Sengupta, Sukanya

[["dc.bibliographiccitation.firstpage","5337"],["dc.bibliographiccitation.issue","17"],["dc.bibliographiccitation.journal","PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA"],["dc.bibliographiccitation.lastpage","5341"],["dc.bibliographiccitation.volume","112"],["dc.contributor.author","Herwartz, Daniel"],["dc.contributor.author","Pack, Andreas"],["dc.contributor.author","Krylov, Dmitri"],["dc.contributor.author","Xiao, Yilin"],["dc.contributor.author","Muehlenbachs, Karlis"],["dc.contributor.author","Sengupta, Sukanya"],["dc.contributor.author","Di Rocco, Tommaso"],["dc.date.accessioned","2018-11-07T09:58:18Z"],["dc.date.available","2018-11-07T09:58:18Z"],["dc.date.issued","2015"],["dc.description.abstract","The oxygen isotopic composition of hydrothermally altered rocks partly originates from the interacting fluid. We use the triple oxygen isotope composition (O-17/O-16, O-18/O-16) of Proterozoic rocks to reconstruct the O-18/O-16 ratio of ancient meteoric waters. Some of these waters have originated from snowball Earth glaciers and thus give insight into the climate and hydrology of these critical intervals in Earth history. For a Paleoproterozoic [similar to 2.3-2.4 gigayears ago (Ga)] snowball Earth, delta O-18 = -43 +/- 3 parts per thousand is estimated for pristine meteoric waters that precipitated at low paleo-latitudes (<= 35 degrees N). Today, such low O-18/O-16 values are only observed in central Antarctica, where long distillation trajectories in combination with low condensation temperatures promote extreme O-18 depletion. For a Neoproterozoic (similar to 0.6-0.7 Ga) snowball Earth, higher meltwater delta O-18 estimates of -21 +/- 3% imply less extreme climate conditions at similar paleolatitudes (<= 35 degrees N). Both estimates are single snapshots of ancient water samples and may not represent peak snowball Earth conditions. We demonstrate how O-17/O-16 measurements provide information beyond traditional O-18/O-16 measurements, even though all fractionation processes are purely mass dependent."],["dc.identifier.doi","10.1073/pnas.1422887112"],["dc.identifier.isi","000353554000040"],["dc.identifier.pmid","25870269"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37341"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0027-8424"],["dc.title","Revealing the climate of snowball Earth from Delta O-17 systematics of hydrothermal rocks"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","18"],["dc.bibliographiccitation.journal","Chemical Geology"],["dc.bibliographiccitation.lastpage","26"],["dc.bibliographiccitation.volume","495"],["dc.contributor.author","Sengupta, Sukanya"],["dc.contributor.author","Pack, Andreas"],["dc.date.accessioned","2019-07-24T07:14:53Z"],["dc.date.available","2019-07-24T07:14:53Z"],["dc.date.issued","2018"],["dc.description.abstract","The oxygen isotope composition of the Earth's oceans is buffered by high- and low-T exchange with the lithosphere. We present a triple oxygen isotope mass balance model for the Earth's oceans. The model is based on triple oxygen isotope measurements of rocks from various reservoirs including high- and low-T alteration products. The modern ocean water composition can be well-matched if the ratio between continental weathering and high-T seafloor alteration is ~25% higher than previously assumed. The mass balance suggests that putative Precambrian low-δ18O ocean water would fall on a trend with slope λ = 0.51 passing through “modern” ice-free-world seawater. Exemplified application to a published Phanerozoic and Archean chert data suggest precipitation in cool oceans with modern-like δ18O followed by diagenetic alteration with involvement of meteoric water."],["dc.identifier.doi","10.1016/j.chemgeo.2018.07.012"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16296"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/61958"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","0009-2541"],["dc.rights","CC BY-ND 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by-nd/4.0"],["dc.title","Triple oxygen isotope mass balance for the Earth's oceans with application to Archean cherts"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1495"],["dc.bibliographiccitation.issue","13"],["dc.bibliographiccitation.journal","Rapid Communications in Mass Spectrometry"],["dc.bibliographiccitation.lastpage","1504"],["dc.bibliographiccitation.volume","30"],["dc.contributor.author","Pack, Andreas"],["dc.contributor.author","Tanaka, Ryoji"],["dc.contributor.author","Hering, Markus"],["dc.contributor.author","Sengupta, Sukanya"],["dc.contributor.author","Peters, Stefan"],["dc.contributor.author","Nakamura, Eizo"],["dc.date.accessioned","2018-11-07T10:11:34Z"],["dc.date.available","2018-11-07T10:11:34Z"],["dc.date.issued","2016"],["dc.description.abstract","RATIONALE: The precise determination of Delta'O-17 values in terrestrial material is becoming increasingly important to understand the mass-dependent fractionation processes that cause variations in oxygen isotope ratios. San Carlos olivine is widely used as the reference material for oxygen isotope measurements of terrestrial and extraterrestrial materials. We report new Delta'O-17 values for San Carlos olivine that were independently determined in two different laboratories (Geoscience Center [GZG], University of Gottingen) and Institute for Study of the Earth's Interior [ISEI], Okayama University, Misasa) in direct comparison with VSMOW2 and SLAP2 water standards. METHODS: The delta O-17 and delta O-18 values of VSMOW2, SLAP2, GISP, and San Carlos olivine were determined relative to reference gas. In both laboratories, water and San Carlos olivine samples were prepared by BrF5 fluorination. In both laboratories, the O-2 released from water and olivine samples was passed through the same purification system and measured using the same mass spectrometer relative to the same reference gas. RESULTS: In both laboratories, the delta O-17(VSMOW2) and delta O-18 (VSMOW2) scales were slightly compressed with respect to the recommended composition of VSMOW2 and SLAP2. The new Delta'O-17(0.528) value (calculated from the VSMOW2-SLAP2 scaled 6 values) of San Carlos olivine from GZG was -36 +/- 9 ppm and, from ISEI, a value of -40 +/- 7 ppm (1(7 standard deviation) was determined. These values are similar to 50 ppm higher than previously reported from the same laboratories. Possible causes for the observed discrepancies are discussed. CONCLUSIONS: The results of this study in comparison with previous data from the same laboratories demonstrated that for high accuracy determination of Delta'O-17 values: (i) calibration of the reference gas relative to O-2 released from primary standards (VSMOW2, SLAP2) in the same laboratory is highly recommended, (ii) non-linearity of the mass spectrometer may not only affect delta O-17 and delta O-18 values but also Delta'O-17 values, and (iii) the VSMOW2-SLAP2 scaling should also be applied to analyses of rocks and minerals. Studies that are concerned with small differences in Delta'O-17 at similar delta O-18 values, however, are not affected by non-linearity of the mass spectrometer. Copyright (C) 2016 John Wiley & Sons, Ltd."],["dc.identifier.doi","10.1002/rcm.7582"],["dc.identifier.isi","000379974500007"],["dc.identifier.pmid","27321837"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/40075"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1097-0231"],["dc.relation.issn","0951-4198"],["dc.title","The oxygen isotope composition of San Carlos olivine on the VSMOW2-SLAP2 scale"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","15702"],["dc.bibliographiccitation.journal","Nature communications"],["dc.bibliographiccitation.lastpage","15702"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Pack, Andreas"],["dc.contributor.author","Höweling, Andres"],["dc.contributor.author","Hezel, Dominik C."],["dc.contributor.author","Stefanak, Maren T."],["dc.contributor.author","Beck, Anne-Katrin"],["dc.contributor.author","Peters, Stefan T. M."],["dc.contributor.author","Sengupta, Sukanya"],["dc.contributor.author","Herwartz, Daniel"],["dc.contributor.author","Folco, Luigi"],["dc.date.accessioned","2019-07-09T11:43:29Z"],["dc.date.available","2019-07-09T11:43:29Z"],["dc.date.issued","2017-06-01"],["dc.description.abstract","Molten I-type cosmic spherules formed by heating, oxidation and melting of extraterrestrial Fe,Ni metal alloys. The entire oxygen in these spherules sources from the atmosphere. Therefore, I-type cosmic spherules are suitable tracers for the isotopic composition of the upper atmosphere at altitudes between 80 and 115 km. Here we present data on I-type cosmic spherules collected in Antarctica. Their composition is compared with the composition of tropospheric O2. Our data suggest that the Earth's atmospheric O2 is isotopically homogenous up to the thermosphere. This makes fossil I-type micrometeorites ideal proxies for ancient atmospheric CO2 levels."],["dc.identifier.doi","10.1038/ncomms15702"],["dc.identifier.pmid","28569769"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14540"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/58894"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","2041-1723"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.subject.ddc","550"],["dc.title","Tracing the oxygen isotope composition of the upper Earth's atmosphere using cosmic spherules"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","116331"],["dc.bibliographiccitation.journal","Earth and Planetary Science Letters"],["dc.bibliographiccitation.volume","544"],["dc.contributor.author","Peters, Stefan T.M."],["dc.contributor.author","Szilas, Kristoffer"],["dc.contributor.author","Sengupta, Sukanya"],["dc.contributor.author","Kirkland, Christopher L."],["dc.contributor.author","Garbe-Schönberg, Dieter"],["dc.contributor.author","Pack, Andreas"],["dc.date.accessioned","2020-11-05T15:10:54Z"],["dc.date.available","2020-11-05T15:10:54Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1016/j.epsl.2020.116331"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/68485"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-352.8"],["dc.relation.issn","0012-821X"],["dc.title",">2.7 Ga metamorphic peridotites from southeast Greenland record the oxygen isotope composition of Archean seawater"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","105"],["dc.bibliographiccitation.journal","Geochimica et Cosmochimica Acta"],["dc.bibliographiccitation.lastpage","119"],["dc.bibliographiccitation.volume","186"],["dc.contributor.author","Sharp, Z. D."],["dc.contributor.author","Gibbons, J. A."],["dc.contributor.author","Maltsev, O."],["dc.contributor.author","Atudorei, V."],["dc.contributor.author","Pack, Andreas"],["dc.contributor.author","Sengupta, Sukanya"],["dc.contributor.author","Shock, E. L."],["dc.contributor.author","Knauth, L. P."],["dc.date.accessioned","2018-11-07T10:11:24Z"],["dc.date.available","2018-11-07T10:11:24Z"],["dc.date.issued","2016"],["dc.description.abstract","It is now recognized that variations in the Delta O-17 of terrestrial materials resulting from purely mass dependent fractionations, though small, have geological significance. In this study, the delta O-18 and delta O-17 values of selected low temperature quartz and silica samples were measured in order to derive the quartz-water fractionation-temperature relationship for the three oxygen isotope system. A O-18/O-16 quartz-water fractionation equation valid for all temperatures was generated from published high temperature exchange experiments and low temperature empirical estimates and is given by 1000 ln alpha(18O/16O)(qz-H2O) = 4.20(0.11)x10(6)/T-2 - 3.3(0.2)x1000/T (T in Kelvins). The equilibrium delta O-17-delta O-18 relationship is given by the equation ln alpha(17O/16O) = theta ln alpha(18O/16O). The variation of theta with temperature for the quartz-water system was determined empirically using low temperature marine diatoms, microcrystalline quartz and a modern sinter sample. A best fit to the data give the equation theta(SiO2-H2O) = - (1.85+0.04)/T + 0.5305 , indistinguishable from an earlier theoretical estimate. Application of the quartz-water triple isotope system to low temperature samples provides constraints on both temperature and composition of the water with which the silica last equilibrated. Authigenic quartz crystallization temperatures cluster around 50 degrees C, which are lower than many previous estimates. The combined delta O-18 and delta O-17 values of samples considered to be in equilibrium with ocean or meteoric waters can be used to estimate both formation temperatures and the delta O-18 value of the meteoric water. Unlike other multiple isotopes systems, such as combined H and O isotopes in cherts, the oxygen source and diagenetic potential for both O-17/O-16 and O-18/O-16 ratios are identical, simplifying interpretations from ancient samples. (C) 2016 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","National Science Foundation [NSF EAR 1551226, EAR 1450802]"],["dc.identifier.doi","10.1016/j.gca.2016.04.047"],["dc.identifier.isi","000378836600007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/40037"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1872-9533"],["dc.relation.issn","0016-7037"],["dc.title","A calibration of the triple oxygen isotope fractionation in the SiO2-H2O system and applications to natural samples"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","119789"],["dc.bibliographiccitation.journal","Chemical Geology"],["dc.bibliographiccitation.volume","554"],["dc.contributor.author","Sengupta, Sukanya"],["dc.contributor.author","Peters, Stefan T.M."],["dc.contributor.author","Reitner, Joachim"],["dc.contributor.author","Duda, Jan-Peter"],["dc.contributor.author","Pack, Andreas"],["dc.date.accessioned","2021-04-14T08:32:05Z"],["dc.date.available","2021-04-14T08:32:05Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1016/j.chemgeo.2020.119789"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/83804"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-399"],["dc.relation.issn","0009-2541"],["dc.title","Triple oxygen isotopes of cherts through time"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]