Auxiliary material for

Diapiric ascent of silicic magma beneath the Bolivian Altiplano

Rodrigo del Potro

1 , Mikel Díez 1

, Jon Blundy


, Antonio Camacho


and Joachim





School of Earth Sciences, University of Bristol, Bristol, United Kingdom,


Instituto de Geociencias (CSIC-UCM), Madrid, Spain)

Geophysical Research Letters


The following auxiliary material provides details of the gravity survey over the

Altiplano-Pune Magma Body and inversion modeling presented in the main text. The auxiliary material comprises additional text and additional figures, which address specific supplementary elements of our work. text01.docx Detailed description of the gravity survey and gravity data reduction procedures used. text02.docx Detailed description of the gravity inversion routine and parameters used

(density contrasts and regional gravity signals). text03.docx Further discussion on the volume and density contrast calculations used in plotting the data in Figure 3 in the main text. text04.docx Description of the analysis of synthetic data carried out in order to show that the inversion routine used is capable of resolving between rooted and rootless anomalous bodies. fs01 (supfig1) Inversion modeling results for a wide range of the models carried out.

The location of the vertical cross-sections is indicated in Minimum ±300 -25 km.

Ticks in cross-sections are every 10 km. Vertical exaggeration on vertical sections is x2. Columns highlighted in green correspond to the preferred models. fs02 (supfig2) a) Bouguer Anomaly for each benchmark using a reduction density of

2270 kg m


. This original data has been interpolated for the Bouguer anomaly shown in Fig. 1b of the main manuscript. b) Best-fit “regional” first-order polynomial for a

Free configuration and a density contrast of ±150 kg m

-3 . c) The “local” anomaly inverted to produce the anomalous bodies shown in Fig. 2a of the main manuscript.

This same local anomaly is inverted using the Bottom Free set-up. fs03 (supfig3) Horizontal cross-sections through the gravity inversion models Bottom

Free ±150 kg m


(left) and Free ±150 kg m


(right), at sea level, -5, -10 -15 and -20 km b.s.l. The negative anomalous bodies are the blue polygons, the Neogene calderas the black lines, gravity benchmarks are black dots, and color fringes correspond to the

18 years of stacked InSAR data presented by Fialko and Pearse [2012]. The top left box shows the residual of the inversion at each benchmark for both models. fs04 (supfig4) Inversion of synthetic models. a) Artificial structure built to which a regional first-order polynomial and white noise have been added. b) Inversion results using a Free configuration and c) using a Bottom Free configuration with domain

depth maximum at 30 km b.s.l. The wiggly green lines indicate the Neogene caldera rims while the green straight lines indicate the position of the cross-sections shown. d)

Histogram of model residuals and e) distance-normalized autocorrelation between resulting inversion residuals for the Free model (b). fs05 (supfig5) a) Top, inversion residuals for the Bottom Free configuration and a density contrast of ±150 kg m -3 at each benchmark. Bottom left is a histogram with the distribution of the residuals and bottom right the distance-normalized autocorrelation between residual values. b) Similar model residuals, for the Free configuration and a density contrast of ±150 kg m -3

. fs06.docx (supfig6) Graph of density contrast change with temperature.