scholarly journals Timescales and thermal evolution of large silicic magma reservoirs during an ignimbrite flare-up: perspectives from zircon

2021 ◽  
Vol 176 (12) ◽  
Author(s):  
Adam Curry ◽  
Sean P. Gaynor ◽  
J. H. F. L. Davies ◽  
Maria Ovtcharova ◽  
Guy Simpson ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
San Juan ◽  
Whole Grain ◽  
Zircon Age ◽  
Magma Reservoirs ◽  
Magmatic Body ◽  
Icp Ms ◽  
Zircon Crystallization ◽  
Accretion Rates ◽  
River Plain

AbstractFour voluminous ignimbrites (150–500 km3) erupted in rapid succession at 27 Ma in the central San Juan caldera cluster, Colorado. To reconstruct the timescales and thermal evolution of these magma reservoirs, we used zircon ID-TIMS U–Pb geochronology, zircon LA-ICP-MS geochemistry, thermal modeling, and zircon age and crystallization modeling. Zircon geochronology reveals dispersed zircon age spectra in all ignimbrites, with decreasing age dispersion through time that we term a ‘chimney sweeping’ event. Zircon whole-grain age modeling suggests that 2σ zircon age spans represent approximately one-quarter of total zircon crystallization timescales due to the averaging effect of whole-grain, individual zircon ages, resulting in zircon crystallization timescales of 0.8–2.7 m.y. Thermal and zircon crystallization modeling combined with Ti-in-zircon temperatures indicates that magma reservoirs were built over millions of years at relatively low magmatic vertical accretion rates (VARs) of 2–5 × 10–3 m y−1 (2–5 × 10–6 km3 y−1 km−2), and we suggest that such low VARs were characteristic of the assembly of the greater San Juan magmatic body. Though we cannot unequivocally discern between dispersed zircon age spectra caused by inheritance (xenocrystic or antecrystic) versus prolonged crystallization from the same magma reservoir (autocrystic), our findings suggest that long-term magma input at relatively low VARs produced thermally mature upper crustal magma reservoirs resulting in protracted zircon crystallization timescales. Compiling all U–Pb ID-TIMS zircon ages of large ignimbrites, we interpret the longer timescales of subduction-related ignimbrites as a result of longer term, lower flux magmatism, and the shorter timescales of Snake River Plain ignimbrites as a result of shorter term, higher flux magmatism.

Magmatic evolution of zoned and unzoned ignimbrites: evidence for a complex crustal architecture feeding four rapid-sequence, caldera-forming eruptions in the San Juan Mountains, Colorado

2021 ◽  
Author(s):  
Adam Curry ◽  
Luca Caricchi ◽  
Peter W Lipman
Keyword(s):  
Trace Element ◽  
The Other ◽  
San Juan ◽  
Volcanic Complex ◽  
Accessory Zircon ◽  
San Juan Mountains ◽  
Reservoir Architecture ◽  
Magma Reservoirs ◽  
Magmatic Body ◽  
Mineral Assemblages

Abstract The last four caldera-forming ignimbrites in the central San Juan caldera cluster, Colorado, erupted 1,400 km3 in ≤ 80 k.y. and alternated between zoned crystal-poor rhyolite to crystal-rich dacite and unzoned, crystal-rich dacite. The zoned 150 km3 Rat Creek Tuff (26.91 Ma), unzoned 250 km3 Cebolla Creek Tuff, and zoned 500 km3 Nelson Mountain Tuff (26.90 Ma) formed the nested San Luis caldera complex with slightly offset calderas, and the unzoned 500 km3 Snowshoe Mountain Tuff (26.87 Ma) formed the Creede caldera to the south. The Rat Creek Tuff, Nelson Mountain Tuff, and Snowshoe Mountain Tuff have similar mineral assemblages of plagioclase, sanidine, quartz, biotite, hornblende, clinopyroxene, Fe-Ti oxides, and accessory zircon, titanite, and apatite. The Cebolla Creek Tuff differs from the other three ignimbrites with more abundant hornblende and lack of quartz and sanidine. Trace element compositions of interstitial glass are unique to each ignimbrite, correlating with mineral assemblages and inferred crystallization depths. Glass, feldspar, hornblende, and clinopyroxene thermobarometry calculations provide evidence for vertically extensive crustal magma reservoirs with a common magmatic zone at ∼435-470 MPa (∼16-17 km) transitioning into shallow pre-eruptive reservoirs between ∼110-340 MPa (∼4-13 km), similar to the estimated magma reservoir architecture of the Altiplano Puna Volcanic Complex. The upper portions of the eruptible parts of the magma reservoirs of the Rat Creek Tuff (215 ± 50 MPa/∼810-820 °C), Cebolla Creek Tuff (340 ± 20 MPa/∼860-880° C), Nelson Mountain Tuff (215 ± 20 MPa/∼745-800 °C), and Snowshoe Mountain Tuff (110 ± 40 MPa/825 ± 10 °C) occupied shallow levels in the crust similar to other magma reservoirs of the central San Juan caldera complex. Trace element modelling correlates with a deep crystallization signature in the unzoned Cebolla Creek Tuff and Snowshoe Mountain Tuff, typified by a flat trend in Ba versus Sr whole-rock and glass chemistry. The zoned Rat Creek Tuff and Nelson Mountain Tuff are typified by a steep trend in Ba versus Sr chemistry interpreted as a shallower crystallization signature. Similarly, the unzoned Cebolla Creek Tuff and Snowshoe Mountain Tuff have flatter slopes in FeO versus An space of plagioclase chemistry interpreted as more abundant deep plagioclase crystallization and a difficulty to physically mix with Fe-rich mafic recharge magma due to higher viscosity. The zoned Rat Creek Tuff and Nelson Mountain Tuff have higher slopes in FeO versus An space of plagioclase chemistry interpreted as more abundant shallow plagioclase crystallization and more feasible mixing with Fe-rich mafic recharge magma due to lower viscosity. The eruption of the Rat Creek Tuff was likely triggered by mafic injection, but the other three ignimbrites lack mingling textures in pumice, suggesting that other mechanisms were important in causing such large eruptions. After a prolonged period of mantle-derived magma injection and crustal heating (∼25,000 km3 Conejos Formation erupted during ∼35-29 Ma), the San Juan magmatic body became a robust and versatile producer of diverse eruptible magmas in short time periods during its Oligocene ignimbrite flare-up.

Caledonian terrane amalgamation of Svalbard: detrital zircon provenance of Mesoproterozoic to Carboniferous strata from Oscar II Land, western Spitsbergen

2013 ◽  
Vol 150 (6) ◽  
pp. 1103-1126 ◽  
Author(s):  
DETA GASSER ◽  
ARILD ANDRESEN
Keyword(s):  
Detrital Zircon ◽  
Large Scale ◽  
Strike Slip ◽  
Western Coast ◽  
Zircon Age ◽  
The North ◽  
Tectonic History ◽  
Icp Ms ◽  
Depositional Age ◽  
Sveconorwegian Orogen

AbstractThe tectonic origin of pre-Devonian rocks of Svalbard has long been a matter of debate. In particular, the origin and assemblage of pre-Devonian rocks of western Spitsbergen, including a blueschist-eclogite complex in Oscar II Land, are enigmatic. We present detrital zircon U–Pb LA-ICP-MS data from six Mesoproterozoic to Carboniferous samples and one U–Pb TIMS zircon age from an orthogneiss from Oscar II Land in order to discuss tectonic models for this region. Variable proportions of Palaeo- to Neoproterozoic detritus dominate the metasedimentary samples. The orthogneiss has an intrusion age of 927 ± 3 Ma. Comparison with detrital zircon age spectra from other units of similar depositional age within the North Atlantic region indicates that Oscar II Land experienced the following tectonic history: (1) the latest Mesoproterozoic sequence was part of a successor basin which originated close to the Grenvillian–Sveconorwegian orogen, and which was intruded byc. 980–920 Ma plutons; (2) the Neoproterozoic sediments were deposited in a large-scale basin which stretched along the Baltoscandian margin; (3) the eclogite-blueschist complex and the overlying Ordovician–Silurian sediments probably formed to the north of the Grampian/Taconian arc; (4) strike-slip movements assembled the western coast of Spitsbergen outside of, and prior to, the main Scandian collision; and (5) the remaining parts of Svalbard were assembled by strike-slip movements during the Devonian. Our study confirms previous models of complex Caledonian terrane amalgamation with contrasting tectonic histories for the different pre-Devonian terranes of Svalbard and particularly highlights the non-Laurentian origin of Oscar II Land.

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 Thermal evolution and quiescent emission of transiently accreting neutron stars

2019 ◽  
Vol 629 ◽  
pp. A88 ◽  
Author(s):  
A. Y. Potekhin ◽  
A. I. Chugunov ◽  
G. Chabrier
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Reactions ◽  
Thermal Evolution ◽  
Theoretical Models ◽  
Equilibrium Temperature ◽  
Theoretical Interpretation ◽  
Quasi Equilibrium ◽  
Accretion Rates

Aims. We study the long-term thermal evolution of neutron stars in soft X-ray transients (SXTs), taking the deep crustal heating into account consistently with the changes of the composition of the crust. We collect observational estimates of average accretion rates and thermal luminosities of such neutron stars and compare the theory with observations. Methods. We performed simulations of thermal evolution of accreting neutron stars, considering the gradual replacement of the original nonaccreted crust by the reprocessed accreted matter, the neutrino and photon energy losses, and the deep crustal heating due to nuclear reactions in the accreted crust. We also tested and compared results for different modern theoretical models. We updated a compilation of the observational estimates of the thermal luminosities in quiescence and average accretion rates in the SXTs and compared the observational estimates with the theoretical results. Results. The long-term thermal evolution of transiently accreting neutron stars is nonmonotonic. The quasi-equilibrium temperature in quiescence reaches a minimum and then increases toward the final steady state. The quasi-equilibrium thermal luminosity of a neutron star in an SXT can be substantially lower at the minimum than in the final state. This enlarges the range of possibilities for theoretical interpretation of observations of such neutron stars. The updates of the theory and observations leave the previous conclusions unchanged, namely that the direct Urca process operates in relatively cold neutron stars and that an accreted heat-blanketing envelope is likely present in relatively hot neutron stars in the SXTs in quiescence. The results of the comparison of theory with observations favor suppression of the triplet pairing type of nucleon superfluidity in the neutron-star matter.

scholarly journals The Paleoproterozoic Kandalaksha-Kolvitsa Gabbro-Anorthosite Complex (Fennoscandian Shield): New U–Pb, Sm–Nd, and Nd–Sr (ID-TIMS) Isotope Data on the Age of Formation, Metamorphism, and Geochemical Features of Zircon (LA-ICP-MS)

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 254 ◽  
Author(s):  
Ekaterina N. Steshenko ◽  
Tamara B. Bayanova ◽  
Pavel A. Serov
Keyword(s):  
Inductively Coupled Plasma ◽  
Early Stage ◽  
Crustal Contamination ◽  
Inductively Coupled ◽  
Granulite Metamorphism ◽  
Icp Ms ◽  
Zircon Crystallization ◽  
Mantle Reservoir ◽  
Single Zircon ◽  
Anorthosite Complex

The paper provides new U–Pb, Sm–Nd, and Nd–Sr isotope-geochronological data on rocks of the Paleoproterozoic Kandalaksha-Kolvitsa gabbro-anorthosite complex. Rare earth element (REE) contents in zircons from basic rock varieties of the Kandalaksha-Kolvitsa area were analyzed in situ using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Plots of REE distribution were constructed, confirming the magmatic origin of zircon. Temperatures of zircon crystallization were estimated using a Ti-in-zircon geochronometer. The U–Pb method with a 205Pb artificial tracer was first applied to date single zircon grains (2448 ± 5 Ma) from metagabbro of the Kolvitsa massif. The U–Pb analysis of zircon from anorthosites of the Kandalaksha massif dated the early stage of the granulite metamorphism at 2230 ± 10 Ma. The Sm–Nd isotope age was estimated on metamorphic minerals (apatite, garnet, sulfides) and whole rock at 1985 ± 17 Ma (granulite metamorphism) for the Kolvitsa massif and at 1887 ± 37 Ma (high-temperature metasomatic transformations) and 1692 ± 71 Ma (regional fluid reworking) for the Kandalaksha massif. The Sm–Nd model age of metagabbro was 3.3 Ga with a negative value of εNd = 4.6, which corresponds with either processes of crustal contamination or primary enriched mantle reservoir of primary magmas.

The ’Little’ Fish Canyon Tuff in Romania: Rejuvenation of granodioritic crystal mush resulting in homogeneous dacite recorded by the Haramul Mic lava dome (Ciomadul)

2020 ◽  
Author(s):  
Emese Pánczél ◽  
Maurizio Petrelli ◽  
Réka Lukács ◽  
Szabolcs Harangi
Keyword(s):  
Lava Dome ◽  
Thermal Evolution ◽  
Bulk Composition ◽  
Volcanic Complex ◽  
Bulk Rock ◽  
Crystal Mush ◽  
Magmatic System ◽  
Zircon Core ◽  
Accessory Zircon ◽  
Zircon Crystallization

<p>Long-dormant volcanoes (quiescence time is several 100’s to 10’s thousand years between eruptions) pose a particular hazard, since the long repose time decreases the awareness and there is mostly a lack of monitoring. The Haramul Mic, a pancake-shaped flat dacitic lava dome is part of the Ciomadul Volcanic Complex in eastern-central Europe (Romania) and serves as an excellent example of such volcanoes. The Haramul Mic lava dome is the earliest product of the Young Ciomadul Eruption Period (YCEP), when the activity recrudesced in the area after about 200.000 years quiescence time. Eruption age of the dome determined by (U-Th)/He dating on zircon gave 154 +/- 16 ka that is in agreement with the youngest zircon U-Th outer rim date (142 +18/-16 ka). In the YCEP zircon crystallization dates record typically long, up to 350-400 kyr lifetime of the magmatic plumbing system, in case of  Haramul Mic the oldest zircon core is 306 +/- 37 ka old.</p><p>The 880.7 m high lava dome covers an area of 1.1 km<sup>2</sup> and has a volume of ~0.15 km<sup>3</sup>. It is composed of crystal-rich homogeneous high-K dacite. The average crystal content is 35-40% and consists of plagioclase, amphibole, biotite and accessory zircon, apatite, titanite and Fe-Ti oxides. The groundmass is mainly built up by perlitic glass with some microlites. The dacite includes mafic enclaves having plagioclase and amphibole besides a large amount of biotite crystals, that eventuates K-rich, shoshonitic bulk composition. The dacite contains abundant felsic crystal clots which comprise plagioclase, amphibole, biotite and interstitial vesicular glass.</p><p>Amphiboles are relatively homogeneous in chemical composition. They are low-Al hornblendes suggesting 700-800 <sup>o</sup>C crystallization condition at 200-300 MPa compared with experimental data. Al-in-hornblende geobarometer and amphibole-plagioclase geothermometer calculations give results reproducing these temperature and pressure ranges. Although the Kis-Haram dacite is fairly rich in 25-45 anorthite mol% plagioclase, no negative Eu anomaly can be observed in the bulk rock and the glass. Similarities between Fish Canyon Tuff and Kis-Haram rocks can be strikingly noted regarding the major and trace element contents of mineral phases, glass and bulk rock that all refer to a wet oxidised calc-alkaline magmatic system. The relatively small volume Kis-Haram lava dome represents a rejuvenated low-temperature granodioritic crystal mush having similar features as the large volume silicic eruption of Fish Canyon Tuff. Their recorded almost similarly long zircon crystallization intervals give an interesting aspect with regard to the thermal evolution of the magmatic system and eruption volumes.</p><p>This research was financed by the Hungarian National Research, Development and Innovation Fund (NKFIH) within No. K116528 project and was supported by the ÚNKP-19-1 New National Excellence Program of the Ministry for Innovation and Technology.</p>

Thermochemical modelling of zircon age distributions from Nevado de Toluca volcano, Trans Mexican Volcanic Belt

2020 ◽  
Author(s):  
Gregor Weber ◽  
Luca Caricchi ◽  
Axel Schmitt ◽  
José Luis Arce
Keyword(s):  
Large Fraction ◽  
Temporal Trends ◽  
Volcanic Belt ◽  
Thermal Modelling ◽  
Zircon Geochronology ◽  
Zircon Age ◽  
Zircon Crystallization ◽  
Plumbing Systems ◽  
Nevado De Toluca ◽  
Rate Of Accumulation

<p>Understanding the assembly of eruptible magma in volcanic plumbing systems through time is key to the evaluation of hazard scenarios at potentially active volcanoes. In this respect, zircon geochronology provides a temporally resolvable record of the presence of magma. However, which specific processes and associated timescales are captured by zircon age distributions is not well constrained. Here we use zircon geochronology and geochemistry and thermal modelling of pulsed magma injection in the Earth crust to quantitatively invert zircon ages and recalculate magma fluxes and the rate of accumulation of eruptible magma in time. Zircon crystals have been analyzed from 4 late Pleistocene eruptions of Nevado de Toluca, a long-lived currently dormant dacitic stratovolcano in Central Mexico. <sup>238</sup>U-<sup>230</sup>Th and <sup>238</sup>U-<sup>206</sup>Pb age distributions show a protracted zircon crystallization history of ~900 ka in the magmatic plumbing system, a large fraction of the 1500 ka record of volcanic activity at the surface for this volcano. The 4 studied eruptions show similar broad age spectra, which are overlapping with each other and comparable peak zircon crystallization ages between 150 and 250 ka. Our dataset suggests that interstitial melt extraction (including zircon crystals) from highly crystallized resident magma and mixing thereof with fresh recharge magma surges is very efficient beneath Nevado de Toluca. Zircon trace element data, together with the geochronology show that the observed temporal trends in zircon geochemistry are consistent with tracking long-term assembly processes beneath the volcano operating over more than 1 million years. The combination of these results and thermal modelling allow us to quantify the rate of magma input, intrusive/extrusive ratio and the rate of accumulation of eruptible magma at Nevado de Toluca, which is essential to estimate the maximum potential size of the next eruption from this system.</p>

scholarly journals U-Pb zircon age of the youngest magmatic activity in the High Tatra granites (Central Western Carpathians)

2013 ◽  
Vol 40 (2) ◽  
pp. 134-144 ◽  
Author(s):  
Jolanta Burda ◽  
Aleksandra Gawęda ◽  
Urs Klötzli
Keyword(s):  
Inductively Coupled Plasma ◽  
Age Groups ◽  
Hydrothermal Activity ◽  
Magmatic Activity ◽  
Zircon Age ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Plasma Mass Spectrometry ◽  
Central Western Carpathians ◽  
High Tatra Mountains

Abstract Detailed cathodoluminescence (CL) imaging of zircon crystals, coupled with Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) U-Pb zircon dating was used to develop new insights into the evolution of granitoids from the High Tatra Mountains. The zircon U-Pb results show two distinct age groups (350±5 Ma and 337±6 Ma) recorded from cores and rims domains, respectively. Obtained results point that the last magmatic activity in the Tatra granitoid intrusion occurred at ca. 330 Ma. The previously suggested age of 314 Ma reflects rather the hydrothermal activity and Pb-loss, coupled with post-magmatic shearing.

High spatial resolution in situ U–Pb dating using laser ablation multiple ion counting inductively coupled plasma mass spectrometry (LA-MIC-ICP-MS)

2017 ◽  
Vol 32 (5) ◽  
pp. 975-986 ◽  
Author(s):  
Lie-Wen Xie ◽  
Jin-Hui Yang ◽  
Qing-Zhu Yin ◽  
Yue-Heng Yang ◽  
Jing-Bo Liu ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Inductively Coupled Plasma ◽  
High Spatial Resolution ◽  
Zircon Age ◽  
Analytical Technique ◽  
Inductively Coupled ◽  
Rapid Measurement ◽  
Icp Ms ◽  
Plasma Mass Spectrometry

A new LA-MIC-ICP-MS analytical technique has been developed for the rapid measurement of 206Pb/238U zircon age (<1%, 2s) at a high spatial resolution. We show that this technique can be routinely employed to date U–Pb in small and/or complex zircons, providing a powerful tool for geochronology.

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