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SUPPLEMENTARY MATERIAL
Here we present: (1) cathodoluminescence (CL) images, 89Y+/94Zr+ ion images, and line profiles of Ti, P, Y, Ce, and Hf concentrations for the remaining zircons analyzed as part of this study (YTT8, Fig. S1; Q3, Fig. S2; Q8, Fig. S3; SN11, Fig. S4; ADK29, Fig. S5; and ADK9, Fig. S6); (2) a more detailed discussion of the pressure and temperature estimates assigned to each of the samples; (3) our synthetic Ti line profiles that allow us to evaluate the potential effects of smoothing on the natural images (e.g., decreasing peak heights and the broadening of peak widths); (4) a discussion of titania activities (aTiO2) focusing on the differences between EMBED Equation.3 and EMBED Equation.3 values as calculated using coexisting glasses and titanomagnetite-ilmenite compositions from low-pressure experiments on silica-rich compositions ADDIN EN.CITE ADDIN EN.CITE.DATA ( HYPERLINK \l "_ENREF_30" \o "Martel, 1999 #530" Martel et al. 1999; HYPERLINK \l "_ENREF_31" \o "Parat, 2008 #531" Parat et al. 2008; HYPERLINK \l "_ENREF_38" \o "Scaillet, 1999 #428" Scaillet and Evans 1999; HYPERLINK \l "_ENREF_49" \o "Tomiya, 2010 #529" Tomiya et al. 2010), and how titania activities evolve in experimental high-silica liquids with decreasing temperature ADDIN EN.CITE ADDIN EN.CITE.DATA ( HYPERLINK \l "_ENREF_9" \o "Costa, 2004 #532" Costa et al. 2004; HYPERLINK \l "_ENREF_30" \o "Martel, 1999 #530" Martel et al. 1999; HYPERLINK \l "_ENREF_31" \o "Parat, 2008 #531" Parat et al. 2008; HYPERLINK \l "_ENREF_36" \o "Rutherford, 2003 #533" Rutherford and Devine 2003; HYPERLINK \l "_ENREF_38" \o "Scaillet, 1999 #428" Scaillet and Evans 1999; HYPERLINK \l "_ENREF_49" \o "Tomiya, 2010 #529" Tomiya et al. 2010); and (5) a discussion of the data set used in our fit of equation (4) in the main text: ln(Ti ppm)zrc + ln(aSiO2) ln(aTiO2) vs. A1 + A2/T(K) + A3(P 1)/T(K).
Line profiles, CL images, and 89Y+/94Zr+ ion maps for the remaining samples
Data for the remaining samples analyzed as part of this study (YTT8, Q3, Q8, SN11, ADK29, and ADK9) are presented in Figs. S1S6. Since these samples are described in the main text, we do not duplicate that discussion here.
Sample descriptions and petrologic estimates of P and T
Youngest Toba Tuff
The ~74 ka Youngest Toba Tuff (abbreviated YTT here) eruption produced ~2800 km3 of tuff and ash-fall deposits; the quartz-bearing silicic pumices range from 6877 wt% SiO2 ADDIN EN.CITE Chesner1998286(Chesner 1998)28628617Chesner, C.A.Petrogenesis of the Toba Tuffs, SumatraJournal of PetrologyJournal of Petrology397-438391998( HYPERLINK \l "_ENREF_6" \o "Chesner, 1998 #286" Chesner 1998). Major crystalline phases are quartz, plagioclase, sanidine, biotite, and amphibole, and accessory minerals include titanomagnetite, allanite, zircon (zrc), ilmenite, apatite, and orthopyroxene as well as rare occurrences of highly oxidized fayalite (Chesner 1998). Matrix glass and quartz-hosted mel t i n c l u s i o n s h a v e s i l i c a c o n t e n t s ( o n a v o l a t i l e - f r e e b a s i s ) o f 7 5 . 7 t o 7 8 . 3 w t % , m e a n = 7 7 . 0 0 . 6 w t % , 1 s, n = 3 0 ( C h e s n e r 1 9 8 8 ; C h e s n e r a n d L u h r 2 0 1 0 ) ; F o u r i e r T r a n s f o r m I n f r a r e d s p e c t r o m e t r y ( F T I R ) m e a s u r e m e n t s o f t h e m e l t i n c l u s i o n s i n d i c a t e w a t e r c o ntents of 4.05.5 wt% ADDIN EN.CITE Chesner2010402(Chesner and Luhr 2010)40240217Chesner, C.A.Luhr, J.F.A melt inclusion study of the Toba Tuffs, Sumatra, IndonesiaJournal of Volcanology and Geothermal ResearchJournal of Volcanology and Geothermal Research2592781972010( HYPERLINK \l "_ENREF_7" \o "Chesner, 2010 #402" Chesner and Luhr 2010). The two zircons described in this study (YTT11 and YTT8) are from sample 87, a welded tuff with ~72.4 wt% SiO2, anhydrous; the matrix glass from this sample has 77.2 wt% silica (Chesner 1988) and its composition overlaps with that of the average of all melt inclusions and matrix glasses at the 1 sigma level.
Experimental results of Gardner et al. ADDIN EN.CITE Gardner2002400(2002)40040017Gardner, J.E.Layer, P.W.Rutherford, M.J.Phenocrysts versus xenocrysts in the youngest Toba Tuff: Implications for the petrogenesis of 2800 km3 of magmaGeologyGeology247350302002( HYPERLINK \l "_ENREF_13" \o "Gardner, 2002 #400" 2002) suggest that the Youngest Toba Tuff magma was nearly water-saturated at pressures of 1 to 1.5 kbar. For the high- and low-silica rhyolites used as starting materials in that study, quartz appearance temperatures at 1.5 kbar vary from ~720 to 770C. If the quartz-hosted melt inclusions were vapor-saturated when entrapped, their dissolved water contents suggest pressures of 1.1 to 1.4 kbar ADDIN EN.CITE Chesner2010402(Chesner and Luhr 2010)40240217Chesner, C.A.Luhr, J.F.A melt inclusion study of the Toba Tuffs, Sumatra, IndonesiaJournal of Volcanology and Geothermal ResearchJournal of Volcanology and Geothermal Research2592781972010( HYPERLINK \l "_ENREF_7" \o "Chesner, 2010 #402" Chesner and Luhr 2010). Applying the thermobarometric expressions of Ridolfi et al. ADDIN EN.CITE Ridolfi2010406(2010)40640617Ridolfi, F.Renzulli, A.Puerini, M.Stability and chemical equilibrium of amphibole in calc-alkaline magmas: an overview, new thermobarometric formulations and applications to subduction-related volcanoesContributions to Mineralogy and PetrologyContributions to Mineralogy and Petrology45661602010( HYPERLINK \l "_ENREF_34" \o "Ridolfi, 2010 #406" 2010) and Ridolfi and Renzulli ADDIN EN.CITE Ridolfi2012405(2012)40540517Ridolfi, F.Renzulli, A.Calcic amphiboles in calc-alkaline and alkaline magmas: thermobarometric and chemometric empirical equations valid up to 1100C and 2.2 GPaContributions to Mineralogy and PetrologyContributions to Mineralogy and Petrology8778951632012( HYPERLINK \l "_ENREF_33" \o "Ridolfi, 2012 #405" 2012) to amphiboles in the Youngest Toba Tuff non-welded and welded pumices yields pressures of ~1.6 kbar [note, however, that Gardner et al. ADDIN EN.CITE Gardner2002400(2002)40040017Gardner, J.E.Layer, P.W.Rutherford, M.J.Phenocrysts versus xenocrysts in the youngest Toba Tuff: Implications for the petrogenesis of 2800 km3 of magmaGeologyGeology247350302002( HYPERLINK \l "_ENREF_13" \o "Gardner, 2002 #400" 2002) argue that amphibole is not an equilibrium phase in the Youngest Toba Tuff magma chamber]. Temperature estimates for non-oxidized coexisting Fe-Ti oxides that pass the Mg-Mn partitioning test ADDIN EN.CITE Bacon1988407(Bacon and Hirschmann 1988)40740717Bacon, C.R.Hirschmann, M.M.Mg/Mn partitioning as a test for equilibrium between coexisting Fe-Ti oxidesAmerican MineralogistAmerican Mineralogist5761731988( HYPERLINK \l "_ENREF_1" \o "Bacon, 1988 #407" Bacon and Hirschmann 1988) range from 660735C ADDIN EN.CITE Sauerzape2008414using model of Sauerzape (using model of Sauerzape 2008)41441417Sauerzape, U.Lattard, D.Burchard, M.Engelmann, R.The titanomagnetiteilmenite equilibrium: New experimental data and thermooxybarometric application to the crystallization of basic to intermediate rocksJournal of PetrologyJournal of Petrology11611185492008[ HYPERLINK \l "_ENREF_37" \o "Sauerzape, 2008 #414" using the model of Sauerzape et al. (2008)] and 642753C [using the model of Ghiorso and Evans ADDIN EN.CITE Ghiorso2008412(2008)41241217Ghiorso, M.S.Evans, B.W.Thermodynamics of rhombohedrakl oxide solid solutions and a revision of the Fe0Ti two-oxide geothermometer and oxygen-barometerAmerican Journal of ScienceAmerican Journal of Science95710393802008( HYPERLINK \l "_ENREF_14" \o "Ghiorso, 2008 #412" 2008)]. Both models yield mean temperatures of ~681C ( either 19 or 27C, 1 s) . I t s e e m s l i k e l y t h a t t h e g e n e r a l l y l o w F e - T i o x i d e t e m p e r a t u r e s r e f l e c t v a r y i n g e x t e n t s o f p o s t - e r u p t i v e r e - e q u i l i b r a t i o n s i n c e a t 1 . 5 k b a r t h e w a t e r - s a t u r a t e d s o l i d u s i n t h e s y s t e m q u a r t z - a l b i t e - o r t h o c l a s e i s c l o s e t o ~ 6 9 5 C ( J o h a n n e s a n d H o l t z A D D IN EN.CITE Johannes1996409(1996)4094096Johannes, W.Holtz, F.Petrogenesis and Experimental Petrology of Granitic Rocks3351996BerlinSpringer-Verlag HYPERLINK \l "_ENREF_24" \o "Johannes, 1996 #409" 1996) and, barring relatively high concentrations of Cl and F (not observed in the melt inclusions), the water-saturated solidus temperature in this simple system establishes, for a given pressure, a lower temperature limit for most granitic and rhyolitic melts. Post-eruptive re-equilibration/alteration is further supported by the fact that over 76% of the 51 paired titanomagnetite-ilmenite compositions reported in Chesner ADDIN EN.CITE Chesner1988408(1988)40840832Chesner, C.A.The Toba Tuffs and caldera complex, Sumatra, Indonesia: Insights into magma bodies and eruptionsGeology and Geological Engineering428Ph.D.1988Michigan Technological University( HYPERLINK \l "_ENREF_5" \o "Chesner, 1988 #408" 1988) appear to be out of Mg-Mn equilibrium. Zr contents (by SIMS) in the matrix glasses and in th e q u a r t z - h o s t e d m e l t i n c l u s i o n s ( C h e s n e r a n d L u h r 2 0 1 0 ) y i e l d z i r c o n - s a t u r a t i o n t e m p e r a t u r e s ( T z r c - s a t , H Y P E R L I N K \ l " _ E N R E F _ 3 " \ o " B o e h n k e , 2 0 1 3 # 5 2 6 " B o e h n k e e t a l . 2 0 1 3 ) o f 6 6 7 7 0 9 C w i t h a n a v e r a g e o f 6 8 4 1 5 C ( 1 s) . T z r c - s a t v a l u e s c a l c u l a t e d f o r m a t r i x g l a s s e s ( a n a l y z e d b y X R F , C h e s n e r 1 9 8 8 ) r a n g e f r o m 6 6 6 7 4 2 C ( m e a n a n d 1 s a r e 6 8 6 1 8 C ) . B u l k r o c k c o m p o s i t i o n s w i t h s i l i c a c o n t e n t s b e t w e e n 7 5 . 7 t o 7 8 . 3 w t % ( a n h y d r o u s , i . e . , t h e s a m e r a n g e a s t h e m a t r i x g l a s s e s a n d m e l t i n c l u s i o n s ) h a v e z i r c o n - s a t u r a t i o n t e m p e r a t u r e s o f 6 7 9 t o 7 3 5 ( m e a n a n d 1 s a r e 7 0 7 1 1 C ) . F r o m t h e s e o v e r l a p p i n g c o n s t r a i n t s , w e i n f e r t h a t n e a r - r i m z i r c o n c r y s t a l l i z a t i o n o c c u r r e d a t t e m p e r a t u r e s o f 6 9 0 7 3 0 C a n d a p r e s s u r e o f ~ 1 . 5 k b a r .
B i s h o p T u f f
T h e ~ 7 8 0 k a L o n g V a l l e y eruption (Simon et al. 2014), which produced the Bishop Tuff (BT), released >600 km3 of compositionally zoned rhyolitic magma (for an alternative view concerning the compositional zoning, see Gualda and Ghiorso 2013). Our zircon sample (BT2-10) is from the ignimbrite package Ig2E ADDIN EN.CITE Hildreth1979283referred to as the Tableland in Hildreth (referred to as the Tableland in Hildreth 1979)28328317Hildreth, W.The Bishop Tuff: Evidence for the origin of compositional zonation in silicic magma chambersGeological Society of America Special PaperGeological Society of America Special Paper43-751801979[ HYPERLINK \l "_ENREF_20" \o "Hildreth, 1979 #283" referred to as Tableland in Hildreth (1979)]; rocks comprising Ig2E contain quartz, sanidine, plagioclase, biotite, augite, and orthopyroxene and accessory titanomagnetite, ilmenite, allanite, apatite, zircon, and pyrrhotite ADDIN EN.CITE ADDIN EN.CITE.DATA ( HYPERLINK \l "_ENREF_20" \o "Hildreth, 1979 #283" Hildreth 1979; HYPERLINK \l "_ENREF_21" \o "Hildreth, 2007 #309" Hildreth and Wilson 2007). Average silica content of the Ig2E ignimbrites is 76.8 wt% ADDIN EN.CITE Hildreth2007309(Hildreth and Wilson 2007)30930917Hildreth, W.Wilson, C.J.N.Compositional zoning of the Bishop TuffJournal of PetrologyJournal of Petrology951-999482007( HYPERLINK \l "_ENREF_21" \o "Hildreth, 2007 #309" Hildreth and Wilson 2007); including the compositions of the stratigraphically associated airfall deposits (F9) has little effect on this average composition. The quenched glasses in quartz-hosted melt inclusions from the Ig2E ignimbrites and F9 deposits contain, on a volatile-free basis, ~77.8 wt% SiO2 (Anderson et al. 2000; Dunbar and Hervig 1992; Wallace et al. 1999) and ~5.7 wt% H2O ADDIN EN.CITE Wallace1999310(Wallace, et al. 1999)31031017Wallace, P.J.Anderson Jr., A.T.Davis, A.M.Gradients in H2O, CO2, and exsolved gas in a large-volume silicic magma system: Interpreting the record preserved in melt inclusions from the Bishop TuffJournal of Geophysical ResearchJournal of Geophysical Research20097-201221041999( HYPERLINK \l "_ENREF_51" \o "Wallace, 1999 #310" Wallace et al. 1999). The presence of vapor bubbles in the early-erupted Bishop Tuff air-fall deposits indicate that at least the upper portions of the magma chamber were vapor-saturated ADDIN EN.CITE Gualda2007413(Gualda and Anderson 2007)41341317Gualda, G.A.R.Anderson, A.T.Magnetite scavenging and the buoyancy of bubbles in magmas. Part 1: Discovery of a pre-eruptive bubble in Bishop rhyoliteContributions to Mineralogy and PetrologyContributions to Mineralogy and Petrology7337421532007( HYPERLINK \l "_ENREF_17" \o "Gualda, 2007 #413" Gualda and Anderson 2007). Volatile contents in quartz-hosted melt inclusions in coeval rocks that comprise the Ig2E ignimbrites a n d F 9 f a l l d e p o s i t s s u g g e s t p r e s s u r e s o f ~ 1 . 9 3 0 . 1 3 k b a r , 1 s A D D I N E N . C I T E <