K-Ar age determinations of late Tertiary and Quaternary Andean volcanic rocks, southern Peru.

Kaneoka, Ichiro; Guevara, Carlos J.

doi:10.2343/geochemj.18.233

Cited by 39 publications

(26 citation statements)

References 12 publications

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“…Previous K-Ar dating of the andesitic bedrocks near Andahua indicated Middle to Late Pleistocene ages (Kaneoka and Guevara 1984). One sample collected north of the Cerro Tichsó (WNW of the town of Andahua) (Table 1).…”

Section: Agesmentioning

confidence: 99%

“…The four morphometric parameters utilized (following Wood 1980) are: (1) the basal diameter Kaneoka and Guevara (1984) D b , (2) the crater diameter D cr , (3) the edifice height H, and (4) the slope average dip S, with S=tan −1 (H/(D b −D cr )). A decrease in the ratio of height (H) to basal diameter (D b ) is the consequence of height reduction due to erosion and to the fact that the basal diameter increases as scree accumulates.…”

Section: Agesmentioning

confidence: 99%

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Magma evolution of Quaternary minor volcanic centres in southern Peru, Central Andes

et al. 2006

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International audienceMinor centres in the Central Volcanic Zone (CVZ) of the Andes occur in different places and are essential indicators of magmatic processes leading to formation of composite volcano. The Andahua–Orcopampa and Huambo monogenetic fields are located in a unique tectonic setting, in and along the margins of a deep valley. This valley, oblique to the NW–SE-trend of the CVZ, is located between two composite volcanoes (Nevado Coropuna to the east and Nevado Sabancaya to the west). Structural analysis of these volcanic fields, based on SPOT satellite images, indicates four main groups of faults. These faults may have controlled magma ascent and the distribution of most centres in this deep valley shaped by en-echelon faulting. Morphometric criteria and 14C age dating attest to four main periods of activity: Late Pleistocene, Early to Middle Holocene, Late Holocene and Historic. The two most interesting features of the cones are the wide compositional range of their lavas (52.1 to 68.1 wt.% SiO2) and the unusual occurrence of mafic lavas (olivine-rich basaltic andesites and basaltic andesites). Occurrence of such minor volcanic centres and mafic magmas in the CVZ may provide clues about the magma source in southern Peru. Such information is otherwise difficult to obtain because lavas produced by composite volcanoes are affected by shallow processes that strongly mask source signatures. Major, trace, and rare earth elements, as well as Sr-, Nd-, Pb- and O-isotope data obtained on high-K calc-alkaline lavas of the Andahua–Orcopampa and Huambo volcanic province characterise their source and their evolution. These lavas display a range comparable to those of the CVZ composite volcanoes for radiogenic and stable isotopes (87Sr/86Sr: 0.70591–0.70694, 143Nd/144Nd: 0.512317–0.512509, 206Pb/204Pb: 18.30–18.63, 207Pb/204Pb: 15.57–15.60, 208Pb/204Pb: 38.49–38.64, and δ 18O: 7.1–10.0‰ SMOW), attesting to involvement of a crustal component. Sediment is absent from the Peru–Chile trench, and hence cannot be the source of such enrichment. Partial melts of the lowermost part of the thick Andean continental crust with a granulitic garnet-bearing residue added to mantle-derived arc magmas in a high-pressure MASH [melting, assimilation, storage and homogenisation] zone may play a major role in magma genesis. This may also explain the chemical characteristics of the Andahua–Orcopampa and Huambo magmas. Fractional crystallisation processes are the main governors of magma evolution for the Andahua–Orcopampa and Huambo volcanic province. An open-system evolution is, however, required to explain some O-isotopes and some major and trace elements values. Modelling of AFC processes suggests the Charcani gneisses and the local Andahua–Orcopampa and Huambo basement may be plausible contaminants

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Section: Agesmentioning

confidence: 99%

Section: Agesmentioning

confidence: 99%

Magma evolution of Quaternary minor volcanic centres in southern Peru, Central Andes

et al. 2006

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“…During the Cenozoic, continental volcanic rocks and volcaniclastic sediments were deposited discontinuously, punctuated by discrete compressive tectonic phases which were coeval with periods of high convergence rate of the lithospheric plates (SØbrier et al 1988;SØbrier and Soler 1991). Tensional faulting prevailed in the Western Cordillera and was associated with voluminous calcalkaline volcanism (Kanokea and Guevara 1984;Soler 1990;SØbrier and Soler 1991). Large volumes of lavas, ignimbrites and volcaniclastic sediments were deposited, forming the Neogene basement of the huge Plio-Quaternary composite volcanoes.…”

Section: Introductionmentioning

confidence: 98%

Role of magma mixing in the petrogenesis of tephra erupted during the 1990–98 explosive activity of Nevado Sabancaya, southern Peru

Gerbe

Thouret

2004

Bull Volcanol

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“…A number of younger units of silicic ash-flow tuff and lava of intermediate and silicic composition, ranging in age from middle Miocene to Quaternary, overlie the older rocks, although the only rocks preserved in the Orcopampa district consist of flows and cinder cones of basalt and basaltic andesite of the Andahua volcanics of Quaternary age (Hoempler, 1962;Weibel et al, 1978;Kaneoka and Guevara, 1984). Landslides, some of considerable size, are common in the general vicinity of the Orcopampa district (Fig.…”

Section: Gibson Etalmentioning

confidence: 97%

Discovery, Development, and Production of a Blind Ag-Au Bonanza in the Calera Vein, Orcopampa District, Peru

Gibson

Noble

Benavides³

et al. 1993

International Geology Review

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K-Ar age determinations of late Tertiary and Quaternary Andean volcanic rocks, southern Peru.

Cited by 39 publications

References 12 publications

Magma evolution of Quaternary minor volcanic centres in southern Peru, Central Andes

Magma evolution of Quaternary minor volcanic centres in southern Peru, Central Andes

Role of magma mixing in the petrogenesis of tephra erupted during the 1990–98 explosive activity of Nevado Sabancaya, southern Peru

Discovery, Development, and Production of a Blind Ag-Au Bonanza in the Calera Vein, Orcopampa District, Peru

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