The origins of Late Quaternary debris avalanche and debris fl ow deposits from Cofre de Perote volcano, México Rodolfo Díaz-Castellón1,*,†, Bernard E. Hubbard2,†, Gerardo Carrasco-Núñez1, and José Luis Rodríguez-Vargas1 1Centro de Geociencias, Universidad Nacional Autónoma de México (UNAM), Campus Juriquilla, 76230 Querétaro, México 2U.S. Geological Survey, Eastern Mineral Resources, MS 954, 12201 Sunrise Valley Drive, Reston, Virginia 20192, USA ABSTRACT on a larger scale. The younger Xico avalanche Scott et al., 1995; Vallance and Scott, 1997) and deposit contains abundant smectite, jarosite, the 16.4–16.6 ka Teteltzingo lahar from Citlalté- Cofre de Perote volcano is a compound, kaolinite, gypsum, and mixed-layered illite/ petl (Carrasco-Núñez et al., 1993, 2006), have shield-like volcano located in the northeast- smectite, which are either defi nitely or most left extensive deposits many tens of kilometers ern Trans-Mexican volcanic belt. Large likely of hydrothermal alteration origin. from their sources, signaling that population debris avalanche and lahar deposits are asso- Smectite in particular appears to be the most centers situated far from a volcanic edifi ce may ciated with the evolution of Cofre. The two abundant and spectrally dominant mineral still be at risk. Volcanic debris avalanches and best preserved of these debris-avalanche and in summit ground truth samples, ASTER debris fl ows are not always accompanied by debris-fl ow deposits are the ~42 ka “Los Pes- mapping results, Xico avalanche deposit, and eruptive activity. They can be triggered by a cados debris fl ow” deposit and the ~11–13 ka an older (pre-Xico avalanche) deposit de rived variety of factors such as increased precipita- “Xico avalanche” deposit, both of which dis- from collapse(s) of ancestral Cofre de Perote tion, as exemplifi ed in 1998 by the Casita ava- play contrasting morphological and textural edifi ce. However, both Xico avalanche and lanche and lahar triggered by Hurricane Mitch characteristics, source materials, origins and Los Pescados debris flow deposits show (Sheridan et al., 1999; Scott et al., 2005); slope emplacement environments. Laboratory some evidence of secondary, postemplace- instability and over steepening caused by gla- X-ray diffraction and visible-infrared refl ec- ment weathering and induration, which cial erosion (Crowley et al., 2003); strong seis- tance spectroscopy were used to identify the is evident by the presence of gibbsite, and mic activity (Martinez et al., 1995; Scott et al., most abundant clay, sulfate, ferric-iron, and hydroxyl interlayered minerals, in addition 2001); or they can occur even without warning. silica minerals in the deposits, which were to recently formed halloysite and hydrous A number of studies have made interpre- either related to hydrothermal alteration or silica (i.e., indurating) cements. Field-based, tations about the origins of ancient volcanic chemical weathering processes. Cloud-free visible infrared image spectroscopy (VIS/IR) debris avalanches and fl ows based on the type Advanced Spaceborne Thermal Emission spectral measurements offer the possibility and distribution of clay, sulfate, and silica min- and Refl ection Radiometer (ASTER) remote of distinguishing primary minerals of hydro- erals indicative of either hydrothermal alteration sensing imagery, supporting EO-1 Hyperion thermal alteration origin in debris-avalanche and/or chemical weathering processes (e.g., image spectra, and fi eld ground truth samples and debris-fl ow deposits from those pro- Crandell, 1971; Carrasco-Núñez et al., 1993; were used to map the mineralogy and distri- duced either by in situ chemical weathering Vallance and Scott, 1997; Vallance, 1999; Capra bution of hydrothermally altered rocks on or bulked from weathered source materials. and Macias, 2000; Capra and Macias, 2002; Pul- the modern summit of Cofre de Perote. The garin et al., 2004; Carrasco-Núñez et al., 2006; results were then compared to minerals iden- INTRODUCTION Murcia et al., 2008). However, few studies have tifi ed in the two debris-avalanche and debris- mapped the distribution of clay-rich, hydrother- fl ow deposits in order to assess possible source Volcanic debris avalanches and debris fl ows mally altered rocks on volcanoes with down- materials and origins for the two deposits. (i.e., lahars) originate as slope failures high on stream populations at risk (e.g., Crowley and The older Los Pescados debris-fl ow deposit volcanic edifi ces and transport enormous vol- Zimbelman, 1997; Hubbard, 2001; Finn et al., contains mostly halloysite and hydrous silica umes of fl uidized rock and soil into surrounding 2001; Crowley et al., 2003; Finn et al., 2007) or minerals, which match the dominant miner- river valleys. In populated areas, these phenom- compared the mineralogy of actual debris-ava- alogy of soils and weathered volcanic deposit ena can be incredibly destructive and deadly, as lanche and debris-fl ow deposits with those of in the surrounding fl anks of Cofre de Perote. tragically exemplifi ed by the >22,000 people potential source rock areas on the volcano (e.g., Its source materials were most likely derived killed by lahars from the Nevado del Ruiz vol- Pevear et al., 1982; Frank, 1983; Hubbard, 2001; from initially noncohesive or clay-poor fl ows, cano, Colombia, in 1985, during a minor erup- Opfergelt et al., 2006), assuming that such rocks which subsequently bulked with clay-rich tion that melted glacial ice and bulked with indeed still remain on the edifi ce. For example, valley soils and alluvium in a manner similar clay-rich soils and alluvium from the surround- Pevear et al. (1982) notes that the 18 May 1980 to lahars from Nevado del Ruiz in 1985, but ing valleys (Lowe et al., 1986; Pierson et al., debris avalanche deposit from Mount St. Helens 1990). Lahars containing abundant hydrother- lacks acid-sulfate minerals such as kaolinite and *Corresponding author: [email protected]. mally produced clays, such as the 5.6 ka Osceola alunite, but contains abundant chlorite, mixed †These authors contributed equally to this work. mudfl ow from Mount Rainier (Crandell, 1971; layered chlorite/smectite (i.e., corrensite), and Geosphere; August 2012; v. 8; no. 4; p. 950–971; doi:10.1130/GES00709.1; 16 fi gures; 3 tables. Received 6 April 2011 ♦ Revision received 23 November 2011 ♦ Accepted 1 February 2012 ♦ Published online 16 July 2012 950 For permission to copy, contact [email protected] © 2012 Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/8/4/950/3343011/950.pdf by guest on 01 October 2021 Late Quaternary debris avalanche and debris fl ow deposits saponite (an Mg/Fe2+ or trioctahedral smectite), and to assess the signifi cance of hydrothermal four months) dry season from January to April, indicative of a sealed hydrothermal system that alteration and/or soil-forming processes in gen- and receives >1400 mm of annual precipitation prevented acidic fl uids from reaching the sur- erating future debris avalanches and lahars from (Elsass et al., 2000). Soils on the eastern fl anks face or near surface oxidizing environments. Cofre de Perote volcano. are also andosols but are typically indurated with Minor amounts of acid-sulfate alteration min- hydrous silica minerals (i.e., silcrete) (Elsass erals such as kaolinite, alunite, cristobalite, BACKGROUND: GEOLOGIC AND et al., 2000). Land use on the east side of Cofre tridymite, and opal were known to exist locally GEOGRAPHIC SETTING de Perote volcano favors a dense vegetation can- around the vicinity of fumarolic and geothermal opy ranging from cloud forest to low jungle and areas on the pre-1980 Mount St. Helens summit Cofre de Perote is the northernmost and savannas with numerous scattered sugar cane dome and goat rocks dome (Pevear et al., 1982 second highest (~4220 masl) volcano of the and coffee plantations. On both sides of Cofre and references therein). These dome rocks were Citlaltépetl–Cofre de Perote volcanic range. de Perote volcano, the weathering zone extends subsequently removed during the 18 May 1980 It is situated at the eastern end of the Trans- to a maximum depth of ~4 m (Dubroeucq et al., rockslide, though (not surprisingly) their altera- Mexican volcanic belt (TMVB; Fig. 1). The 1998; Elsass et al., 2000), although this varies tion products are not evident in the resulting Trans-Mexican volcanic belt is a Neogene vol- with slope and often grades into saprolite on the debris-avalanche deposit as shown by Pevear canic arc characterized by its oblique geometry western side (Elsass et al., 2000). et al. (1982). In contrast, Hubbard (2001) used with respect to the Middle American subduc- Morphologically, Cofre de Perote volcano airborne visible–infrared imaging spectrometer tion zone trench. It contains a wide range of could be described as a compound, shield-like (AVIRIS) hyperspectral data to map a variety of volcanic structures, including large silicic cal- volcano with a broad and gently sloping profi le hydrothermal alteration minerals on the modern deras, andesitic stratovolcanoes, silicic domes, (Fig. 2) (Carrasco-Núñez et al., 2010). Consid- edifi ce of Citlaltépetl, as well as the remnants and large basaltic monogenetic fi elds (Demant, ering that Cofre de Perote volcano is probably of two ancestral edifi ces, and compared them 1978). The easternmost Trans-Mexican volcanic extinct because its last eruptive episode ended with the mineralogy of the debris-avalanche belt comprises the Citlaltépetl–Cofre de Perote ~200 ka (Carrasco-Núñez et al., 2006), detailed and debris-fl ow deposits that resulted from their volcanic range and the Serdán-Oriental Basin, geologic mapping and study of its potential haz- collapse . marked by a bimodal volcanism with numer- ards have received little attention until recent This study focuses on Cofre de Perote vol- ous maars, domes, and cinder cones compris- times. Nevertheless, the young-looking scarps cano, one of the main volcanoes of the Citlal- ing a scattered monogenetic fi eld.