A combined Y/Ho, high field strength element (HFSE) and Nd isotope perspective on basalt weathering, Deccan Traps, India

Abstract

Please cite this article as: Babechuk, M.G., Widdowson, M., Murphy, M., Kamber, B.S., A combined Y/Ho, high field strength element (HFSE) and Nd isotope perspective on basalt weathering, Deccan Traps, India, Chemical Geology (2014), doi: 10.1016/j.chemgeo.2014 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The chemical fingerprints of dust were identified in a paleo-flow top of the saprolite profile, A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTsuggesting that dust accumulation occurred during periods of quiescence between basaltic eruptions. During protracted exposure and laterite development, the magnitude to which dust overprints the basalt chemistry increases substantially as evident from much less radiogenic Nd isotope ratios and higher Th/Nb ratios in the Bidar profile relative to the protolith basalt. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTAttempts at quantifying the magnitude of dust accumulation in the laterite based on Th enrichment indicate a mass fraction of greater than 0.5 when the dust is assumed to have the chemistry of average upper continental crust. Although mixing models between the basalt and assumed dust composition cannot unambiguously constrain the dust source, the Nd isotope mixture preserved in the laterite points to a relatively young crustal dust source (e.g., similar to loess in composition) rather than the Precambrian shield rocks in the vicinity of the

87Sr/86Sr and trace element mapping of geosphere-hydrosphere-biosphere interactions: A case study in Ireland

“…For the H2O leach, the basalt and shale soils show a lower Y/Ho ratio than the normalising composition (i.e., less than ~27), whereas the sandstone and shale show a (Babechuk et al, 2015;Thompson et al, 2013).…”

“…In contrast to Sr content, ultramafic igneous and calcareous rocks have the lowest concentrations of REE. In differences in complexation behaviour, such as the fractionation of Y and Ho (Thompson et al, 2013;Babechuk et al, 2015), which have highly contrasting affinity for complexation due to their differences in orbital chemistry, but are otherwise tightly coupled in the absence of ligands (Bau, 1996). Although the overall budget of REE available in soils in parent lithology and mineralogy specific, most parent materials have REE concentrations ranging from 0.1 to 100 mg/kg (Aide and Aide, 2012).…”

Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard)

“…Variations within soil profiles are either attributed to dust inputs (Viers and Wasserburg, 2004;Ma et al, 2010) and/or the dissolution of accessory phases such as phosphate minerals or Fe-Mn oxyhydroxides (Goldstein and Jacobsen, 1987;Öhlander et al, 2000;Aubert et al, 2001;Babechuk et al, 2015). Additionally, εNd variations in ocean sediments are often interpreted in terms of changing source regions with the isotopic composition of individual source regions remaining constant though time.…”

Th/U and U series systematics of saprolite: importance for the oceanic 234U excess

“…It, therefore, departs from simplified textbook examples of decreasing weathering intensity with depth. The profile has been the subject of very detailed earlier geochemical studies (Babechuk et al, 2014(Babechuk et al, , 2015 in which sample context, mineralogy, geochemistry and weathering behaviour are documented. Here we analysed the same samples for U series compositions (27 samples, including 4 samples from a corestone) with a quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS) and representative samples of both flows with a high precision multi collector inductively coupled plasma mass spectrometer (MC-ICP-MS).…”

“…It is exposed to 640 cm depth in an artisan quarry east of Chhindwara, India on the very top of a flat-lying mesa, thus minimising effects of lateral element transport with water. The sampling area is also not subjected to significant atmospheric dust inputs (Babechuk et al, 2015), and the lack of an excessive vegetation cover and biomass-dominated topsoil minimise the amount and effects of organic matter in the profile. The limited degree of weathering permits recognition of two basalt flows (Figs.…”