Az alábukó lemezből felszabaduló fluidumok és szerepük szubdukciós környezetben
Patkó Levente Szubdukció és köpenyék Ph.D. kurzus 2014.11.22.
Vázlat • Szükségszerű‐e a devolatilizáció – archaikumi TTG, adakit • Devolatilizáció – kőzettani modell • Alábukó lemez – köpeny kölcsönhatása (Catalina Schist) • Devolatilizáció – numerikus modell • Devolatilizáció – elem konzerválás/felszabadulás (természetes minták és kísérletek) • Devolatilizáció – fázis diagramok
Bevezetés Diagram of a typical ocean ocean subduction zone.
Davidson JP, Reed W, and Davis PM (2002)
Van‐e mindig fluidum felszabadulás?
‐ Archaikumi TTG gránát reziduum a forrásrégióban ‐ 2,5 Ga‐nál fiatalabb granitoidok plagioklász a forrásrégióban
Arndt, 2013
Van‐e mindig fluidum felszabadulás?
Arndt, 2013 Present PT útvonal modern szubdukciós zónákban Archean PT útvonal archaikumi szubdukciós zónákban Kiindulási alap: az archaikumi óceáni kéreg nagyobb hőmérsékletű, mint a jelenlegi óceáni kéreg. Következmény: az archaikumi óceáni kéreg parciális olvadása beindul a víztartalmú fázisok elbomlása előtt felzikus olvadékok direkt képződése
Van‐e mindig fluidum felszabadulás? H = hornblende-out A = anthophyllite-out C = chlorite-out Ta = talc-out Tr = tremolite-out Z = zoisite-out The stability fields of both garnet and plagioclase are delimited by the G and P lines. The grey field is the P –T domain where a magmatic liquid generated by partial melting.
OC = oceanic crust CC = continental crust ms = solidus of an hydrated mantle black areas = magma dotted areas = fluids
Archaikumi TTG
Adakitok
Mészalkáli kőzetek
Martin, 1999
Adakitok geokémiai jegyei • Adakites are intermediate to felsic volcanic rocks, andesitic to rhyolitic in composition. • Adakites have trondhjemitic affinities (high Na2O contents and K2O/Na2O ~ 0.5) and their #Mg (0.5), Ni (20–40 ppm) and Cr (30–50 ppm) contents are higher than in typical calc‐alkaline magmas. • Their Sr contents are high (>300 ppm, until 2000 ppm) and REE show strongly fractionated patterns with very low heavy REE contents (Yb ≤ 1.8 ppm, Y ≤ 18 ppm). • Consequently, high Sr/Y and La/Yb ratios are typical and discriminating features of adakitic magmas, indicative of melting of a mafic source where garnet and/or hornblende are residual phases. • Adakitic magmas are only found in subduction zone environments, exclusively where the subduction and/or the subducted slab are young ‐20 Ma.
Adakitok geokémiai jegyei
A) Üres kör (Costa Rica) és négyzet (Equador) tipikus adakit REE lefutást jelez, míg a fekete négyzet mészalkáli dácitot mutat be (Chile)
B) Archaikumi TTG REE lefutás Martin, 1999
Adakitok geokémiai jegyei
The HREE are compatible in garnet and the presence of this phase in the residue of melting provides a ready explanation for this distinctive geochemical feature. The Sr-Y ratio and Y concentration are commonly used in conjunction with La/Yb and Yb: classical island arc basalts generally do not show the depletion of the HREE and have relatively low Sr/Y and high Y, features that are ascribed to the presence of plagioclase (in which Sr is compatible) in the solid residue of melting.
Martin, 1999
Adakitos vulkanizmus
Martin, 1999
Adakitos vulkanizmus ismert helyei: 1. Austral Chile; 2. Ecuador; 3. Panama and Costa Rica; 4. Mexico; 5. Cascade; 6. Aleutians; 7. Kamchatka; 8. Japan; 9. Philippines; 10. New Guinea
KPR magmás kőzetei
Harangi és Lenkey, 2007
Adakitok a KPR‐ben A mészalkáli kőzetsorozaton belül Segedhi és Downes 4 alcsoportot különített el, amelyek közül az egyik az adakitszerű kőzetek alcsoportja. Jellemzőjük az amfibol és biotit fenokristályok jelenléte, a nagy Sr/Y arány. Megjelenésük: Erdélyi‐Érchegység (12,5‐7,5 ma) és Dél‐Hargita (3,5‐0,03). „Generation of most adakite‐like magmas suggests delamination and partial melting of a high density garnet‐bearing (eclogitic) lower crust.” /Seghedi and Downes, 2011/
Kenyér‐hegy Arany (falu) mellett, Hunyad megye
Devolatizáció – kőzettani modellKöpenyék stabilitás Fekete nyíl – olvadék Fehér nyíl ‐ fluidum Vékony nyíl ‐ köpeny áramlás
klorit stabilitás
alábukó kéreg
alábukó köpeny
Stabilitás nő krizotil ~ lizardit antigorit
Hideg lemez esetén a szerpentin (azaz ilyen mélységben antigorit) stabilitása nem szűnik meg az A‐fázis megjelenése előtt. Következésképp az A fázis, amely szintén víztartalmú, Schmidt még nagyobb mélységbe and Poli, képes fluidumot szállítani. 1998
OH‐tartalmú ásványok stabilitása – óceáni kéreg Experimentally determined phase relationships for watersaturated MOR basalt: amph = amphibole chl = chlorit cld = chloritoid cpx = jadeitic or omphacitic clinopyroxene epi = epidote gar = garnet law = lawsonite zo = zoisite. Schmidt and Poli, 1998
OH‐tartalmú ásványok stabilitása – óceáni Phase diagram for litoszféra H2O-saturated average mantle peridotite and maximum H2O contents bound in hydrous phases in average peridotites. Upper value: harzburgite; middle value: lherzolite; lower value: pyrolite. ‘A’ = phase A amph = amphibole chl = chlorite cpx = clinopyroxene gar = garnet ol = olivine opx = orthopyroxene serp = serpentine sp = spinel tc = talc
Schmidt and Poli, 1998
Devolatizáció – kőzettani modell átalakulás a köpenyékben és a hangingwall köpenyrészen
Serpentine and the 10Å phase are two hydrous minerals, in addition to chlorite, that are stable to considerable depths in the subducted oceanic lithosphere (up to 150 km, depending on the pressure–temperature structure of the slab). Amphibole was once proposed as a carrier for transporting water to depth in the mantle, but amphibole becomes unstable at depths shallower than the depths at which melting begins beneath most arc volcanoes. As shown in the new vapour-saturated peridotite melting experiments, amphibole is stable from ,0.8 to 2 GPa on the solidus and chlorite is stable from 2 to 3.6 Gpa. Grove et al., 2009
Felszabaduló elemek forrása Lithologic thicknesses used: sedimentary rocks (400 m), altered oceanic crust (1000 m), fresh oceanic crust (1000 m), gabbro (3000 m), depleted mantle (6000 m), serpentinite (2000 m).
Tenthorey and Hermann, 2004
Serpentinites contain significant amounts of fluid‐mobile elements such as B, Cs, As, and Ba, which during seafloor alteration are incorporated into mantle rocks. During the later high‐ pressure breakdown of the serpentinites, these trace elements are redistributed among the residual olivine, orthopyroxene and fluid. We find that B is far more compatible in these minerals than previously assumed. High B concentrations in mantle olivines might be a fingerprint for previous metasomatism or serpentinization.
Alábukó lemez – köpeny kölcsönhatása Catalina Schist ‐ Kalifornia A Catalina Schist különféle tektonometamorf egységekből áll. Ezek az egységek mélange-ként értelmezhetők, amely mafikus, ultramafikus, metaszediment blokkokból és mátrixból építkeznek különböző arányokban.
Keletkezési modell ‐ mechanikus keveredés • A vizsgált egységben mafikus‐ ultramafikus blokkok keveredése. • Al‐Cr összefüggésnél a mechanikus keveredés magyarázza a mátrix összetételét. • Az Al‐Si diagramnál a 2 blokk mechanikus keveredésével nem kapjuk meg a mátrix Si tartalmát, ami szükségessé teszi összetettebb modell felállítását metaszomatózis integrálása a modellbe. Bebout and Barton, 2002
Keletkezési modell ‐ mechanikus keveredés és metaszomatózis
Plot of trace element concentrations in metasedimentary rock having undergone metasomatic exchange with ultramafic mélange matrix, relative to the concentrations in the same layer but away from the interface with this mélange matrix (from. Breeding et al 2004). (a) Cartoon demonstrates schematically the textural and mineralogical relationships between the siliceous ultramafic mélange matrix and mafic and ultramafic blocks floating in the mélange. (b) Sketch illustrating the complex mineralogical zonations at the rims of ultramafic blocks in the mélange, indicating additions of Si and other components.
Bebout and Barton, 2002
A Catalina Schist geodinamikai elhelyezése
Bebout, 2007
Képaláírás az előző diához Sketch of an ocean–continent subduction zone, illustrating key structural elements, some selected flux pathways. Oceanic crust (and its associated mantle part of the oceanic lithosphere), variably altered geochemically at mid‐ocean ridges (MOR), and sediment deposited onto this crust, are deeply subducted, contributing fluids and elements to the mantle wedge (hanging wall). It is possible that fluids are also contributed from the ultramafic part of the subducting oceanic lithosphere previously hydrated during slab bending in trench regions. On this figure (insets and main figure), the blue arrows indicate additions of slab‐derived “fluids” to the mantle wedge. At shallower levels (forearc regions, in particular), these fluids are thought to be aqueous fluids, whereas the fluids added to the mantle wedge at greater depths (beneath volcanic arcs and into the deeper mantle) likely transition into being silicate melts.
Alábukó lemez – köpeny kölcsönhatása
assumed kilometre-scale dragging folds
Angiboust et al., 2012
H2O eloszlás a köpenyékben
Olvadék eloszlás a köpenyékben
Numerikus modellek A) eset peremfeltételei: öreg, 130 ma korú óceáni lemez 6 cm/év sebesség, köpenyék T-je 1250C B) eset peremfeltételei: fiatal, 10 ma korú óceáni lemez 6 cm/év sebesség, köpenyék T-je 1250C Mindkét eset az „equilibrium transport” feltételezésével készült (azaz nincsenek törések és inhomogenitások miatt kitüntetett irányok), viszont van köpenyék áramlás. Iwamori, 1998
Numerikus modellek – Iwamori, 1998 Idős lemez (A kép) The subducted oceanic crust, which initially contains ~6 wt. % H2O mainly in chlorite, lawsonite and amphibole, undergoes dehydration and produces aqueous fluids of total ~3 wt. % at a depth of 50 km. As it enters the mantle wedge, a layer of serpentinite thinner than the oceanic crust is formed to accommodate all H2O released, since it can absorb 8 wt. % H2O. The serpentine breaks down where this layer thickens to reach an inner wedge region of above 600°C. At ~150 km depth, serpentine and chlorite break down to form a vertical column through which H2O is transported by a ‘fluid’ discussed. When the fluid reaches a depth of ~80 km, the temperature of the system exceeds the practical solidus temperature to cause significant melting. Then H2O is absorbed into the melt and transported towards the trench side along the solid stream lines, resulting in a horizontal melting layer. Fiatal lemez (B kép) By subduction of a relatively hot slab (age about 10 Myr), with the same parameters due to the higher temperature along the slab, the relevant dehydration reactions occur at shallower depths. Consequently, hydrous columns are formed at shallower levels, closer to the trench.
Devolatizáció ‐ szerpentin Az alábukó óceáni litoszféra szerpentinesedését elősegítik a nagy számban jelentkező lisztrikus vetők. A felszabaduló fluidum szerpentinek kialakulásához vezet a köpenyékben (serpentinization 2).
Guillot and Hattori, 2013
A possible phase diagram for the MgO–SiO2–H2O system. To illustrate the uncertainty, two steep H2O-conserved reactions are shown as wide gray bands (modified after Evans 2004). Mineral compatibilities in the divariant fields are shown on the MgO–SiO2 binary line after projection from H2O. Abbreviations: A, Atg = antigorite; B, Brc = brucite; F, Fo = forsterite; L, Liz = lizardite; T, Tlc = talc.
Evans et al., 2013
Numerikus modellek – fluidum vándorlás A T a szilikátok oldhatóságátot jobban befolyásolja, hiszen csökkenő P melett is nő a Szilikátos részarány a fluidumban. A felszabaduló fluidum karaktere útja során is jelentősen változik (köpeny karakterekben gazdagodik).
Manning, 2004
A fluidum jellege szubdukciós környezetekben
L. P.1
• A szubdukciós zónában a víz a domináns fluidum fázis • A devolatizáció jellege/mértéke elsősorban a szubdukáló lemez OH‐tartalmú ásványok stabilitásától függ • A többi illóhoz képest a poláris vízmolekula jóval nagyobb mértékben képes elemek oldására, ezáltal szállítására • A víz, mint oldószer tulajdonságai függ a sűrűségétől, a rendezettségétől, a hidrogén‐kötéstől és a molekula disszociációs tulajdonságaitól. • Növekvő hőmérséklettel a rövidtávú rend felbomlik a H2O molekulákban. A szuperkritikus H2O esetén a hidrogén‐ kötések hálózata már szétszakadozott. Ennek ellenére a H2O a fő oldóképes fluidum egészen 10 Gpa és 1000 °C kondícióig, bár egyre kisebb hatékonysággal.
Slide 28 L. P.1
H2O density is 1.2–1.4 g/cm3 at sub-arc depths and 1.0–1.1 g/cm3 at the thermal maximum in the mantle wedge Levente Patkó, 11/21/2014
Fluidum változatosság szubdukciós környezetekben
Poli et al., 2009 Schematic illustration showing the complexities in fluid speciation, from ocean floor metamorphism to volatile release at high pressure. A heterogeneous pattern of volatile addition is suggested by heterogeneity in vent chemistry in the oceans. Relatively CO2-rich fluids can be released in the forarc region, whereas fluids dominated by H2O are liberated at higher pressure. Similarly to what observed at very low temperature conditions, H2O–CH4 fluid mixtures might form locally at high-pressure, assuming that Fe3+-mineral phases (e.g. skiagitic garnet) sequester oxygen. Fluid-mixing promotes graphite/diamond precipitation. Depth and extent of carbonate–hydrate phase assemblages are a function of volatile addition.
Felszabaduló fluidum főelemgeokémiája ‐ The deeper fluids are similar to the direct, shallow samples in one important way: total solute concentrations are low, regardless of pressure, temperature, or chlorinity. Deep fluids have TDS only two to three times that of seawater, and no more than 50% higher than shallow fluids from near the entrance to the subduction zone. ‐ TDS, though generally modest, nevertheless increases with depth. This arises from changes in solubility of rock‐forming minerals due to the PT‐enhancement of the solvent power of H2O. ‐ There are important changes in major elements with depth. The dominant solutes in deep fluids are Si and Na. Al concentrations are higher than Ca, Fe, and usually Mg. Thus, the solutes in H2O‐rich fluids in subduction zones are dominated by alkali and aluminosilicate components. This contrasts with fluids from shallow environments, where alkali and other metals predominate and Al is virtually insoluble. Manning, 2004
Felszabaduló elemek A diagramok bemutatják az AOC (altered oceanic crust = tengeralatti metamorfózis által érintett) és a szubdukció során metamorfizálódott bazaltos kéreg (metabazalt) geokémiai összevetését.
A: K és Rb átfedésben tenger alatti mmf során felvett elemtartalom a szubdukció során nem módosul B: Ba és K csökkenése mmf dehidratáció során Th‐hoz képest ΣAB ‐ LILE elememek szubdukció folyamán kevéssé mobilisak C: Pb mobilisek lehetnek HP és UHP fluidumokban és olvadékokban D: az U koncentrációja a tengerfenéki mm során nő viszonyítva a REE, HFSE, Pb és TH‐ hoz képest. E: Th hozzáadódás mmf. Körülmények között történő metaszomatózis során F: LREE veszteség metamorfózis során MREE‐hez képest Bebout, 2007
Felszabaduló elemek‐ metamorf analógia Trace element data for a range of pelitic rocks of varying metamorphic grade. All of the samples are from northern New Caledonia and are understood to originally comprise part of the same sedimentary sequence. There is some variation in the trace element composition of the pelitic rocks, but there is no systematic loss (or gain) of trace elements (including the fluid‐mobile elements) associated with prograde metamorphism. We suggest that the trace element variations are not due to metamorphism, but are largely inherent variations in the composition of the original sedimentary rocks. Spandler et al., 2004
N isotopic composition in the Schistes Lustrés metasediments (deep-sea J-C sediments)
With increasing metamorphic conditions, δ15N range remains constant N was preserved during subduction The Alpine and Corsican Schistes lustrés (SL) are Jurassic-Cretaceous metasediments often associated with ophiolites. Deep-sea sediments, and particularly the SL, are made up of a hemipelagic-pelagic background (HPB) associated with detrital components of local or distant origin. The nature of the HPB, mostly conditioned by Tethyan and world- wide events, is of great help as an at least rough stratigraphic marker.
Busigny et al., 2003
Instruments for high‐pressure research
Diamond anvil cell (DAC)
Piston cylinder press
Multi‐anvil press
100 GPa (> 1 Mbar) > 5000 ˚C
6 GPa (60 kbar) 1700 ˚C
25 GPa (250 kbar) 3000 ˚C
Keppler, short course slide
Kísérleti munkák ‐ módszerek
Keppler, short course slide
Kísérleti munkák ‐ módszerek
Hermann, 2009 EURISPET
Felszabaduló elemek ‐ szerpentinitit
Trace element concentrations (normalized to primitive mantle values) of starting serpentinite (squares), dehydrated olivine-rich residual phase (dark gray shading), and dehydration fluid (light gray shading) as measured from quench precipitate in diamond traps. In starting material only B, As, and Cs are significantly enriched with respect to primitive mantle values. Nearly all fluid-mobile elements are greatly enriched in fluid phase relative to their concentration in residue, except for B, which is only enriched by factor of ~5. We suggest that B release is limited during dehydration of serpentinite.
Piston cylinder kísérlet
Tenthorey and Hermann, 2004
L. P.4
Felszabaduló elemek – kísérleti munkák P = 2.2 GPa, T = 600-750°C, time 10-20 days under H2O saturated conditions
EPSM = experimental pelite starting material Quartz for synthetic fluid inclusions
Spandler et al., 2007
Slight T gradient driven circulation inside the capsule.
Piston cylinder kísérlet
Slide 38 L. P.4
The trapping and subsequent analysis of synthetic fluid inclusions in quartz is routinely used to quantify hydrothermal fluid compositions and element solubilities at relatively low P. Levente Patkó, 2/3/2015
Felszabaduló elemek – kísérleti munkák Subsolidus fluid inclusions
Supersolidus mixed fluid+melt inclusions
Photomicrographs of synthetic fluid and melt inclusions trapped in quartz during experiments. A. Pure water inclusions with distinct vapour bubbles from experiment TEST 1 (1.0 GPa, 650 °C). B. high-density (N1.0 g/cm3) pure water inclusions from experiment TEST 2 (1.5 GPa, 650 °C). C. High-density fluid inclusions from experiment PFI 3 (2.2 GPa, 600 °C). Note, the distinct daughter crystals in the inclusion in focus. D. Highdensity fluid inclusions from experiment PFI 2 (2.2 GPa, 650 °C). Note, the cluster of daughter crystals. E. Quartz chip from experiment PFI 7 (2.2 GPa, 675 °C) with abundant large fluid/melt inclusions. F. Cluster of large quasi-rectangular fluid/melt inclusions from experiment PFI 4 (2.2 GPa, 700 °C). G. Large rectangular fluid/melt inclusion within a trail of smaller fluid/melt inclusions from PFI 4 (2.2 GPa, 700 °C). Note, the large vapour bubbles and complex daughter Spandler et al., 2007 crystals in the inclusions.
Felszabaduló elemek – kísérleti munkák
Residue method: is simply the ratio of the extrapolated subsolidus fluid composition to the analysed EPSM residue composition. Mass‐balance method: using the following formula: Spandler et al., 2007
where X is the starting mass ratio of fluid to EPSM and Ci is the element concentration.
Felszabaduló elemek – kísérleti munkák Gránát növekedése az EPSM reziduumban
The degree of element loss is calculated to be less than 0.1% of the original composition for almost all elements!
‐Na and Cs are the most ‘fluid soluble’ elements ‐HFSE and REE are the most ‘fluid insoluble’ elements ‐Aqueous fluids are surprisingly dilute Spandler et al., 2007
Felszabaduló elemek – kísérleti munkák Megfigyelések: ‐ As Pb alloys with the capsule during the experiments, only the residue method was used to calculate Pb partitioning. ‐ The partition coefficients produced using the two methods are remarkably similar for all other elements, indicating that most elements are not significantly affected by fluid transport and precipitation during the experiments. ‐ The precipitated alkali sheet silicates on the capsule walls of explains the significantly lower partition coefficients calculated for Na, Rb, and Cs using the residue method. ‐ It should be noted that the solid/fluid partitioning data for U is regarded as a maximum value, as U‐oxides are most likely present in the residue of the subsolidus experiments. These U‐ oxides probably form due to the high initial U content of the EPSM starting material. ‐ Examination of the partitioning data reveals that all elements preferentially partition into the solid residue rather than the fluid at subsolidus conditions.
Fluidum összetétele ‐ oldódás • The solubility of rutile was measured in a piston‐cylinder apparatus. • Solubility was determined by weight loss using a double‐ capsule method. • Variation in rutile solubility in H2O with inverse temperature at 1 GPa (a) and with pressure at 800 °C (b). • Rutile solubility rises with increasing P and T. Antignano és Manning, 2008
Fluidum összetétele ‐ oldódás 800°C and 2.6 GPa
2.6 GPa
REE concentration versus ionic radius a) in pure H2O and in various solutions containing ligands; each solution, shown in different color and symbol, displays a distinct REE pattern d) In pure H2O (circles) and in NaCl‐bearing solution (diamonds) at 600 and 800 ◦C; arrows and numbers next to them show the difference in La solubility with addition of NaCl to the solution. Tsay et al., 2014
Képaláírás az előző diához • All the ligands promoted the increase in REE solubility relative to pure H2O. • In case of the NaCl‐bearing aqueous solution, experiments performed at 600◦C show that at this lower temperature the presence of NaCl yields a relatively larger increase in REE solubility in the fluid phase compared to that observed at 800 ◦C. Furthermore, the fractionation between LREE and HREE due to the presence of chloride was even more pronounced.
Szubdukálódó lemez és az elemfelszabadulás kapcsolata
A Catalina Schist különböző egységeinek P‐T útjai
Minél hidegebb a szubdukálódó lemez (kor és lebukási szög függés) annál több fluidmobilis elemet szállít a mélybe.
Bebout, 2007
L. P.2
A fluidum összetétele ‐ fázisdiagramok A kritikus görbe és az oldódási görbe teljes hosszukban elkülönülnek.
pl. NaCl-H2O rendszer
Manning, 2004
Slide 47 L. P.2
This figure possess a critical point marking termination of the distinction between the liquid and the vapor phase. At T and P above this point, there is only one phase, a supercritical fluid. In a system with both A and H2O, the two critical points are linked together by a ‘‘critical curve’’ that marks the boundary between the stability region of a single supercritical fluid, and that of two fluids, a denser liquid and a less-dense vapor. Another curve extends from the point at which ice and mineral A coexist with liquid and vapor (the A-ice eutectic). This is the ‘‘solubility curve,’’ which marks the stable coexistence of mineral A with liquid and vapor. Compositions of liquid, gas, and supercritical fluid vary along critical and solubility curves. For example, with increasing T along the solubility curve, the liquid composition changes continuously from nearly pure H2O to pure A. Levente Patkó, 11/21/2014
L. P.3
A fluidum összetétele ‐ fázisdiagramok pl. albit-H2O rendszer
A kritikus görbe és az oldódási görbe keresztezi egymást és így két kritikus pont alakul ki.
Manning, 2004
Slide 48 L. P.3
In some, the critical curve and solubility curve remain separated over their entire lengths; in others, they intersect to yield two ‘‘critical end-points.’’ The lower (first) critical end-point typically lies near the critical point of H2O. The upper, or second, critical end-point lies at high P and T, potentially near subduction paths. Levente Patkó, 11/21/2014
A fluidum összetétele ‐ fázisdiagramok Teoretikus megközelítésben az SiO2‐ H2O rendszert szokták alkalmazni leegyszerűsítve a kőzet‐ fluid rendszert. Addition of H2O to anhydrous systems significantly lowers melting temperatures, giving rise to the so called wet solidus, which is also commonly called the vapor‐ or fluid‐ saturated melting curve. Hermann et al., 2006
Transiti‐ onal
A fluidum összetétele ‐ fázisdiagramok
solute‐ rich
Aqueous fluid dilute
Hydrous melt
At high pressure the wet solidus terminates at a position known as the second critical endpoint and marks the condition where hydrous melt and aqueous fluid become completely miscible on the wet solidus.
very concentrated
Hermann, 2009 EURISPET
Szubdukálódó lemez és belőle felszabaduló fluidum oldási képessége
Hermann et al., 2006
Fázisdoagrammok és lehetséges p‐T utak ‐ Trace element concentrations in
Hermann and Rubatto, 2009
hydrous melts are at least one order of magnitude higher than in aqueous fluids. Therefore, sediment melts provide an efficient way of extracting incompatible elements from the subducted slab. ‐ Thermal models for top of slab T (I: Peacock et al., 1994, II: Kincaid and Griffiths, 2004, III: van Keken et al., 2002) determines whether an aqueous fluid, hydrous melt or a transitional fluid is released from subducted sediments at sub‐arc depth. ‐ Squares refer to experiments where trace element concentrations of the hydrous melts have been analysed. Also shown is the stability of phengite, which is the major host for LILE in the solid residue (Hermann and Spandler, 2008). The transition from accessory allanite (A) to monazite (M), which are the main hosts for LREE, Th and U in the residue, is shown.
Hydrous melt vs. aqueous fluid The concentration of buffered elements in the produced hydrous melts (open symbols) compared to aqueous fluid from Spandler et al. (2007), red symbols (A); Green and Adam (2003), green symbols (B); and Antignano and Manning (2008), yellow symbol (C). Note the strong drop in concentration of elements at the transition from hydrous melt to aqueous fluid. Concentration buffered Phengite: K Rutile: Ti Zircon: Zr Allanite/Monazite La, Ce, Th
Hermann and Rubatto, 2009
A szubdukálódó lemez és belőle felszabaduló fluidumok elemtranszportja Az eredmények azt mutatják, hogy a szubdukciós övek vulkáni kőzeteiben nagy koncentrációval bíró elemek (LILE, LREE, B, Pb) felszabadulása a szubdukálódó lemezből csak nagy mélységben történik meg. Mindez ezen elemek hatékony transzportjára utal, amiből a köpenyék erőteljes átjárhatósága következik (highly chanellized mantle wedge).
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