Correlation of eruptive products, Volcán Azufral, Colombia: Implications for rapid emplacement of domes and pyroclastic flow units

Accepted Manuscript Correlation of eruptive products, Volcán Azufral, Colombia: Implications for rapid emplacement of domes and pyroclastic flow units

Matthew Williams, M.I. Bursik, G.P. Cortes, A.M. Garcia PII: DOI: Reference:

S0377-0273(16)30225-6 doi: 10.1016/j.jvolgeores.2017.05.001 VOLGEO 6086

To appear in:

Journal of Volcanology and Geothermal Research

Received date: Revised date: Accepted date:

26 July 2016 1 May 2017 3 May 2017

Please cite this article as: Matthew Williams, M.I. Bursik, G.P. Cortes, A.M. Garcia , Correlation of eruptive products, Volcán Azufral, Colombia: Implications for rapid emplacement of domes and pyroclastic flow units, Journal of Volcanology and Geothermal Research (2017), doi: 10.1016/j.jvolgeores.2017.05.001

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ACCEPTED MANUSCRIPT Correlation of eruptive products, Volcán Azufral, Colombia: implications for rapid emplacement of domes and pyroclastic flow units Williams, Matthew1; Bursik, M.I.1; Cortes, G.P.2; Garcia, A.M.2 1 2

Department of Geology, University at Buffalo, Buffalo, NY Servicio Geologico Colombiano, Manizales, Colombia

ABSTRACT

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The eruptive history and morphology of Azufral volcano, Colombia, is explored and

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analyzed to provide a more complete picture of past eruptions, as well as to infer what eruption styles may occur in the future. Through the use of principal component analysis

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on Fe-Ti oxides, domes can be correlated to the pyroclastic deposits, enabling the identification of a full eruptive sequence. The findings suggest that eruptive activity at

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Azufral volcano is largely explosive, experiencing long periods of quiescence, punctuated

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by short periods of pyroclastic activity and volcanic debris avalanches. Geomorphology of

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the dome complex is reinterpreted to better understand the sequence of dome growth. This reinterpretation, along with geochemical analysis and comparison via PCA, allows for

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reclassification of a major deposit, originally thought to be a juvenile block-and-ash flow, as

1. Introduction

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a volcanic debris avalanche.

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1.1 Azufral Volcano

Azufral Volcano (1.09N, -77.72E, ~4050 m a.s.l.) is a stratovolcano topped by a dome complex located in the Cordillera Occidental, Nariño, Colombia. The cordillera sits east of, and approximately parallel to, the trench produced by the subduction of the Nazca plate beneath the South American plate. A somma rim on Azufral provides an enclosing fringe to the north for a crater lake and the summit dome complex (Fig. 1). There are at least ten individual domes within the complex (Fontaine and Stix, 1993). Fumarolic activity

ACCEPTED MANUSCRIPT occurs proximal to the youngest dome, on the northwest margin of the complex. Fans of pyroclastic and debris flow deposits at low slope angle (<5-10) dominate Azufral’s morphology to the east and south of the summit, with steep-sided valleys to the north and west.

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The lowest exposed units erupted from Azufral are massive, grey andesite lavas that

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are dated at 0.58±0.03 K-Ar Ma (Bechon and Monsalve, 1991). These lavas are almost

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completely covered by pyroclastic deposits. Six pyroclastic units are identified at Azufral:

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Tuquerres, Calera, Cortadera, Espino, Carrizo, and Laguna Verde (Fig. 2). The oldest identified pyroclastic deposit, Tuquerres, which immediately overlies the basal lavas, is

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dated at 17,970±190 14C yr. Laguna Verde is the youngest deposit, recorded at ~280 yr (Calvache et al., 2003). The pyroclastic deposits consist of units interpreted to have

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originated from pyroclastic surges, pumice-rich pyroclastic flows, and block-and-ash flows.

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Bulk composition of these units ranges from dacitic to rhyodacitic (Fontaine, 1994). Fall

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deposits were reported by Fontaine (1994); however, Calvache et al. (2003) interpret the same deposits as pyroclastic surges. The domes range from andesitic to rhyodacitic in bulk

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composition, showing a general trend towards more silicic over time (Fontaine and Stix,

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1993).

The precise timing and source vents of specific eruptions remain uncertain. Through the use of principal component analysis of titanomagnetite geochemical composition, to correlate eruptive products with dome materials, morphologic analysis, and radiocarbon ages, we seek to further constrain the eruptive history of this volcano. 1.2 Geochemistry 1.2.1 Fe-Ti oxides 2

ACCEPTED MANUSCRIPT Iron-titanium (Fe-Ti) oxides, titanomagnetite and ferroilmenite (hereafter, referred to as magnetite and ilmenite, respectively), exhibit compositional change depending on temperature, oxygen fugacity, and melt composition conditions in the silicic magma from which they erupt (Buddington and Lindsley, 1964; Marcaida et al., 2014). Previous studies

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show that Fe-Ti oxides can be used to correlate rhyolitic tephra and pyroclastic flow

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deposits through the use of Fe-Ti compositional data or derived thermodynamic

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information (Shane, 1998; Mangan et al., 2003; Marcaida et al., 2014), e.g., temperature or

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oxygen fugacity, calculated by the geothermobarometer of Ghiorso and Sack (1991) or Ghiorso and Evans (2008). Fe-Ti oxides have also been used successfully to correlate

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deposits with more mafic compositions, such as andesite (Devine et al., 2003). 1.2.2 Principal Component Analysis

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Principal component analysis (PCA) has been applied to geochemical datasets to

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identify unknown tephra layers. The method projects the original dataset onto axes having

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the greatest variance, and is used to differentiate analyses that appear geochemically similar when observed by traditional methods, such as bivariate plots. Pouget et al. (2014)

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used PCA on glass compositional data after log-ratio transformation, with prediction

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intervals, to correlate glass shards from tephra layers of unknown origin to known eruption deposits. The transformation was necessary because of glass hydration and the lack of statistical independence common in major oxides. These findings posit that it is possible to correlate unknown deposits to known, even in cases where the geochemistry of candidates may be strikingly similar on bivariate plots (Pouget et al., 2014). 2. Methodology 2.1 Sampling 3

ACCEPTED MANUSCRIPT A total of 14 samples were collected at Azufral Volcano for this study (Table 1). Samples of pyroclastic density current (PDC) deposits were collected from outcrops representative of each of the 6 previously identified pyroclastic units; however, we only analyzed four of these samples, representing the most voluminous eruptions (Tuquerres,

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Calera, Espino, and Carrizo). Samples from Cortadera and Laguna Verde were not analyzed

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because of difficulty in separating lithics from juvenile material. The faces of outcrops were

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scraped clean prior to sample collection to reduce the possibility of contamination. Each

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sample contained 500 to 900 g of material representing 3-5 cm depth from a ~10 cm by 10-20cm exposure.

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Samples from domes identified by Fontaine and Stix (1993) were collected from outcrops on the dome complex (Fig. 3). Sampling locations were selected to minimize the

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amount of weathering and post-emplacement hydrothermal alteration based on visual

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2.2 Sample Preparation

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inspection. Each sample contained 500 g to 1 kg of material.

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To retrieve the Fe-Ti oxides and glass shards from PDC samples, lapilli-sized pumices were selected from the 2-8 mm size fractions of sieved samples to avoid minerals derived from lithics. PDC and dome samples were crushed and sieved to <500 m. Magnetic minerals were separated using a permanent magnet from the >125 m size fraction. Sufficient amounts of glass were preserved in the magnetic separates, eliminating the need for separate glass sampling. The separates were mounted in epoxy resin and polished using conventional methods. Examination by backscatter electron imaging prior 4

ACCEPTED MANUSCRIPT to analysis revealed homogenous magnetites and ilmenites. Crystals from one dome sample (Dome 7) were dominated by exsolution lamellae. Glasses were vesiculated in texture with varying concentrations of microlites.

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2.3 Sample Analysis

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Major element compositions of ~ 400 magnetite crystals, 35 ilmenites and ~100

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glass shards from four pyroclastic flow units and ten domes were analyzed by the Cameca

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SX100 electron microprobe at the Laboratoire Magmas et Volcans, Université Blaise Pascal, Clermont-Ferrand, France. Magnetite and ilmenite crystals were analyzed once per crystal

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using a focused beam, 15 kV accelerating voltage, and a beam current of 20 nA. Standardization was performed using natural and synthetic oxides and silicate minerals of

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known compositions. If exsolution lamellae were visible in backscatter electron imagery,

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no microprobe analysis was performed on that crystal. Glass analyses were performed

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using a 5 micron defocused beam and a beam current of 8 nA. Only one analysis per glass

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shard was possible due to the vesiculation of the glass.

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2.4 Fe-Ti Oxide Geothermometry The magnetite-ilmenite geothermometer of Ghiorso and Evans (2008) was applied, using the methods available in Hora et al. (2013), to samples where both phases were present. Due to the loss of textural context caused by the crushing process, magnetite and ilmenite pairs from each sample were tested for equilibrium by the model of Bacon and Hirschmann (1988), and those pairs passing this test were analyzed by the geothermometer. Resulting temperatures and oxygen fugacities were recorded. In some 5

ACCEPTED MANUSCRIPT cases, touching pairs of magnetite and ilmenite were preserved and analyzed with the geothermometer, without the Bacon and Hirschmann (1988) equilibrium test, under the assumption that coexistence of both phases approximates equilibrium conditions.

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2.5 Radiocarbon Date Calibration

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Radiocarbon dates were gathered from the literature and calibrated using the IntCal

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09 calibration curve in the Calib radiocarbon calibration program Rev 6.1.0 (Reimer et al.,

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2009; Stuiver and Reimer, 2011). Calibrated ages were first grouped according to statistical significance, and then by the presence of soils between deposits to create pooled

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2.6 Principal Component Analysis

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radiocarbon age means.

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PCA was performed on magnetite compositions using the functions in the

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FactoMineR package in R (Lê et al., 2008). It is important to note that we consider oxide abundances as independent variables. To remove possible analytical error, analyses were

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removed if FeO, Al2O3, or MgO values were more than 2 from the respective oxide

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average. To limit other potential noise, CaO and Cr2O3 elemental analyses were removed prior to PCA because of the proximity of concentrations of these elements to microprobe detection limits. After performing PCA, plots of principal components 1 and 2 with 95% confidence ellipses on barycenters of each unit were compared, to determine similarity. We further qualified similarity by the size, shape, and spatial coverage of confidence ellipses and distances between these ellipses.

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ACCEPTED MANUSCRIPT 2.7 Geomorphologic Analysis Following the previous work of Fontaine and Stix (1993) and Fontaine (1994), the dome complex morphology was reinterpreted to produce an updated map of the volcano’s summit dome complex, utilizing recent (2006-2011) aerial photographs and a 3-meter

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resolution, Fugro Geospatial GeoSAR digital elevation model. With these data, we used

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ground cover, spatial relations, and various digital elevation model-derivative rasters (e.g.,

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surface slope and aspect) to identify distinct domes, as well as infer temporal relations of

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dome growth and collapse. Utilizing this new dome map, in combination with calibrated radiocarbon ages and interpretations based on geochemistry, we correlated dome

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eruptions with eruptive episodes indicated from the history of pyroclastic deposits. The total volume of the Azufral dome complex was also calculated. A basal surface

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was inferred from edifice-dome contact elevation data and an inverse-distance weighting

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method. The basal surface was then subtracted from the digital elevation model. Volume

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of the resulting surface was then calculated using the Surface Volume tool of 3D Analyst in

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3. Results

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ArcMap 10.2.2.

3.1 Geochemical Analysis Glass geochemistry shows variability within each unit, and is relatively similar across all units (Table 4). SiO2 composition varies between 74 wt% and 80 wt% making the matrix glass rhyolite to high-silica rhyolite (Le Bas et al., 1986). Ranges of composition for most samples overlap. It was observed by scanning electron microscopy that the glass,

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ACCEPTED MANUSCRIPT in some cases, appeared altered or contained plagioclase microlites, preventing accurate and consistent pure-glass analyses. For samples collected from a single pyroclastic deposit, scatter in magnetite composition is generally low, except for the Carrizo unit (Figs. 4, 5). Individual analyses

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from dome samples reveal a wider range of compositions (Table 2). FeO and TiO2 vary

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inversely with one another between 78.7 wt% and 87.6 wt%, and 2.5 wt% and 7.8 wt%,

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respectively. Ilmenite analyses are presented in Table 3. When plotted with traditional

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binary plot methods, identification of more than two clusters of analyses is difficult due to geochemical similarity (Fig. 4). The Tuquerres unit is the only deposit with oxide

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geochemistry appreciably different from all other units, represented by a minor

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3.1.1 Fe-Ti oxide geothermometry

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compositional gap evident even in binary plots.

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The phases required for geothermometric calculation were present in 10 of the 14 samples analyzed (Table 5), and 5 samples contained pairs of magnetite and ilmenite that

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can be assumed to be in equilibrium (Table 6). Comparison of temperature to oxygen

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fugacity is presented in Figure 6. In general, dome samples have large 2 (>50 C, >0.1 logfO2) values for both temperature and fO2, whereas samples from pyroclastic deposits have low 2 values. The Carrizo sample is an exception to this trend, with the largest 2 values among both pyroclastic and dome materials. Calculated oxygen fugacity at Azufral is consistent with oxygen fugacity calculated by the same method for other arc volcanoes (Ghiorso and Evans, 2008).

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ACCEPTED MANUSCRIPT 3.1.2 Principal Component Analysis The use of PCA allowed for the differentiation of various units one from another based on magnetite geochemistry, even if they were not separable using traditional comparison methods, such as bivariate plots (Fig. 4). A representation of PCA with all samples is shown

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in Figure 7a. Comparison of individual domes to pyroclastic samples showed that the

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domes exposed at Azufral do not correlate to the Tuquerres or Calera deposits. Domes F1,

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F2, and F3 are distinct from the other domes morphologically, and F3 can be correlated to

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Espino. Domes F5, F8, F9, and F10 can also be correlated to Espino. Figure 7b shows that all pyroclastic deposits except Carrizo produce relatively compact, distinct clusters,

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whereas Carrizo produces a more diffuse cluster.

Comparison of multiple domes and the use of a control sample (a sample that is

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definitively different from other plotted samples) allows for dome grouping. Domes F5 and

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F10 share the same space, and are the only domes that plot together when using this

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control sample method (Fig. 7c). The Carrizo block-and-ash flow unit may have

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contributions from multiple domes: F4, F8, and F9 (Fig. 7d).

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3.2 Ages of Deposits

We find three groups of statistically different ages in the available radiocarbon dates (Table 7). Eruptions that created the Calera, Cortadera, Espino, and Carrizo deposits occurred within a relatively short time (~600 yr) when compared to the long period of apparent inactivity between Tuquerres and Calera. When considering soils developed between pyroclastic units, as observed in the field and similarly reported in stratigraphic sections and descriptions in Fontaine (1994), we can separate the Calera to Carrizo group 9

ACCEPTED MANUSCRIPT into three separate mean pooled radiocarbon age ranges (Table 7). Results show a long period of quiescence between the eruption sequence that produced Tuquerres and Calera, ~14,000 yr, and between that of Carrizo and Laguna Verde of ~3500 yr. Two sets of moraines occur near the summit of Azufral (Fig. 1). The western set is

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clearly beheaded by the modern somma rim. The source for the eastern set is a broad

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cirque still clearly connected with the lateral moraines downstream. These data provide

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additional age constraints. The most recent late Pleistocene advance (Rodbell et al., 2009)

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has a minimum limiting radiocarbon age on Chimborazo, central Ecuador of 10.62 ± 0.09 to 11.37 ± 0.06 14C kyr BP, on Pinchincha, northern Ecuador (closest to Azufral) of 8.2 – 9.09

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to 13.1 ± 0.1 14C kyr BP and on the High Plain of Bogota, Colombia of 12.76 ± 0.16 to 14.66 ± 0.28 14C kyr BP. Maximum limiting ages at Pinchincha are 10.6 – 11.15 14C kyr BP. The

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indication is therefore that the Azufral moraines post-date the Tuquerres eruption (17.97 ±

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0.19 14C kyr BP). The beheading of the western set of moraines is consistent with the

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modern somma being younger than the late Pleistocene moraines. The existence of the eastern cirque, which modifies an older somma rim, and moraines suggests that the eastern

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side of the somma is associated with eruptions older than the late Pleistocene advance, and

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thus may be associated with the Tuquerres eruption.

3.3 Geomorphologic Analysis Through the use of high-resolution topographic data, ground observations, and aerial photography, detailed mapping of the Azufral dome complex was completed (Fig. 3). We recognize collapse scarps that provide evidence for multiple mass wasting events, and one previously unrecognized dome. Previously mapped contacts between individual domes 10

ACCEPTED MANUSCRIPT have also been updated based on the high-resolution elevation model. Collapse scarps, at the crowns of slumps, were identified using DEM-derivative products, such as topographic profiles, and maps of surface aspect. Mapped contacts from Fontaine (1994) were updated by observing changes in slope and aspect of the dome complex surface, and aerial

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photographs. A relative timeline of dome formation was inferred using cross-cutting

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relations seen in the new mapping, geochemistry, and observations from various DEM-

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derivative products.

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Volume calculations revealed that the total dome complex volume is ~0.25 km3. This estimate varies depending on inverse-distance weighting parameters used in

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interpreting a basal surface from which volume is calculated, but the volume can

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confidently be said to lie between 0.2 and 0.3 km3.

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4. Discussion

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4.1 Geochemistry

Compact clustering of compositions is demonstrated by all samples of juvenile

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magnetites from the Tuquerres, Calera and Espino units (Figs. 4, 5, 7), whereas

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compositions of magnetites from dome material and the Carrizo unit have greater variance, and do not exhibit similarly compact clusters. We attribute this to post-emplacement hydrothermal alteration, as evidenced by apparent alteration of glass in several dome samples. This type of alteration would have effectively oxidized the iron in some magnetites, and transported some cations preferentially but to varying degrees. Carrizo displays a distinct reddish color locally towards the top of the deposit, indicating pre- or post-emplacement alteration of oxides. Because of this alteration, it is difficult to correlate 11

ACCEPTED MANUSCRIPT this deposit unequivocally to any of the extant domes, so we rely more heavily on morphology to determine deposit source region. Results from geothermometry show little variability for pyroclastic samples, and a wide range of temperatures and oxygen fugacities for Carrizo and dome samples, and can

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be attributed to the hydrothermal alteration. Data from a single pyroclastic unit generally

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show a negative slope of temperature against oxygen fugacity (Fig. 6). These pairs may be

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representative of pre-eruptive magmatic conditions (Ghiorso and Gualda, 2013). Some data

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from domes F2, F3, and F6 show a positive slope at higher temperatures. Although all data presented here have passed the Bacon and Hirschmann (1988) equilibrium test, these pairs

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may not be representative of actual pre-eruptive magmatic conditions (Ghiorso and Gualda, 2013). Furthermore, many points that failed the equilibrium test plot in the same area as

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data that do pass, meaning that some data points have been excluded that may represent

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some state close to equilibrium. This lends credence to the idea, presented in Bacon and

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Hirschmann (1988) that some magnetite-ilmenite pairs that fail the equilibrium test may not necessarily need to be excluded from use in geothermobarometric analysis.

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Nevertheless, the results speak of some spreading of the distribution of analytical results

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by processes not consistent with pre-eruptive conditions in some of the dome samples, and thus hydrothermal alteration, suggesting that further statistical exploration may be prove useful.

4.2 Dome eruption sequence From cross-cutting contact relations, we find that domes were emplaced in the following order, from oldest to youngest: F9, F8, F7, F5 and F10, F4, F6, F2b (a previously 12

ACCEPTED MANUSCRIPT unrecognized dome), F2, F3, F1 (Fig. 3). Domes F9, F8, and F7 are believed to have formed earliest because of their spatial placement around the outermost portions of the dome complex, and appear to be overlain by material from younger domes. Dome F5 appears to cross-cut dome F7, based on DEM-derived surface slope between the domes and aerial

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photographs. F5 and F10 appear to be separate domes, but were likely originally one, as

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evidenced by geochemistry. The original dome was bisected after what was possibly a

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phreatic explosion that created the crater in which Dome F2 now lies. Domes F4 and F6

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were likely emplaced following F5/10, as suggested by surface slopes indicative of placement of newer material over dome F5. Ambiguity remains in the timing of these two

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events because of the absence of spatial relations, such as with domes F4 and F6, which are on opposite sides of the dome complex, and therefore can exhibit no cross-cutting relations.

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We also infer that mass-wasting events in the southeastern portion of the dome complex

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occurred prior to the formation of dome F3, as evidenced by lack of dome deformation and

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pyroclastic cover.

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4.3 Correlation of domes to pyroclastic deposits

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The use of barycentric mean and 95% confidence intervals on the mean of the first two moments of the principle components were necessitated by the compositional variations present in magnetite grains. The use of these means and confidence intervals give us a method to differentiate samples by what is effectively a visual t-test on the mean. We find that no domes are correlative to either the Tuquerres or Calera deposit (Fig. 7a). Domes that we hypothesize to have formed early are similar to the Espino deposit, possibly representing viscous degassed magma that was erupted late-syn- to post-eruption 13

ACCEPTED MANUSCRIPT Espino time. Geochemically, younger domes from the same generation defined by F5 and F6 are less similar to Espino, and when spatial relations are taken into account, these domes likely erupted later than the early-erupted domes, F8 and F9. The youngest three domes (F1, F2 and F3) exhibit larger geochemical and surface morphology differences from

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the older domes.

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The Carrizo unit was interpreted to be a juvenile block-and-ash flow deposit by

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Calvache et al. (2003); however, the magnetite data do not cluster well in PCA plots, similar

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to other analyses that demonstrate qualities of hydrothermal alteration. Morphology of the southeastern portion of the dome complex suggests that the Carrizo deposit may in fact

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have had contributions from three different domes, due to the presence of collapse scarps that intersect them. PCA shows that Carrizo magnetites are similar to those from domes

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F4, F8, and F9 (Fig. 7c), supporting our morphologic interpretation. The alteration suggests

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that multiple domes were in-place long enough for alteration to occur, indicating that the

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dome material that contributed to the Carrizo deposit was likely fully emplaced prior to collapse. This suggests that the Carrizo unit was not formed as a juvenile block-and-ash

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flow, but perhaps more as a monolithologic volcanic debris avalanche that occurred after

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the contributing domes had completed their growth. Sedimentologic evidence from the deposit is ambiguous, as outcrops are not sufficiently good to differentiate between debris avalanche and block and ash flow type materials (Dennen et al., 2014). Extensive hydrothermal alteration could have contributed to loss of strength within the emplaced dome material, causing enough destabilization for the debris avalanche to occur. Through analysis of the mean pooled radiocarbon dates and results from PCA, we can give a rough estimation of dome complex age. These observations suggest that most of 14

ACCEPTED MANUSCRIPT the dome complex was emplaced either late syn- or post-emplacement of Espino (3720±33 ya), but before the emplacement of Carrizo (3500±34 ya). The lack of a soil between the Espino and Carrizo deposits and the small time interval between their emplacements demonstrate that the Espino eruption and dome formation probably comprised one single

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eruptive sequence lasting approximately 100 to 200 years.

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The youngest four domes, (F1, F2, F2b, F3) were emplaced on the order of hundreds

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of years later, as evidenced by their crisper and blockier surface morphology. Dome F3

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emplacement occurred after mass wasting on the southeast flank of the dome complex that produced the Carrizo deposit. The emplacement times of domes F2 and F2b are difficult to

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characterize precisely, in that no pyroclastic deposits are associated with their emplacement. Morphology demonstrates that F2b is older than F2, and was emplaced

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around the same time or after the emplacement of Carrizo and dome F3. Dome F1 is the

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eruption, around ~280 yr.

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youngest, and is associated with the Laguna Verde deposit, either emplaced syn-or post-

Possible vent locations are identified using mainly morphologic indicators and, to a

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lesser extent, geochemistry and relative dates (Fig. 3). Due to the geochemical similarity

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between the Espino deposit and older domes and the inferred timing relation to dome edifice collapse, we infer that the Espino vent is expressed by the overall current summit morphology partially covered by the current dome complex. The vent for the Laguna Verde deposit sits within this larger structure, evidenced by the rounded end of the lake and presence of dome F1. The Calera vent is most likely preserved in the northern portion of the somma crater, as the rim appears to be outboard from the remainder of the crater formed during the eruption of Espino. Due to the relatively smaller size of the Cortadera 15

ACCEPTED MANUSCRIPT eruption, the vent region is difficult to ascertain, probably due to the effects of the Espino eruption. We infer that the Tuquerres vent is not preserved in the volcano’s current morphology. Vents relating to the Calera and Espino units are preserved by the current summit crater morphology, as there were large edifice-disrupting eruptions after

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Tuquerres time. Any domes erupted prior to the Espino eruption were likely covered by

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younger erupted material and now compose the larger edifice or were destroyed by

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subsequent eruptions. The source region for the Carrizo unit is most likely the collapse

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scarp on the southeastern side of the dome complex, and formed ~ 200 years after the

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main episode of dome complex formation.

4.4 Espino—Carrizo eruption sequence

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All domes except dome 1 have been correlated to the time between the end of the

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Espino pyroclastic phase and the beginning of the Carrizo debris avalanche/block and ash

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flow phase. The domes lie within a partial somma margin that is certainly younger than Late Glacial Maximum moraines. There is no soil between Espino and Carrizo deposits.

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The data thus imply that this was a single eruption sequence that started with voluminous

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explosive eruptions and somma collapse and ended with dome formation and finally, block and ash flows.

5. Conclusions We have demonstrated that PCA can be applied successfully to titanomagnetite geochemical data to differentiate units with similar geochemistry, which cannot be separated using conventional bivariate plotting methods. By combining chronologic data 16

ACCEPTED MANUSCRIPT and information derived from high-resolution elevation data, we make inferences upon the sources for various deposits associated with Azufral Volcano in order to elucidate more of the eruptive history. One previously unrecognized dome has been identified morphologically, and we

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propose the grouping of two more due to geochemical similarity. We reclassify the Carrizo

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unit as a volcanic debris avalanche due to geochemical qualities that indicate alteration,

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and morphologic clues that indicate material sourced from multiple domes, precluding the

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original classification as a juvenile block-and-ash flow deposit. Furthermore, through review and calibration of previously published radiocarbon dates, we demonstrate that the

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current dome complex (excluding domes F1-F3) at Azufral formed within approximately 200 years of the eruption producing the Espino deposit, between 3720 and 3500 cal BP,

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created the Carrizo unit.

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representing one long-lasting eruption sequence, which includes the mass-wasting that

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Review of Azufral’s history shows that over the past 20 ka volcanic activity has been infrequent and sporadic, characterized by long repose intervals punctuated by extended

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periods of pyroclastic activity followed by dome formation. Pyroclastic activity tends to

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produce PDCs more often and more voluminous than ash falls. Morphology indicates that when eruptions do occur, the volcanic edifice experiences major disruption. If this type of behavior continues into the next eruption sequence, the present findings may be of use in the creation of a hazard map for the areas surround Azufral Volcano. Future work should focus on attempting to constrain the duration of eruption sequences better, as well as identification of any eruptions occurring in the extended time period between the eruption of basal andesite lavas and the oldest identified pyroclastic deposit, Tuquerres. 17

ACCEPTED MANUSCRIPT Acknowledgments. This work was supported by NASA grant NNX12AQ10G and by the US Department of Education INVOGE grant. We thank personnel of the Laboratoire Magmas et Volcans, Universite Blaise Pascal, Clermont-Ferrand, France, for use of the EPMA facility. The reviews of J. Stix and an anonymous reviewer were helpful in improving the scientific

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References

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presentation.

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Bacon, C. R., and M. M. Hirschmann (1988), Mg/Mn partitioning as a test for equilibrium between coexisting Fe-Ti oxides, American Mineralogist, 73(1-2), 57-61. Bechon, F., and M. L. Monsalve (1991), Activité récente préhistorique du volcan Azufral (SW de la Colombie), Comptes rendus de l'Académie des sciences. Série 2, Mécanique, Physique, Chimie, Sciences de l'univers, Sciences de la Terre, 313(1), 99-104. Betancur, T., & Correa, A. (1992). Estudio geológico de los depósitos piroclásticos proximales del volcán Azufral, Colombia (Doctoral dissertation, Tesis pregrado Facultad de Ciencias, Universidad Nacional. 171pp. Medellin). Buddington, A., and D. Lindsley (1964), Iron-titanium oxide minerals and synthetic equivalents, Journal of Petrology, 5(2), 310-357. Calvache, M. L., G. P. Cortés, M. P. Torres, and M. L. Monsalve (2003), Geología y estratigrafia del Volcan Azufral, Colombia, edited by INGEOMINAS, p. 52, Bogotá, Colombia. Dennen, R. L., M. I. Bursik, and O. Roche (2014). Dome collapse mechanisms and block-andash flow emplacement dynamics inferred from deposit and impact mark analysis, Mono Craters, CA. Journal of Volcanology and Geothermal Research, 276, 1-9. Devine, J. D., M. J. Rutherford, G. E. Norton, and S. R. Young (2003), Magma storage region processes inferred from geochemistry of Fe–Ti oxides in andesitic magma, Soufriere Hills Volcano, Montserrat, WI, Journal of Petrology, 44(8), 1375-1400. Fontaine, E., and J. Stix (1993), Evolution pétrologique et géochimique du complexe de dômes du volcan Azufral (Colombie, Amérique du Sud), Comptes rendus de l'Académie des sciences. Série 2, Mécanique, Physique, Chimie, Sciences de l'univers, Sciences de la Terre, 317(11), 1501-1508. Fontaine, E. (1994), Evolution Volcanologique et Geochimique du Volcan Azufral. Colombie, Amerique du Sud., 215 pp, University of Montreal. Ghiorso, M. S., and O. Sack (1991), Fe-Ti oxide geothermometry: thermodynamic formulation and the estimation of intensive variables in silicic magmas, Contributions to Mineralogy and Petrology, 108(4), 485-510. Ghiorso, M. S., and B. W. Evans (2008), Thermodynamics of rhombohedral oxide solid solutions and a revision of the Fe-Ti two-oxide geothermometer and oxygen-barometer, American Journal of Science, 308(9), 957-1039.

18

ACCEPTED MANUSCRIPT

AC

CE

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US

CR

IP

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Ghiorso, M. S., and G. A. R. Gualda (2013), A method for estimating the activity of titania in magmatic liquids from the compositions of coexisting rhombohedral and cubic iron– titanium oxides, Contributions to Mineralogy and Petrology, 165(1), 73-81. Hora, J. M., A. Kronz, S. Möller-McNett, and G. Wörner (2013), An Excel-based tool for evaluating and visualizing geothermobarometry data, Computers & Geosciences, 56, 178185. Le Bas, M. J., R. Le Maitre, A. Streckeisen, and B. Zanettin (1986), A chemical classification of volcanic rocks based on the total alkali-silica diagram, Journal of petrology, 27(3), 745-750. Lê, S., J. Josse, and F. Husson (2008), FactoMineR: an R package for multivariate analysis, Journal of statistical software, 25(1), 1-18. Mangan, M. T., C. F. Waythomas, T. P. Miller, and F. A. Trusdell (2003), Emmons lake volcanic center, Alaska Peninsula: source of the Late Wisconsin Dawson tephra, Yukon territory, Canada, Canadian Journal of Earth Sciences, 40(7), 925-936. Marcaida, M., M. Mangan, J. Vazquez, M. Bursik, and M. Lidzbarski (2014), Geochemical fingerprinting of Wilson Creek formation tephra layers (Mono Basin, CA) using titanomagnetite compositions, Journal of Volcanology and Geothermal Research, 273, 1-14. Pouget, S., M. Bursik, J. A. Cortés, and C. Hayward (2014), Use of principal component analysis for identification of Rockland and Trego Hot Springs tephras in the Hat Creek Graben, northeastern California, USA, Quaternary Research, 81(1), 125-137. Reimer, P. J., M. G. Baillie, E. Bard, A. Bayliss, J. W. Beck, P. G. Blackwell, R. C. Bronk, C. E. Buck, G. S. Burr, and R. L. Edwards (2009), IntCal09 and Marine09 radiocarbon age calibration curves, 0-50,000 years cal BP. Rodbell, D. T., J. A. Smith, and B. G. Mark (2009) Glaciation in the Andes during the Lateglacial and Holocene, Quaternary Science Reviews, 28, 2165–2212. Shane, P. (1998), Correlation of rhyolitic pyroclastic eruptive units from the Taupo volcanic zone by Fe–Ti oxide compositional data, Bulletin of Volcanology, 60(3), 224-238. Stuiver, M., and P. Reimer (2011), CALIB 6.1.0.

19

ACCEPTED MANUSCRIPT Table 1: Coordinates for sampling locations of PDCs and domes.

AC

CE

PT

ED

M

AN

*All coordinates are in WGS84, UTM Zone 18N.

20

T

Northing 120713 119964 119943 120324 120242 119916 120416 119643 119570 119823 118338 116028 116928 118825

IP

Easting 197041 197170 197683 197644 197313 196908 197220 197714 197738 196876 198660 199792 192539 205028

CR

Sample Domo 1 Domo 2 Domo 3 Domo 4 Domo 5 Domo 6 Domo 7 Domo 8 Domo 9 Domo 10 13AZ007 13AZ006 13AZ011-1 13AZ004-2

US

Unit Dome 1 Dome 2 Dome 3 Dome 4 Dome 5 Dome 6 Dome 7 Dome 8 Dome 9 Dome 10 Carrizo Espino Calera Tuquerres

ACCEPTED MANUSCRIPT Table 2: Average magnetite compositions of individual units. Unit

Dome 1

(wt%)

Avg

± SD

SiO2

0.04

TiO2

4.85

Al2O3

Dome 2 Avg

± SD

0.02

0.06

1.07

4.86

2.79

0.43

FeO*

81.42

MnO MgO

Dome 3 Avg

± SD

0.04

0.07

0.82

4.73

2.55

0.40

1.12

81.32

0.51

0.09

1.15

0.24

Cr2O3

0.03

CaO

0.02

n

23

Dome 4 Avg

± SD

0.03

0.07

1.03

5.80

2.48

0.41

1.54

84.22

0.57

0.08

1.33

0.15

0.02

0.03

0.02

0.02

43

Dome 5 Avg

± SD

0.07

0.06

2.06

4.84

2.97

1.20

1.19

83.21

0.58

0.08

1.24

0.17

0.04

0.03

0.02

0.03

Dome 6

± SD

Tuquerres ± Avg SD

Calera

Avg

Avg

± SD

0.02

0.06

0.02

0.04

0.02

0.05

0.71

4.56

0.82

3.29

0.12

4.06

2.65

0.47

2.54

0.32

1.85

0.08

1.91

84.38

0.99

84.42

0.92

87.07

0.56

0.12

0.54

0.05

0.56

0.07

0.52

1.05

0.20

1.09

0.15

0.02

0.03

0.02

0.04

0.03

0.02

0.02

0.02

0.02

0.02

Avg

± SD

0.03

0.06

0.61

4.99

2.54

0.41

2.91

84.39

0.53

0.08

0.89

0.19

0.02

0.02

0.04

0.01

30

Dome 8 Avg

± SD

0.02

0.05

0.48

4.42

2.50

0.30

0.94

83.82

0.51

0.04

1.15

0.15

0.02

0.03

0.02

0.02

38

Dome 9 Avg

± SD

0.03

0.05

1.20

4.80

3.48

1.11

0.89

83.71

0.60

0.05

1.37

0.12

0.03

0.02

0.03

0.02

31

28

Dome 10

31

A

± SD

0.02

0.06

0.21

4.68

2.00

0.15

0.34

85.87

Carrizo Avg

± SD

0.02

0.07

0.04

0.24

6.03

5.82

2.21

0.12

3.16

1.24

0.45

85.12

0.49

82.34

5.31

0.06

0.66

0.05

0.58

0.06

0.53

0.09

1.24

0.15

0.67

0.05

0.92

0.12

1.10

0.08

1.05

0.27

0.05

0.16

0.02

0.02

0.04

0.06

0.01

0.02

0.02

0.02

0.03

0.02

0.02

0.02

0.02

0.02

0.03

0.04

0.03

0.02

C S

U N

33

Avg

T P

I R

El Espino

28

28

26

26

30

*FeO represents total Fe content. Analyses are presented as average (Avg) and standard deviation (SD). n is the total number of analyses per unit. For complete data, see Appendix.

T P

D E

C A

E C

M

ACCEPTED MANUSCRIPT Table 3: Average ilmenite compositions of individual units. Unit

Dome 2

(wt%)

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

SiO2

0.03

0.02

0.02

0.01

0.07

-

0.04

-

0.02

0.02

0.03

0.04

0.01

0.02

0.03

0.02

0.01

0.01

0.07

-

TiO2

28.25

2.09

30.32

3.32

31.61

-

28.89

-

29.16

1.83

30.15

6.07

26.75

1.17

29.09

1.92

31.99

2.18

35.90

-

Al2O3 FeO (total)

0.38

0.04

0.41

0.06

0.46

-

0.28

-

0.41

0.07

0.35

0.04

0.34

0.02

0.36

0.06

0.36

0.04

0.26

-

61.72

1.70

62.35

3.20

60.69

-

65.12

-

63.32

1.72

63.00

5.09

66.57

0.89

1.56

61.39

2.11

57.12

-

MnO

0.32

0.07

0.32

0.06

0.45

-

0.19

-

0.32

0.08

0.28

0.24

0.25

0.03

0.12

0.45

0.11

0.58

-

MgO

1.08

0.26

1.07

0.01

1.40

-

0.69

-

1.18

0.21

1.06

0.55

0.60

0.06

0.89

0.15

1.33

0.24

1.50

-

Cr2O3

0.00

0.00

0.02

0.03

0.03

-

0.04

-

0.01

0.01

0.00

0.00

0.01

0.02

0.01

0.02

0.02

0.02

0.02

-

CaO

0.04

0.01

0.09

0.04

0.01

-

0.02

-

0.04

0.03

0.03

0.04

0.02

0.03

0.05

0.01

0.05

0.03

0.06

n

4

Dome 3

Dome 4

2

Dome 5

1

Dome 6

1

Dome 10

Tuquerres

2

A

7

T P

I R

C S

U N

4

El Espino

Calera

64.03 0.43

4

9

Carrizo

1

Footnote: FeO represents total Fe content. Analyses are presented as average (Avg) and standard deviation (SD). n is the total number of analyses per unit. For complete data, see Appendix.

T P

D E

E C

C A 22

M

ACCEPTED MANUSCRIPT Table 4: Average glass composition of individual units. Unit

Dome 1

Dome 2

Dome 3

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Avg

± SD

Tuquerres ± Avg SD

Calera

(wt%)

Avg

± SD

Avg

± SD

Avg

± SD

SiO2

77.43

2.31

77.83

0.96

79.72

0.57

77.47

2.22

77.51

1.02

77.84

1.09

78.43

3.32

80.83

0.81

76.54

1.06

76.92

0.48

74.96

1.69

76.42

1.44

74.46

1.43

76.58

1.22

Al2O3

13.22

1.44

11.46

0.52

12.02

0.45

12.66

0.95

12.68

0.29

11.97

0.70

11.89

3.62

11.41

0.76

12.25

0.84

12.09

0.37

13.15

0.76

13.32

0.91

13.12

1.15

11.90

0.64

MgO

0.05

0.06

0.23

0.04

0.30

0.23

0.39

0.22

0.29

0.13

0.19

0.05

0.31

0.20

0.19

0.07

0.34

0.25

0.20

0.09

0.08

0.05

0.20

0.07

0.26

0.06

0.20

0.07

K2O

2.98

0.92

3.51

0.14

3.47

0.19

3.46

0.91

3.56

0.34

3.39

0.21

1.89

0.94

1.59

0.85

3.59

0.23

3.34

0.18

2.46

1.50

3.25

0.46

3.03

0.32

4.14

0.58

Na2O

4.01

0.48

3.34

0.21

3.12

0.25

3.62

0.17

3.45

0.16

3.51

0.22

3.51

1.38

3.56

0.07

3.38

0.31

3.64

0.23

4.06

0.47

3.84

0.22

3.73

0.18

3.11

0.38

CaO

1.56

0.45

0.64

0.22

0.78

0.19

1.46

0.28

1.05

0.32

0.87

0.35

1.88

0.75

1.82

0.04

1.07

FeO*

0.47

0.28

1.01

0.10

1.02

0.24

1.02

0.40

1.01

0.22

0.94

0.11

0.79

0.24

0.61

0.20

1.18

TiO2

0.17

0.11

0.21

0.04

0.17

0.04

0.20

0.05

0.19

0.05

0.20

0.05

0.13

0.08

0.15

0.03

0.20

MnO

0.03

0.03

0.07

0.04

0.07

0.04

0.06

0.04

0.04

0.04

0.07

0.03

0.03

0.01

0.03

0.02

0.06

C S

Cr2O3

0.01

0.02

0.02

0.03

0.02

0.01

0.01

0.01

0.02

0.02

0.02

0.02

0.01

0.01

0.01

0.02

0.01

n

8

10

Dome 4

10

Dome 5

7

Dome 6

12

Dome 7

10

Dome 8

8

2

Dome 9

U N

T P

I R

El Espino

Carrizo

0.37

1.08

0.24

1.87

0.93

1.53

0.41

1.66

0.68

1.02

0.29

0.38

1.02

0.18

0.99

0.40

0.95

0.16

1.30

0.60

0.93

0.17

0.02

0.18

0.04

0.07

0.03

0.15

0.04

0.16

0.03

0.20

0.02

0.04

0.07

0.03

0.05

0.05

0.05

0.04

0.04

0.03

0.03

0.02

0.01

0.00

0.00

0.01

0.01

0.01

0.01

0.01

0.01

0.02

0.03

9

A

M

Dome 10

9

5

9

10

9

*FeO represents total Fe content. Analyses are presented as un-normalized with average and standard deviation. n is the number of

D E

analyses per unit. For complete data, see Appendix.

T P

E C

Table 5: Results of application of Fe-Ti oxide geothermometer. Dome 2

Dome 3

C A

Dome 4

Dome 5

Dome 6

Dome 10

Calera

Carrizo

Espino

Tuquerres

Avg.

2σ

Avg.

2σ

Avg.

2σ

Avg.

2σ

Avg.

2σ

Avg.

2σ

Avg.

2σ

Avg.

2σ

Avg.

2σ

Avg.

2σ

T (C)

793.0

162.7

748.5

172.1

803.1

121.2

754.0

101.1

776.7

57.7

747.5

95.6

709.3

27.9

762.9

193.2

753.9

23.0

647.7

11.0

fO2

1.60

0.19

1.62

0.29

1.49

0.22

1.56

0.11

1.57

0.09

1.62

0.26

1.62

0.06

1.58

0.54

1.57

0.05

1.64

0.04

Data presented as average temperature and oxygen fugacity (fO2) with 2 values per unit with both magnetite and ilmenite phases.

23

ACCEPTED MANUSCRIPT Table 6: Results of ilmenite-magnetite touching pair geothermometry. Unit Calera Carrizo Espino

Tuquerres

Dome 3

D E

T P

E C

C A 24

Pair# 1 2 1 2 1 2 3 4 1 2 3 4 1

T (°C) 686 716 804 749 760 759 749 757 659 659 642 668 709

T P

I R

C S

U N

A

M

fO2 1.61 1.61 1.40 1.54 1.56 1.55 1.58 1.57 1.63 1.63 1.64 1.60 1.64

ACCEPTED MANUSCRIPT Table 7: Radiocarbon calibration results reported with mean pooled radiocarbon ages. Data from Fontaine (1994) and Calvache et al. (2003).

1.000

3744

50

3641 - 3894

1.000

3772

3540

70

3638 - 3988 4046 - 4066

0.987 0.013

3825

CP5-2

3660

70

3734 - 3741 3776 - 3788 3827 - 4161 4169 - 4178 4199 - 4228

0.003 0.006 0.971 0.004 0.016

CP5-3

3680

60

3846 - 4156 4207 - 4221

3500

CP5-1

4018

0.967 0.019 0.011 0.002

4115

3720± 33

70

3903 - 4299 4327 - 4354 4369 - 4386 4393 - 4398

CP5-4

3780

80

3930 - 3944 3967 - 4413

0.010 0.990

4164

Esp-1

3800

100

3901 - 4437 4491 - 4495

0.998 0.002

4193

Cort-2

3920

4104 - 4106 4149 - 4528

0.001 0.999

4349

80

4095 - 4120 4145 - 4579 4770 - 4780

0.012 0.984 0.004

4362

ED

M

AN

3750

70

CE 3930

AC

Tuquerres

0.990 0.010

Esp-3

Cort-1

Calera

3990

PT

Espino

3500±34

IP

Esp-4

Mean Pooled Radiocarbon age

T

3589 - 3884

CP6-1

Sample

CR

Carrizo

2σ range

Median Calibrated age

C14 SD 60

US

Unit

Relative area under probability distribution

C14 Age 3470

CP3-1

3990

60

4247 - 4620 4765 - 4785

0.980 0.020

4467

Cal-1

4070

90

4299 - 4327 4354 - 4369 4399 - 4838

0.014 0.008 0.979

4588

CP3-2

4100

70

4438 - 4488 4497 - 4826

0.093 0.907

4629

Tuq-1

17970

190

21242-22296

1.000

21761

3924±52

4055±35

ACCEPTED MANUSCRIPT 7. FIGURE CAPTIONS Figure 1: Elevation and shaded relief map of Azufral Volcano. The current crater area is occupied by a dome complex and crater lake (Laguna Verde). To the north and west of the edifice are steep river valleys, while to the south is comprised mainly of depositional fans

T

of pyroclastic and debris flow material. Important gorphological features of the summit

CR

IP

region are shown.

Figure 2: Generalized stratigraphic column of Azufral Volcano eruptive products, showing

US

relations between pyroclastic units and domes with calibrated ages and deposit types. Tie

AN

lines from domes to pyroclastic units show relationships of dome growth to emplacement of pyroclastic deposits. Unit thicknesses are not to scale. (After Fontaine (1994) and

ED

M

Calvache et al. (2003))

Figure 3: Map of Azufral summit dome complex showing dome sample locations (stars),

PT

certain and uncertain contacts between domes (solid and dashed lines), and collapse

CE

scarps (lines with ticks on collapse side), and potential vent regions (colored lines) overlain on shaded relief map and elevation color scale. Eleven domes are presently identified with

AC

the addition of dome F2b. Multiple collapse scarps are evident indicating mass wasting after dome emplacement in the southeast portion of the complex. Dome nomenclature from Fontaine (1994).

Figure 4: Binary oxide plot showing the relationship of FeO (wt%) and TiO2 (wt%) in titanomagnetite crystals measured by microprobe. FeO and TiO2 vary inversely with one

26

ACCEPTED MANUSCRIPT another. Only analyses from the Tuquerres sample can be readily separated by this method.

Figure 5: Plot showing results of single analyses of oxides in titanomagnetite crystals

T

measured by microprobe. Analyses of pyroclastic samples (except Carrizo) have a smaller

CR

IP

range of values than analyses from dome samples.

Figure 6: Plot of geothermobarometric results shown by sample. Data from Carrizo and

US

dome samples show a larger range than samples from pyroclastic units. Two trends in data

AN

can be observed: a trend with negative slope where the majority of data lie, and a trend with positive slope where data from only a few samples exist. The range of data shown is

ED

M

similar to other arc volcanoes of similar composition (See: Ghiorso and Gualda, 2013).

Figure 7a-d: Plots of principal component 1 (x-axis) against component 2 (y-axis) from four

PT

PCAs showing relationships between titanomagnetite composition between various

CE

samples. Points are individual data points, hollow squares represent the barycentric mean,

AC

and ellipse represent the 95% confidence intervals around the barycentric mean.

27

ACCEPTED MANUSCRIPT

Figure 7: Possible vent and source locations for previous eruptions. Solid lines represent the interpreted approximate vent locations for Laguna Verde (green), Espino (yellow), and Calera (blue). Dashed lines are inferred boundaries with less confidence in placement than

T

solid lines. The collapse scar left by the Carrizo volcanic debris avalanche is represented by

IP

the red curve. A potential source of “secondary deposits” indicated by Fontaine (1994) is

AC

CE

PT

ED

M

AN

US

CR

also identified.

28

PT

ED

M

AN

US

CR

IP

T

ACCEPTED MANUSCRIPT

AC

CE

Fig. 1

29

AC

Fig. 2

CE

PT

ED

M

AN

US

CR

IP

T

ACCEPTED MANUSCRIPT

30

Fig. 3

31

AC

CE

PT

ED

M

AN

US

CR

IP

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ACCEPTED MANUSCRIPT

ED

M

AN

US

CR

IP

T

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Fig. 5

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Fig. 7

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ACCEPTED MANUSCRIPT Correlation of eruptive products, Volcán Azufral, Colombia: implications for rapid emplacement of domes and pyroclastic flow units

Through the use of principal component analysis on Fe-Ti oxides, domes of Azufral

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volcano, Colombia, can be correlated to the pyroclastic deposits, enabling the identification of a full eruptive sequence.

Eruptive activity at Azufral volcano is largely explosive, experiencing long periods of

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quiescence, punctuated by short periods of pyroclastic activity and volcanic debris avalanches.

Geomorphology of the dome complex is reinterpreted to better understand the

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sequence of dome growth.

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This reinterpretation, along with geochemical analysis and comparison via PCA,

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allows for reclassification of a major deposit, originally thought to be a juvenile

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block-and-ash flow, as a volcanic debris avalanche.

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