Germanium isotopic variations in igneous rocks and marine sediments

Rouxel, Olivier; Galy, Αlbert; Elderfield, Henry

doi:10.1016/j.gca.2006.04.025

Cited by 79 publications

(170 citation statements)

References 42 publications

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“…High-precision isotopic measurements of nontraditional isotope systems, such as chromium (Frei et al, 2009), uranium (Weyer et al, 2008), and germanium (Rouxel et al, 2006), have also revealed small, but significant, mass-dependent fractionations in iron formations and cherts. For example, the chromium isotope composition of iron formations has been explored to constrain biogeochemical cycling of chromium in Precambrian surface environments and oceans (Frei et al, 2009) in order to provide an independent secular record of the redox state of the atmosphere and oceans.…”

Section: Other Isotope Systemsmentioning

confidence: 99%

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

854

494

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Iron formations are economically important sedimentary rocks that are most common in Precambrian sedimentary successions. Although many aspects of their origin remain unresolved, it is widely accepted that secular changes in the style of their deposition are linked to environmental and geochemical evolution of Earth. Two types of Precambrian iron formations have been recognized with respect to their depositional setting. Algoma-type iron formations are interlayered with or stratigraphically linked to submarine-emplaced volcanic rocks in greenstone belts and, in some cases, with volcanogenic massive sulfide (VMS) deposits. In contrast, larger Superior-type iron formations are developed in passive-margin sedimentary rock successions and generally lack direct relationships with volcanic rocks. The early distinction made between these two iron-formation types, although mimimized by later studies, remains a valid first approximation. Texturally, iron formations were also divided into two groups. Banded iron formation (BIF) is dominant in Archean to earliest Paleoproterozoic successions, whereas granular iron formation (GIF) is much more common in Paleoproterozoic successions. Secular changes in the style of iron-formation deposition, identified more than 20 years ago, have been linked to diverse environmental changes. Geochronologic studies emphasize the episodic nature of the deposition of giant iron formations, as they are coeval with, and genetically linked to, time periods when large igneous provinces (LIPs) were emplaced. Superior-type iron formation first appeared at ca. 2.6 Ga, when construction of large continents changed the heat flux at the core-mantle boundary. From ca. 2.6 to ca. 2.4 Ga, global mafic magmatism culminated in the deposition of giant Superior-type BIF in South Africa, Australia, Brazil, Russia, and Ukraine. The younger BIFs in this age range were deposited during the early stage of a shift from reducing to oxidizing conditions in the ocean-atmosphere system. Counterintuitively, enhanced magmatism at 2.50 to 2.45 Ga may have triggered atmospheric oxidation. After the rise of atmospheric oxygen during the GOE at ca. 2.4 Ga, GIF became abundant in the rock record, compared to the predominance of BIF prior to the Great Oxidation Event (GOE). Iron formations generally disappeared at ca. 1.85 Ga, reappearing at the end of the Neoproterozoic, again tied to periods of intense magmatic activity and also, in this case, to global glaciations, the so-called Snowball Earth events. By the Phanerozoic, marine iron deposition was restricted to local areas of closed to semiclosed basins, where volcanic and hydrothermal activity was extensive (e.g., backarc basins), with ironstones additionally being linked to periods of intense magmatic activity and ocean anoxia.Late Paleoproterozoic iron formations and Paleozoic ironstones were deposited at the redoxcline where biological and nonbiological oxidation occurred. In contrast, older iron formations were deposited in anoxic oceans, where ferrous iron oxid...

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Section: Other Isotope Systemsmentioning

confidence: 99%

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

854

494

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“…Li et al (2009a, b) and Li and Liu (2010) estimated isotope fractionation factors among Ge-bearing phases and predicted that sulfides will be depleted in heavy Ge isotopes relative to Ge-oxides. Based on a few measurements of basalts and granites Rouxel et al (2006) concluded that the bulk silicate earth has a homogeneous isotope composition. However, chemical sediments like sponges and authigenic glauconites are enriched in δ 74 Ge by about 2 ‰.…”

Section: Germaniummentioning

confidence: 99%

Isotope Fractionation Processes of Selected Elements

Hoefs

2015

Stable Isotope Geochemistry

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“…However, small variations of 70 Ge/ 74 Ge ratio spanning from -4.0 to +3.0 per mill relative to Sigma-Aldrich Ge standard have been documented in various geological and environmental samples. [13][14][15]34 Since the atomic weight of Ge in this study was measured for the same Sigma-Aldrich Ge material, the observed relative natural variations can be readily compared to the measurement uncertainty reported in this work. As shown in Figure 2, the expanded measurement uncertainty of the Ge atomic weight in this material effectively covers the observed variations of Ge isotope ratios.…”

Section: R I/74mentioning

confidence: 99%

Resolving the Germanium Atomic Weight Disparity Using Multicollector ICPMS

Yang

Meija

2010

Anal. Chem.

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Two most recent mass spectrometric measurements of natural isotopic composition germanium gave discordant Ge atomic weight values of 72.6276(64) k=2 and 72.6390(69) k=2 , respectively, a decade ago. Each measurement was performed with a different mass spectrometry platform, gas source isotope ratio mass spectrometry and thermal ionization mass spectrometry, respectively. Herein we report results obtained by multicollector inductively coupled plasma mass spectrometry yielding an atomic weight of germanium 72.6296(19) k=2 which is in support of the upcoming 2009 Standard Atomic Weight adjustment by IUPAC. Germanium isotope ratios were calibrated using a regression mass bias correction model and NIST SRM 994 gallium isotopic reference material. In this model, no assumptions are made regarding the mass bias differences between gallium and germanium or between the isotopes of germanium. Isotope ratios of 0.5620(21), 0.7515(16), 0.2125(7) and 0.2121(12) were obtained for n( 70

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Germanium isotopic variations in igneous rocks and marine sediments

Cited by 79 publications

References 42 publications

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Isotope Fractionation Processes of Selected Elements

Resolving the Germanium Atomic Weight Disparity Using Multicollector ICPMS

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