Partial melt generation and evolution of magma reservoir conditions at the Paka volcanic complex in Kenya: Constraints from geochemistry, petrology and geophysics

Lithos ◽  
2021 ◽  
pp. 106385
Author(s):  
Geoffrey Mibei ◽  
Enikő Bali ◽  
Halldór Geirsson ◽  
Guðmundur H. Guðfinnsson ◽  
Björn S. Harðarson ◽  
...  
Keyword(s):  
Magma Reservoir ◽  
Volcanic Complex ◽  
Partial Melt ◽  
Reservoir Conditions ◽  
Melt Generation

Magma reservoir conditions beneath Tsurumi volcano, SW Japan: Evidence from amphibole thermobarometry and seismicity

Lithos ◽  
2017 ◽  
Vol 278-281 ◽  
pp. 153-165 ◽  
Author(s):  
Shiho Nagasaki ◽  
Hidemi Ishibashi ◽  
Yukiko Suwa ◽  
Atsushi Yasuda ◽  
Natsumi Hokanishi ◽  
...  
Keyword(s):  
Magma Reservoir ◽  
Reservoir Conditions ◽  
Sw Japan

Variable magma reservoir depths for Tongariro Volcanic Complex eruptive deposits from 10,000 years to present

2017 ◽  
Vol 79 (7) ◽  
Author(s):  
Maria Carmencita Arpa ◽  
Georg F. Zellmer ◽  
Bruce Christenson ◽  
Gert Lube ◽  
Gregory Shellnutt
Keyword(s):  
Magma Reservoir ◽  
Volcanic Complex

Extraction of high-silica granites from an upper crustal magma reservoir: Insights from the Narusongduo magmatic system, Gangdese arc

2020 ◽  
Vol 105 (10) ◽  
pp. 1572-1584 ◽  
Author(s):  
Jin-Sheng Zhou ◽  
Zhu-Sen Yang ◽  
Qiang Wang ◽  
Yuan-Chuan Zheng ◽  
Zeng-Qian Hou ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Magma Reservoir ◽  
Igneous Rocks ◽  
Volcanic Complex ◽  
Differentiated Products ◽  
Magmatic System ◽  
Andesitic Magma ◽  
Melt Separation ◽  
High Silica ◽  
Crustal Magma

Abstract The genesis of high-silica igneous rocks is important for understanding the behavior of shallow magmatic systems. However, although many such studies have focused on the eruption of crystal-poor high-SiO2 rhyolites, the origin of high-silica granites (HSGs) has received comparatively little attention. Here, we present a detailed study of HSGs from the Narusongduo volcanic complex, Gangdese arc. Combining zircon U-Pb geochronology with stratigraphic investigations, we show that the Narusongduo magmatic system was constructed over a period of ≥3.7 Myr with or without lulls. On the basis of zircon textures and ages, diverse zircon populations, including antecrysts and autocrysts, are recognized within the HSGs and volcanic rocks. All of the igneous rocks within the Narusongduo volcanic complex have highly radiogenic Sr–Nd isotopic compositions. Our results indicate the presence of an andesitic magma reservoir in the upper crust at a paleodepth of ~8 km. Ubiquitous zircon antecrysts in the HSGs, combined with compositional similarities between the HSGs and evolved melts of the andesitic magma reservoir, indicate that the Narusongduo HSGs represent melts extracted from the shallow magma reservoir. In addition, our results suggest that magma recharge promoted the escape of high-silica melts to form the Narusongduo HSGs. This work presents an excellent case that kilometer-scale high-silica granites are the differentiated products from an upper crustal magma reservoir. It would make a contribution to contemporary debates concerning the efficiency of crystal–melt separation in upper crustal magmatic systems.

Constraints on the pre-eruption thermal and fO2 conditions in the magma reservoir of Ciomadul (SE Carpathians, Romania) based on Fe-Ti oxide geochemistry

2021 ◽  
Author(s):  
Máté Szemerédi ◽  
Katalin Mészáros ◽  
Réka Lukács ◽  
Zoltán Kovács ◽  
Szabolcs Harangi
Keyword(s):  
Oxygen Fugacity ◽  
Magma Reservoir ◽  
Heavy Minerals ◽  
Volcanic Complex ◽  
Quaternary Volcanism ◽  
Andesitic Lava ◽  
Eruptive Centre ◽  
Volcanic Chain ◽  
Magmatic Plumbing System ◽  
American Geophysical

<p>Ciomadul is the southernmost eruptive centre of the post-collisional Călimani-Gurghiu-Harghita andesitic-dacitic volcanic chain (SE Carpathians, Romania) and represents the latest manifestation of the Neogene to Quaternary volcanism in the Carpathian-Pannonian Region. Ciomadul consists of older, peripheral shoshonitic to dacitic lava domes formed episodically between 1 Ma and 300 ka and a voluminous, central volcanic complex developed within the last 200 ka. Although several lines of evidence (based on petrology, geophysics and gas monitoring) suggest a long-lived magmatic plumbing system holding a potentially active magma storage (“PAMS” volcano) beneath Ciomadul, the pre-eruptive conditions of the upper crustal magma reservoir (including temperature, oxygen fugacity and TiO<sub>2</sub> activity) are not completely explored so far. In this study 23 rock samples, representing the whole volcanic activity of Ciomadul in time, were involved. Fe-Ti oxide (magnetite-ilmenite) grains were selected from magnetic heavy minerals, but only a few of the samples contained both magnetite and ilmenite crystals. Equilibrium between Ti-magnetite and ilmenite was tested by their chemical composition (Mg/Mn ratios).</p><p>Various geothermobarometer calibrations, including Andersen and Lindsley (1985, 1988) as well as Ghiorso and Evans (2008), were applied to calculate temperature and oxygen fugacity from Fe-Ti oxide compositions. Our results show that, in case of dacitic pyroclastic rocks, temperature values gained by the method of Ghiorso and Evans are significantly lower (640–780 °C) than those obtained by the geothermometers of Andersen and Lindsley (1985, 1988), showing 750–830 and 710–790°C temperatures, respectively. On the other hand, andesitic lava dome rocks of Dealul Mare show higher, 800–900 °C temperature according to all of these methods. The obtained temperature was compared with amphibole-plagioclase thermometry results and this shows a better agreement with the values yielded by the Andersen and Lindsley (1985) Fe-Ti oxide thermometry, particularly for the pumice samples.</p><p>In case of oxygen fugacity, the Ghiorso and Evans (2008) and Andersen and Lindsley (1985) methods showed fairly similar values (fO<sub>2</sub>=0.9–1.8) whereas the Andersen and Lindsley (1988) calculations gave higher oxygen fugacity (fO<sub>2</sub>=1.1–2.5). Nevertheless, these results, irrespective the applied calculation methods, suggest relatively oxidized conditions (ΔNNO>1) what is comparable with many other andesitic to dacitic volcanic systems (e.g. Mount St. Helens, Mount Unzen, Santorini). Values of TiO<sub>2</sub> activity was calculated and obtained a range between 0.76 and 0.98 what is consistent with the common presence of titanite.</p><p> </p><p>This study was financed by NKFIH K135179 project.</p><p> </p><p>Andersen, D.J. & Lindsley, D.H. (1985). EOS Transactions of the American Geophysical Union, 66, 416.</p><p>Andersen, D.J. & Lindsley, D.H. (1988). Amer Miner 73:714–726.</p><p>Ghiorso, M.S. & Evans, B.W. (2008). Amer J Sci 308:957–1039.</p>

The first results of isotopic (U-Pb, ID-TIMS) dating of individual zircon grains from dolerite dikes of the Eastern zone of the Urals

LITOSFERA ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 224-230
Author(s):  
V. N. Smirnov ◽  
K. S. Ivanov ◽  
T. V. Bayanova
Keyword(s):  
Isotope Geochemistry ◽  
Early Carboniferous ◽  
Dynamic Mode ◽  
Middle Urals ◽  
Volcanic Complex ◽  
The Urals ◽  
Electron Multiplier ◽  
The Middle Urals ◽  
Eastern Zone ◽  
First Results

Research subject. The article presents the results of dating two dolerite dikes differing in geochemical features from a section along the Iset river in the area of Smolinskoe settlement (the Eastern zone of the Middle Urals). Materials and methods. The dating was performed by an U-Pb ID-TIMS technique for single zircon grains using an artificial 205Pb/235U tracer in the laboratory of geochronology and isotope geochemistry of the Geological Institute of the Kola Science Centre of the Russian Academy of Sciences. The lead isotopic composition and uranium and lead concentrations were measured using a Finnigan-MAT (RPQ) seven-channel mass spectrometer in dynamic mode using a secondary electron multiplier and RPQ quadrupole in ion counting mode. Results. The dikes were dated 330 ± 3 Ma and 240 ± 2 Ma. Conclusions. The research results indicate different ages of dolerite dikes developed within the Eastern zone of the Middle Urals. The oldest of the two established age levels corresponds to the Early Carboniferous era. This fact, along with the proximity of the dolerites to the petrochemical features of the basaltoids of the Early Carboniferous Beklenischevsky volcanic complex, allows these bodies to be considered as hypabyssal comagmates of these volcanics. The youngest obtained age level – Triassic – indicates that the introduction of some dolerite dikes was associated with the final phases of the trapp formation developed rarely within the eastern outskirts of the Urals and widely further east in the foundation (pre-Jurassic basement) of the West-Siberian Plate.

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