Geochemistry Of Non-Traditional Stable Isotopes Research Articles

Non-traditional stable isotope geochemistry of marine ferromanganese crusts and nodules

Marine ferromanganese crusts and nodules, which contain a variety of metals, are potential seabed mineral resources. Given their low growth rates, they are regarded as condensed stratigraphic sections that archive millions of years of paleoceanographic information. Ferromanganese crusts and nodules incorporate trace elements like Cu, Zn, Mo, Tl and Ni during growth. The non-traditional isotopic systems of these metals are increasingly being developed as powerful tracers in the modern ocean and as proxies for the paleo-ocean, due to their tendency to be fractionated by redox-related and/or biological processes. In recent years, both the global variations of metal stable isotopes in ferromanganese crust/nodule surface scrapings and some depth profiles through the ferromanganese crusts were systematically analysed. These studies established the isotopic variability present in ferromanganese crusts, nodules and seawater, explored the isotopic fractionation mechanisms associated with the formation of ferromanganese deposits, and determined whether these ferromanganese crusts can be used as documents of deep water metal isotope compositions and long-term seawater isotope variations. In addition, some isotopes of ferromanganese deposits have been successfully applied to constrain the metal sources and geochemical cycles in the ocean, reconstruct paleo-oceanic redox conditions and seawater isotope record, and reveal continental weathering and climate changes. Nevertheless, it is worth noting that a few limitations of current applications of some non-traditional isotopes as paleoceanographic proxies still remain. Therefore, there is still a great need for a community effort to develop and enhance non-traditional isotope geochemistry of marine ferromanganese crusts and nodules.

Book Review: Non-Traditional Stable Isotopes

Book Review: Non-Traditional Stable Isotopes. Edited by Fang-Zhen Teng, James Watkins, Nicolas Dauphas. (2017) RiMG Volume 82, Mineralogical Society of America, i–xvi + 885 pages. Price, 978-0-939950-98-0. Thirteen years have passed since the publication of the pioneering Geochemistry of Non-Traditional Stable Isotopes (RiMG 55). This early review summarized the incipient promise of non-traditional isotope research. This second volume (RiMG 82), more sparingly entitled Non-Traditional Stable Isotopes, shows that this promise has been fulfilled and non-traditional isotope research has now expanded into a major discipline of isotope geochemistry. It has broadened into a mature field; not only in the range of cosmological, geological, biogeochemical, oceanographic, hydrological, and even medicinal questions addressed, but also in the range of isotopic systems being studied. Much of this progress reflects the development of multicollector-inductively coupled plasma mass spectrometer (MC-ICPMS) techniques, particularly the increased use of double spike methods. But …

Recent Developments in Mercury Stable Isotope Analysis

The first Reviews in Mineralogy volume on the Geochemistry of Non-Traditional Stable Isotopes was compiled before it was appropriate to include a chapter on mercury (Hg) stable isotope geochemistry. At that time there were only a few papers on this new topic (Jackson 2001; Lauretta et al. 2001; Hintelmann and Lu 2003), and there were still some important analytical issues that needed to be resolved. But the field has come a long way in a decade. Now we have a different problem; at our last count there were well over 100 publications utilizing mercury stable isotopes and it is becoming very difficult to synthesize this vast amount of exciting and rapidly developing research. Experimental studies have expanded our knowledge of the mechanisms of mercury isotope fractionation and applications of mercury isotope measurements have touched virtually every area of research in mercury biogeochemistry. There have been a number of previous reviews of the mercury stable isotope literature as it has developed (Ridley and Stetson 2006; Bergquist and Blum 2009; Yin et al. 2010; Blum 2011; Hintelmann 2012; Blum et al. 2014). It is our view that the field has become too large to comprehensively review the entire literature on mercury stable isotopes. Ten years ago Hg isotope researchers were just beginning to explore the boundaries of natural Hg isotope variation and the mechanisms that cause this variation in the environment. At that time large and relatively easily measured isotope signals were of great interest and mercury isotope researchers were beginning to develop theories to explain mass dependent isotope fractionation (MDF) and mass independent isotope fractionation of the odd mass-numbered isotopes of mercury (odd-MIF). More recently researchers have discovered a wider range of types of isotopic variability (even-MIF), some of which are subtle and …

Non-Traditional Stable Isotopes: Retrospective and Prospective

Traditional stable isotope geochemistry involves isotopes of light elements such as H, C, N, O, and S, which are measured predominantly by gas-source mass spectrometry (Valley et al. 1986; Valley and Cole 2001). Even though Li isotope geochemistry was developed in 1980s based on thermal ionization mass spectrometry (TIMS) (Chan 1987), the real flourish of so-called non-traditional stable isotope geochemistry was made possible by the development of multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) (Halliday et al. 1995; Marechal et al. 1999). Since then, isotopes of both light (e.g., Li, Mg) and heavy (e.g., Tl, U) elements have been routinely measured at a precision that is high enough to resolve natural variations (Fig. 1). The publication of RIMG volume 55 ( Geochemistry of Non-Traditional Stable Isotopes ) in 2004 was the first extensive review of Non-Traditional Stable Isotopes summarizing the advances in the field up to 2003 (Johnson et al. 2004). When compared to traditional stable isotopes, the non-traditional stable isotopes have several distinctive geochemical features: 1) as many of these elements are trace elements, their concentrations vary widely in different geological reservoirs; 2) these elements range from highly volatile (e.g., Zn and K) to refractory (e.g., Ca and Ti); 3) many of these elements are redox-sensitive; 4) many of them are biologically active; 5) the bonding environments, especially for the metal elements, are different from those of H, C, N, O and S; and finally, 6) many of these elements have high atomic numbers and more than two stable isotopes. These features make the different elements susceptible to different fractionation mechanisms, and by extension, make them unique tracers of different cosmochemical, geological and biological processes, as highlighted throughout this volume. Figure 1 Non-traditional stable isotope systems covered in this volume. Figure 2 The terrestrial isotopic variation vs. the relative mass difference for non-traditional …

Equilibrium Fractionation of Non-traditional Stable Isotopes: an Experimental Perspective

In 1986, O’Neil wrote a Reviews in Mineralogy chapter on experimental aspects of isotopic fractionation. He noted that in order to fully understand and interpret the natural variations of light stable isotope ratios in nature, it was essential to know the magnitude and temperature dependence of the isotopic fractionation factor amongst minerals and fluids. At that time it was difficult to imagine that this would become true for the heavier, so called non-traditional stable isotopes, as well. Since the advent of the multiple collector inductively coupled plasma-source mass spectrometer (MC–ICP–MS), natural variations of stable isotope ratios have been found for almost any polyisotopic element measured. Although it has been known that as temperature and mass increase, isotope fractionation decreases very quickly, the MC–ICP–MS has revolutionized the ability of a geochemist to measure very small differences in isotope ratios. It was then that the field of experimental non-traditional stable isotope geochemistry was born. As O’Neil (1986) pointed out there are three ways to obtain isotopic fractionation factors: theoretical calculations, measurements of natural samples with well-known formation conditions, and laboratory calibration studies. This chapter is devoted to explaining the techniques involved with laboratory experiments designed to measure equilibrium isotope fractionation factors as well as the best practices that have been learned. Although experimental petrology has been around for a long time and basic experimental methods have been well-refined, there are additional considerations that must be taken into account when the goal is to measure isotopic compositions at the end of the experiment. It has been only about ten years since these initial studies were published, but much has been learned in that time about how best to conduct experiments aimed at determining equilibrium fractionation factors. We will not focus on the scientific results that have been determined by such experiments, as each …

A review of Mg isotope analytical methods by MC-ICP-MS

Application of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has led to big breakthrough of analytical methods for metal stable isotopes, resulting in rapid progresses in non-traditional stable isotope geochemistry. As a new geological tracer, Mg isotopes have been widely applied in studies of almost all important disciplines of geochemistry. High precision Mg isotope data measured by MC-ICP-MS are now available with precision about 0.05‰ amu−1 (2SD) or better. Because mass bias caused by chemical procedure and instrument can easily cause significant analytical error, it is still a challenge to obtain accurate Mg isotope data for natural samples. In this paper, we systematically review the development of analytical technique of Mg isotopes, with a detailed description of a series of important techniques used in the measurement process, including calibration of instrumental mass-bias, chemical purification process, matrix effect, and pitfalls for high precision isotope analyses. We compare standard data from different labs and establish a guideline for Mg isotope analysis procedure. Additionally, we briefly discuss the behaviors of Mg isotopes during geological processes including equilibrium and kinetic Mg isotope fractionations, such as magma differentiation, chemical and thermal diffusion, and continental weathering. Finally, we propose some future prospects for Mg isotope geochemistry in both high and low temperature geological processes.

Determination of radiogenic and stable strontium isotope ratios (87Sr/86Sr; δ88/86Sr) by thermal ionization mass spectrometry applying an 87Sr/84Sr double spike

Recent findings of natural strontium isotope fractionation have opened up a new field of research in non-traditional stable isotope geochemistry. While previous studies were based on data obtained by MC-ICP-MS we here present a novel approach combining thermal ionization mass spectrometry (TIMS) with the use of an 87Sr/84Sr double spike (DS). Our results for the IAPSO sea water and JCp-1 coral standards, respectively, are in accord with previously published data. The strontium isotope composition of the IAPSO sea water standard was determined as δ88/86Sr = 0.386(5)‰ (δ values relative to the SRM987), 87Sr/86Sr* = 0.709312(9) n = 10 and a corresponding conventionally normalized 87Sr/86Sr = 0.709168(7) (all uncertainties 2SEM). For the JCp-1 coral standard we obtained δ88/86Sr = 0.197(8)‰, 87Sr/86Sr* = 0.709237(2) and 87Sr/86Sr = 0.709164(5) n = 3. We show that by applying this DS-TIMS method the precision is improved by at least a factor of 2–3 when compared to MC-ICP-MS.

The evolution and applications of multicollector ICPMS (MC-ICPMS)

Inductively coupled plasma mass spectrometry (ICPMS) instrumentation has evolved rapidly in the 25 years since the introduction of the first commercial ICPMS instruments. All possible analyzers have been explored (and many commercialized), including magnetic sector (single and double focusing), time of flight, ion trap, triple quadrupole, Fourier transform ion cyclotron resonance (FT-ICR), and Orbitrap, as well as various hybrid analyzers. ICPMS instruments predominantly use quadrupole mass filters, but magnetic-sector ICPMS, in the form of single collector (HR-ICPMS) and multicollector (MC-ICPMS), has garnered a significant portion of the market. Since the introduction of the first MC-ICPMS in 1992 (the Plasma 54 from VG Elemental), 190 MC-ICPMS have been installed in 170 different labs worldwide. The initial hope for MC-ICPMS was that it would simplify measurements normally made with thermal ionization mass spectrometry (TIMS) (e.g., Pb, Sr, Nd, U, Th, Pu, Os) by marrying the favorable characteristics of an ICP source with the precision that can be attained with a multicollector array. While this goal has been largely met, if not exceeded, exploration of the periodic table with MCICPMS has led to the discovery of small but meaningful isotopic variations in nature in a number of elements that were hitherto not accessible or were difficult to analyze. This field is sometimes referred to as “non-traditional stable isotope geochemistry” [1], in contrast to “traditional” stable isotope geochemistry which encompasses the isotopic variations of HCNOS [2], and it includes elements from Li to U. MC-ICPMS, increasingly an essential analytical technique in isotope geoand cosmochemistry, is also expected to find widespread acceptance in other disciplines, such as environmental biology, biochemistry, ecology, and archaeology, to name but a few.