1,721,096 research outputs found
Constraining uncertainty in boron isotope systematics using a Bayesian inversion engine reveals contrasting parameter sensitivities
No full textPhysical parameters within boron isotope systematics form a complex interplay that determine the boron isotopic composition of rocks, minerals, and fluids, but to date, providing constraints on uncertainty within boron equilibrium isotope modelling remains elusive. This underlying uncertainty limits the potency of boron isotopes as a tool for detecting fluid-rock exchange. A new equilibrium boron mineral-fluid fractionation modelling approach, named EquiB, coupled with a Bayesian inversion engine is presented, providing robust and reproducible constraints on the uncertainty of physical parameters encoded into a boron isotopic composition of a rock in equilibrium with a fluid. We demonstrate the validity of our approach by applying the model to several basalt-fluid and peridotite-fluid exchange scenarios. The model output generates multi-dimensional posterior probability distributions that show temperature is the greatest control on mineral-fluid fractionation in all applied scenarios. At high temperatures (defined as >50 °C) pH-dependent fractionation is negligible, but at low temperatures (defined as <50 °C) pH-dependent fractionation is a control on boron isotopic compositions. At geologically reasonable conditions other parameters such as salinity, fluid density, and pressure have little effect on the extent of boron mineral-fluid fractionation. Model outputs agree with experimentally derived fractionation factors at typical hydrothermal conditions but diverge at low temperatures. This approach provides robust constraints of parameter uncertainty, enabling meaningful interpretation of boron isotope analyses and the ability to fingerprint isotopic compositions with greater confidence.</p
Determination of ultra-trace Au, Ag, As, Pt and Re mass fractions in volcanic glasses and rock powders by LA-ICP-MS
No full textPractical methods for determining the ultra-trace abundances of precious metals in geological materials are needed for research into magmatic and hydrothermal processes and to expand the geochemical footprints of concealed ore deposits. This study presents a new protocol for determining Au, Ag, As, Pt and Re mass fractions in both volcanic glasses and in rock powders prepared as nano-powder pellets, through the synthesis and refinement of published LA-ICP-MS methods. This matrix flexibility allows the method and its limitations to be rigorously assessed for the first time using different volcanic materials. High-yield laser parameters, interference corrections and low oxide production rates facilitated by laser ablation sampling enabled accurate measurements without chemical pre-separation. A key finding is that ablation-remobilised system contamination must be quantified and corrected to make accurate ng g−1-level Au determinations by LA-ICP-MS, resulting in a mean + 2s quantification limit for Au of 0.38 ng g−1. This approach is likely necessary for other ultra-trace LA-ICP-MS analyses of certain elements. Following this correction, the protocol can be usefully applied to both in situ analysis of volcanic materials and efficiently integrated into methods for the determination of major and trace elements in nano-powder pellets
Public engagement with emerging technologies: Does reflective thinking affect survey responses?
No full textResearchers disagree on the extent that brief survey methods accurately reflect citizens’ opinions of unfamiliar scientific concepts. We examine whether encouraging participants to engage in more reflective thinking affects their perceptions of emerging climate technologies. Drawing on dual-process theories of reasoning, we apply experimental manipulations to encourage fast, intuitive thinking or slow, reflective thinking when responding to an online survey. Similarities in concept evaluation time between the Control and the Intuitive treatment groups indicates that citizens default to fast intuitive judgements to form opinions. However, despite a successful manipulation check, the reflective treatment group did not show any substantively different results. Therefore, encouraging additional thinking is unlikely to shift public perceptions. Post hoc analysis suggests participants with stronger views may nonetheless take more time to consider their response, without prompting. These findings support the validity of surveys as a method for eliciting stable and meaningful public perceptions of emerging technologies.</p
The public remain uninformed and wary of climate engineering
No full textInternational CO2 emissions reduction commitments are insufficient to avert damaging global warming and imperil a sustainable future. Climate engineering approaches are increasingly proposed as near-term intervention strategies, but deployment of these controversial techniques will require careful engagement with and the support of the public. New quantitative measurements of public perceptions for six climate engineering approaches show that the public of the United Kingdom (UK), United States (US), Australia (AU) and New Zealand (NZ) continue to have little knowledge of climate engineering. All approaches are regarded unfavourably, albeit less so for carbon dioxide removal (CDR) than solar radiation management (SRM). Knowledge and perceptions are remarkably similar between countries although UK and US respondents are more favourable towards SRM and UK respondents are more favourable towards CDR. Stratospheric aerosol injection is the most negatively perceived approach. Support for small-scale trials is also higher for CDR approaches than SRM. Statistical analyses yield mixed relationships between perceptions of climate engineering and age, political affiliation and pro-ecological views. Thus far, attempts to engage the public with climate engineering have seen little change over time and consequently, there is growing urgency to facilitate careful citizen deliberation using objective and instructive information about climate engineering
Determination of the volcanostratigraphy of oceanic crust formed at superfast spreading ridge: electrofacies analyses of ODP/IODP Hole 1256D
Full text linkThe objective of this study is to construct a representative volcanostratigraphy of Ocean Drilling Program Hole 1256D, the first complete penetration of intact upper oceanic crust formed at a superfast spreading rate. An accurate knowledge of the volcanostratigraphy is vital to understand processes of crustal construction and submarine magmatism and to estimate chemical exchange with seawater, but this is rarely achieved due to very low recovery rates in most basement holes. We used two approaches to determine the rock types that form the wall rocks in the basement sections of Hole 1256D: (1) user guided interpretations of electrofacies acquired by imaging tools combined with other wireline tools; and (2) the use of an artificial neutral network to objectively classify the responses of all available logging information. Great availability of formation microscanner (FMS) images provided superior coverage of the borehole wall compared to previous attempts at core-log integration. This has resulted in more confident and detailed lithologic classifications, such as with the distinction between pillows and different styles of breciation. Ten lithology types are suggested for a volcanostratigraphy model: massive flows, ponded lava, fractured massive flows, fragmented flows, thin flows or thick pillows, pillows, breccias, dikes in dike complex, isolated dikes, and gabbros. Three major lithology types in the extrusive section are massive flows (both massive and fragmented massive flow, 22%), fragmented flows (32%), and breccias (19%). Pillow lavas make up only 1.9% of the volcanic section and are confined to a 100 m interval. Below the extrusive section, subvertical contacts interpreted to be dike margins are typically observed every 1 to 2 m with brecciated zones along the contacts. The dikes dip steeply to the northeast indicating slight rotation away from the ridge axis. We used an artificial neural network (ANN) approach to determine a quantitative lithostratigraphy. The ANN is most strongly influenced by porosity and alteration degrees and the resulting stratigraphy most closely resembles the above classifications when clustered by FMS texture as opposed to lithologic interpretation. The ANN thus provides a porosity-based stratigraphy of the basement rather than the traditional lithology-based stratigraphy
The significance of heat transport by shallow fluid flow at an active plate boundary; the Southern Alps, New Zealand
No full textFluid flow can influence fault behavior. Here we quantify the role of groundwater heat advection in establishing the thermal structure of the Alpine Fault, a major tectonic boundary in southern New Zealand that accommodates most of the motion between the Australian and Pacific Plates. Convergence on the Alpine Fault has rapidly uplifted the Southern Alps, resulting in high geothermal gradients and a thin seismogenic zone. A new equilibrium temperature profile from the 818 m‐deep Deep Fault Drilling Project 2B (DFDP‐2B) borehole has been interrogated using one‐dimensional analytical models of fluid and rock advection. Models indicate a total heat flux of 720 mW·m‐2 results from groundwater flow with Darcy velocities approximating to 7.8×10‐10 m·s‐1. Groundwaters advect significantly more heat than rock advection in the shallow orogen (<6 km depth) and are the major control on the subsurface temperature field
Mineral occurrence maps of Oman Drilling Project Holes GT1A, GT2A, and GT3A
No full textThese datasets are maps of the occurrences of key minerals and mineral groups (clinopyroxene, amphibole, chlorite, epidote, prehnite, zeolite, gypsum, calcite, and kaolinite/montmorillonite) for the International Continental Scientific Drilling Program (ICDP) Oman Drilling Project (OmanDP) Holes GT1A, GT2A, and GT3A. The maps were derived from imaging spectroscopy measurements of the archive half of the OmanDP cores, with methods for data acquisition described in Kelemen et al. (2020) and data analysis in Greenberger et al. (in review, JGR Solid Earth). The mineral occurrence maps archived here are part of the supplement of Greenberger et al. (in review) but are too large to be published through the journal. Data descriptions are in the supplement of Greenberger et al. (in review), and that paper must be cited with use of these datasets. Included files: 1. GT1A_MineralOccurrenceMaps.pdf: Maps of the occurrence of key minerals and mineral groups in Hole GT1A. 2. GT2A_MineralOccurrenceMaps.pdf: Maps of the occurrence of key minerals and mineral groups in Hole GT2A. 3. GT3A_MineralOccurrenceMaps.pdf: Maps of the occurrence of key minerals and mineral groups in Hole GT3A.,
Cite this record as:
Greenberger, R. N., Harris, M., Ehlmann, B. L., Crotteau, M., Kelemen, P. B., Manning, C. E., Teagle, D. A. H., &amp; Team, T. O. D. P. S. (2021). Mineral occurrence maps of Oman Drilling Project Holes GT1A, GT2A, and GT3A (Version 1.0) [Data set]. CaltechDATA. https://doi.org/10.22002/D1.2010
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(Table 1) Chemical composition of upper oceanic crust rocks from ODP Site 129-801C
No full text(Table 1) Chemical composition of upper oceanic crust rocks from ODP Site 129-801
(Table 3) Oxygen isotopic data for silicate minerals from upper oceanic crust rocks, ODP Site 129-801C
No full text(Table 3) Oxygen isotopic data for silicate minerals from upper oceanic crust rocks, ODP Site 129-801
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