Quantification of excess 231Pa in late Quaternary igneous baddeleyite

2020 ◽  
Vol 105 (12) ◽  
pp. 1830-1840 ◽  
Author(s):  
Yi Sun ◽  
Axel K. Schmitt ◽  
Lucia Pappalardo ◽  
Massimo Russo
Keyword(s):  
Late Quaternary ◽  
Central Italy ◽  
Direct Analysis ◽  
Weight Percent ◽  
Volcanic Field ◽  
Distribution Coefficients ◽  
Secular Equilibrium ◽  
Melt Distribution ◽  
D Values ◽  
Significant Figures

Abstract Initial excess protactinium (231Pa) is a frequently suspected source of discordance in baddeleyite (ZrO2) geochronology, which limits accurate U/Pb dating, but such excesses have never been directly demonstrated. In this study, Pa incorporation in late Holocene baddeleyite from Somma-Vesuvius (Campanian Volcanic Province, central Italy) and Laacher See (East Eifel Volcanic Field, western Germany) was quantified by U-Th-Pa measurements using a large-geometry ion microprobe. Baddeleyite crystals isolated from subvolcanic syenites have average U concentrations of ~200 ppm and are largely stoichiometric with minor abundances of Nb, Hf, Ti, and Fe up to a few weight percent. Measured (231Pa)/(235U) activity ratios are significantly above the secular equilibrium value of unity and range from 3.4(8) to 14.9(2.6) in Vesuvius baddeleyite and from 3.6(9) to 8.9(1.4) in Laacher See baddeleyite (values within parentheses represent uncertainties in the last significant figures reported as 1σ throughout the text). Crystallization ages of 5.12(56) ka (Vesuvius; MSWD = 0.96, n = 12) and 15.6(2.0) ka (Laacher See; MSWD = 0.91, n = 10) were obtained from (230Th)/(238U) disequilibria for the same crystals, which are close to the respective eruption ages. Applying a corresponding age correction indicates average initial (231Pa)/(235U)0 of 8.8(1.0) (Vesuvius) and 7.9(5) (Laacher See). For reasonable melt activities, model baddeleyite-melt distribution coefficients of DPa/DU = 5.8(2) and 4.1(2) are obtained for Vesuvius and Laacher See, respectively. Speciation-dependent (Pa4+ vs. Pa5+) partitioning coefficients (D values) from crystal lattice strain models for tetra- and pentavalent proxy ions significantly exceed DPa/DU inferred from direct analysis of 231Pa for Pa5+. This is consistent with predominantly reduced Pa4+ in the melt, for which D values similar to U4+ are expected. Contrary to common assumptions, baddeleyite-crystallizing melts from Vesuvius and Laacher See appear to be dominated by Pa4+ rather than Pa5+. An initial disequilibrium correction for baddeleyite geochronology using DPa/DU = 5 ± 1 is recommended for oxidized phonolitic melt compositions.

scholarly journals Seismogenesis in Central Apennines, Italy: an integrated analysis of minor earthquake sequences and structural data in the Amatrice-Campotosto area

2009 ◽  
Vol 47 (6) ◽  
Author(s):  
P. Boncio ◽  
G. Lavecchia ◽  
G. Milana ◽  
B. Rozzi
Keyword(s):  
Late Quaternary ◽  
Central Italy ◽  
Normal Fault ◽  
Structural Data ◽  
Integrated Analysis ◽  
Fault Plane Solutions ◽  
Small Magnitude ◽  
Fault Surface ◽  
Displacement Profile ◽  
Earthquake Sequences

We present a seismotectonic study of the Amatrice-Campotosto area (Central Italy) based on an integrated analysis of minor earthquake sequences, geological data and crustal rheology. The area has been affected by three small-magnitude seismic sequences: August 1992 (M=3.9), June 1994 (M=3.7) and October 1996 (M=4.0). The hypocentral locations and fault plane solutions of the 1996 sequence are based on original data; the seismological features of the 1992 and 1994 sequences are summarised from literature. The active WSWdipping Mt. Gorzano normal fault is interpreted as the common seismogenic structure for the three analysed sequences. The mean state of stress obtained by inversion of focal mechanisms (WSW-ENE-trending deviatoric tension) is comparable to that responsible for finite Quaternary displacement, showing that the stress field has not changed since the onset of extensional tectonics. Available morphotectonic data integrated with original structural data show that the Mt. Gorzano Fault extends for ~28 km along strike. The along-strike displacement profile is typical of an isolated fault, without significant internal segmentation. The strong evidence of late Quaternary activity in the southern part of the fault (with lower displacement gradient) is explained in this work in terms of displacement profile readjustment within a fault unable to grow further laterally. The depth distribution of seismicity and the crustal rheology yield a thickness of ~15 km for the brittle layer. An area of ~530 km2 is estimated for the entire Mt. Gorzano Fault surface. In historical times, the northern portion of the fault was probably activated during the 1639 Amatrice earthquake (I = X, M~ 6.3), but this is not the largest event we expect on the fault. We propose that a large earthquake might activate the entire 28 km long Mt. Gorzano Fault, with an expected Mmax up to 6.7.

Eruptive frequency of the Bora-Baricha-Tullu Moye (BBTM) volcanic system in the Central Main Ethiopian Rift

2021 ◽  
Author(s):  
Amdemichael Zafu Tadesse ◽  
Karen Fontijn ◽  
Abate Assen Melaku ◽  
Ermias Filfilu Gebru ◽  
Victoria Smith ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Volcanic Eruptions ◽  
Volcanic Field ◽  
Tectonic Activity ◽  
Explosive Eruptions ◽  
Ethiopian Rift ◽  
Rift System ◽  
Diagnostic Features ◽  
Volcanic System ◽  
Main Ethiopian Rift

<p>The Main Ethiopian Rift (MER) is the northern portion of the East African Rift System and separates the Eastern and Western plateaus of Ethiopia. The recent volcanic and tectonic activity is largely focused within the rift basin along a 20 km wide zone on the rift floor. Large silicic volcanic complexes are aligned along this central rift axis but their eruptive histories are not well constrained.</p><p>The Bora-Baricha-Tullu Moye (BBTM) volcanic field is situated in the central Main Ethiopian Rift and has a different appearance than the other MER volcanic systems. The BBTM constitutes several late Quaternary edifices, the major ones are: Tullu Moye, Bora and Baricha. In addition, there are multiple smaller eruptive vents (e.g. Oda and Dima), cones, and domes across the ca. 20 X 20 km wide area. Currently, there is very little information on the frequency and magnitude of past volcanic eruptions. We present a new dataset of field observations, componentry, petrography, geochronology (<sup>40</sup>Ar/<sup>39</sup>Ar), and glass major and trace element chemistry. The data are assessed as potential fingerprints to assign diagnostic features and correlate units across the area, and establish a tephrostratigraphic framework for the BBTM volcanic field.</p><p>Two large-volume and presumably caldera-forming eruptions are identified, the younger of which took place at 100 ka. The volcanic products exposed in the BBTM area show that the volcanic field has undergone at least 20 explosive eruptions since then. The post-caldera eruptions have comenditic (Tullu Moye) and pantelleretic (Bora and Baricha) magma compositions. Other smaller edifices such as Oda and Dima also erupted pantelleritic magmas, and only differ slightly in composition than tephra of Bora and Baricha. Tullu Moye had two distinct explosive eruptions that dispersed tephra up to 14 km away and on to the eastern plateau. Bora and Baricha together had at least 8 explosive eruptions. Their deposits can be distinguished by their light grey color and unique lithic components. Oda had 7 eruptions, the most recent of which generated a pyroclastic density current that travelled up to 10 km away from the vent. Dima experienced at least 3 eruptions, generating tephra with a bluish-grey colour.</p><p>This mapping and compositional analysis of the deposits from the BBTM in the MER indicates that the region has been more active in the last 100 ka than previously thought, which has implications for hazards assessments for the region.</p>

Trace element abundances and mineral/melt distribution coefficients in phonolites from the Laacher See volcano (Germany)

1983 ◽  
Vol 84 (2-3) ◽  
pp. 152-173 ◽  
Author(s):  
G. W�rrier ◽  
J. -M. Beusen ◽  
N. Duchateau ◽  
R. Gijbels ◽  
H. -U. Schmincke
Keyword(s):  
Trace Element ◽  
Distribution Coefficients ◽  
Element Abundances ◽  
Melt Distribution

Geology and volcanology of San Venanzo volcanic field (Umbria, Central Italy)

2005 ◽  
Vol 142 (6) ◽  
pp. 683-698 ◽  
Author(s):  
VITTORIO ZANON
Keyword(s):  
Spatial Distribution ◽  
Central Italy ◽  
Volcanic Field ◽  
Tectonic Activity ◽  
Complex Morphology ◽  
Field Evidence ◽  
Field Investigations ◽  
Volcanic Deposits ◽  
Groundwater Reservoir ◽  
History Of

The purpose of this paper is to integrate, or even modify where necessary, the geo-volcanological setting outlined by other authors on the history of the small volcanic field of San Venanzo (Umbria, Central Italy). To attain this goal, new accurate field investigations were carried out in that area, coupled with detailed stratigraphic studies and laboratory analyses, to support field evidence with experimental results. The first objective was to stress the importance of a groundwater reservoir whose interaction with magma at various degrees was responsible not only for the explosive character of volcanism in that area, but also for the complex morphology of the volcanic deposits that are widely scattered on the underlying sedimentary basement. Another objective was to clarify the role played by tectonic activity in enhancing the fast and discontinuous ascent of batches of magma from the mantle to the surface, through two different sets of faults, opened by tectonic unrest into the crust, that were also responsible for the morphology and spatial distribution of volcanic centres. This was considered to be very important in consideration of the still-active stress field of the region. Finally, special attention was focused on the presence of a palaeosol between two eruptive sequences, as it most likely denoted a split in the volcanic activity of this site into two separate phases. This observation leads to the conclusion that, in spite of its eruptive characteristics, the small volcano of San Venanzo is not monogenic. For all of these topics, a number of conclusions have been drawn and they are reported with more data in the following sections of this paper.

Late Quaternary soil erosion and landscape development in the Apennine region (central Italy)

2013 ◽  
Vol 312 ◽  
pp. 96-108 ◽  
Author(s):  
Pasquale Borrelli ◽  
Philipp Hoelzmann ◽  
Daniel Knitter ◽  
Brigitta Schütt
Keyword(s):  
Soil Erosion ◽  
Late Quaternary ◽  
Central Italy ◽  
Landscape Development

Tephrostratigraphical investigation of lake sediments and a peat bog in Northeastern China since 20,000 years

The Holocene ◽  
2016 ◽  
Vol 27 (5) ◽  
pp. 765-778
Author(s):  
Hongli Zhao ◽  
Jiaqi Liu ◽  
Valerie A Hall ◽  
Xiaoqiang Li
Keyword(s):  
Late Quaternary ◽  
Volcanic Field ◽  
Northeastern China ◽  
Historical Period ◽  
Published Data ◽  
Tianchi Volcano ◽  
Tephra Layers ◽  
Millennium Eruption ◽  
Reference Samples ◽  
Glass Shards

This is a detailed tephrostratigraphical investigation of late Quaternary deposits in the Longgang and Changbaishan Volcanic Fields of northeastern China. A total of 45 reference samples which were collected from either side of the Chinese/Korean border showed very similar geochemical characteristics to the Millennium eruption of Tianchi Volcano. Through comparing the published data of the glass shards detected in Gushantun with these reference samples, further description is that the glass shards in the sediment of Gushantun came from the Tianchi Volcano eruption in AD 1702, 1668, and 1597. A basaltic tephra layer found in the sediment of Hanlongwan associated with an eruption of the Jinlongdingzi Volcano which happened in 1500–2100 cal. yr BP by comparing with the published data from Sihailongwan and Xiaolongwan. Tianchi and Jinlongdingzi Volcano are both active and erupted several times during the historical period. Reference samples and the tephra layers detected in Hanlongwan, Sihailongwan, Gushantun, Erlongwan, and Xiaolongwan can be used as marker horizons beyond the Longgang Volcanic Field and Changbaishan Volcanic Field, including, for example, in Japan, Korea, nearby coastal area of Russia, and marine records.

Late Quaternary Eolian Deposition in Central Italy

2000 ◽  
Vol 54 (2) ◽  
pp. 246-252 ◽  
Author(s):  
Biancamaria Narcisi
Keyword(s):  
North Africa ◽  
Late Holocene ◽  
Late Quaternary ◽  
Ice Core ◽  
Central Italy ◽  
Last Interglacial ◽  
Central Mediterranean ◽  
Volcanic Lakes ◽  
Dust Loading ◽  
The Antarctic

Records of eolian quartz from two continuous sediment sequences drilled in Lagaccione and Lago di Vico volcanic lakes in central Italy contribute to the knowledge of eolian deposition in the central Mediterranean during the last 100,000 years. The chronology is based on 14C and 40Ar/39Ar dating and tephra analysis. Pollen data provide the paleoenvironmental framework and enable correlation between the cores. Eolian inputs were high during the steppe phases corresponding to oxygen isotope stages 4 and 2. Low inputs correspond to the forest phases of the last interglacial and the middle Holocene. Eolian inputs have increased in the late Holocene. Patterns of eolian deposition in central Italy resemble the Antarctic dust record from the Vostok ice core. The Italian patterns may also correspond with hydrological changes registered in North Africa. The main source of dust loading over the Mediterranean now, North Africa, may have played an important role in dust supply throughout the last climatic cycle.

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