Aimeryc Schumacher

@article{Kokh_etal2021,

title = {Quantitative measurement of rare earth elements in brines: Isolation from the charged matrix versus direct LA-ICP-MS measurements -- A comparative study},

author = {M. A. Kokh and B. Luais and L. Truche and M. C. Boiron and C. Peiffert and A. Schumacher},

doi = {10.1111/ggr.12376},

year  = {2021},

date = {2021-01-01},

journal = {Geostandards and Geoanalytical Research},

abstract = {The quantification of the rare earth elements (REEs) in natural rocks and fluids is important not only for the sustainable use of geological resources but also for fundamental geological research. Due to significant improvements in experimental, modelling and analytical techniques, it was discovered that the REEs could be efficiently mobilised and transported by hydrothermal fluids. Thus, determining the REEs in fluids, especially in highly saline solutions, is aprerequisite to understand their fate in hydrothermal fluids. An analytical methodology was established to determine the trace quantities of the REEs in aqueous solutions with compositions typical to seawater and brines. The developed protocol was applied for the quantification of REEs in experimental sodium-rich carbonate-bearing hydrothermal solutions. For this purpose, we used two analytical approaches: (a) the REEs were chromatographically isolated from the charged matrix and introduced into a single collector quadrupole ICP-MS and (b) direct determination of the REEs by LA-ICP-MS in experimental solutions loaded into glass capillaries without any additional isolation procedure. Both LA-ICP-MS and solution nebulisation ICP-MS analysis after isolation of the REEs provide identical data in terms of REE concentrations in brines and are consistent within analytical uncertainties. Being an express method, LA-ICP-MS can be recommended for REE quantification in brines. At the same time, isolation of the REEs from the charged matrix with subsequent ICP-MS measurement provides higher accuracy and precision, giving additional information for the REEs mass fractions that are below the detection limit of the LA-ICP-MS that was estimated at the textasciitilde 10 ng g-1 level.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Morino_etal2017,

title = {Chemical stratification in the post-magma ocean Earth inferred from coupled 146,147Sm--142,143Nd systematics in ultramafic rocks of the Saglek block (3.25--3.9 Ga; northern Labrador, Canada},

author = {P. Morino and G. Caro and L. Reisberg and A. Schumacher},

doi = {10.1016/j.epsl.2017.01.044},

year  = {2017},

date = {2017-01-01},

journal = {Earth and Planetary Science Letters},

volume = {463},

pages = {136--150},

abstract = {The coupled 146,147Sm--142,143Nd chronometer has the potential to provide precise constraints on both the age and the composition of silicate reservoirs generated by magma ocean processes on accreting planets. Application of this chronometer to early Earth differentiation, however, is made difficult by the poor preservation and complex geological history of Eoarchean rocks hosting 142Nd anomalies, which often prevents accurate determination of their initial 143Nd/144Nd ratios. In order to better constrain the chronological aspects of Earthtextquoterights formation, we investigated the 146,147Sm--142,143Nd systematics of well-preserved mafic/ultramafic enclaves of the Archean Saglek block of northern Labrador (3.25--3.9Ga). Our results show that two distinct ultramafic suites are present within the Hebron/Saglek fjords region. The first group of samples, with $mu$142Nd=1.6 textpm2.8 and $epsilon$143Ndi=0.4 textpm0.4, yields a whole-rock isochron age of 3365 textpm100 Ma and is tentatively suggested to be associated with the Mesoarchean Upernavik formation. The second group, with $mu$142Nd= 8.6 textpm3.3ppm and $epsilon$143Ndi=1.4 textpm0.6, yields an Eoarchean date of 3782 textpm93 Ma, and is assigned to the Nulliak assemblage. Application of coupled 146,147Sm--142,143Nd chronometry to the Nulliak suite yields a model age of differentiation of 4.40+0.05−0.06Ga, and a corresponding (147Sm/144Nd) source ratio of 0.211 textpm0.007 for the early depleted mantle. These estimates are remarkably similar to those obtained for a tholeiitic lava of the Abitibi greenstone belt (Theotextquoterights flow, 2.7Ga) based on the 142,143Nd dataset of Debaille et al.(2013). Viewed in conjunction with previous 142,143Nd data, our results provide a precise estimate of the age of primordial differentiation of Earthtextquoterights mantle, 160+30−20Myrafter formation of the solar system. This chronological constraint, combined with evidence for late solidification of the lunar magma ocean, strongly supports a young age for the giant impact and the Earth--Moon system. Further, the similarity of 146,147Sm--142,143Nd model ages and (Sm/Nd) source ratios inferred for Nulliak, Isua and Theotextquoterights flow suggests that their parent magmas were derived from a common mantle reservoir. This early depleted domain appears to have evolved as a closed-system on a multi-billion year timescale despite efficient mixing in the hot Hadean/Archean mantle. We thus propose that the occurrence of positive 142Nd anomalies in the Archean rock record reflects episodic melting of a depleted reservoir otherwise isolated from the convective system, rather than progressive homogenization of a highly depleted Hadean mantle.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}