Volcano-sedimentary processes at Las Derrumbadas rhyolitic twin domes, Serdán-Oriental Basin, Eastern Trans-Mexican Volcanic Belt

Abstract

The eruption of the c. 10 km3 rhyolitic Las Derrumbadas twin domes about 2000 years ago gener-ated a wide range of volcano-sedimentary deposits in the Serdán-Oriental lacustrine basin, Trans-Mexican Volcanic Belt. Some of these deposits have been quarried, creating excellent exposures. In this paper we describe the domes and related products and interpret their mode of formation, reconstructing the main phases of the eruption as well as syn-and post-eruptive erosional processes. After an initial phreatomagmatic phase that built a tuff ring, the domes grew as an upheaved plug, lifting a thick sedimentary pile from the basin floor. During uplift, the domes collapsed repeatedly to form a first generation of hetero-lithologic hummocky debris avalanche deposits. Subsequent dome growth produced a thick talus and pyroclastic density currents. Later, the hydrothermally altered over-steepened dome peaks fell to generate second-generation, mono-lithologic ava-lanches. Subsequently, small domes grew in the collapse scars. From the end of the main eruptive episode onwards, heavy rains remobilized parts of the dome carapaces and talus, depositing lahar aprons. The Las Der-rumbadas domes are still an important source of sediments in the basin, and ongoing mass-wasting processes are associated with hazards that should be assessed, given their potential impact on nearby populations.