Multistage growth of Fe–Mg–carpholite and Fe–Mg–chloritoid,from field evidence to thermodynamic modelling

We provide new insights into the prograde evolution of HP/LT metasedimentary rocks on the basis of detailed petrologic examination, element-partitioning analysis, and thermodynamic modelling of well-preserved Fe–Mg–carpholite- and Fe–Mg–chloritoid-bearing rocks from the Afyon Zone (Anatolia). We document continuous and discontinuous compositional (ferromagnesian substitution) zoning of carpholite (overall X _Mg = 0.27–0.73) and chloritoid (overall X _Mg = 0.07–0.30), as well as clear equilibrium and disequilibrium (i.e., reaction-related) textures involving carpholite and chloritoid, which consistently account for the consistent enrichment in Mg of both minerals through time, and the progressive replacement of carpholite by chloritoid. Mg/Fe distribution coefficients calculated between carpholite and chloritoid vary widely within samples (2.2–20.0). Among this range, only values of 7–11 correlate with equilibrium textures, in agreement with data from the literature. Equilibrium phase diagrams for metapelitic compositions are calculated using a newly modified thermodynamic dataset, including most recent data for carpholite, chloritoid, chlorite, and white mica, as well as further refinements for Fe–carpholite, and both chloritoid end-members, as required to reproduce accurately petrologic observations (phase relations, experimental constraints, Mg/Fe partitioning). Modelling reveals that Mg/Fe partitioning between carpholite and chloritoid is greatly sensitive to temperature and calls for a future evaluation of possible use as a thermometer. In addition, calculations show significant effective bulk composition changes during prograde metamorphism due to the fractionation of chloritoid formed at the expense of carpholite. We retrieve P–T conditions for several carpholite and chloritoid growth stages (1) during prograde stages using unfractionated, bulk-rock XRF analyses, and (2) at peak conditions using compositions fractionated for chloritoid. The P–T paths reconstructed for the Kütahya and Afyon areas shed light on contrasting temperature conditions for these areas during prograde and peak stages.     

http://www.sciencedirect.com/science/article/pii/S1674987112001569

The southeastern Anatolia comprises numbers of tectono-magmatic/stratigraphic units such as the metamorphic massifs,the ophiolites,the volcanic arc units and the granitoid rocks.All of them play important role for the late Cretaceous evolution of the southern Neotethys.The spatial and temporal relations of these units suggest the progressive development of coeval magmatism and thrusting during the late Cretaceous northward subduction/accretion.Our new U-Pb zircon data from the rhyolitic rocks of the wide-spread volcanic arc unit show ages of(83.1±2.2)-(74.6±4.4) Ma. Comparison of the ophiolites,the volcanic arc units and the granitoids suggest following late Cretaceous geological evolution.The ophiolites formed in a suprasubduction zone(SSZ) setting as a result of northward intra-oceanic subduction.A wide-spread island-arc tholeiitic volcanic unit developed on the top of the SSZ-type crust during 83-75 Ma.Related to regional plate convergence, northward under-thrusting of SSZ-type ophiolites and volcanic arc units was initiated beneath the Tauride platform(Malatya-Keban) and followed by the intrusion of l-type calc-alkaline volcanic arc granitoids during 84-82 Ma.New U-Pb ages from the arc-related volcanic-sedimentary unit and granitoids indicate that under-thrusting of ophiolites together with the arc-related units beneath the Malatya-Keban platform took place soon after the initiation of the volcanic arc on the top of the SSZtype crust.Then the arc-related volcanic-sedimentary unit continued its development and lasted at～75 Ma until the deposition of the late Campanian—Maastrichtian shallow marine limestone.The subduction trench eventually collided with the Bitlis-Ptrge massif giving rise to HP-IT metamorphism of the Bitlis massif.Although the development of the volcanic arc units and the granitoids were coeval at the initial stage of the subduction/accretion both tectono-magmatic units were genetically different from each other.     

Geochemistry and geodynamics of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq

The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ? _Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D″ layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous.     

Malaysia's Three Major Ethnic Group Preferences in Creating a Malaysian Garden Identity

Malaysia has a complex multiracial population, predominantly defined by three major ethnic groups: Malay, Chinese and Indian races, with diverse cultural backgrounds. Despite this, the country has a vision to be the most beautiful garden nation, and its National Landscape Policy (NLP) puts emphasis on creating a unique landscape and garden identity. Because of ethnic and cultural differences, there are differences between preferences for developing a garden identity for Malaysia. Hence, this study focused on the visual quality of gardens. Representative images of four well-established gardens of the world including Persian-Islamic, English, Japanese and Chinese gardens were presented to the study's respondents through preference photo surveys. Respondents from the three major ethnic groups in Malaysia were asked to rate their preferred garden types, elements and scenes that they would like to see in Malaysian gardens. The results pinpointed expectations of the visual quality of gardens. These highlighted some similarities and differences between the three major ethnic groups in their preferences for the scenes and elements that they sought in gardens. Diverse factors must be considered when creating Malaysian gardens that will be accepted by Malaysians of different ethnic groups. Garden development reveals preferences attached to visual qualities and emphasises cultural differences between garden users.     

Interaction of surface water and groundwater in the Nile River basin: isotopic and piezometric evidence

Hydrogeology Journal - Past discussions around water-resources management and development in the River Nile basin disregard groundwater resources from the equation. There is an increasing interest...     

Heterogeneity analysis of reservoir porosity and permeability in the Late Ordovician glacio-fluvial Sarah Formation paleovalleys,central Saudi Arabia

The Late Ordovician glacio-fluvial Sarah Formation is an important tight gas reservoir target in Saudi Arabia. This study uses statistical methods to characterize the petrophysical heterogeneity of the paleovalleys of the Sarah Formation that crop out in central Saudi Arabia. Four paleovalleys were studied: Bukayriyah, Hanadir, Sarah, and Khanasir Sarah. Several lithofacies were identified in each that vary in texture, porosity, permeability, and facies abundance that reflect periods of ice advance and retreat. The heterogeneity analysis is based on three statistical measures, namely, the coefficient of variation, the Dykstra-Parsons coefficient, and the Lorenz coefficient. The coefficient of variation values is in the 0.62–1.94 range, indicating an extremely heterogeneous distribution. The Dykstra-Parsons coefficient values are in the 0.56–0.88 range, suggesting very high to extremely high heterogeneity in the reservoirs. The Lorenz coefficient correlates well with the Dykstra-Parsons coefficient for paleovalleys of the Sarah Formation. The heterogeneity parameters studied here indicate that the outcrops of Sarah Formation paleovalleys represent heterogeneous to very heterogeneous reservoirs, which may be attributed to complex depositional and diagenetic variations that have affected the porosity and permeability distribution.     

Groundwater recharge/discharge in semi-arid regions interpreted from isotope and chloride concentrations in north White Nile Rift, Sudan

Deuterium, oxygen-18 and chloride were analyzed for 84 samples from deep and shallow wells, precipitation and the river White Nile to investigate groundwater recharge/discharge relations in the semi-arid central Sudan. Spatial and vertical variation in isotopic signature and chloride concentration in the groundwater show similar patterns and indicate local recharge and evaporative discharge. Progressive decrease in isotopic composition along the regional groundwater flow path demonstrates aquifer continuity down the NW–SE recharge-discharge path. Isotope-heavy recharged water progressively mixes with lighter older groundwater formed during cooler and humid conditions in the late Pleistocene. However, evaporative fractionation in the flow path’s final reach in the southeast re-enriches the isotopic composition and suggests evaporative loss of groundwater as the plausible discharge mechanism. Chloride concentration increases down the gradient from the recharge area and reaches its peak in the discharge zones indicating: lack of recharge from direct infiltration down the gradient, evaporation and prolonged rock/water interaction. Head differences and increased isotopic concentration in the vicinity of the White Nile suggest recharge from the river from subsurface flow. Reduced chloride content and relatively heavier isotopic composition in the deep groundwater beneath the wadi of Khor Abu Habil indicate recharge from the streambed into the deep aquifer.     

Sr–Nd isotopes and geochemistry of the infrastructural rocks in the Meatiq and Hafafit core complexes, Eastern Desert, Egypt: Evidence for involvement of pre-Neoproterozoic crust in the growth of Arabian–Nubian Shield

Abstract Meatiq and Hafafit core complexes are large swells in the Eastern Desert of Egypt, comprising two major tectono‐stratigraphic units or tiers. The lower (infrastructure) unit is composed of variably cataclased gneissose granites and high‐grade gneisses and schists. It is structurally overlain by Pan–African ophiolitic mélange nappes (the higher unit). The two units are separated by a low‐angle sole thrust, along which mylonites are developed. Major and trace element data indicate formation of the gneissose granites in both volcanic arc and within‐plate settings. Nevertheless, all analyzed gneissose granites and other infrastructural rocks, exhibit low initial ratios (Sr_i) (<0.7027), positive ε_Nd(t) (+4.9 to +10.3) and Neoproterozoic Nd model age (T_DM) (592–831 Ma for the gneissose granite samples). Although these values are compatible with other parts of the Arabian– Nubian Shield considered to be juvenile, the ε_Nd(t) values and several incompatible element ratios of the gneissose granites are too low to be derived from a mantle source without contribution from an older continental crust. Our geological, Sr–Nd isotopic and chemical data combined with the published zircon ages indicate the existence of a pre‐Neoproterozoic continent in the Eastern Desert that started to break up at ca 800 Ma. Rifting and subsequent events caused the formation of oceanic crust and emplacement within‐plate alkali basalts in the hinterland domains of the old continent. The emplacement of basaltic magma might have triggered melting of lower crust in the old continent and resulted in emplacement of the within‐plate granite masses between 700 Ma and 626 Ma. The granite masses and other rocks in the old continent have been subjected to deformation during the over‐thrusting of Pan–African nappes, probably because of the oblique convergence between East and West Gondwanaland. Rb–Sr isotopes of the gneissose granites in both Meatiq and Hafafit core complexes defines an isochron age of 619 ± 25 Ma with Sr_i of 0.7009 ± 0.0017 and mean squares of weighted deviates = 2.0. We interpret this age as the date of thrusting of the Pan–African nappes in the Eastern Desert. Continued oblique convergence between East and West Gondwanaland could have resulted in the formation northwest–southeast‐trending Meatiq and Hafafit anticlinoriums.     

Improving the Quality of Municipal Solid Waste Compost by Using Expanded Perlite and Natural Zeolite

The scope of this study was to investigate the effects of natural zeolite and expanded perlite on the quality of municipal solid waste compost. Various ratios of the materials were added as supplements to the organic fraction of municipal solid waste. These applications were periodically compared with an untreated control process. The results obtained from experimental studies clearly showed that municipal solid waste collected from the metropolitan city center of Samsun, Turkey could not be composted without any additions due to the very high moisture content, which reached up to 75–80%. In the untreated control process, thermophilic temperatures were not supported during the composting. In this system, ammonia and other odors became a problem because of the high pH levels, and the electrical conductivity was too high for aged compost. However, the addition of natural zeolite and expanded perlite had a positive affect on the quality of the final compost. Natural zeolite trapped ammonium and reduced nitrogen losses from the compost. Expanded perlite held excess moisture and supported improved aeration. The results also indicated that the use of natural zeolite together with expanded perlite in municipal solid waste composting processes produced mature and stable compost.     

Distances of Galaxies from the Apparent Size Distribution of Dark Clouds. II NGC 224, NGC 2841 and NGC 7331

The distances of three Sb galaxies NGC 224, NGC 2841 and NGC 7331 have been determined using the apparent size distribution of dark interstellar clouds in each of them. The distances of NGC 224, NGC 2841, NGC 7331 were found to be 727.7 ± 63 kpc, 8.07 ± 0.16 Mpc and 7.22 ± 0.15 Mpc, respectively.