Mesozoic high-Mg andesites from the Daohugou area, Inner Mongolia: Upper-crustal fractional crystallization of parental melt derived from metasomatized lithospheric mantle wedge
16
Citation
91
Reference
10
Related Paper
Citation Trend
Keywords:
Fractional crystallization (geology)
Andesites
Andesites
Cite
Citations (1)
We determined K-Ar ages for four andesites of the Hisatsu volcanic rocks from Minamata and for rhyolite of the Gesujima welded tuff from Amakusa Shimoshima, southwest Kyushu Japan. The andesites include three Yahazudake volcanic rocks and one Ontake volcanic rocks. The obtained K-Ar ages for the Yahazudake type andesite range from 1.98 to 2.08 Ma. The ages of Ontake type andesite and Gesujima welded tuff are 2.15 Ma and 2.89 Ma respectively. From our new K-Ar age data combined with previously reported geological, petrological and chronological data of the Hisatsu volcanic rocks, we discussed the space and time distribution of these volcanic rocks. Andesites from Hisatsu volcanic rocks are divided into two categories, “Ontake type andesite (K2O>1.7 wt. %)” and “Yahazudake type andesite (K2O<1.2 wt. %)”, based on potassium content in andesite at given SiO2 range (57-63 wt.%). In terms of this criterion, most of the Hisatsu volcanic rocks and andesites from Kirishima volcano are defined as the “Ontake type andesite”. Consequently, the Ontake type andesite distributes whole area of the Hisatsu volcanic province extending from Nagashima area to Kirishima volcano. Andesites of this type, as a whole, have a positive correlation between latest eruption age of each volcano and the distance from the present volcanic front. This spatial arrangement of the Ontake type andesite implies that the width of volcanic zone has narrowed from Nagashima to Kirishima volcano during last three million years. Although the distribution area of Yahazudake type andesites overlaps the Ontake type andesites, the volcanism of the Yahazudake type andesites is quite limited in age ranging from 1.6 to 2.0 Ma. The production of each magma types may belong to different tectonic events.
Andesites
Cite
Citations (1)
Andesites
Breccia
Metasomatism
Cite
Citations (47)
We determined K-Ar ages for four andesites of the Hisatsu volcanic rocks from Minamata and for rhyolite of the Gesujima welded tuff from Amakusa Shimoshima, southwest Kyushu Japan. The andesites include three Yahazudake volcanic rocks and one Ontake volcanic rocks. The obtained K-Ar ages for the Yahazudake type andesite range from 1.98 to 2.08 Ma. The ages of Ontake type andesite and Gesujima welded tuff are 2.15 Ma and 2.89 Ma respectively. From our new K-Ar age data combined with previously reported geological, petrological and chronological data of the Hisatsu volcanic rocks, we discussed the space and time distribution of these volcanic rocks. Andesites from Hisatsu volcanic rocks are divided into two categories, “Ontake type andesite (K2O>1.7 wt. %)” and “Yahazudake type andesite (K2O<1.2 wt. %)”, based on potassium content in andesite at given SiO2 range (57-63 wt.%). In terms of this criterion, most of the Hisatsu volcanic rocks and andesites from Kirishima volcano are defined as the “Ontake type andesite”. Consequently, the Ontake type andesite distributes whole area of the Hisatsu volcanic province extending from Nagashima area to Kirishima volcano. Andesites of this type, as a whole, have a positive correlation between latest eruption age of each volcano and the distance from the present volcanic front. This spatial arrangement of the Ontake type andesite implies that the width of volcanic zone has narrowed from Nagashima to Kirishima volcano during last three million years. Although the distribution area of Yahazudake type andesites overlaps the Ontake type andesites, the volcanism of the Yahazudake type andesites is quite limited in age ranging from 1.6 to 2.0 Ma. The production of each magma types may belong to different tectonic events.
Andesites
Cite
Citations (2)
Abstract Andesite volcanoes of the North Island of New Zealand are divided on the basis of their potash contents into two groups; a low potash group which includes the Northland, Coromandel, and Taupo Volcanic Zone andesites, and a high potash group which contains the volcanoes of western Taranaki. There are no significant differences among the chemistries of the low potash andesites from the different regions, leading to the proposition that they have a similar origin. It is suggested that an andesite "source zone" developed in the upper mantle beneath the old arcuate structure during Miocene time and has propagated eastwards across the North Island. The high potash andesites appear to be associated with events beneath the old arcuate structure rather than with the active margin of the east coast of the North Island. The chemistries of the New Zealand andesites are compared with analyses from other active regions and the invariance of the soda content is contrasted with the large potash variation.
Andesites
Potash
Cite
Citations (58)
Andesites
Amphibole
Fractional crystallization (geology)
Basaltic andesite
Cite
Citations (3)
Peridotite
Andesites
Fractional crystallization (geology)
Basaltic andesite
Igneous differentiation
Cite
Citations (40)
Andesites
Caldera
Hornblende
Basaltic andesite
Cite
Citations (40)
Abstract Potassium-argon total rock, sanidine, and plagioclase ages are presented for 24 rhyolite, dacite, andesite, and basalt rocks of the Upper Cretaceous, Mt Somers Volcanics of mid Canterbury. Ages are grouped as follows: (1) total-rock ages of andesites and dacites: 45–94 Ma, but with a significant concentration at 82–91 Ma; (2) plagioclase ages of andesites and dacites: 87–93 Ma; (3) sanidine ages of pitchstone flows and rhyolitic intrusives: 88–99 Ma. The wide range of andesite total-rock ages, which do not correlate with co-existing plagioclase ages, indicate that substantial argon loss (up to 50%) may, in a few cases, have occurred from a second potassic phase, most probably volcanic glass. The majority of total-rock/plagioclase pairs show concordant ages, which in turn are similar to sanidine ages of closely associated rhyolitic rocks. Detailed stratigraphic evidence and potassium variations in the feldspars show that argon loss (about 5%) has occurred in most plagioclases (K < 0·8%) and some sanidines (K < 7%), causing younger ages than anticipated. In addition, despite favourable potassium concentrations (7% < K < 0·9%) of their feldspars, andesites known to predate rhyolites none the less yield younger ages. To some extent this pattern is explained by slight differences in the andesite-rhyolite sequences at the three main eruptive centres at Mt Somers, Malvern Hills, and Rangitata Gorge. Both andesite and rhyolite volcanism at Mt Somers (94–98 Ma) may predate rhyolites in the Malvern Hills area, 91–94 Ma. Mt Somers Volcanics extend from about 98 Ma (upper Albian) to at least 92 Ma (Turonian). Owing to the slight argon loss problem, the younger age limit for volcanism cannot be assessed. A basalt sample from Malvern Hills, dated as 37 Ma, is probably related to widespread tholeiitic Oligocene volcanism in North Canterbury, rather than to Mt Somers Volcanics. Mt Somers Volcanics show age similarities with more basic alkaline volcanics of inland Marlborough (and may form part of an Upper Cretaceous volcanic arc in the South Island). More distant age correlations can be made with rhyolites on Lord Howe Rise (Tasman Sea) and in central Marie Byrd Land, West Antarctica.
Andesites
Sanidine
Dacite
K–Ar dating
Cite
Citations (16)