An exotic Cretaceous kimberlite linked to metasomatized lithospheric mantle beneath the southwestern margin of the S?o Francisco Craton,Brazil

We present major and trace element compositions of mineral concentrates comprising garnet xenocrysts,ilmenite,phlogopite,spinel,zircon,and uncommon minerals(titanite,calzirtite,anatase,baddeleyite and pyrochlore)of a newly discovered Late Cretaceous kimberlite(U-Pb zircon age 90.0±1.3 Ma;2σ)named Osvaldo Franca 1,located in the Alto Paranaíba Igneous Province(APIP),southeastern Brazil.Pyrope grains are lherzolitic(Lherz-1,Lherz-2 and Lherz-3),harzburgitic(Harz-3)and wehrlitic(Wehr-2).The pyrope xenocrysts cover a wide mantle column in the subcratonic lithosphere(66–143 km;20–43 kbar)at relatively low temperatures(811–875°C).The shallowest part of this mantle is represented by Lherz-1 pyropes(20–32 kbar),which have low-Cr(Cr_(2)O_(3)=1.74–6.89 wt.%)and fractionated middle to heavy rare earth elements(MREE-HREE)pattern.The deepest samples are represented by Lherz-2,Lherz-3,Harz-3,and Wehr-2 pyropes(36–43 kbar).They contain high-Cr contents(Cr_(2)O_(3)=7.36–11.19 wt.%)and are characterized by sinusoidal(Lherz-2 and Wehr-2)and spoon-like(Lherz-3 and Harz-3)REE patterns.According to their REE and trace elements,pyrope xenocrysts have enriched nature(e.g.,Ce and Yb vs.Cr_(2)O_(3)),indicating that the cratonic lithosphere has been affected by a silicate melt with subalkaline/tholeiite composition due to their low Zr,Ti and Y concentrations.Besides minerals with typical kimberlitic signatures,such as ilmenite and zircon,the exotic compositions of phlogopite and ulvöspinel suggest an enriched component in the magma source.The formation of rare mineral phases with strong enrichment of light-REE(LREE)and high field strength elements(HFSE)is attributed to the late-stage kimberlitic melt.We propose a tectonic model where a thermal anomaly,represented by the low-velocity seismic anomaly observed in P-wave seismic tomography images,supplied heat to activate the alkaline magmatism from a metasomatized cratonic mantle source during the late-stages of Gondwana fragmentation and consequent South Atlantic Ocean opening.The metasomatism recorded by mineral phases is a product of long-lived recycling of subducted oceanic plates since the Neoproterozoic(Brasiliano Orogeny)or even older collisional events,contributing to the exotic character of the Osvaldo Fran?a 1 kimberlite,as well as to the cratonic lithospheric mantle.

Exploring the impact of evaluation methods on Global South building design—A case study in Brazil

Energy simulation is a valuable tool for evaluating and improving the thermal performance and energy efficiency of buildings during the design phase.Common evaluation methods are thermal load(TL),degree-hour(DH),and design days(DD).The choice of method and its settings may vary depending on regional factors and researchers’preferences,leading to diverse and often incompatible metrics and results.Therefore,this study aims to investigate the influence of these evaluation methods on the assessment of buildings’performance and,consequently,on design choices.For this purpose,this study compared the results of the 3 evaluation methods and different settings for 3 different wall systems,4 ranges of comfort temperature,and 2 residential models located in the 8 Brazilian bioclimatic zones.As result,the best and worst wall systems varied depending on the evaluation method and the threshold/setpoint temperature range considered.Warmer regions showed greater variability in the results.We noticed that it is not possible to compare and interpret results from different evaluation methods,and that the variation of only 1℃in the setpoint temperatures can lead to entirely different practices being considered the best for a given building model.In conclusion,the most suitable evaluation method is the one that best portrays the operation and dynamic reality of the building to be designed,and building regulations and standards can occasionally lead to unrealistic assessments.