Element partitioning in magnetite under low-grade metamorphic conditions – a case study from the Proterozoic Belt Supergroup, USA

IR spectroscopy was used to compare diamonds from 12 pipes, Arkhangelsk region. Based on positive correlation between average N and H values in diamonds from various deposits, it was found that crystals from low-grade diamond pipes are relatively enriched in hydrogen compared with diamonds from Lomonosov and Grib deposits. In terms of structural impurity distribution, Arkhangelsk deposit diamonds differ from Yakutian diamonds; it could be due to various composition of compared diamonds’ source matter and thermodynamic conditions of their growth. It is shown that hydrogen is a negative factor of diamond potential in both Yakutian and Arkhangelsk diamonds. This can partly be explained by impuri-ty blocking effect on diamond crystal growth.

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Thermo-economic optimization of small-scale Organic Rankine Cycle: A case study for low-grade industrial waste heat recovery

Energy ◽

10.1016/j.energy.2020.118898 ◽

2020 ◽

Vol 213 ◽

pp. 118898

Author(s):

Bernardo Peris ◽

Joaquín Navarro-Esbrí ◽

Carlos Mateu-Royo ◽

Adrián Mota-Babiloni ◽

Francisco Molés ◽

...

Keyword(s):

Heat Recovery ◽

Waste Heat Recovery ◽

Waste Heat ◽

Organic Rankine Cycle ◽

Rankine Cycle ◽

Small Scale ◽

Low Grade ◽

Economic Optimization ◽

Industrial Waste Heat

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Polybaric/polythermal magma transport and trace element partitioning recorded in single crystals: A case study of a zoned clinopyroxene from Mt. Etna

Lithos ◽

10.1016/j.lithos.2020.105382 ◽

2020 ◽

Vol 356-357 ◽

pp. 105382 ◽

Cited By ~ 4

Author(s):

Silvio Mollo ◽

Teresa Ubide ◽

Flavio Di Stefano ◽

Manuela Nazzari ◽

Piergiorgio Scarlato

Keyword(s):

Trace Element ◽

Single Crystals ◽

Trace Element Partitioning ◽

Magma Transport ◽

Element Partitioning ◽

Mt Etna

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Correlation of very low grade data to calibrate a thermal maturity model in a nappe tectonic setting, a case study from the Alps

Tectonophysics ◽

10.1016/s0040-1951(01)00022-1 ◽

2001 ◽

Vol 334 (1) ◽

pp. 1-33 ◽

Cited By ~ 32

Author(s):

Rafael Ferreiro Mählmann

Keyword(s):

Tectonic Setting ◽

Low Grade ◽

Maturity Model ◽

Thermal Maturity ◽

The Alps

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Chlorite and Epidote Mineral Chemistry in Porphyry Ore Systems: A Case Study of the Northparkes District, New South Wales, Australia

Economic Geology ◽

10.5382/econgeo.4700 ◽

2020 ◽

Vol 115 (4) ◽

pp. 701-727 ◽

Cited By ~ 8

Author(s):

Adam Pacey ◽

Jamie J. Wilkinson ◽

David R. Cooke

Keyword(s):

New South ◽

New South Wales ◽

Mineral Chemistry ◽

Ore Deposits ◽

Low Grade ◽

South Wales ◽

Spatial Trends ◽

Propylitic Alteration ◽

Mineral Partitioning

Abstract Propylitic alteration, characterized by the occurrence of chlorite and epidote, is typically the most extensive and peripheral alteration facies developed around porphyry ore deposits. However, exploration within this alteration domain is particularly challenging, commonly owing to weak or nonexistent whole-rock geochemical gradients and the fact that similar assemblages can be developed in other geologic settings, particularly during low-grade metamorphism. We document and interpret systematic spatial trends in the chemistry of chlorite and epidote from propylitic alteration around the E48 and E26 porphyry Cu-Au deposits of the Northparkes district, New South Wales, Australia. These trends vary as a function of both distance from hydrothermal centers and alteration paragenesis. The spatial trends identified in porphyry-related chlorite and epidote at Northparkes include (1) a deposit-proximal increase in Ti, As, Sb, and V in epidote and Ti in chlorite, (2) a deposit-distal increase in Co and Li in chlorite and Ba in epidote, and (3) a pronounced halo around deposits in which Mn and Zn in chlorite, as well as Mn, Zn, Pb, and Mg in epidote, are elevated. Chlorite Al/Si ratios and epidote Al/Fe ratios may show behavior similar to that of Mn-Zn or may simply decrease outward, and V and Ni concentrations in chlorite are lowest in the peak Mn-Zn zone. In comparison to porphyry-related samples, chlorite from the regional metamorphic assemblage in the district contains far higher concentrations of Li, Ca, Ba, Pb, and Cu but much less Ti. Similarly, metamorphic epidote contains higher concentrations of Sr, Pb, As, and Sb but less Bi and Ti. These chlorite and epidote compositional trends are the net result of fluid-mineral partitioning under variable physicochemical conditions within a porphyry magmatic-hydrothermal system. They are most easily explained by the contribution of spent magmatic-derived ore fluid(s) into the propylitic domain. It is envisaged that such fluids experience progressive cooling and reduction in fs2 during outward infiltration into surrounding country rocks, with their pH controlled by the extent of rock-buffering experienced along the fluid pathway.

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REE Enrichment during Magmatic–Hydrothermal Processes in Carbonatite-Related REE Deposits: A Case Study of the Weishan REE Deposit, China

Minerals ◽

10.3390/min10010025 ◽

2019 ◽

Vol 10 (1) ◽

pp. 25 ◽

Cited By ~ 3

Author(s):

Yu-heng Jia ◽

Yan Liu

Keyword(s):

Rare Earth ◽

Late Stage ◽

Earth Element ◽

Low Grade ◽

Scattered Electron ◽

Ree Mineralization ◽

Hydrothermal Processes ◽

Informative Case ◽

Main Factors

The Weishan carbonatite-related rare earth element (REE) deposit in China contains both high- and low-grade REE mineralization and is an informative case study for the investigation of magmatic–hydrothermal REE enrichment processes in such deposits. The main REE-bearing mineral is bastnäsite, with lesser parisite and monazite. REE mineralization occurred at a late stage of hydrothermal evolution and was followed by a sulfide stage. Barite, calcite, and strontianite appear homogeneous in back-scattered electron images and have high REE contents of 103–217, 146–13,120, and 194–16,412 ppm in their mineral lattices, respectively. Two enrichment processes were necessary for the formation of the Weishan deposit: Production of mineralized carbonatite and subsequent enrichment by magmatic–hydrothermal processes. The geological setting and petrographic characteristics of the Weishan deposit indicate that two main factors facilitated REE enrichment: (1) fractures that facilitated circulation of ore-forming fluids and provided space for REE precipitation and (2) high ore fluorite and barite contents resulting in high F− and SO42− concentrations in the ore-forming fluids that promoted REE transport and deposition.

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The potential of coffee stems gasification to provide bioenergy for coffee farms: a case study in the Colombian coffee sector

Biomass Conversion and Biorefinery ◽

10.1007/s13399-019-00480-8 ◽

2019 ◽

Vol 10 (4) ◽

pp. 1137-1152 ◽

Cited By ~ 2

Author(s):

Samira Garcia-Freites ◽

Andrew Welfle ◽

Amanda Lea-Langton ◽

Paul Gilbert ◽

Patricia Thornley

Keyword(s):

Rural Areas ◽

Internal Combustion Engines ◽

Smallholder Farmers ◽

Thermochemical Conversion ◽

Small Scale ◽

Low Grade ◽

Coffee Production ◽

Coffee Sector ◽

Low Grade Heat

AbstractThe coffee industry constitutes an important part of the global economy. Developing countries produce over 90% of world coffee production, generating incomes for around 25 million smallholder farmers. The scale of this industry poses a challenge with the generation of residues along with the coffee cultivation and processing chain. Coffee stems, obtained after pruning of coffee trees, are one of those abundant and untapped resources in the coffee supply chain. Their high lignocellulosic content, the low calorific value ranging between 17.5 and 18 MJ kg−1 and the low ash content make them a suitable solid fuel for thermochemical conversion, such as gasification. This research evaluates the feasibility of using these residues in small-scale downdraft gasifiers coupled to internal combustion engines for power and low-grade heat generation, using process modelling and the Colombian coffee sector as a case study. The producer gas properties (5.6 MJ Nm−3) and the gasifier’s performance characteristics suggest that this gas could be utilized for power generation. A cogeneration system efficiency of 45.6% could be attainable when the system’s low-grade heat is recovered for external applications, like in the coffee drying stage. An analysis of the energy demand and coffee stems availability within the Colombian coffee sector shows that the biomass production level in medium- to large-scale coffee farms is well matched to their energy demands, offering particularly attractive opportunities to deploy this bioenergy system. This work assesses the feasibility of providing coffee stem–sourced low-carbon energy for global coffee production at relevant operating scales in rural areas.

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