首页 | 本学科首页   官方微博 | 高级检索  
     检索      


Ein Beitrag zur Vulkanologie Süd-Perus
Authors:Prof Dr M Weibel  Dr M Frangipane-Gysel  PD Dr J Hunziker
Institution:1. Geochemisches Labor, ETH-Zentrum, CH-8092, Zürich
2. Geochronologisches Labor, Universit?t, Sahlistr. 6, CH-3012, Bern
Abstract:The Nevado Coropuna (6400 m/19 500 ft) is the largest and highest volcano of Peru and is situated 150 km NW of the town of Arequipa at a distance of 110 km from the Pacific coast. Results of a thorough petrographic study are presented including microprobe and radiometric measurements.
  1. The constituent rocks building up the Coropuna volcano are lavas and rhyodacitic ash flows intercalated between older and younger lavas at the foot of the cone. The volcanic edifice rests on older ignimbrite sheets (14 m. y.) exposed only in the surrounding valleys.
  2. The lavas are typically latite-andesites which contain some normative quartz in the groundmass. Plagioclase has 37–47% An. The depth of the phenocryst crystallization is calculated at 8–12 km based on the equilibrium between plagioclase, clinopyroxene and groundmass.
  3. The Coropuna volcano has existed since the Late Miocene (5 m. y.). Approximately 2 m. y. ago a catastrophic explosion produced large rhyodacitic ignimbrite deposits around the foot of the mountain. Thereafter the effusion of lavas was dominant through Holocene times with the latest lavas becoming slightly more acidic (62% SiO2).
  4. 30–40 km to the W and SW of the Coropuna some outliers of the coastal batholites are exposed. Both their radiometric age (Cretaceous, 97 m. y.) and their chemical composition are in disagreement with the notion of these granodioritic to gabbroic rocks as the intrusive equivalents of the young volcanics.
Keywords:
本文献已被 SpringerLink 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号