Volcanological studies of Neogene flood basalt groups in eastern Iceland

• Main Author: Birgir Vilhelm Óskarsson 1982-
• Other Authors: Háskóli Íslands
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2015
• Subjects: Doktorsritgerðir; Reyðarfjörður; Grænavatn; Hólmar; Hólmatindur; Kumlafell; Iceland
• Online Access: http://hdl.handle.net/1946/22929

Included in the supplementary files are seven photogrammetric panels and one geological map (1:100 000) of eastern Iceland. Flood basalt groups in the Neogene lava piles of eastern Iceland are subject to investigation. The groups form the stratigraphic section above the Reyðarfjörður central volcano up to the Thingmuli central volcano, mapped by the British geologist G. P. L. Walker and his students in the 1950s and 60s. The groups were chosen as representative of the three predominant basalt types in Iceland, namely the Hólmar and Grjótá olivine basalt groups, the Kumlafell, Hólmatindur and Hjálmadalur aphyric basalt groups (mostly tholeiitic) and the Grænavatn porphyritic basalt group. Ground mapping and aerial photogrammetry were applied to assess the facies architecture of the groups, map their extent and distribution, measure the thickness of the lava flows and log the internal structure of representative flows. The source origin of each group was identified and the mode of emplacement of the flow types assessed with constraints on effusion rates. A new tectono-magmatic model for scale, geometry and evolution of the Neogene rift systems and mantle anomaly in Iceland is put forward, building on structural volcanological and geochemical evidence. Í jarðlagastafla Austfjarða eru mjög víðáttumiklar hraunlagasyrpur sem myndast hafa í miklum flæðigosum á míósen. Sex syrpur voru rannsakaðar en þær liggja í staflanum á milli megineldstöðva sem kenndar eru við Reyðarfjörð og Þingmúla. Syrpurnar endurspegla meginflokka íslenskra basalthrauna samkvæmt feltskiptingu G. P. L. Walkers, sem kortlagði þær ásamt samstarfsmönnum sínum upp úr miðri síðustu öld. Hólmasyrpa og Grjótársyrpa eru úr ólivínbasalti, Kumlafellssyrpa, Hólmatindssyrpa og Hjálmadalssyrpa að mestu úr dílalitlum hraunum af þóleiískri gerð en Grænavatnssyrpan að mestu úr dílabasalti. Uppbygging hraunlagasyrpanna var könnuð með nákvæmri loftljósmyndun. Þá var innri gerð hraunlaganna athuguð og henni lýst með aðferðum eðlisrænnar eldfjallafræði og ...