Phlogopite- and clinopyroxene-dominated fractional crystallization of an alkaline primitive melt: petrology and mineral chemistry of the Dariv Igneous Complex,Western Mongolia

We present field relationships, petrography, and mineral major and trace element data for the Neoproterozoic Dariv Igneous Complex of the Altaids of Western Mongolia. This unique complex of high-K plutonic rocks is composed of well-exposed, km-scale igneous intrusions of wehrlites, phlogopite wehrlites, apatite-bearing phlogopite clinopyroxenites, monzogabbros, monzodiorites, and clinopyroxene-bearing monzonites, all of which are intruded by late stage lamprophyric and aplitic dikes. The biotite-dominated igneous complex intrudes depleted harzburgitic serpentinite. The observed lithological variability and petrographic observations suggest that the plutonic rocks can be ascribed to a fractionation sequence defined by olivine + clinopyroxene ± Fe–Ti oxides → phlogopite + apatite → K-feldspar + plagioclase → amphibole + quartz. Notably, phlogopite is the dominant hydrous mafic mineral. Petrogenesis of the observed lithologies through a common fractionation sequence is supported by a gradual decrease in the Mg# [molar Mg/(Fe_total + Mg) × 100] of mafic minerals. Crystallization conditions are derived from experimental phase petrology and mineral chemistry. The most primitive ultramafic cumulates crystallized at ≤0.5 GPa and 1,210–1,100 °C and oxygen fugacity (fO₂) of +2–3 ?FMQ (log units above the fayalite–quartz–magnetite buffer). Trace element modeling using clinopyroxene and apatite rare earth element compositions indicates that the dominant mechanism of differentiation was fractional crystallization. The trace element composition of a parental melt was calculated from primitive clinopyroxene compositions and compares favorably with the compositions of syn-magmatic lamprophyres that crosscut the fractionation sequence. The parental melt composition is highly enriched in Th, U, large ion lithophile elements, and light rare earth elements and has a pronounced negative Nb–Ta depletion, suggestive of an alkaline primitive melt originating from a subduction-imprinted mantle. Comparison with a global compilation of primitive arc melts demonstrates that Dariv primitive melts are similar in composition to high-K primitive melts found in some continental arcs. Thus, the high-K fractionation sequence exposed in the Dariv Igneous Complex may be a previously unrecognized important fractionation sequence resulting in alkali-rich upper crustal granitoids in continental arc settings.     

Benchmark-based allocations in EU ETS Phase 3: an early assessment

Phase 3 of the European Union Emissions Trading Scheme (EU ETS; 2013–2020) sees the introduction of new rules governing the free allocations of emissions allowances given to energy-intensive industries. In contrast to Phases 1 and 2, allocations will be based on historical production multiplied by best available emissions technology benchmarks. This article exploits an original database to provide a first analysis of the distributional and economic efficiency implications of the new rules. It is shown empirically that the new allocation rules reduce the scope for windfall gains by EU ETS firms while also effectively mitigating carbon leakage risks, even assuming optimistic forecasts of Phase 3 carbon prices. The example of the cement sector is used to show that benchmarking significantly improves the harmonization of the levels of free allocations to competing firms throughout the EU compared to Phase 2. However, it is also found that the use of ex ante output levels to determine allocations still leaves considerable scope for windfall gains and possible distortions of the internal market.     

A geochemistry study of arsenic speciation in overburden from Mae Moh Lignite Mine, Lampang, Thailand

The aim of this study was to investigate the geochemical characteristics of arsenic in the solid material samples of the Mae Moh Mine and also the Mae Moh power plants fly ash samples were systematically studied. Arsenic concentration in overburden, coal lignite and fly ash are variable (depending on source of solid samples). The results show that the strata of overburden, J seam of coal and fly ash are rich in arsenic and also relatively soluble from fly ash; it occurs as a surface precipitate on the ash particle. The experimental study on speciation in the strata also indicates that the arsenic speciation of Mae Moh solid samples are mainly arsenate, As (V), which are approaching exceed 80%. Arsenic content in the main of overburden is in the range of 14.3–888.8 mg/kg, which is larger than the arsenic background soil values. Solid materials polluted wastewater; the arsenic speciation was present predominantly as arsenate in the surface water of a series of Mae Moh solid materials basins.     

The deep geothermal potential of the Berlin area

In this study, we model the geothermal potential of deep geological formations located in the Berlin region in Germany. Berlin is situated in a sedimentary geological setting (northeastern German basin), comprising low-enthalpic aquifers at horizons down to 4–5 km depth. In the Berlin region, the temperature increases almost linearly with depth by about 30 K per kilometer, thus allowing for direct heating from deep aquifer reservoirs in principle. Our model incorporates eight major sedimentary units (Jurassic, Keuper, Muschelkalk, Upper/Middle/Lower Buntsandstein, Zechstein Salt and Sedimentary Rotliegend). Owing to lack of available petro-physical rock data for the Berlin region, we have evaluated literature data for the larger northeastern German basin to develop a thermodynamic field model which regards depth-corrected equations of state within statistical intervals of confidence. Integration over the thicknesses of the respective structural units yields their “heat in place”—energy densities associated with the pore fluid and the rock matrix under local conditions in Joule per unit area at the surface. The model predicts that aquifers in the Middle Buntsandstein and in the Sedimentary Rotliegend may well exhibit energy densities about 10 GJ m^?2 for the pore fluids and 20 GJ m^?2 to 40 GJ m^?2 for the rock matrices on average. Referring these figures to the city area of Berlin (about 892 km²), a significant hydrothermal potential results, which however remained undeveloped until today for the reason of present development risks. The model accounts for these risks through statistical intervals of confidence which are in the order of ±60 to ±80 % of the trend figures. To minimize these uncertainties, scientific field explorations were required in order to assess the petro-physical aquifer properties locally.     

The causes of land-use and land-cover change: moving beyond the myths

Common understanding of the causes of land-use and land-cover change is dominated by simplifications which, in turn, underlie many environment-development policies. This article tracks some of the major myths on driving forces of land-cover change and proposes alternative pathways of change that are better supported by case study evidence. Cases reviewed support the conclusion that neither population nor poverty alone constitute the sole and major underlying causes of land-cover change worldwide. Rather, peoples’ responses to economic opportunities, as mediated by institutional factors, drive land-cover changes. Opportunities and constraints for new land uses are created by local as well as national markets and policies. Global forces become the main determinants of land-use change, as they amplify or attenuate local factors.     

Multivariate interpolation and information entropy for optimizing raingauge network in the Mekong River Basin

ABSTRACT

The applicability of multivariate interpolation and information entropy to optimize the raingauge network in the Mekong River Basin (MRB) is investigated. Three different spatial interpolation methods are tested: inverse distance squared (IDS), ordinary kriging (OK) and gradient plus inverse distance squared (GIDS). The validated results confirm that the GIDS method outperformed IDS and OK. The application of information entropy together with GIDS on a network of 57 gauges provided the same information content (7.34 nat) as could be obtained using all 6788 gauges in the MRB. Combining this result with meteorological and hydrological indicators revealed that the number of gauges for the optimum raingauge network could be reduced to 40. The results imply good applicability of the proposed method, which may be used to help prioritize efforts and funds to maintain the raingauge network in a given river basin.     

Late Pleistocene and Holocene terrestrial geomorphodynamics and soil formation in northeastern Germany: a review of geochronological data

ABSTRACT

This study is based on 616 geochronological ages from aeolian and colluvial sediments as well as paleosols, representing the largest database of geochronological data from northeastern Germany available to date. Cumulative probability density functions for radiocarbon data and kernel density estimates for luminescence data were created covering the last 15 ka. The data analysis aimed at the identification of changes and their drivers in geomorphodynamics and soil formation. The ages representing aeolian activity cluster in the Late Glacial, the Early Holocene, and the Late Holocene, where the first two clusters are assumed to result mostly from climatic impact with only a minor share of human impact triggering the mobilization of aeolian sediments. The third cluster is considered to result mainly from human impact. The Late Glacial to Early Holocene activity phase is interrupted by a phase of surface stability around 11.5–12.7 ka, which is indicated by the occurrence of initial soil formations of Finow and Usselo types. Colluvial sedimentation predominantly occurred during the last 7 ka and clearly accelerated since the last 1000 a. According to the ages of specific paleosol types, related soil-forming processes started already in the Late Glacial and were completed in the Holocene.     

An example of structural and metamorphic relationships in the Musgrave orogenic belt,central Australia

The western Musgrave Ranges are broadly divided into three groups of metamorphic rocks. A central granulite‐facies core is bounded on the north by rocks of amphibolite grade and on the south by rocks transitional between the granulite and amphibolite facies. Faults trending east‐west separate the three groups of rocks.

The detailed structural relationships between the granulites and the lower grade rocks are described and discussed. The granulites are structurally relatively simple and are characterised by the presence of a strong southwesterly‐plunging, mineral‐streaking lineation. In marked contrast, the transitional rocks are more complexly folded on a macroscopic scale and they also have a well‐developed mineral lineation plunging to the southeast. These two lineation orientations are considered to be directions of maximum elongation. The amphibolite‐facies rocks are also complexly folded and at least two lineations related to different phases of deformation have been recognized.

A suite of foliated and lineated dolerite dykes which occurs throughout the area inherited their fabric during a period of intense deformation and recrystallization, which resulted in the development of numerous mylonite zones.

It is suggested that the granulite‐facies rocks may represent a suite of cover rocks which have been thrust in a northerly direction over a pre‐existing amphibolite‐facies basement.     

The metamorphic geology of the Windmill Islands,Antarctica: A preliminary account

Rocks of the Windmill Islands, Antarctica (Lat. 66°S, Long. 110°E) consist of a layered sequence of schists, gneisses, and migmatites (the Windmill Metamorphics) intruded by a charnockite (the Ardery Charnockite) and a porphyritic granite (the Ford Granite), and cut by two swarms of easterly‐trending dolerite dykes.

The rocks have undergone four deformations. The first two produced tight isoclinal folds, the third developed broader less appressed concentric folds, and the last deformation produced gentle warps which plunge steeply southwards.

The metamorphic grade of the Windmill Metamorphics ranges from (i) upper amphibolite facies (sillimanite‐biotite‐orthoclase) in the north, through (ii) biotite‐cordierite‐almandine granulite to (iii) hornblende‐orthopyroxene‐granulite in the south. The boundary between (i) and (ii) above is marked by the incoming ortho‐pyroxene and also the outgoing of sphene, and that between (ii) and (iii) by the outgoing of cordierite. Other metamorphic variations, apparent in the field are (i), the southward colour change of biotite (sepia—>red‐brown) and hornblende (blue‐green—>brown‐green) and (ii) the greater abundance of migmatites and pegmatites in the north of the area.

Major‐element rock chemistry suggests that the pre‐metamorphic nature of the schists and gneisses probably consisted of acid and basic volcanics interbedded with sediments ranging from greywacke‐type sandstones to shales. Partial melting of these rocks is thought to have produced some of the more acidic gneisses of the area.

The abundances of the elements K, Rb, and Th are lower than those of terrains of similar grade elsewhere. This is regarded as reflecting original rock composition. The ratios K/Rb, Th/K, and K/(Rb/Sr), however, are comparable with those from similar terrains elsewhere where K, Rb, and Th enrichment by crustal fractionation has been suggested. This suggests that the Windmill Metamorphics were not derived by retrogression from upper granulite‐facies rocks.