2008)Post-Entrapment Modification of Melt InclusionsDiffusive loss of H2 or molecular H2OCrystalMeltinclusionInclusi

7、on entrapmentCoolingShrinkage vaporbubbleCrystallization alongmelt crystal interfaceFe Diffusive loss of H-species Should be limited to 1 wt% H2O by redox equilibria & melt FeO if loss occurs by H2 diffusion (Danyushevsky, 2001). Leaves distinct textural features magnetite dust from oxidation. Possi

8、ble rapid diffusion of molecular H2O (Almeev et al., 2008).V 收縮泡/ V 包裹體 0.5 % ,該收縮泡內(nèi)幾乎不含揮發(fā)份,近于真空參考文獻：(Tait 1992; Schiano and Bourdon 1999).(Sobolev 1996; Newman et al. 2000; Saal et al. 2002).Solubilities with 2 Volatile Components Present H2O and CO2 contribute the largest partial pressures, so peo

9、ple often focus on these when comparing pressure & volatile solubilitySolid lines show solubility atdifferent constant total pressuresDashed lines show the vaporcomposition in equilibrium withmelts of different H2O & CO2From Dixon & Stolper (1995)熔體與礦物再平衡熔體與礦物再平衡1200在接近均一溫度停留時間長時（b-c），斜長石的橄欖石微晶重結(jié)晶成單

10、個晶體給定主礦物成分下均一溫度的過熱現(xiàn)象（Sobolev and Danyushevsky, 1994）EMP和SIMS要求玻璃質(zhì)熔體包裹體或?qū)Ξ愘|(zhì)包裹體淬火均一化！nLA-ICP-MS作為最新發(fā)展起來的原位微區(qū)測試技術(shù)，具有高靈敏度、快速測定多種元素等特點，廣泛用于微量元素測試和富U礦物定年。nTaylor（1997）首次應(yīng)用于熔體包裹體測試,展示了不受包裹體礦物相控制、不需要均一化等優(yōu)點；nLA-ICP-MS測試結(jié)果與EMP、SIMS相媲美（Pettke T. et. Al.,2004）二、單個熔體包裹體LA-ICPMS測試技術(shù)中國地質(zhì)大學（武漢）地質(zhì)過程與礦產(chǎn)資源國家重點實驗室mixih

11、ostiincliC1CxCx)-(1)/( ,)(100C1isamjrmjrmjNjjjsamiisamcpsCllcpslcpsl是利用USGS標準物質(zhì)（BCR-2G、BHVO-2G、BIR-1G）作為多外標回歸分析計算獲得，分子中的“100”代表全部金屬氧化物總和為100%。 l)1/()()(100C11iinclxlcpscpsxlcpscpslNjjjhostihostNjjjmiximixi要獲得 只要知道主礦物占混合物的質(zhì)量因子x，即可計算得到包裹體中的元素含量。cpxMg#186. 0109. 0Kdmelt/CpxMgFe)1 (03. 030. 0Kdmelt/OlMg

12、Fe)1 (037. 027. 0Kdmelt/CpxMgFe主要為二輝橄欖巖，并有少量方輝橄欖巖，多為原變粒結(jié)構(gòu)、鑲嵌粒狀結(jié)構(gòu)及殘碎斑結(jié)構(gòu)，含黑色的輝石脈流體包裹體中碳酸鹽礦物的成因捕獲 or 反應(yīng)菱鎂礦只在斜方輝石中發(fā)育, 白云石(或富Mg 碳酸鈣)只在單斜輝石中發(fā)育(熔體包裹體與寄主礦物的反應(yīng)？)n喬山橄欖巖中，兩中輝石中兩種碳酸鹽礦物都有捕獲！地幔碳酸鹽質(zhì)熔體的成因n(1) 含碳酸鹽橄欖巖的部分熔融（Frezzotti M L, et al. 2002）（伴隨富Al, Na質(zhì)玻璃的發(fā)育） n(2) 地幔中富硅碳酸鹽熔體的不混溶作用（Schiano P, et al. 1994; Fre

13、zzotti M L, et al. 1994 ） （硅酸鹽、碳酸鹽共生）n(3) 硅酸鹽-碳酸鹽熔體/流體與橄欖巖之間 的交代作用（Schrauder M, et al. 2002）（富硅碳酸鹽熔體/流體具富堿特征）與碳酸鹽熔體和斜方輝石同時相關(guān)的主要反應(yīng)n2Mg2SiO4( 橄欖石)+CaMgSi2O6( 單斜輝石)+2CO2=4Mg2Si2O6(斜方輝石)+CaMg(CO3)2(碳酸鹽)n2Mg2SiO4( 橄欖石)+2CO2 =Mg2Si2O6 ( 斜方輝石)+2MgCO3(碳酸鹽)早期富CO2 流體包裹體沿斜方輝石生長環(huán)帶發(fā)育的現(xiàn)象說明CO2 參與了與斜方輝石生長有關(guān)的反應(yīng). 在這些

14、反應(yīng)中由于斜方輝石和碳酸鹽都在反應(yīng)的一側(cè), 所以碳酸鹽是斜方輝石生長過程中捕獲的根據(jù)i2含量，熔體玻璃成分可以分為低硅（ ）和高硅（ ）兩類，但它們普遍富堿（2a2 ）、Al2O3（變化于 ，少數(shù) ）n潿洲島低硅熔體分布于解體的橄欖石礦物中，它們將橄欖石分隔成不同的塊體，熔體圍繞塊體隙間分布（圖、），直接提供了低硅熔體是由富硅熔體與橄欖石發(fā)生交代作用生成的證據(jù)。這可以用富熔體貧熔體反應(yīng)解釋，其結(jié)果是消耗橄欖石生成斜方輝石（，）。MORB ：Ol（Fo90-87）；Cpx（Mg#89-87）； Pl（An86-80）； Sp（Cr#38-47）從早期結(jié)晶的礦物中獲得相對原始的熔體組成OlOpxC

15、px虧損熔體是和二輝橄欖巖虧損熔體是和二輝橄欖巖/方輝橄欖巖殘余平衡的方輝橄欖巖殘余平衡的原始地幔熔體原始地幔熔體離子探針，兩個點，不扣除重結(jié)晶影響虧損并分異虧損并分異REE、Zr、Tioceanic-crust gabbroic rocks enriched in cumulus plagioclase?謝謝 謝！謝！QuickTime and a decompressorare needed to see this picture. Ni-NiOH2O-CO2 fluidMoore et al, 2008Figure 4Rhyolite500 MPa200 MPaDaciteXH2O(fl

16、uid)0.45P 400 MPaT = 1200CVolatile Abundances in Basaltic Magmas & Their Degassing Paths Tracked by Melt InclusionsNicole MtrichLaboratoire Pierre SueCNRS-CEA, FrancePaul WallaceDept. of Geological SciencesUniversity of Oregon, USAVolcan Colima, MexicoPhoto by Emily JohnsonReview of Experimentally M

17、easured Solubilities for Volatiles Volatiles occur as dissolved species in silicate melts & also in a separate vapor phase if a melt is vapor saturated. In laboratory experiments, melts can be saturated with a nearly pure vapor phase (e.g., H2O saturated). In natural systems, however, multiple volat

18、ile components are always present (H2O, CO2, S, Cl, F, plus noble gases, volatile metals, alkalies, etc.). When the sum of the partial pressures of all dissolved volatiles in a silicate melt equals the confining pressure, the melt becomes saturated with a multicomponent (C-O-H-S-Cl-F-noble gases, et

19、c.) vapor phase. Referring to natural magmas as being H2O saturated or CO2 saturated is, strictly speaking, incorrect because the vapor phase always contains other volatiles.Some key things to remember:Solubilities with 2 Volatile Components Present H2O and CO2 contribute the largest partial pressur

20、es, so people often focus on these when comparing pressure & volatile solubilitySolid lines show solubility atdifferent constant total pressuresDashed lines show the vaporcomposition in equilibrium withmelts of different H2O & CO2From Dixon & Stolper (1995)Estimating Vapor-Saturation Pressures for M

21、elt InclusionsEtna 3900 BP eruption Melt inclusions (12-14wt% MgO) in olivine Fo91 (Kamenetsky et al., Geology 2007)Etna 2001,2002Ca,Mg-bearing carbonatesArc basalts (Wallace 2005)CO2 diffuses into a shrinkage bubble during cooling CO2 loss demonstrated in heating experiments on olivine (Fo88) from

22、a Mauna Loa picrite. Melt inclusions re-homogenized at 1400C for 10 min. As much as 80% of the initial CO2 can be transferred to a shrinkage bubble over a cooling interval of 100C.Carbonate crystals lining bubble wallsTotal vapor pressure (PH2O+PCO2) for an inclusion can be calculated assuming: Vapo

23、r saturation how do we know melts were vapor saturated? Large variations in ratios of bubble volume to inclusion volume Presence of dense CO2 liquid in bubbles Homogenization not possible in heating experiments No post-entrapment loss of CO2 or H2O to bubbles, no leakage, no H2O diffusive loss. CO2

24、lost to bubbles lowers vapor saturation pressure. Cervantes et al., (2002)Chlorine Solubility in Basaltic Melts In this simplified experimental system, basaltic melts are either saturated with H2O-Cl vapor or molten NaCl with dissolved H2O (hydrosaline melt) Natural basaltic melts typically have 200

25、MPa - Melt interaction with CO2-rich gas CO2-rich gas fluxing depletes melt in H2O and thereby causes olivine crystallizationJorullo (Mexico) monogenic basaltic cinder coneCentral part of the subduction-related Trans-Mexican Volcanic Belt Phase diagram for early Jorullo melt composition (10.5 wt.% M

26、gO) constructed using MELTS (Ghiorso & Sack,1995; Asimow & Ghiorso,1998) and pMELTS (Ghiorso et al., 2002). Crystallization recorded by melt inclusions mainly driven by H2O loss during magma ascent- At 400-200 MPa: Water loss likely due to gas fluxing olivine crystallization- At low pressure: CO2-de

27、pleted melts lose H2O by its direct exsolution in the vapor phaseJorullo (Mexico) monogenic basaltic cinder coneH2O loss and crystallizationJohnson et al., 2008 , EPSL 269Melt inclusion studies provide evidence for crystallization driven by H2O loss (+ cooling) at many volcanoes.Message can be diffi

28、cult to decipher because of additional processes such as: - Mixing involving degassed and undegassed magmas (Popocatpetl & Colima; Atlas et al., 2006) - Mingling (e.g. Fuego, Roggensack 2001) - Assimilation (Paricutin, Lurh 2001; Jorullo, Mexico, Johnson et al., 2008) A case of efficient control of

29、H2O degassing on magma crystallization is Stromboli - an open conduit volcanoe with low magma production rate and high degassing excess - where magmas share same chemical composition but have contrasting textures, crystal abundances (10-50%) and viscosities (Mtrich et al., 2001, Landi et al., 2004;

30、Bertagnini et al., 2003, 2008)H2O loss and crystallization Sulfur and halogen degassing140 MPa140 MPa 80% S is lost between 140 and 10 MPa, whereas Cl starts degassing at low pressure (Ptot20-10MPa) and F at Ptot submarine sulfide-saturated basalts (Dixon et al., 1991)Iraz: Benjamin et al. 2007, JVG

31、R,168, 68-92Arenal: Wade et al. 2006, JVGR,157, 94-120 Etna: Spilliaert et al., 2006, EPSL, 248, 772-786Sulfide saturationEruption styles and degassing budgetInformation from melt inclusionsWhat are the recent improvements?Stromboli - 2006Basalt: LK: Laki 1783-84 eruption; K: Kilauea, annual average

32、; ML Mauna Loa; PC Pacaya 1972 eruption; St: Stromboli annual averageVolatile budget for basaltic fissure eruptions Predicted relationship between SO2 emissions and eruptive magma volume assuming that SO2 released during eruption is provided by the sulfur dissolved in silicate melt Compared to sulfu

33、r emissions measured by independent methods as ulraviolet correlation spectrometer (COSPEC), atmospheric turbidity and Total Ozone Mapping Spectrometer (TOMS)Uncertainties in SO2 emission data are generally considered to be about 30% for the TOMS data and 2050% for COSPEC. Pre-requisite: no differen

34、tial transfer of gas DS = CS(M.I.) CS(res) Wallace 2005, JVGR CS(M.I.): S content in primitive melt (melt inclusion)CS(res.) : Residual S content in bulk lava or in matrix glass corrected for crystallizationPetrologic estimates of the sulfur output 1,3 Thordarson &Self: (1993) Bull Vocanol 93 and (1

35、996) JVGR 74; 2 Thordarson et al., (2001), JVGR, 108Eldgj 2Laki 1Melt inclusionsp-tephra*s-tephralava M.I. and W.R. have comparable composition 95% of initial sulfur releasedSulfur partly exsolved in gas phase during magma ascent at shallow depth prior to eruption 75% escaped at vents, lofted by the

36、 eruptive column (strong fire fountaining) to 5-15 km altitudes at the beginning of each eruptive phase and 25% during the lava flowing*p-tephra : quenched melts indicative of magma degassing during during ascent Approach used for assessing the impact of large flood basalts on the atmosphere (Self e

37、t al; 2008 Science)Volatile budget for basaltic fissure eruptions Petrologic estimates commonly used for assessing the degassing budget of other volatiles in particular Cl and F The 94 days long flank eruption that occurred in 2002 at Mt Etna: Modelling of the pressure related behavior of sulfur at

38、Etna (2002 eruption) 80% sulfur released in the gas phase during magma ascent (between 140 and 10 MPa) in agreement with conclusions drawn by Self, Thordarson and co-authorsSO2 flux: 6.9 108 kg (Petrologic estimates, Spilliaert et al. 2006) / 8.6 108 kg (COSPEC, Caltabiano et al. 2006)Comparable S/C

39、l molar ratio (5) in vapor phase derived from melt inclusion data and measured in gas emissions no differential degassing of S (or Cl) Arenal (COSPEC 0.41 Mt of SO2 released since 1968 )Better agreement with COSPEC when considering the S content (2000 ppm) of olivine-hosted melt inclusions represent

40、ative of the undegassed basaltic andesitic magma rather than partly degassed melt trapped in Plag & CpxPetrologic estimates even COSPEC a part of sulfur could be lost?Sulfur partly exsolved in gas phase during magma ascent at shallow depth without differential transfer of sulfur Consistency between

41、petrologic estimates of SO2 budget and independent estimates (COSPEC or others)(Wade et al., 2007)Volatile budget for basaltic fissure eruptionsDifferential transfer of gas bubbles Excessive degassing- Izu-Oshima in Japan (Kazahaya et al 1994) - Villarica in Chile (Witter et al., 2004), - Popocatepe

42、tl in Mexico (Delgado-Granados et al., 2001; Witter et al., 2005) - Etna & Stromboli in Italy (Allard., 1997; Burton et al., 2007) - Masaya in Nicaragua (Delmelle et al., 1999, Stix, 2007). Stromboli Magma supply rate is assessed to be 0.001 km3 y-1, 154 higher than the magma extrusion rateAssuming

43、0.22 wt% S dissolved in magma as derived from M.I. 10% of magma is extruded given that quiescent degassing contributes to 95% total SO2 degassing (Allard et al., 2008) Excessive degassing at persistently active basaltic volcanoes such as:e.g. Jaupart et Vergniolle, 1988, Vergniolle, 1996; Philips an

44、d Wood 1998 Differential transfer of gas bubbles MI data used for assessing the mass (volume) of unerupted magma when combined with gas flux measurements Qm = SO2 /2D DSQm : Mass flux of magma2DS = SO2 degassed from the magmaSO2 = SO2 flux measured by COSPEC or other techniquesUnresolved questions a

45、nd directions for future studiesBenbow (Ambrym, Vanuatu) Most suitable melt inclusions for volatile studies quenched pyroclastites Efforts dedicated in the last 15 years basic data for assessing:- the SO2 output from syn-eruptive degassing of basaltic magmas ascending in closed system conditions, with no differential gas transfer (gas loss) prior to eruption- the vo