scholarly journals Magmatic history of the Oldest Toba Tuff inferred from zircon U–Pb geochronology

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hisatoshi Ito
Keyword(s):  
Caldera Collapse ◽  
Zircon Dating ◽  
Icp Ms ◽  
Zircon Crystallization ◽  
History Of ◽  
Eruption Age ◽  
Magmatic History

Abstract The magmatic history of the Oldest Toba Tuff (OTT), the second largest in volume after the Youngest Toba Tuff (YTT), northern Sumatra, Indonesia, was investigated using U–Pb zircon dating by LA-ICP-MS. Zircon dates obtained from surface and interior sections yielded ages of 0.84 ± 0.03 Ma and 0.97 ± 0.03 Ma, respectively. The youngest OTT zircon ages were in accordance with the 40Ar/39Ar eruption age of ~ 0.8 Ma, whereas the oldest zircon dates were ~ 1.20 Ma. Therefore, the distribution of zircon U–Pb ages is interpreted to reflect protracted zircon crystallization, suggesting that the estimated 800–2,300 km3 of OTT magma accumulated and evolved for at least 400,000 years prior to eruption. This result is comparable to the volume and timescales of YTT magmatism. The similarities of both magmatic duration and geochemistry between OTT and YTT may indicate that they are similar in size and that the caldera collapse that generated OTT might be much larger previously interpreted.

scholarly journals Mineralogy and Geochemistry of Ultramafic Rocks from Rachoni Magnesite Mine, Gerakini (Chalkidiki, Northern Greece)

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 934
Author(s):  
Evangelos Tzamos ◽  
Micol Bussolesi ◽  
Giovanni Grieco ◽  
Pietro Marescotti ◽  
Laura Crispini ◽  
...  
Keyword(s):  
Raw Materials ◽  
Mining Area ◽  
Ultramafic Rocks ◽  
Northern Greece ◽  
Icp Ms ◽  
Time In Literature ◽  
History Of ◽  
First Time ◽  
The Eu

The importance of magnesite for the EU economy and industry is very high, making the understanding of their genesis for the exploration for new deposits a priority for the raw materials scientific community. In this direction, the study of the magnesite-hosting ultramafic rocks can be proved very useful. For the present study, ultramafic rock samples were collected from the magnesite ore-hosting ophiolite of the Gerakini mining area (Chalkidiki, Greece) to investigate the consecutive alteration events of the rocks which led to the metallogenesis of the significant magnesite ores of the area. All samples were subjected to a series of analytical methods for the determination of their mineralogical and geochemical characteristics: optical microscopy, XRD, SEM, EMPA, ICP–MS/OES and CIPW normalization. The results of these analyses revealed that the ultramafic rocks of the area have not only all been subjected to serpentinization, but these rocks have also undergone carbonation, silification and clay alteration. The latter events are attributed to the circulation of CO2-rich fluids responsible for the formation of the magnesite ores and locally, the further alteration of the serpentinites into listvenites. The current mineralogy of these rocks was found to be linked to one or more alteration event that took place, thus a significant contribution to the metallo- and petrogenetic history of the Gerakini ophiolite has been made. Furthermore, for the first time in literature, Fe inclusions in olivines from Greece were reported.

scholarly journals The emplacement age of the Muntele Mare Variscan granite (Apuseni Mountains, Romania)

2009 ◽  
Vol 60 (6) ◽  
pp. 495-504 ◽  
Author(s):  
Ioan Balintoni ◽  
Constantin Balica ◽  
Monica Cliveţi ◽  
Li-Qiu Li ◽  
Horst Hann ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Variscan Orogeny ◽  
Weighted Mean ◽  
Apuseni Mountains ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Plasma Mass Spectrometry ◽  
History Of ◽  
The Alps ◽  
Last Stage

The emplacement age of the Muntele Mare Variscan granite (Apuseni Mountains, Romania)Like the Alps and Western Carpathians, the Apuseni Mountains represent a fragment of the Variscan orogen involved in the Alpine crustal shortenings. Thus the more extensive Alpine tectonic unit in the Apuseni Mountains, the Bihor Autochthonous Unit is overlain by several nappe systems. During the Variscan orogeny, the Bihor Unit was a part of the Someş terrane involved as the upper plate in subduction, continental collision and finally in the orogen collapse and exhumation. The Variscan thermotectonic events were marked in the future Bihor Unit by the large Muntele Mare granitoid intrusion, an S-type anatectic body. Zircon U-Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating yielded a weighted mean age of 290.9 ± 3.0 Ma and a concordia age of 291.1 ± 1.1 Ma. U-Pb isotope dilution zircon analyses yielded a lower intercept crystallization age of 296.6 + 5.7/-6.2 Ma. These two ages coincide in the error limits. Thus, the Muntele Mare granitoid pluton is a sign of the last stage in the Variscan history of the Apuseni Mountains. Many zircon grains show inheritance and/or Pb loss, typical for anatectic granitoid, overprinted by later thermotectonic events.

Chapter 13 Eruptive, volcano-tectonic and magmatic history of the Stromboli volcano (north-eastern Aeolian archipelago)

2013 ◽  
Vol 37 (1) ◽  
pp. 397-471 ◽  
Author(s):  
L. Francalanci ◽  
F. Lucchi ◽  
J. Keller ◽  
G. De Astis ◽  
C. A. Tranne
Keyword(s):  
Stromboli Volcano ◽  
North Eastern ◽  
History Of ◽  
Magmatic History ◽  
Aeolian Archipelago

A geochronological framework for sedimentation and Mesoproterozoic tectono-magmatic activity in lower Belt–Purcell rocks exposed west of Kimberley, British Columbia

2015 ◽  
Vol 52 (7) ◽  
pp. 444-465 ◽  
Author(s):  
Christopher R.M. McFarlane
Keyword(s):  
British Columbia ◽  
Minor Component ◽  
Structural Level ◽  
Peraluminous Granite ◽  
Icp Ms ◽  
Ductile Shearing ◽  
History Of ◽  
Metamorphic Zone ◽  
A Minor ◽  
Plate Reconstruction

The Matthew Creek Metamorphic Zone (MCMZ) exposes what is inferred to be the lowest structural level of the lower Aldridge Formation in the Canadian portion of the Belt–Purcell Supergroup. Zircon, monazite, and titanite were dated using the U–Pb system by LA–ICP–MS. The detrital zircon populations of quartzite layers in these rocks define a provenance dominated by sources of Laurentian affinity with a minor component of non-North American ages between 1600 and 1490 Ma. Special attention was paid to monazite in sillimanite-grade metapelitic schists that was analyzed using in situ LA–ICP–MS techniques guided by BSE imaging and compositional mapping. Textural and geochronological evidence indicate that coupled dissolution–reprecipitation affected detrital monazite at 1413 ± 10 Ma. This was followed by prograde monazite growth at 1365 ± 10 Ma, synchronous with crystallization of the nearby Hellroaring Creek peraluminous granite at 1365 ± 5 Ma. Late-stage pegmatite emplacement and ductile shearing along the contact of the MCMZ and overlying rocks occurred at 1335 ± 5 Ma, interpreted as a period of post-collisional extension, core complex formation, exhumation, and decompression melting. The entire package was subsequently affected by a pervasive ∼1050 Ma hydrothermal overprint that partially reset U–Pb dates in monazite, zircon, and titanite contained in all lithologies examined. The lowermost Belt–Purcell stratigraphy in southeast British Columbia preserves a detailed record of sedimentary provenance and a long history of episodic collision and extension that must be reconciled with plate reconstruction models for the break-up of the Nuna supercontinent and assembly of Rodinia.

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