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The extent and volcanic structures of the Quaternary Andahua Group, Andes, southern Peru

Gałaś A.

Annales Societatis Geologorum Poloniae

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2011

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Vol. 81, No 1

1-19

EN

The Quaternary Andahua volcanic group in southern Peru has been studied by present author since 2003. The Andahua Group stretches out at intervals within an area, which is 110 km long and 110 km wide. Seven regions bearing centres of volcanic eruptions have been distinguished: the Valley of the Volcanoes, Antapuna, Rio Molloco, Laguna Parihuana, Rio Colca Valley, Jaran, and Huambo. The Valley of the Volcanoes, where the Andahua Group was identified for the first time, contains the biggest variety of volcanic landforms. The valley is covered by a nearly 60 km long, continuous cover of lava flows. 165 individual eruption centres of the Andahua Group were distinguished including apparent pyroclastic cones, 50–300 m high, and usually smaller lava domes and fissure vents. Domes, eruptive vents and lava craters greatly outnumber pyroclastic cones. Most commonly, lava flows start from lava domes or craters. Small domes are often aligned along their feeding fissures. Lava domes and pyroclastic cones of the Andahua Group are aligned mainly along N–S and WNW–ESE trending fault systems. Projection points of the analysed Andahua lavas on the TAS diagram concentrate in the lower part of the trachyandesite field, entering also the basaltic trachyandesite or trachyte/trachydacite fields.

2

Zasięg i budowle wulkaniczne grupy Andahua

Gałaś A.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2008

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T. 34, z. 2/1

107-135

PL

W 2003, 2004 i 2006 roku grupa geologów z Akademii Górniczo-Hutniczej w Krakowie prowadziła badania terenowe młodej grupy wulkanicznej Andahua, w południowym Peru. Została ona poznana zaledwie 45 lat temu i do chwili obecnej nie określono definitywnie jej zasięgu i genezy. Największym obszarowo i jednocześnie najbogatszym w produkty wulkanizmu grupy Andahua jest rejon Doliny Wulkanów. Lawy zwartą pokrywą wypełniają tę dolinę, między Misahuanca a Ayo na długości około 60 km. W trakcie prac zidentyfikowano około 150 centrów erupcyjnych, w tym: stożki piroklastyczne o wysokości 50-300 m oraz bardziej liczne kopuły i szczeliny lawowe. Morfologia i rozprzestrzenienie skał grupy Andahua wykazują pewne związki z tektoniką i budową geologiczną podłoża.

EN

In 2003,2004 and 2006 small groups of geologists of AGH - The University of Science and Technology in Kraków investigated young Andahua volcanic group of Southern Peru. It was identified first some 45 years ago but its extension is not definitely determined yet. The greatest area of the Andahua group, where at the same time the volcanism products are the most common, is the Valley of Volcanoes. This valley, between the Misahuanca and Ayo, is covered by a dense cover of lava, which is about 60 km long. Field work resulted in discovery of about 150 individual emission centres: apparent pyroclastic cones 50-300 metres high, and usually smaller lava domes and vents controlled by fractures. Morphology of the Andahua lava flows coalescing into composite lava fields as well as criteria for their stratigraphy and tectonic controls are given.

3

Karłowate wulkany formacji Andahua w południowym Peru

Gałaś A., Paulo A.

Przegląd Geologiczny

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2005

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Vol. 53, nr 4

320--326

EN

In July 2003 and 2004 small groups of geologists of AGH — The University of Science and Technology in Kraków investigated recent Andahua volcanic formation of Southern Peru. It was identified first some 45 years ago but its extension is not definitely determined yet. Field work resulted in discovery of about 100 individual emission centres: apparent pyroclastic cones 50–300 metres high, and usually smaller lava domes and vents by controlled fractures. Morphology of the Andahua lava flows coalescing into composite lava fields as well as criteria for their stratigraphy and tectonic controls are given.