Thermal and porosity properties of meteorites : A compilation of published data and new measurements

We report direct measurements of thermal diffusivity and conductivity at room temperature for 38 meteorite samples of 36 different meteorites including mostly chondrites, and thus almost triple the number of meteorites for which thermal conductivity is directly measured. Additionally, we measured porosity for 34 of these samples. Thermal properties were measured using an optical infrared scanning method on samples of cm-sizes with a flat, sawn surface. A database compiled from our measurements and literature data suggests that thermal diffusivities and conductivities at room temperature vary largely among samples even of the same petrologic and chemical type and overlap among, for example, different ordinary chondrite classes. Measured conductivities of ordinary chondrites vary from 0.4 to 5.1 W m(-1) K-1. On average, enstatite chondrites show much higher values (2.33-5.51 W m(-1) K-1) and carbonaceous chondrites lower values (0.5-2.55 W m(-1) K-1). Mineral composition (silicates versus iron-nickel) and porosity control conductivity. Porosity shows (linear) negative correlation with conductivity. Variable conductivity is attributed to heterogeneity in mineral composition and porosity by intra- and intergranular voids and cracks, which are important in the scale of typical meteorite samples. The effect of porosity may be even more significant for thermal properties than that of the metal content in chondrites.Peer reviewe

Raskaat harvinaiset maa-alkuaineet ja laakiobasalttien lähteet

Editor's ChoiceHeavy rare earth elements (HREEs) in mafic and ultramafic volcanic rocks are useful recorders of mantle source processes because their ratios are not easily modified by differentiation. Here we utilize REEBOX PRO, a simulator of adiabatic decompression melting of the mantle, to study the behavior of HREEs in the formation of continental flood basalt (CFB) parental magmas in the mantle. We simulate partial melting of depleted peridotite, pyrolitic peridotite, pyroxenite, and peridotite-pyroxenite mixtures at mantle potential temperatures of 1350-1650 degrees C and lithospheric thicknesses of 50-150 km, and compare the results to natural data. Many large igneous provinces are typified by low-Ti and high-Ti CFBs with contrasting HREE patterns. Our results show that low-Ti CFBs originate mainly from peridotitic sources. Flat mid-ocean ridge basalt-like HREE patterns typical of low-Ti CFBs can be generated beneath thick lithosphere (similar to 100 km), given that mantle potential temperatures are high (>1500 degrees C) and garnet is completely consumed from the source. We thus challenge the common interpretation that flat HREE patterns always indicate shallow sources for CFB parental magmas. High-Ti CFBs require pyroxenite-bearing sources (>= 10%). Contrary to a common view, their steep oceanic island basalt-like HREE patterns can be generated beneath quite a thin lithosphere (similar to 50 km), which is due to increased garnet stability in pyroxenite sources. When applied to CFBs of the Karoo large igneous province, the results are compatible with a model where a mantle plume penetrates a progressively thinning Gondwana lithosphere.Peer reviewe

Luenhan pikriitit keskisestä Mosambikista - Viestintuojia Karoon laakiobasalttien vaippapluumilähteestä?

We present geochemical and isotopic (Nd, Sr) data for a picrite lava suite from the Luenha River and adjacent areas in Mozambique. The Luenha picrites represent a previously unknown type of picrites related to the Karoo large igneous province (LIP) and are distinguished by their notably low TiO2 contents (0.3-1.0 wt%) and coupling of high Nb/Y with low Zr/Y and Sm/Yb. Relatively high CaO and low Zn/Fe point to a peridotitic mantle source. Contamination-sensitive incompatible element ratios show that one lava flow is likely to be uncontaminated by the crust and its composition suggests a mantle source with primitive mantle-like incompatible element ratios and mildly depleted isotopic ratios (initial Sr-87/Sr-86 = 0.7041 and epsilon(Nd) = +1.4 at 180 Ma). The primary melts of the Luenha picrites had MgO contents in the range of 13-21 wt%. Our preferred estimate for a primary melt composition (MgO = 18 wt%) resembles experimental melts of fertile mantle peridotite at 3-4 GPa and indicates liquidus temperature of 1445-1582 degrees C. Geochemical similarities suggest the Luenha picrites were generated from the same overall primitive mantle-like reservoir that produced the main volume of Karoo flood basalts in the Karoo, Kalahari, and Zambezi basins, whereas the previously identified enriched and depleted (upper) mantle sources of Karoo picrite suites (Mwenezi, Antarctica) were subordinate sources for flood basalts. We propose that the Luenha picrites record melting of a hot, chemically primitive mantle plume source that may have been rooted in the sub-African large low shear velocity province boundary and that such a source might have been the most significant magma source in the Karoo LIP. (C) 2019 The Author(s). Published by Elsevier B.V.Peer reviewe

Theoretical predictions for vehicular headways and their clusters

This article presents a derivation of analytical predictions for steady-state distributions of netto time gaps among clusters of vehicles moving inside a traffic stream. Using the thermodynamic socio-physical traffic model with short-ranged repulsion between particles (originally introduced in [Physica A \textbf{333} (2004) 370]) we firstly derive the time-clearance distribution in the model. Consecutively, the statistical distributions for the so-called time multi-clearances are calculated by means of theory of functional convolutions. Moreover, all the theoretical surmises used during the above-mentioned calculations are proven by the statistical analysis of traffic data. The mathematical predictions acquired in this paper are thoroughly compared with relevant empirical quantities and discussed in the context of three-phase traffic theory.Comment: 23 pages, 10 figure

Microscopic features of moving traffic jams

Empirical and numerical microscopic features of moving traffic jams are presented. Based on a single vehicle data analysis, it is found that within wide moving jams, i.e., between the upstream and downstream jam fronts there is a complex microscopic spatiotemporal structure. This jam structure consists of alternations of regions in which traffic flow is interrupted and flow states of low speeds associated with "moving blanks" within the jam. Empirical features of the moving blanks are found. Based on microscopic models in the context of three-phase traffic theory, physical reasons for moving blanks emergence within wide moving jams are disclosed. Structure of moving jam fronts is studied based in microscopic traffic simulations. Non-linear effects associated with moving jam propagation are numerically investigated and compared with empirical results.Comment: 19 pages, 12 figure

Criterion for traffic phases in single vehicle data and empirical test of a microscopic three-phase traffic theory

A microscopic criterion for distinguishing synchronized flow and wide moving jam phases in single vehicle data measured at a single freeway location is presented. Empirical local congested traffic states in single vehicle data measured on different days are classified into synchronized flow states and states consisting of synchronized flow and wide moving jam(s). Then empirical microscopic characteristics for these different local congested traffic states are studied. Using these characteristics and empirical spatiotemporal macroscopic traffic phenomena, an empirical test of a microscopic three-phase traffic flow theory is performed. Simulations show that the microscopic criterion and macroscopic spatiotemporal objective criteria lead to the same identification of the synchronized flow and wide moving jam phases in congested traffic. It is found that microscopic three-phase traffic models can explain both microscopic and macroscopic empirical congested pattern features. It is obtained that microscopic distributions for vehicle speed difference as well as fundamental diagrams and speed correlation functions can depend on the spatial co-ordinate considerably. It turns out that microscopic optimal velocity (OV) functions and time headway distributions are not necessarily qualitatively different, even if local congested traffic states are qualitatively different. The reason for this is that important spatiotemporal features of congested traffic patterns are it lost in these as well as in many other macroscopic and microscopic traffic characteristics, which are widely used as the empirical basis for a test of traffic flow models, specifically, cellular automata traffic flow models.Comment: 27 pages, 16 figure

Björnnutane and Sembberget basalt lavas and the geochemical provinciality of Karoo magmatism in western Dronning Maud Land, Antarctica

Geochemical provinciality of the Karoo continental flood basalt (CFB) province is complicated by the great diversity of magma types. Our geochemical and Nd and Sr isotopic data indicate derivation of Karoo-related low-Ti CFBs of Björnnutane and Sembberget, Dronning Maud Land, Antarctica, from different magma plumbing systems that were typified by generation of magma subtypes largely by variable degrees of fractional crystallization and crustal contamination. We associate these plumbing systems with different mantle sources and propose that the Karoo CFBs of Dronning Maud Land can be grouped into two provinces derived from these sources. The Grunehogna province magmas include high-Ti and some low-Ti magma types, have high (Sm/Yb)N (> 2), are enriched in Sr and Eu, and show wide range of initial εNd (+ 9 to − 16). Grunehogna province magmas dominate at Björnnutane, Vestfjella, and Ahlmannryggen. The Maud province magmas show low-Ti affinity, have low (Sm/Yb)N (< 2), lack Sr and Eu enrichment, and have relatively narrow range of initial εNd (+ 3 to − 4). Maud province magmas are restricted to Sembberget, Kirwanveggen and the Utpostane gabbros in Vestfjella. The enrichment of Sr and Eu and the depletion of heavy rare earth elements in Grunehogna province magmas, and, specifically, geochemical indications of recycled oceanic crust in the least-contaminated high-Ti and low-Ti basalts and picrites lend support to a recycled source component. Grunehogna magmas are ascribed to partial melting of eclogite-bearing asthenospheric mantle source at depth below the Grunehogna craton and contamination of the magmas with lithospheric mantle (high-Ti types) and crust (low-Ti types). The Maud province magmas can be ascribed to relatively low-pressure partial melting probably of a lithospheric mantle source within the zone of rifted lithosphere associated with the Weddell triple junction and lateral flow of magmas to present outcrops overlying thick Maud Belt lithosphere. Geochemical comparison with Karoo CFBs in southern Africa implies a broadly similar division between the high-Ti and low-Ti magma types associated with the Limpopo structure and the low-Ti magma types of the Central Area and Botswana