John B Creech

• PhD
• Research Associate at Macquarie University

The double-spike approach for instrumental mass bias correction of mass spectrometry data is well established. However, there is very little consistency within the scientific community in terms of double-spike data reduction. Double-spike solutions require computer calculation, using either geometric or algebraic approaches, and are often performed...

We present a new technique for the precise determination of platinum (Pt) stable isotope ratios by multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) using two different Pt double-spikes (192Pt–198Pt and 196Pt–198Pt). Results are expressed relative to the IRMM-010 Pt isotope standard as the parts per million difference in 19...

We have used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to measure elemental (Mg/Ca, Al/Ca, Mn/Ca, Zn/Ca, Sr/Ca, and Ba/Ca) ratios of 13 species of variably preserved early to middle Eocene planktonic and benthic foraminifera from New Zealand. The foraminifera were obtained from Ashley Mudstone, mid-Waipara River, South...

Cadmium stable isotope ratios can serve as valuable tracers for biological and geological processes, including nutrients sampling from the surrounding medium, volatilization events, and terrestrial differentiation. However, studies of the isotope fractionation occurring during geological processes require the characterization of the isotope composi...

Earth's accretion history for volatile elements, and the origin of their depletions with respect to the Sun and primitive meteorites, continue to be debated. Two end‐member scenarios propose either that volatile elements were delivered during the main phases of accretion and differentiation, or that the Earth accreted from materials largely devoid...

The stable isotopic composition of insoluble, refractory elements such as titanium (Ti) or zirconium (Zr), which are modified by magmatic differentiation but, a priori, are poorly affected by weathering or diagenesis, serve as powerful potential proxies to reconstruct the compositional evolution of the continental crust. Here we present the evoluti...

Recent fluid flow in ancient meteorites Carbonaceous chondritic meteorites are thought to be fragments broken off parent bodies that orbit in the outer Solar System, largely unaltered since their formation. These meteorites contain evidence of reactions with liquid water that was thought to have been lost or completely frozen billions of years ago....

We report stable Zr isotope compositions of four common natural zircon grains: Penglai, 91500, GJ-1 and Mud Tank, and 22 whole rocks reference materials which include fifteen magmatic rocks, one metamorphic rock, six sediments or sedimentary rocks. In addition, the isotopic calibration of the three Zr standard solutions used in different publicatio...

Recent developments in amplifier hardware enable low‐noise measurements of exceedingly small ion beams in isotope ratio analysis, yielding higher precision from smaller samples than ever before. To date, these amplifiers have largely been employed in thermal ionisation instruments, with few applications using plasma source (i.e., MC‐ICP‐MS) instrum...

Alzheimer’s disease is associated with the production of Cu rich aβ fibrils. Because monitoring the changes in Cu level of organs has been proposed to follow the evolution of the disease, we analyzed the copper isotopic composition of serum and brain of APPswe/PSEN1dE9 transgenic mice, a model of Alzheimer’s disease, and wild-type (WT) controls. Se...

High-precision double-spike Zr stable isotope measurements (expressed as δ 94/90 Zr IPGP-Zr , the permil deviation of the ⁹⁴ Zr/ ⁹⁰ Zr ratio from the IPGP-Zr standard) are presented for a range of ocean island basalts (OIB) and mid-ocean ridge basalts (MORB) to examine mass-dependent isotopic variations of zirconium in Earth. Ocean island basalt sa...

Moderately volatile elements show variable depletion in terrestrial planets compared to the Sun. Isotopic ratios can be used as a signature of the processes at the origin of this depletion. Using a new method, the Sn stable isotope composition and elemental abundance in 36 primitive meteorites (chondrites) have been characterised to high precision....

Zirconium plays a major role in geochemistry as it is the major cation of zircons - the oldest preserved minerals on Earth. While Zr isotopic anomalies in meteorites have been widely studied, mass dependant Zr stable isotope fractionation during geological processing has been untouched. Here, we report Zr stable isotopic data for terrestrial igneou...

Tin exists both under the 2+ and 4+ oxidation states in igneous systems, and thus its geochemical behaviour changes as a function of oxygen fugacity. To characterise the redox state of Sn during magmatic differentiation and how this affects its isotope composition, we have measured Sn isotopic and elemental abundances in a suite of samples from the...

The processes associated with magma ocean formation and solidi cation can control the earliest compositional differentiation and volatile inventory of planetary bodies. Thus, eluci- dating the scale and extent to which magma oceans existed in the Solar System is critical for a full understanding of planet formation. Here we show that the magnesium...

Stable isotope studies of highly siderophile elements (HSE) have the potential to yield valuable insights into a range of geological processes. In particular, the strong partitioning of these elements into metal over silicates may lead to stable isotope fractionation during metal-silicate segregation, making them sensitive tracers of planetary diff...

Tin is a volatile as well as chalcophile and siderophile element, and this geochemical behaviour gives rise to a broad range of potential applications for Sn as a stable isotope tracer in geological processes. We present the first high-precision method to analyse the stable isotopic composition of Sn in geological materials using ion-exchange chrom...

Deciphering the ultimate source of chalcophile metals (e.g., Cu, Zn, Pb) in volcanogenic massive sulfide (VMS) deposits and the volatiles that help drive their formation is critical for understanding where, how, and why VMS deposits form. The southern Kermadec arc volcanic front is known to be highly hydrothermally active and host to at least three...

We present a new multiproxy (TEX86, δ18O and Mg/Ca), marine temperature history for Canterbury Basin, eastern New Zealand, that extends from middle Paleocene to middle Eocene, including the Paleocene–Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). In light of concerns that proxy-based sea surface temperature (SST) estimates...

We present methods for the separation of platinum from geological materials and measurement of stable isotopes of platinum by MC-ICPMS. These are applied to a range of meteorites and terrestrial samples to investigate Earth's differentiation.

Asteroid 4 Vesta has long been postulated as the source for the howardite-eucrite-diogenite (HED) achondrite meteorites. Here we show that Al-free diogenite meteorites record variability in the mass-independent abundance of 26Mg (26Mg*) that is correlated with their mineral chemistry. This suggests that these meteorites captured the Mg-isotopic evo...

New multi-proxy records of sea and land temperature variation from late Paleocene to early Eocene, eastern South Island, New Zealand suggest a much more dramatic climate history for the region than the mild climatic changes previously inferred from local oxygen isotope records, which are now known to have been compromised by diagenesis. Our tempera...

Sea-surface temperature (SST) estimates of similar to 30 degrees C from planktic foraminifera and archaeal membrane lipids in bathyal sediments in the Canterbury Basin, New Zealand, support paleontological evidence for a warm subtropical to tropical climate in the early Eocene high-latitude (55 degrees S) southwest Pacific. Such warm SSTs; call int...