scholarly journals Oxygen isotopic heterogeneity of Pali Aike basaltic magmas from southern Patagonia as evidenced by oxygen isotope compositions of olivines

2015 ◽  
Vol 49 (1) ◽  
pp. 83-101
Author(s):  
Mi Kyung Choo ◽  
Kyu Han Kim ◽  
Jong Ik Lee ◽  
Mi Jung Lee ◽  
Sung Hi Choi ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotopic Heterogeneity ◽  
Southern Patagonia ◽  
Basaltic Magmas ◽  
Oxygen Isotopic

Magmas of the El Quemado Complex (Chon Aike Silicic Igneous Province, Patagonia): Elevated Oxygen Isotope Signatures Across Space and Time

2020 ◽  
Author(s):  
Michelle Foley ◽  
Benita Putlitz ◽  
Lukas Baumgartner ◽  
Zoé Guillermin ◽  
Florence Bégué
Keyword(s):  
Oxygen Isotope ◽  
Oxygen Isotopic Composition ◽  
Crustal Material ◽  
Zircon Crystallization ◽  
Eruptive Episode ◽  
Southern Patagonia ◽  
Igneous Province ◽  
Single Zircon ◽  
Oxygen Isotopic ◽  
Silicic Magmas

<p>The generation and source of ~230,000 km<sup>3</sup> of total erupted volume of the predominately silicic (>90 %; Pankhurst et al., 2000) magmas which comprise the Jurassic Chon Aike Large Silicic Igneous Province (CASP) of Southern Patagonia is currently debated. In this study, we conducted a widespread sampling of multiple eruptive units, primarily ignimbrites and minor rhyolitic flows, along the Eastern Andean front (~47°S to 49°S), owning to the third and youngest eruptive episode of the CASP (El Quemado Complex; EQC). To determine the magmatic source and potential role of a significant crustal contribution proposed in the generation of these magmas, we analyzed the in-situ δ<sup>18</sup>O composition of both quartz and zircon by SIMS. We combined these data with LA-ICP-MS U/Pb analyses on single zircon crystals to characterize the potential for changing oxygen isotopic values through time and space within the EQC units along this ~230 km long transect.</p><p>The northern-most units sampled have the lightest average δ<sup>18</sup>O (relative for the EQC) analyzed in zircon and quartz (7.7 and 10.4 ‰, respectively). Oxygen isotope values increase towards the South, with the highest δ<sup> 18</sup>O values previously reported in El Chaltén, reaching up to 10.1 ‰ for zircon and 12.5 ‰ for quartz (Seitz et al., 2018). Eruptive units from the same locality appear to be homogeneous in their oxygen isotopic composition.</p><p>U/Pb zircon ages for the EQC range overall from ~148 to 155 Ma, though no obvious trend from North to South in zircon crystallization ages is noticeable. Multiple inherited zircon cores (at ~230, 460, 500, 1300 Ma) with Jurassic magmatic overgrowths were discovered. Isotopic compositions of these inherited magmatic cores are variable in their δ<sup>18</sup>O values throughout time. However, and more significantly, most of these inherited cores record high δ<sup> 18</sup>O values, with the highest value at 9.5 ‰ measured for a ~460 Ma core. These high values measured within inherited cores are found at all locations sampled for the EQC.</p><p>The δ<sup>18</sup>O values of the EQC rocks are significantly higher than what would be expected for silicic magmas formed by simple closed-system fractionation from any mantle-derived melt (6­-7‰; Valley, 2003). Thus, our oxygen isotope data support significant input of crustal material - of either a sedimentary origin or from hydrothermally altered crust - to generate these ignimbrites and rhyolites with elevated δ<sup>18</sup>O values all along this transect.</p>

scholarly journals Oxygen isotopic heterogeneity in the early Solar System inherited from the protosolar molecular cloud

2020 ◽  
Vol 6 (42) ◽  
pp. eaay2724
Author(s):  
Alexander N. Krot ◽  
Kazuhide Nagashima ◽  
James R. Lyons ◽  
Jeong-Eun Lee ◽  
Martin Bizzarro
Keyword(s):  
Solar System ◽  
Molecular Cloud ◽  
Limited Range ◽  
Terrestrial Planets ◽  
Carbonaceous Chondrites ◽  
The Sun ◽  
Early Solar System ◽  
Isotopic Heterogeneity ◽  
Oxygen Isotopic ◽  
O 24

The Sun is 16O-enriched (Δ17O = −28.4 ± 3.6‰) relative to the terrestrial planets, asteroids, and chondrules (−7‰ < Δ17O < 3‰). Ca,Al-rich inclusions (CAIs), the oldest Solar System solids, approach the Sun’s Δ17O. Ultraviolet CO self-shielding resulting in formation of 16O-rich CO and 17,18O-enriched water is the currently favored mechanism invoked to explain the observed range of Δ17O. However, the location of CO self-shielding (molecular cloud or protoplanetary disk) remains unknown. Here we show that CAIs with predominantly low (26Al/27Al)0, <5 × 10−6, exhibit a large inter-CAI range of Δ17O, from −40‰ to −5‰. In contrast, CAIs with the canonical (26Al/27Al)0 of ~5 × 10−5 from unmetamorphosed carbonaceous chondrites have a limited range of Δ17O, −24 ± 2‰. Because CAIs with low (26Al/27Al)0 are thought to have predated the canonical CAIs and formed within first 10,000–20,000 years of the Solar System evolution, these observations suggest oxygen isotopic heterogeneity in the early solar system was inherited from the protosolar molecular cloud.

scholarly journals Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica

2007 ◽  
Vol 7 (8) ◽  
pp. 1925-1945 ◽  
Author(s):  
J. Savarino ◽  
J. Kaiser ◽  
S. Morin ◽  
D. M. Sigman ◽  
M. H. Thiemens
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Transition Period ◽  
Isotope Effects ◽  
Isotope Ratios ◽  
Background Concentration ◽  
Night Time ◽  
Oxygen Isotope Ratios ◽  
Period 2 ◽  
Oxygen Isotopic

Abstract. Throughout the year 2001, aerosol samples were collected continuously for 10 to 15 days at the French Antarctic Station Dumont d'Urville (DDU) (66°40' S, l40°0' E, 40 m above mean sea level). The nitrogen and oxygen isotopic ratios of particulate nitrate at DDU exhibit seasonal variations that are among the most extreme observed for nitrate on Earth. In association with concentration measurements, the isotope ratios delineate four distinct periods, broadly consistent with previous studies on Antarctic coastal areas. During austral autumn and early winter (March to mid-July), nitrate concentrations attain a minimum between 10 and 30 ng m−3 (referred to as Period 2). Two local maxima in August (55 ng m−3) and November/December (165 ng m−3) are used to assign Period 3 (mid-July to September) and Period 4 (October to December). Period 1 (January to March) is a transition period between the maximum concentration of Period 4 and the background concentration of Period 2. These seasonal changes are reflected in changes of the nitrogen and oxygen isotope ratios. During Period 2, which is characterized by background concentrations, the isotope ratios are in the range of previous measurements at mid-latitudes: δ18Ovsmow=(77.2±8.6)‰; Δ17O=(29.8±4.4)‰; δ15Nair=(−4.4±5.4)‰ (mean ± one standard deviation). Period 3 is accompanied by a significant increase of the oxygen isotope ratios and a small increase of the nitrogen isotope ratio to δ18Ovsmow=(98.8±13.9)‰; Δ17O=(38.8±4.7)‰ and δ15Nair=(4.3±8.20‰). Period 4 is characterized by a minimum 15N/14N ratio, only matched by one prior study of Antarctic aerosols, and oxygen isotope ratios similar to Period 2: δ18Ovsmow=(77.2±7.7)‰; Δ17O=(31.1±3.2)‰; δ15Nair=(−32.7±8.4)‰. Finally, during Period 1, isotope ratios reach minimum values for oxygen and intermediate values for nitrogen: δ18Ovsmow=63.2±2.5‰; Δ17O=24.0±1.1‰; δ15Nair=−17.9±4.0‰). Based on the measured isotopic composition, known atmospheric transport patterns and the current understanding of kinetics and isotope effects of relevant atmospheric chemical processes, we suggest that elevated tropospheric nitrate levels during Period 3 are most likely the result of nitrate sedimentation from polar stratospheric clouds (PSCs), whereas elevated nitrate levels during Period 4 are likely to result from snow re-emission of nitrogen oxide species. We are unable to attribute the source of the nitrate during periods 1 and 2 to local production or long-range transport, but note that the oxygen isotopic composition is in agreement with day and night time nitrate chemistry driven by the diurnal solar cycle. A precise quantification is difficult, due to our insufficient knowledge of isotope fractionation during the reactions leading to nitrate formation, among other reasons.

scholarly journals Climate history of the Southern Hemisphere Westerlies belt during the last glacial-interglacial transition revealed from lake water oxygen isotope reconstruction of Laguna Potrok Aike (52° S, Argentina)

2014 ◽  
Vol 10 (3) ◽  
pp. 2417-2465 ◽  
Author(s):  
J. Zhu ◽  
A. Lücke ◽  
H. Wissel ◽  
C. Mayr ◽  
D. Enters ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Southern Hemisphere ◽  
Lake Water ◽  
Source Water ◽  
Climate History ◽  
Climatic Fluctuations ◽  
Last Glacial ◽  
Southern Patagonia ◽  
Aquatic Mosses ◽  
The Last Glacial

Abstract. The Southern Hemisphere westerly winds (SHW) play a crucial role in the large-scale ocean circulation and global carbon cycling. Accordingly, the reconstruction of its latitudinal position and intensity is essential for understanding global climatic fluctuations during the last glacial cycle. The southernmost part of the South American continent is of great importance for paleoclimate studies as the only continental mass intersecting a large part of the SHW belt. However, continuous proxy records back to the last Glacial are rare in southern Patagonia, owing to the Patagonian Ice Sheets expanding from the Andean area and the scarcity of continuous paleoclimate archives in extra-Andean Patagonia. Here, we present an oxygen isotope record from cellulose and purified bulk organic matter of aquatic moss shoots from the last glacial-interglacial transition preserved in the sediments of Laguna Potrok Aike (52° S, 70° W), a deep maar lake located in semi-arid, extra-Andean Patagonia. The highly significant correlation between oxygen isotope values of aquatic mosses and their host waters and the abundant well-preserved moss remains allow a high-resolution oxygen isotope reconstruction of lake water (δ18Olw) for this lake. Long-term δ18Olw variations are mainly determined by δ18O changes of the source water of lake, surface air temperature and evaporative 18O enrichment. Under permafrost conditions during the Glacial, the groundwater may not be recharged by regional precipitation. The isolated groundwater could have had much less negative δ18O values than glacial precipitation. The less 18O depleted source water and prolonged lake water residence time caused by reduced interchange between in- and outflows could have resulted in the reconstructed glacial δ18Olw that was only ca. 3‰ lower than modern values. The significant two-step rise in reconstructed δ18Olw during the last deglaciation demonstrated the response of isotope composition of lake water to fundamental climatic shifts. Rapid deglacial warming is supposed to cause the 18O enrichment of lake water by ca. 2‰ during the first rise between 17 600 and 15 600 cal BP by increasing temperature-induced evaporation and more 18O enriched precipitation. After a millennial transition period of receding values by up to 0.7‰, the reconstructed δ18Olw resumed pronounced increase since 14 600 cal BP. This cumulative enrichment in 18O of lake water could be interpreted as a response to the strengthened wind-driven evaporation, implying the intensification and establishment of the SHW at the latitude of Laguna Potrok Aike (52° S). During the early Holocene the SHW exerted its full influence on the lake water balance, reflected by reconstructed δ18Olw approaching modern values, indicating a strongly evaporative steppe climate in the Laguna Potrok Aike region.

scholarly journals Oxygen Isotopic Heterogeneity in the Solar System Inherited from the Protosolar Molecular Cloud

2020 ◽  
Author(s):  
Alexander N. Krot ◽  
Kazuhide Nagashima ◽  
James Lyons ◽  
Jeong-Eun Lee ◽  
Martin Bizzarro
Keyword(s):  
Solar System ◽  
Molecular Cloud ◽  
Isotopic Heterogeneity ◽  
Oxygen Isotopic

scholarly journals Supplemental Material: Oxygen isotope (d18O) trends measured from Ordovician conodont apatite using secondary ion mass spectrometry (SIMS): Implications for paleo-thermometry studies

2021 ◽  
Author(s):  
Cole T Edwards ◽  
et al.
Keyword(s):  
Mass Spectrometry ◽  
Oxygen Isotope ◽  
Secondary Ion Mass Spectrometry ◽  
Isotopic Data ◽  
Ion Mass Spectrometry ◽  
Oxygen Isotopic ◽  
Stable Oxygen ◽  
Secondary Ion

Table S1: Stable oxygen isotopic data of each conodont measured using SIMS; Table S2: Stable oxygen isotopic data using SIMS of the Durango apatite standard and a modern shark tooth; Figure S1: Cross plot of d18Omean values and OH/16O from the Shingle Pass (blue), Antelope Range (green), and Cincinnati Arch (white) sections.

Molecular Cloud Origin for Oxygen Isotopic Heterogeneity Recorded by a Primordial Spinel-rich Refractory Inclusion

2019 ◽  
Vol 884 (2) ◽  
pp. L29
Author(s):  
Justin I. Simon ◽  
D. Kent Ross ◽  
Ann N. Nguyen ◽  
Steven B. Simon ◽  
Scott Messenger
Keyword(s):  
Molecular Cloud ◽  
Isotopic Heterogeneity ◽  
Oxygen Isotopic ◽  
Refractory Inclusion

The oxygen isotope stratigraphic record of the Late Pleistocene

1977 ◽  
Vol 280 (972) ◽  
pp. 169-182 ◽  
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Late Pleistocene ◽  
World Ocean ◽  
Oxygen Isotopic Composition ◽  
Stratigraphic Correlation ◽  
Equatorial Atlantic ◽  
Deep Sea Sediment ◽  
Oxygen Isotopic ◽  
Isotope Measurements

Oxygen isotope measurements have been made in foraminifera from over 60 deep-sea sediment cores. Taken together with the oxygen isotope measurements published by Emiliani from Caribbean and Equatorial Atlantic cores, this comprises a unique body of stratigraphic data covering most of the important areas of calcareous sediment over the whole world ocean. The oxygen isotopic composition of foraminifera from cores of Late Pleistocene sediment varies in a similar manner in nearly all areas; the variations reflect changes in the oxygen isotopic composition of the ocean. The oceans are mixed in about 1 ka so that ocean isotopic changes, resulting from fluctuations in the quantity of ice stored on the continents, must have occurred almost synchronously in all regions. Thus the oxygen isotope record provides an excellent means of stratigraphic correlation. Cores accumulated at rates of over about 5 cm/ka provide records of oxygen isotopic composition change that are almost unaffected by post-depositional mixing of the sediment. Thus they preserve a detailed record of the advance and retreat of the ice masses in the northern hemisphere, and provide a unique source of information for the study of ice-sheet dynamics.

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