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It is well recognised that endothermic processes such as dehydration and partial melting have the potential to exert measurable effects on the maximum temperatures reached in metamorphic rock systems. We show migmatitic metapelitic and mafic granulites record temperatures of ~ 820 °C, while spatially associated refractory Mg–Al-rich granulites record temperatures between 865 °C and > 920 °C. These thermally contrasting samples are separated by ~ 1500 m, with no apparent intervening faults or shear zones to explain the apparent difference in peak metamorphic conditions. Temperature versus enthalpy modelling of these samples along simple prograde P–T paths imply migmatisation slows the rate of temperature increase relative to rocks that do not melt. We speculate refractory rocks in the present study are created through early hydrothermal alteration and metamorphism, resulting in melt-resistant bulk compositions. There are many potential geological contexts where neighbouring rocks may have contrasting melt fertility; the deposition of a cover sequence, pre-metamorphic alteration, and the intrusion of igneous protoliths are all possibilities. With this in mind, variations in maximum modelled temperatures in granulite facies domains should be relatively common. [ABSTRACT FROM AUTHOR]

In the southernmost part of the Svecofennian province in Finland, leucogranites and migmatites stemming from both igneous and sedimentary protoliths reflect the complex magmatic history of the Svecofennian orogeny between 1.89 and 1.82 Ga. Although the migmatites and leucogranites in southernmost Finland display similar ages as their counterparts elsewhere in the Southern Finland Subprovince, they differ in field appearance and composition. Field and petrographical observations reveal K-feldspar megacrysts of varying sizes in the migmatized early Svecofennian (c. 1.89–1.87 Ga) supracrustal rocks and granitoids. Whole-rock geochemical analyses likewise display anomalously high K-contents in the early Svecofennian granitoids. Zircon U-Pb dating of migmatites and related leucogranites shows that a late Svecofennian partial melting event occurred at 1.84–1.82 Ga, possibly in several pulses. The morphological features of the migmatites as well as neosome mineralogy indicate a formation mechanism different from the dehydration melting prevalent elsewhere in the Subprovince.

The Tongbai complex plays an important role in the understanding of the tectonic evolution of the Tongbai‐Dabie orogenic belt. By detailed structural analysis, new zircon U–Pb dating, zircon Lu–Hf analysis and whole‐rock elements for the rocks in the Tongbai complex and the wrapped shear zones, we suggested that the Tongbai complex was derived from the partial melting of the basement of Yangtze Block and experienced a uniform orogen‐parallel extension with a top‐to‐NW shearing at 142–133 Ma. The migmatites yield a migmatization age of 116 ± 2 Ma and are identical to the metamorphic age of 115–111 Ma from the L and LS tectonites in the Tongbai complex. The late Early Cretaceous migmatization may give rise to the severance of the uniform top‐to‐NW shear zone and lead to an antiform folding of the Tongbai complex. The similar deformation and migmatization of the complexes in both the Tongbai and Dabie orogenic belts suggest that the Tongbai‐Dabie orogenic belt is likely to have a similar tectonic transformation from orogen‐parallel to orogen‐perpendicular extension in the Early Cretaceous, namely a uniform orogen‐parallel extension of the ductile lithosphere during the early Early Cretaceous and a widespread migmatization during the late Early Cretaceous. [ABSTRACT FROM AUTHOR]

Mantle magmas interact with surrounding rocks during their ascent and storage in the continental crust, leading to open system processes as wall rock partial melting. In this study, we have experimentally investigated the reactions between a leucosome depleted migmatite and a primitive K-basaltic of Campi Flegrei (Italy). Experiments were carried out at pressure of 0.8 GPa temperatures from 1250 °C to 1050 °C and constant temperature and thermal gradient conditions. The experimental products consist of biotite-free migmatite, glass and crystals of clinopyroxene, olivine, plagioclase and Cr-spinel with proportions that vary as a function of temperature. Open system isothermal experiments indicate that the chemistry of melts and phase relationships are controlled by the high Al2O3 content of leucosome depleted migmatite with the glass composition shifting from K-trachybasalt towards shoshonite as the temperature decreases from 1200 °C to 1125 °C. At temperatures 1150°C, migmatite assimilation is not exclusively due to the assimilation fractional crystallization process because evidence of mingling and mixing is observed. T-gradient experiment shows melt composition ranging from shoshonite to phono-tephrite moving from the slightly crystalline zone (T = 1250 –1210 °C) at the bottom of the capsule towards the highly crystalline zone (T = 1160 –1140 °C). This SiO2-constant trend indicates that at temperature below the basalt solidus, the assimilation of leucosome depleted crust is represented almost exclusively by the biotite breakdown, leading to the increase in Al, Mg, Fe, Ti, and K activities in the system. The shoshonitic composition obtained in our experiments could represent the parental magma for both Campi Flegrei volcanic district and Vesuvius magmatic systems, indicating modification in a deep storage zone through mixing with the partial melts derived from restitic continental crust. [ABSTRACT FROM AUTHOR]

The timing of partial melting in high-grade metamorphic rocks is critical for constraining tectonic histories and processes. However, uncertainties exist about the behavior of monazite and zircon during partial melting, especially about the timing of crystallization with respect to melting reactions. This study is focused on a single sample (16TG143) of finely layered, migmatitic gneiss from the Adirondack Highlands, New York, interpreted to have undergone extensive biotite dehydration melting (i.e., Bt + Pl + Als + Qz = Grt + Kfs + melt). The rock contains one distinct leucosome layer. The non-leucosome (gray gneiss) portion of the migmatite has millimeter-scale sublayers with distinct differences in modes and mineralogy. The layers are interpreted to reflect the differential preservation of reactants and products formed during the forward and reverse progress of the melting reaction. Monazite and zircon modes, and to some degree, texture, composition, and geochronology all vary from layer to layer. Both minerals have up to three domains: ca. 1150 Ma anhedral cores, ca. 1050 Ma monazite mantles/fir tree textured zircon, and ca. 1030 Ma rims. The heterogeneous layered gray gneiss provides robust constraints on the timing of melting (ca. 1050 Ottawan orogenesis), melt crystallization, and post-melting retrogression, in addition to information about earlier metamorphic events. Early-formed monazite and zircon grains were largely dissolved during progressive melting, except where preserved as relicts or inclusions. Monazite mantles and fir tree zircon grains precipitated upon cooling during progressive melt crystallization between temperatures of 800 and 750 °C. Rims are interpreted to have precipitated during subsolidus, solid-state retrogression after ca. 1050 Ma. Correlations between the gneissic layering, melting reactions, and the character of geochronometers emphasize the importance of characterizing the layer-forming and chronometer petrogenesis processes as a critical part of deconvoluting the history of migmatitic gneisses. [ABSTRACT FROM AUTHOR]

The Zanjan-Takab complex is a metamorphic belt with NW-SE trend that includes gneiss, amphibolite and gneissic amphibolite, old metagranites, pelitic schists with migmatites and metaophiolites. Takab mafic migmatites, based on field evidence and partial melting degree, are divided into two main groups of metatexites with patchy, ophthalmitic, diktyonitic, agmatic, stromatic structures and diatexites with schollen, ptygmatic, folded, stictolithic, phlebetic, schliren, nebulitic structures. These migmatites consist of mesosome part with textures of porphyroblastic, xinoblastic, granoblastic and nematoblastic and main minerals plagioclase, hornblende, biotite, melanosome part with nematoblastic, xinoblastic, granoblastic and oriented textures and main minerals hornblende and plagioclase. The leucosome part is composed of granular, sympletic and myrmekitic textures and the main minerals are plagioclase, quartz, k-feldspare, titanite, hornblende and biotite. Investigating the shape of the crystal size scatter diagrams (CSD) shows the physical conditions and petrological processes are effective in the studied rocks. In order to investigate these processes, plagioclase crystals in 4 leucosome samples were quantitatively analyzed with the help of Jmicro vision and CSD Corrections software, and then the results obtained from the analysis of different leucosome samples were compared. The crystal size scatter diagrams of plagioclase crystals show two stages of growth with different speeds in the studied samples, so that the larger crystals (the end part of the curved diagram on the right) belong to a melt that is at greater depths or it cooled in a calmer environment. Nevertheless, the initial part of the diagram on the left side crystallized in more superficial areas and at a higher speed. Introduction The crystallization history of a rock is recorded in the size and distribution of its minerals (Muller et al., 2009). The most common method of quantitative measurement of textures is investigation of crystal size dispersion (CSD) (Higgins, 1998). Crystal size dispersion (CSD) deals with the quantitative measurement of crystals of a specific mineral with a unit volume in size intervals (Cashman, 1993; O'Driscoll et al., 2007). Many researchers, including Cashman and Marsh (1988), Cashman (1993), Zieg and Marsh (2002), Higgins and Roberge (2003), Higgins and Roberge (2007), Kaneko et al., (2005), Cashman and Ferry (1988), Higgins (1996) and O'Driscoll et al., (2007) in their studies of CSD diagrams to determine kinetic indices of crystallization of magmatic systems, cooling history, temperature, magmatic mixing, texture maturity, dominant size of crystals, density Crystals and partial volume of crystals and thermodynamic and kinetic models were used. In addition, researchers such as Kaneko et al., (2005), Cashman and Ferry (1988), Moazzen and Modjarrad (2005) and Muller et al., (2009) studied the crystal size distribution in metamorphic rocks. In this research, an attempt has been made to investigate the plagioclase crystals in the leucosome section in the migmatites of North-Eastern Takab using the crystal size dispersion (CSD) technique, and by examining the resulting diagrams, the petrological processes and the nucleation rate of the crystals plagioclase should be expressed during melting and finally the formation of leucosomal parts. Materials and methods In the study of Ghareh naz migmatites, after taking digital photos of the leucosomal part, they were put together with Adobe Illustrator software for better coverage, and then all the plagioclase crystals were drawn and measured separately. Then the images were transferred to JMicroVision v1.2.7 software and the necessary measurements for all 4 locosome samples (7n, 6p, 6m, mh) including length, width, area, angle, location of the center of crystals (coordinates of X and Y points) in the environment of this software was done. It should be mentioned that considering that the studies are done on thin section images, so to eliminate the errors caused by this problem, all the software settings were entered based on the Higgins (1998) method. Then the obtained data were transferred to CSD Corrections 1.40 software and according to the information obtained from the frequency and size of plagioclase crystals, a natural semi-logarithmic diagram based on the method provided by Higgins (1998) for 4 leucosome samples of migmatite Ghareh naz was drawn separately. In these diagrams, the population density axis, Ln(n)(mm-4) is plotted against the size axis of the largest crystal dimension, (mm) equal to L. The unit of measurement for bulk density is mm-4 (Marsh, 1988; Higgins, 2006; Bindeman, 2003; Higgins ana Roberge, 2003, Higgins ana Roberge, 2007; Gulda, 2006; Higgins and Chandrasekharam, 2007; Brugger and Hammer, 2010) and for crystal size is mm. Result Studies show that downward concavity in the direction of small crystal sizes indicates coarsening (Higgins ana Roberge, 2007; Vanderzwan et al., 2013) or, in other words, indicates the cessation of nucleation along with successive crystal growth (Lentz and Mcsween, 2000; Higgins ana Roberge, 2007; Vanderzwan et al., 2013). The amount of low concavity in some samples can be considered as an almost linear trend. The almost linear trend on the right side of some graphs indicates the successive growth and nucleation of crystals, the process of subtraction (crystal separation during subtractive crystallization) and crystal accumulation (Higgins, 2009). As can be seen in the diagrams, the very small break created in the crystal size scatter diagram indicates the accumulation or increase of large grains, or in other words, the sedimentation and separation of crystals (Lentz and Mcsween, 2000). In other words, the coarsening process in the studied migmatite locosome occurs when small grains in multiphase mixtures have a higher surface free energy per unit volume than large grains and for this reason, they are less stable (Higgins, 1998, Higgins, 1999). Discussion The scatter diagrams of the crystal size in the studied leucosomal samples show that the larger crystals (the end part of the curved diagram on the right) belong to a melt that cooled at greater depths or in a calmer environment. Nevertheless, the initial part of the diagram in the left side crystallized in more superficial areas and at a higher speed. Based on the studies conducted on the plagioclase crystals in the migmatite locosome, it was observed that the plagioclase crystals have a non-linear CSD trend, which indicates two stages of growth with different speeds for these crystals. In the initial stages of crystallization, plagioclase is in the form of coarse crystals with low number of spores, high gradient and high growth rate, and in the next stage, smaller plagioclase with high nucleation rate, low gradient and low growth rate are developed. Plagioclase crystals with their large number and relatively large size indicate their slow cooling and low nucleation.

Several important processes in the petrogenesis of granite are still debated due to a poor understanding of complex interactions between minerals during the melting and melt segregation processes. To promote an improved understanding of the mineral-melt relationships, we present a systematic petrographic and geochemical analysis for melanosome and leucosome samples from the Triassic Jindong migmatite, South China. Petrographic observations and zircon U-Pb geochronology indicate that the Jindong migmatite was formed through water-fluxed melting of the Early Paleozoic gneissic granite (437 ± 2 Ma) during the Triassic (238 ± 1 Ma), with the production of melt dominated by the breakdown of K-feldspar, plagioclase, and quartz. The Jindong leucosomes may be divided into lenticular and net-structured types. Muscovite, plagioclase, and K-feldspar in the net-structured leucosome show higher Rb and much lower Ba and Sr contents than those in the lenticular leucosome. This may be attributed to the elevation of Rb and decreasing Ba and Sr abundances in melts during the segregation process due to early fractional crystallization of K-feldspar and plagioclase. These leucosomes show negative correlation between εNd(t) and P2O5, reflecting increasing dissolution of low-εNd(t) apatite during the melting process. The continuous dissolution of apatite caused saturation of monazite and xenotime in melt, resulting in the growth of monazite and xenotime around apatite in the melanosome. This process led to a sharp decrease of Th, Y, and REE with increasing P2O5 in the leucosome samples. This complex interplay of accessory mineral reactions in the source impacts REE geochemistry and Nd isotope ratios of granites. As the granites worldwide exhibit similar compositional and isotopic patterns to the Jindong leucosomes, we suggest that both the melting and melt segregation processes strongly control the granitic melt compositions. [ABSTRACT FROM AUTHOR]

Migmatites and granitic-gneisses exhumed in Archean to Phanerozoic segments are former partially molten crustal roots, display typical domes structures ranging in size from kilometres to decakilometres, and are often interpreted as resulting from the development of diapiric or convective gravitational instabilities. In previous work (part I), we determined various regimes of gravity-driven segregation, by considering a thick continental crust heated from below and containing melt related heterogeneities. These heterogeneities, represented by inclusions of distinct densities and viscosities with respect to the ambient partially molten material, can be entrained into convection cells (in the 'suspension' and 'layering' regimes) and/or accumulate as clusters (in the 'layering' and 'diapirism' regimes). Here we further investigate the specific conditions that allow for the formation and preservation of domes resulting from diapirism at the top of convective cells. We show that both the cessation of basal heating and the freezing of the buoyant inclusions density favour their stacking and preservation at ca. 15 km depth, within about 10 Myr. The buoyant inclusions form domes, 5–20 km in size, that also record several convective cycles at velocities ranging from 0.5–4 cm yr−1. 3-D models demonstrate their radial geometrical nature. The influence of the size and concentration of the inclusions is also assessed, complementing the characteristics of crustal heterogeneity in driving its differentiation and the formation of migmatite domes. [ABSTRACT FROM AUTHOR]

One of the most used geophysical tools for characterization of the near surface is electrical resistivity tomography (ERT). The 2D resistivity survey was conducted along ten (10) buildings in Federal University Lokoja (Fulokoja), Adonkolo Campus. Dipole-dipole electrode configuration was conducted for data collection. Enhancing of measured field and calculated apparent resistivity details/data and interpretation of Electrical Resistivity Tomography (ERT) were generated using RES2DINV software which reveal a change in soil resistivity and type. From the result it is observed that the soil is made up of weathered migmatite rock which exist in layers of low resistivity, intermediate resistivity and high resistivity zone. The low resistivity zone is the uncompacted soil which provide an unstable foundation for the building while intermediate and high resistivity zone representing the fairly compacted to compacted soil which provide stable foundations for the buildings. The presence of clayey materials and oversaturated soil around the central part of the campus is the cause of the uneven ground settlement underneath these buildings causing the apparent cracks on some superstructures. The foundation of structures and buildings should be strengthened by mixing of the soil with gravels to enhance stability. Proper electrical resistivity survey and soil penetration test on the soil should be carried out prior to construction of buildings in the campus. [ABSTRACT FROM AUTHOR]

The titanium (Ti) concentrations in zircon and quartz and corresponding thermometers have been regarded as powerful monitors that constrain petrogenetically meaningful temperature conditions of crystallization and metamorphism. The precise measurement of trace elements by electron probe microanalyzer (EPMA) is quite challenging as their x‐ray intensities are only slightly higher than the Bremsstrahlung background, leading to significant errors while quantifying the elemental abundances (e.g., Ti‐in‐zircon). We present EPMA‐based protocols for analysing Ti concentrations in zircon and quartz by considering recent analytical and instrumental improvements. High counting times at peak and background positions, simultaneous acquisition of Ti in multiple (three) spectrometers and data processing using the non‐central chi2 test for risk determination in sub‐counting method were employed in Ti‐in‐zircon and Ti‐in‐quartz protocols. Applying these protocols to the Mongolian garnet, San Carlos olivine and NIST 610 glass standards yielded Ti concentrations of 0.60 ± 0.02 wt%, 18 ± 3 ppm and 437 ± 26 ppm (in ±2σ), respectively. The Ti concentrations obtained from these standards are consistent with those published based on high‐precision analytical methods. We use the existing Ti‐in‐zircon and Ti‐in‐quartz thermometers to understand the thermal evolution of various lithologies in the Sandmata Complex, Aravalli Craton (north‐western India). The investigated samples include garnet–biotite gneiss, migmatite gneiss, mafic granulite and Anjana granite. The Ti‐in‐zircon temperatures calculated from the patchy‐zoned zircon cores yield HT–UHT conditions (892–959°C) for garnetiferous granite gneiss, migmatite gneiss and mafic granulite, whereas the zircon overgrowths yield temperatures of 725–871°C. The homogeneous zircon cores from Anjana granite yield temperatures (914–984°C) comparable to zirconium saturation conditions (920–960°C), indicating zircon crystallization from "hot" granitic melt. The oscillatory overgrowths on the zircon core obtain variable temperature conditions for inner overgrowth (811–877°C) and outer overgrowth (714–782°C), suggesting the episodic growth of zircon grains from different magma pulses. Additionally, the application of pressure‐dependent Ti‐in‐quartz thermometry yields quartz recrystallization conditions for garnet–biotite gneiss (430–556°C), migmatite gneiss (423–593°C), mafic granulite (430–679°C) and Anjana Granite (444–533°C). The combination of Ti‐in‐zircon thermometry, Ti‐in‐quartz and conventional thermobarometry demonstrates cooling histories for various high‐grade metamorphic and magmatic rocks in the Sandmata Complex. Based on this study, we emphasize that trace element thermometers can decipher high‐temperature metamorphism, which is otherwise erased in conventional thermometers due to diffusional readjustments during long‐lasting near‐peak and post‐peak metamorphism. [ABSTRACT FROM AUTHOR]

Multicriteria decision analysis for groundwater potential mapping utilizing analytical hierarchical process of six hydrogeologic parameters including aquifer layer thickness, aquifer layer resistivity, overburden thickness, transverse resistance, transmissivity, and coefficient of anisotropy; in relation to groundwater yield was carried out in Ile Oluji, Southwestern Nigeria. The aim was to develop groundwater potential map using calculated groundwater potential index values (GWPIV). The obtained GWPIV which ranged from 1.53 (granite) - 3.50 (migmatite) with an average of 2.18 suggestive of moderate groundwater potential (90 % of the study area). The low potential zone (10 %) are observed sporadically in the central and northwestern parts. All the geological units recorded overlapping hydrogeologic properties. The longitudinal unit conductance recorded regional average of 0.219876 mhos. Therefore the protective capacity of groundwater system in the study area is weak, and relatively less-weaker in granite environment; and in northwestern and central parts. Nevertheless, the water table aquifer (accounts for 80%) and the fracture basement (constitutes 20%, frequently occurring in gneissic environment) are the water bearing units, with average overburden thickness in migmatite, granite, and gneiss 24.3 m, 24.5 m, and 27.9 m respectively. The average coefficient of anisotropy (1.12); hydraulic conductivity (0.37 m/d), transmissivity 6.86 m²/d (migmatite: 7.17 m²/d, granite: 7.14 m²/d, and gneiss: 6.02 m²/d). Hence gneissic offered both thick weathered layer and fractured aquifer. Empirical model for plot of formation factor and hydraulic conductivity in migmatite, granite, and gneiss, showed positive correlations in descending order as: granite (0.3778), migmatite (0.1057), and gneiss (0.0641). [ABSTRACT FROM AUTHOR]

In migmatitic environments the behaviour of the system is controlled by the generation and amount of the anatectic melt. Accordingly, migmatites typically show a genetic linkage between the tectonic deformation and melt migration. We investigated this relationship in Olkiluoto (SW Finland) and identified four phases of ductile deformation, which are distinguished by the multiple folding phases, ductile shear events and cross-cutting features associated with pegmatitic leucosomes and/or a specific type of diatexitic migmatite with feldspar megacrysts. U–Pb LA-MC-ICPMS data on zircon cores and rims from migmatites and cross-cutting pegmatites indicate two distinct metamorphic events associated with melt generation and migration at 1.87–1.84 Ga and 1.82–1.78 Ga. These two migmatitic events suggest that the orogenic evolution of the area was long-lasting and characterized by slow cooling. The structural data and the age constraints presented in this paper support the idea of similar tectonic evolution and metamorphic environment in SW Finland and central E Sweden.

The Zanjan-Takab complex is a metamorphic belt with NW-SE trend that includes gneiss, amphibolite and gneissic amphibolite, old metagranites, pelitic schists with migmatites and metaophiolites. Takab mafic migmatites, based on field evidence and partial melting degree, are divided into two main groups of metatexites with patchy, ophthalmitic, diktyonitic, agmatic, stromatic structures and diatexites with schollen, ptygmatic, folded, stictolithic, phlebetic, schliren, nebulitic structures. These migmatites consist of mesosome part with textures of porphyroblastic, xinoblastic, granoblastic and nematoblastic and main minerals plagioclase, hornblende, biotite, melanosome part with nematoblastic, xinoblastic, granoblastic and oriented textures and main minerals hornblende and plagioclase. The leucosome part is composed of granular, sympletic and myrmekitic textures and the main minerals are plagioclase, quartz, k-feldspare, titanite, hornblende and biotite. Investigating the shape of the crystal size scatter diagrams (CSD) shows the physical conditions and petrological processes are effective in the studied rocks. In order to investigate these processes, plagioclase crystals in 4 leucosome samples were quantitatively analyzed with the help of Jmicro vision and CSD Corrections software, and then the results obtained from the analysis of different leucosome samples were compared. The crystal size scatter diagrams of plagioclase crystals show two stages of growth with different speeds in the studied samples, so that the larger crystals (the end part of the curved diagram on the right) belong to a melt that is at greater depths or it cooled in a calmer environment. Nevertheless, the initial part of the diagram on the left side crystallized in more superficial areas and at a higher speed. [ABSTRACT FROM AUTHOR]

In the course of mining and processing of almost all petrographic varieties of rock raw materials for the production of building and materials, aggregates for road and railway construction, waste is generated. These are usually fine-grained fractions of these rocks that are difficult to manage and are deposited at dumps. The article presents and describes the results of the physical, chemical, and mineralogical properties of fine-grained waste from the production of amphibolite aggregate from Pilawa Gorna in Lower Silesia (S-W Poland). Such studies have not been carried out on this waste before. The tested waste is a very fine-grained dusty material (<0.100 mm) originating from the dedusting of the crushing and classification operations during the production of aggregates. Preliminary studies of the separation of the tested material using collector-less flotation and gravity separation are also presented. Detailed chemical analysis shows that most of the elements in the studied rock dust occur in abundance close to the average in the Earth's crust. The collector-free flotation of the investigated sample allows effective separation of graphite and the part of sulfide minerals Cu, Ni, and Mo. The presented results may be the basis for further research and development of the concept of their economic use. [ABSTRACT FROM AUTHOR]

We present zircon and titanite U-Pb ages from granulite-facies transtensional shear zones and a greenschist facies strike-slip shear zone in the Karkkila-Vihti area, West Uusimaa. The zircon rim and titanite ages of c. 1815−1820 Ma from the transtensional shear zones constrain the evolution of the orogenic deformation from compression dominated to syn-compressional lateral-escape within this part of the Fennoscandian shield while the zircon rim and titanite ages of 1790−1800 Ma give the timing of the late- to post-orogenic low-grade reactivation of the large-scale Somero-Karkkila fault zone. The new age data further constrain the timing of the changes in the crustal deformation style during orogenesis from i) compression-dominated to combined transpression - lateral stretching and escape, to ii) the late- to post-orogenic transition into retrograde conditions.

Taking the influence of lithological characteristics differences on the genesis of pores in migmatite reservoirs as the main line, the genesis and characteristics of pores were analyzed from the perspective of the relationship between rock fabric and grain deposition. (1) Based on hydrodynamic conditions, mineral assemblage and rock structure characteristics, and taking three endmembers of clastic particles, clay minerals and carbonate minerals for classification, the "sweet spots" in the Lucaogou Formation are mainly composed of tuffaceous sandy dolomite, tuffaceous feldspar detrital siltstone, tuffaceous dolomitic sandstone and tuffaceous dolomitic siltstone. The migmatites have mixed sources, and various types of migmatite layers can be superimposed on each other vertically to form facies marginal mixing. (2) Based on the spherical accumulation model, when the content of debris particles is lower than 52.4%, the porosity decreases with the increase of particle content. When the content of clastic particles reaches 52.4%, if the content of clastic particles[JP]continues to increase, large number of ntergranular pores will appear, and the porosity will increase rapidly, gradually evolving into a conventional sandstone reservoir. (3) According to the relationship between the three end components of clastic particles, clay minerals and carbonate minerals and the pore types, the pores of the migmatites in the Lucaogou Formation can be classified into three types including intergranular pore, intragranular dissolved pore and intercrystalline pore. The pores in tuffaceous sandy dolomites and tuffaceous feldspar detrital siltstones are mainly intergranular and intragranular dissolved ones supported by particles, while those in tuffaceous dolomitic sandstones and tuffaceous dolomitic siltstones are mainly intercrystalline ones. The development of high-quality migmatite reservoirs is mainly controlled by the content of clastic particle components, and the content of soluble clastic components and dissolution effect can improve the physical properties of the reservoirs.

Aluminosilicates (kyanite, sillimanite and andalusite) are useful pressure–temperature (P–T) indicators that can form in a range of rock types through different mineral reactions, including those that involve partial melting. However, the presence of xenocrystic or inherited grains may lead to spurious P–T interpretations. The morphologies, microtextural positions, cathodoluminescence responses and trace element compositions of migmatite-hosted kyanite from Eastern Bhutan were investigated to determine whether sub-solidus kyanite could be distinguished from kyanite that crystallised directly from partial melt, or from kyanite that grew peritectically during muscovite dehydration reactions. Morphology and cathodoluminescence response were found to be the most reliable petrogenetic indicators. Trace element abundances generally support petrographic evidence, but protolith bulk composition exerts a strong control over absolute element abundance in kyanite. Sample-normalised concentrations show distinctive differences between petrogenetic types, particularly for Mg, Ti, V, Cr, Mn, Fe and Ge. LA-ICP-MS element maps, particularly combined to show Cr/V, provide additional information about changing geochemical environments during kyanite growth. Most kyanite in the studied migmatitic leucosomes is of sub-solidus origin, with less widespread evidence for peritectic crystallisation. Where present, grain rims commonly crystallised directly from the melt; however, entire grains crystallised exclusively from melt are rare. The presence of kyanite in leucosomes does not, therefore, necessarily constrain the P–T conditions of melting, and the mechanism of growth should be determined before using kyanite as a P–T indicator. This finding has significant implications for the interpretation of kyanite-bearing migmatites as representing early stages of melting during Himalayan evolution. [ABSTRACT FROM AUTHOR]

This paper presents a detailed field characterization of boudinage in a high- strain zone several kilometers wide in Northern China to establish relationships between boudin types and rheological contrasts between different parts of migmatites during the migmatization process. This zone contains nearly all types of boudins: foliation boudins, block- torn boudins, pinch- and- swell structures, tapering boudins, object boudins, and modified boudins. These boudinage structures record the different stages of meltinvolved and solid- state deformation. The boudinage of migmatites is significantly controlled by the evolving rheological contrasts between the leucosome and melanosome. During the melting stage, the deformation and boudinage of rocks are controlled by the melt fraction. Migmatite strength progressively decreases with increasing melt fraction. The occurrence of melt- filled foliation boudins and melanosome block boudins suggests that the residuum and melanosome are more competent than the leucosome. During solid- state deformation after crystallization, the existence of recrystallized solid- state leucosomes and the intrusion of pegmatites cause the migmatite strength to increase. The relationship is reversed: the leucosome is much more competent than the melanosome. The type and geometry of boudins and pinch- and- swell structures are correlated to the fraction of leucosome in the migmatites. The mechanical strength and strain localization of migmatites after crystallization depend on the presence and volume fraction of the different mineral phases, as well as the mineral grain size. The type and geometry of boudins suggest that the effective viscosity of migmatite can be ranked, from high to low, as: quartz veins; coarse- grained, thick pegmatite; coarse- grained, diatexite migmatite; medium- grained leucosome; and fine- grained melanosome. While experiencing partial melting and migmatization, a rheologically homogeneous protolith is turned into two dominant lithologic domains: a competent diatexite migmatite domain and an incompetent melanosome migmatite domain. Spatially, with the increasing leucosome fraction in migmatites, the migmatite rheology of rock changes from homogeneous to heterogeneous and anisotropic, and then back to homogeneous. The strain distribution likewise changes from uniform to partitioned, and then back to uniform. This evolutionary process of strength and rheological properties of rocks during migmatization may promote strain localization at mid- crustal conditions. [ABSTRACT FROM AUTHOR]

Sequence identification and division is an important basis for oil and gas exploration research. In view of the complex sedimentary environment, based on the previous element logging correction lithology, through the combination of logging curve and lithology data, in this paper, two methods of maximum entropy spectrum analysis and wavelet transform are used to identify the logging curve and divide the interface, and the high-resolution sequence identification of migmatite in the study area was completed. Compared with AC and SP logging curves, the overall and local trend inflection points of INPEFA-GR curve can improve the accuracy of medium-term and short-term cycle interface identification; wavelet transform and time–frequency spectrum analysis of different scale factors can realize the identification and comparison of medium-term and short-term cycle interfaces. The results show that maximum entropy spectrum analysis is more suitable for determining the third-level and fourth-level sequence interfaces. Wavelet transform is more suitable for the division of fifth-level sequences. By comparing and adjusting the two methods, the lower Es3 of KL Oilfield in Laizhouwan Sag can be divided into 1 long-term base-level cycle, 3 medium-term base-level cycle and 8 short-term base-level cycle. This study has certain reference significance for the construction of sequence stratigraphic framework in migmatite area and helps to better describe the reservoir. [ABSTRACT FROM AUTHOR]

We present new U–Pb ages and Hf and O isotope data for zircon from I-, S- and A-type granites from both the western and eastern edges of the Delamerian Orogen in southeastern Australia. The I-type Tanunda Creek Gneiss contains zircon populations of 507 ± 4 and 492 ± 6 Ma inferred to reflect igneous and metamorphic ages, respectively. The I-type Palmer Granite yielded an age of 509 ± 3 Ma, and the Port Elliot S-type Granite has a magmatic age of 508 ± 7 Ma. Inherited zircon in these granites range from 1092 to 3343 Ma, probably derived from assimilation of Adelaide Group sediments. The Murray Bridge A-type Granite is 490 ± 2 Ma in age and lacks inherited zircon. In the Glenelg River Complex, an S-type migmatite from near Harrow contains a complex zircon population. It is most likely ~500 Ma in age and has inherited zircon of 550–700, 1000–1100 and 2437 Ma, hence matching those from the Kanmantoo Group. From this and detrital zircon ages, we infer that only the Kanmantoo Group extends across the Murray Basin into the Glenelg River Complex. The Wando Tonalite and Loftus Creek I-type granites yielded ages of 501 ± 2 and 486 ± 3 Ma, respectively. Zircon from the Dergholm Granite has suffered Pb loss, and the best age estimate for this granite is 488 ± 5 Ma. Combining all the granite data together, εHft and δ18O in the magmatic zircon range from 5.6 to −10.3 and from 5.8 to 8.1, respectively, and are well correlated. The zircon indicates the same temporal and compositional evolution of granitic petrogenesis across ~300 km of strike, reaffirming the notion that these terranes form part of the same orogen. Westward-directed subduction caused orogenic thickening, heating and increasing amounts of crustal contribution. This was followed by convective thinning of the thickened mantle lithosphere and a return to more primitive magmas lacking significant crustal contributions. It contrasts significantly with inferred granite petrogenesis and tectonic style in the younger Lachlan and New England Fold Belts further east that were not built upon extended cratonic lithosphere. [ABSTRACT FROM AUTHOR]

Abundant primary fluid and melt inclusions occur in zircons from a stromatic migmatite sample in the Chinese Sulu ultrahigh-pressure (UHP) metamorphic belt, reflecting an immiscible melt-fluid coexistence during the partial melting process. Raman analysis shows that the fluid inclusions include whewellite, highly disordered carbonaceous matter (CM), diamond, calcite, dawsonite, quartz, cristobalite, H2O-bearing silica glass, muscovite, chalcopyrite, molybdenite, pyrite/pyrrhotite, magnetite, hematite, rutile, CO2 and H2O. The inclusions were entrapped during the exhumation of the rock from UHP to granulite-facies metamorphic conditions. The presence of whewellite suggests that the primary fluids during the entrapment of the inclusions contained some kind of dicarboxylic compound. The highly disordered CM still includes aliphatic hydrocarbon species revealed by the C-H stretching bands at ~2886 and ~2941 cm−1, and a subsidiary band at 1250 cm−1 on the low-frequency side of the D band at 1350 cm−1, indicating that it was derived from incomplete carbonization of an organic compound. The identification of whewellite as well as highly disordered CM in the fluid inclusions provides evidence that abiotic synthesis of organic compounds can happen at elevated pressures and temperatures where both melt and fluids are stable, and in which magnetite and sulphides may play a catalyzing role. [ABSTRACT FROM AUTHOR]

A contaminated inclusion is characteristic of deposition and mechanical mixing, in which diamond fragments from diamond paste are mixed with epoxy resin and debris from the polishing process is deposited in inclusion ([12]). Especially, nanometer diamonds in inclusion 4 are enclosed inside the C-Si-O and Zr-Si-O materials, and HRTEM images show that the interface between diamond and host amorphous materials is fully coupled and welded (Figs. Discussion Diamond origin Two diamond-bearing inclusions were exposed in the polished surface, leading to a reasonable suspicion that diamonds are from diamond paste in sample preparation. Several crucial lines of evidence support the indigenous origin of diamond and highly disordered CM, including: (1) the C-Si-O and Zr-Si-O materials, as well as vaterite and aragonite in our sample, are natural materials. Keywords: Ultrahigh-pressure metamorphism; vaterite; diamond; fluid inclusion; migmatite; Dabie-Sulu orogenic belt EN Ultrahigh-pressure metamorphism vaterite diamond fluid inclusion migmatite Dabie-Sulu orogenic belt 1410 1424 15 07/05/22 20220701 NES 220701 Introduction Vaterite, as one of the three polymorphs of CaCO SB 3 sb (vaterite, calcite, and aragonite), is a rare mineral in natural rocks, but biogenic vaterite is remarkably widespread, occurring in human calculi ([37]), pearls ([52]), fish otoliths ([48]), etc. [Extracted from the article]

The aim of this study is to determine the variation of soil-gas radon concentrations from different rock formations in Ogbomoso, southwestern Nigeria. The radon concentrations at different five geological domains in Ogbomoso are determined with respect to depth. The measurements varied from the surface (0 cm) to 100 cm depth, with an interval of 20 cm. At all the geological domains (Porphyroclastic, Granite, Quartzite, Migmatite and Banded gneiss), radon has its minimum emission over migmatite at 0 cm, while its maximum emissions occured over granite and banded gneiss at 80 cm. The overall soil-gas radon concentrations in Ogbomoso varied from 0.06 to 26.5 kBq/m3, which is within the natural limit of 0.4 to 40 kBq/m3 based on the International Commission on Radiological Protection's recommendation. An F-ratio of 6.989 and a p-value of 0.001 were obtained for the first inferential hypothesis, while an F-ratio of 2.489 and a p-value of 0.076 were obtained for the second inferential hypothesis using ANOVA test. The post hoc (using Tukey HSD and Duncan) tests revealed that at 60 + cm, depth controls the level of radon concentrations being emanated from the subsurface. The pollution index in Ogbomoso is of level 1 at 80 cm and level 0 (safe limit) at other depths. In conclusion, the soil-gas radon emission depends on the local geology and lithological sequences (depths). Cracks that could act as passage for indoor radon at the floors of the buildings around the polluted zones should be avoided in order to have a sustainable city. [ABSTRACT FROM AUTHOR]

In migmatitic environments the behaviour of the system is controlled by the generation and amount of the anatectic melt. Accordingly, migmatites typically show a genetic linkage between the tectonic deformation and melt migration. We investigated this relationship in Olkiluoto (SW Finland) and identified four phases of ductile deformation, which are distinguished by the multiple folding phases, ductile shear events and cross-cutting features associated with pegmatitic leucosomes and/or a specific type of diatexitic migmatite with feldspar megacrysts. U-Pb LA-MC-ICPMS data on zircon cores and rims from migmatites and cross-cutting pegmatites indicate two distinct metamorphic events associated with melt generation and migration at 1.87-1.84 Ga and 1.82-1.78 Ga. These two migmatitic events suggest that the orogenic evolution of the area was long-lasting and characterized by slow cooling. The structural data and the age constraints presented in this paper support the idea of similar tectonic evolution and metamorphic environment in SW Finland and central E Sweden. [ABSTRACT FROM AUTHOR]

This study presents new petrological and fluid inclusion datasets of migmatites from the Karakorum Shear Zone, Ladakh, India, to know the P–T–fluid evolution of mineral assemblages and the associated tectonic history. The presence of plagioclase, quartz, and biotite inclusions in the coarse-grained poikiloblastic pargasite (amphibole) is indicative of the hydration reaction b t + p l + qtz + H 2 O = prg + melt , which is consistent with diffusive H2O-fluxed melting. Phase equilibria calculations are consistent with migmatization at 0.85–1.02 GPa and 640–670 °C in water-saturated conditions (i.e., 0.7 wt% H2O). The monophase primary and secondary carbonic fluid inclusions present in quartz display eutectic temperatures between − 56.9 and − 56.6 °C, suggesting pure CO2 composition. The isochores of primary CO2 inclusions reveal that the post-peak migmatization event took place between 0.59–0.55 GPa and 550–670 °C, which occurred due to density reversal during the re-equilibration. The fluid inclusion microtextures preserved the signature of isothermal decompression, which is well corroborated with mineralogical P–T calculations. Primary inclusions were preserved initially as carbonic-aqueous fluids; however, the H2O phase diffused out subsequently and dissolved with the melt such that the inclusions became pure carbonic. Fluid infiltration along the Karakorum Shear Zone played a critical role in forming migmatites. The P–T path derived from thermodynamic modeling and fluid inclusion data are consistent with isothermal decompression during exhumation following crustal thickening of the Asian continent (or South Tibaten Crust) between 18 and 15 Ma. [ABSTRACT FROM AUTHOR]

New data include additional garnet Sm-Nd ages, garnet Lu-Hf ages, new zircon U-Pb ages, and zircon and garnet trace element concentrations. Keywords: Zircon U-Pb; garnet Sm-Nd; migmatite; lower crust; rates of intrusion; duration of metamorphism EN Zircon U-Pb garnet Sm-Nd migmatite lower crust rates of intrusion duration of metamorphism 1116 1132 17 06/01/22 20220601 NES 220601 Introduction and geologic setting Zircon and garnet isotopic dates are widely used for understanding local and orogenic scale processes in magmatic arcs, lower-crustal rocks, and high-grade metamorphic terrains. Garnet occurrences are classified according to [77]: Type 1 garnet occurs in discrete garnet reaction zones, Type 2 garnet forms planar to sub-planar arrays as selvages to trondhjemite veins, and Type 3 garnet are porphyroblasts in diffuse leucosomes. The young zircon ages, rejected from the weighted means for the host and garnet reaction zone overlap with garnet Sm-Nd ages for this sample and others from the Malaspina Pluton ([77]), and metamorphic zircon and titanite in the region ([66]). [Extracted from the article]

We investigate numerically some thermomechanical conditions for the development of crustal scale diapirism and convection in a heterogeneous continental crust independently from the action of regional tectonics. Here, we consider a hot crust, with unmolten and partially molten domains of specific temperature and strain-rate dependent power-law rheologies. We take advantage of the volume of fluid (VOF) method to capture the coalescence and separation of deformable inclusions in the partially molten domain. The inclusions, of several hundred metres in size, are more or less dense and viscous with respect to the ambient medium (they also behave with a power-law rheology). We restrict our study to a 20 Myr time scale, during which gravitational dynamics may dominate over lateral tectonics and lithospheric thermal re-equilibration. The motion of these inclusions during the development of gravitational instabilities displays distinct flow regimes that depend on two Rayleigh numbers denoted Ra UM and RaPM , for the unmolten and partially molten rock properties, respectively. A 'suspension' regime occurs at high Ra UM and high Ra PM, in which most of the light compositional heterogeneities remain entrained in the convective cells. In contrast at low Ra UM and high Ra PM, a 'layering' regime is characterized by merging of the light inclusions as floating clusters below the rigid upper crustal lid. This regime occurs in association with a sharp viscosity gradient at upper-to-middle crust transitional depths. In these two regimes, the dense inclusions accumulate at the bottom of the partially molten zone. Finally at moderate Ra PM, a 'diapiric' regime reflects the segregation of the heavy and the light inclusions, respectively downward and upward, without global convection. These numerical experiments lead to a first order evaluation of the physical parameters required for the segregation of deformable inclusions of variable densities and convection, in a partially molten crust, and provide insights on the conditions for the development of migmatite domes. Geological data indicate that these processes likely occur in a large number of settings from Archean to Phanerozoic times, and contribute to the differentiation of the continental crust. [ABSTRACT FROM AUTHOR]

The shale in the upper part of the 4th member of Paleogene Shahejie Formation in the Dongying Sag of Bohai Bay Basin can be divided into two lithology types: calcareous mudstone and argillaceous limestone. The differences of organic matter abundance, oil-bearing properties, reservoir properties and movable shale oil in the different lithologies were investigated using X-ray diffraction, microscopic observation, geochemical analysis, porosity tests and mercury injection. The calcareous mudstone has relatively higher organic matter abundance and better oil-bearing properties than the calcareous mudstone. The calcareous mudstone has relatively higher porosity, but the pore throats are generally smaller, while the argillaceous limestone porosity is relatively lower with more large pore throats. The shale oil mobility in the calcareous mudstone and argillaceous limestone was compared using the oil saturation index, mineral adsorption capacity for crude oil and clay mineral transformation degree. The shale oil in the argillaceous limestone has better mobility than the shale oil in the calcareous mudstone.

This brief note presents geochemical data from rock samples from the Cabo Ortegal Complex (NW Spain). The samples belong to acid lithologies within the mainly basic to intermediate granulite unit that have been poorly investigated so far. For this communication, five samples of the migmatites and an amphibolitic enclave within them have been analysed. The whole-rock major and trace-element analyses were accomplished by means of Q-ICPMS. The dataset provides new and useful information relevant to the origin of the acid migmatites and can be used in addition to information from neighbouring lithologies to enhance understanding of the geological evolution of the Western Variscan Belt.

This study combines field observations, mineral and whole-rock geochemistry, phase equilibrium modeling, and U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon geochronology to investigate sillimanite-bearing felsic migmatites exposed on Ledge Mountain in the central Adirondack Highlands (New York, USA), part of an extensive belt of mid-crustal rocks comprising the hinterland of the Mesoproterozoic Grenville orogen. Phase equilibrium modeling suggests minimum peak metamorphic conditions of 960-1025 °C and 11-12.5 kbar during the Ottawan orogeny--significantly higher pressure-temperature conditions than previously determined--followed by a period of near-isothermal decompression, then isobaric cooling. Petrography reveals abundant melt-related microstructures, and pseudosection models show the presence of at least ~15%-30% melt during buoyancy-driven exhumation and decompression. New zircon data document late Ottawan (re)crystallization at ca. 1047 ± 5 to 1035 ± 2 Ma following ultrahigh-temperature (UHT) metamorphism and anatexis on the retrograde cooling path. Inherited zircon cores give a mean date of 1136 ± 5 Ma, which suggests derivation of these felsic granulites by partial melting of older igneous rocks. The ferroan, anhydrous character of the granulites is similar to that of the ca. 1050 Ma Lyon Mountain Granite and consistent with origin in a late- to post-Ottawan extensional environment. We present a model for development of a late Ottawan migmatitic gneiss dome in the central Adirondacks that exhumed deep crustal rocks including the Snowy Mountain and Oregon anorthosite massifs with UHT Ledge Mountain migmatites. Recognition of deep crustal meta-plutonic rocks recording UHT metamorphism in a migmatite gneiss dome has significant implications for crustal behavior in this formerly thickened orogen. [ABSTRACT FROM AUTHOR]

The high‐grade Higher Himalayan Crystallines (HHC), located between the South Tibetan Detachment System and Main Central Thrust in the collision zone between the Indo‐Australian and Eurasian plates, have been subject to at least four significant phases of deformation and metamorphism. The earliest of those significantly predates the Cenozoic continent‐continent collision, but has been difficult to date isotopically because of later overprinting. Migmatitic paragneiss from the Badrinath Formation in the Dhauliganga Valley, northern Uttarakhand, some of the highest‐grade rocks in the HHC, preserves direct evidence of mid‐Ordovician metamorphism in the form of 465.8 ± 6.4 Ma zircon overgrowths with extremely low Th/U (0.0038–0.0074). The overgrowths have formed on ca. 2.63–0.71 Ga detrital zircon cores and are themselves overgrown by two generations of Miocene metamorphic zircon with mean Pb/U ages of ca. 21.5 and 18.2 Ma. Monazite from the same sample has a mean Pb/Th age of 19.4 ± 0.2 Ma. The oxygen isotopic compositions of the monazite (δ18O: 7.69 ± 0.08‰) and youngest zircon overgrowths (δ18O: 7.95 ± 0.12, 8.24 ± 0.09‰) are consistent with mineral growth in a metasediment, but either of the two minerals did not grow in isotopic equilibrium with each other, or the original composition of the monazite has not been preserved. If the quartz (δ18O: 13.29 ± 0.11‰) equilibrated with the youngest zircon and its composition has been preserved, then the last episode of zircon growth took place at low temperature, ca. 420°C, after the migmatization. The protolith of the Badrinath migmatite was a Neoproterozoic or Early Palaeozoic metasediment partially melted (and probably migmatized) in the Middle Ordovician. The strong planar foliation currently present in the migmatite is probably the result of mid‐crustal extrusional channel flow and HT decompressional partial melting in the Miocene. [ABSTRACT FROM AUTHOR]

Several outcrops of migmatitic rocks (metatexite to diatexite) developed in the northern part of the Sanandaj-Sirjan zone (Hamedan, Touyserkan and Boroujerd). Two types of inherited zircons (2590 to 190 Ma) and metamorphic zircons (180 to 160 Ma) are found in the mesosome of migmatites. As the cathodoluminescence images display, inherited zircons are euhedral to subhedral with oscillatory zoning, and are jagged their margins in some cases. Metamorphic zircons as thick form grains are characterized by the lack of magmatic zoning and the presence of ghost texture, growing on the margins of the inherited zircons as a thin sheath. In some cases, metamorphic zircons are found as single crystals without any inherited nuclei. As the structural evidence suggests the process of recrystallization formed metamorphic zircons and their elements were moved under sub-solidus conditions. During migmatization, on one hand, the presence of fluid phase due to partial melting, gave rise to the formation of metamorphic zircons showing oscillating zoning and on the other hand, it has precluded the deformation due to shearing in the internal structure of these phases. Metamorphic zircons, belonging to 180 Ma, and younger are possibly nucleated through the Jurassic period thermaldynamic metamorphism. [ABSTRACT FROM AUTHOR]

We present zircon and titanite U-Pb ages from granulite-facies transtensional shear zones and a greenschist facies strike-slip shear zone in the Karkkila-Vihti area, West Uusimaa. The zircon rim and titanite ages of c. 1815-1820 Ma from the transtensional shear zones constrain the evolution of the orogenic deformation from compression-dominated to syn-compressional lateral-escape within this part of the Fennoscandian shield while the zircon rim and titanite ages of 1790-1800 Ma give the timing of the late- to post-orogenic low-grade reactivation of the large-scale Somero-Karkkila fault zone. The new age data further constrain the timing of the changes in the crustal deformation style during orogenesis from i) compression-dominated to combined transpression - lateral stretching and escape, to ii) the late- to post-orogenic transition into retrograde conditions. [ABSTRACT FROM AUTHOR]

Determination of the potential reactivity of slow-reacting aggregates has been an openly debated subject worldwide for decades, and it remains ongoing. The province of Buenos Aires is the main producer of concrete aggregates in Argentina, and many quarries exploit migmatites and granites affected by deformation processes. Therefore, it is important to determine their potential behavior in concrete as they can cause alkali–silica reactions. The objective of this study is to determine the potential reactivity of aggregate samples from seven quarries of this sector by different methods and evaluate their performance. Petrographic studies were carried out according to the Instituto Argentino de Racionalización de Materiales (Argentine Normalization and Certification Institute; IRAM) 1649 standard, and different microstructural characteristics of quartz were quantified. The potential reactivity of the aggregates was evaluated by three expansion test methods, namely, the accelerated mortar-bar test (AMBT), the concrete prism test at 38 °C (CPT), and the accelerated concrete prism test at 60 °C (ACPT). The content of microcrystalline quartz (grain size < 60 μm) was found to correlate very well with the expansion measured in the AMBT and CPT when the limits and testing time of the IRAM standards were adopted. However, no correlation was found with the ACPT, and the results of this test were contradictory to those of the AMBT and CPT. Based on these results, a limit of 5 vol% of microcrystalline quartz appears to be adequate to differentiate reactive from non-reactive behaviors in the rocks studied. [ABSTRACT FROM AUTHOR]

The soda granite (~Paleoproterozoic) of the Singhbhum Craton (SC) of eastern India occurs along the entire stretch of the Singhbhum Shear Zone (SSZ; or Copper Belt Thrust Zone). The SSZ (marking a thrust contact between the adjacent North Singhbhum mobile belt and SC) serves as the important locale to host apatite‐magnetite, copper sulphide, and uraniferous mineralization. Typical field occurrence of soda granite is either as tongues (or patches) within a shear zone or as lit‐per‐lit style injections into surrounding country rocks which are generally highly sheared and mylonitized. Experimental studies on granite bodies can potentially throw light on their mineralogical and petrogenetic aspects; however, these studies are hitherto unreported in case of soda granites for almost the last 60 years. In this view, during the present research, experimental studies on soda granites have been carried out and these decipher the nature of the stability relationship of K‐feldspar (and transgression to more disordered anorthoclase), amphibole (both Ca‐amphibole and Fe–Mg–Mn amphibole and breaking down of Ca‐amphibole to Fe–Mg–Mn amphibole + non‐quad pyroxene + quartz at an appropriate temperature), biotite, muscovite, and albite (high albite‐ low albite displacive transformation). Whole‐rock chemistry (deduced from homogenized glass compositions) indicates its peraluminous, S‐type nature with an affinity towards Caledonian post‐collisional plutons. Characteristic geochemical plots suggest a pelitic source material for melting (and subsequent internal differentiation of the melt) and this has given rise to both migmatite as well as patchy soda granite exposures in the field. It is suggested that partial melting of mainly metapelitic (and minor mafic magmatic rocks) source (belonging to Singhbhum Series) gave rise to soda granites in this region. [ABSTRACT FROM AUTHOR]

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The heterogeneous, peraluminous Särkilahti garnet-cordierite leucogranite occupies ~ 75 km2 area in Svecofennian granulite-grade terrain of SE Finland. Country rocks are metasedimentary garnet-cordierite-biotite migmatites with some orthopyroxenegarnet paragneisses and orthopyroxene metatonalites. The leucogranite represents the exhumed upper portion of an extensive horizontal magma layer in the crust. Regional scale heat flow (initiated by energy input from the mantle) caused the formation of this magma layer and it also gave rise to granulite-grade migmatization (formation of in-situ leucosomes) in the above country rocks by heat conduction. When the magma layer slowly rose, country rocks at its upper limit were melted and partly merged in the magma. Within the magma layer, lighter granitic melt ascended as a consequence of the residue sinking. Late-stage crystallization products of the layer resulted in cross-cutting granite dykes in the above migmatites. U–Pb ages on monazite for the Särkilahti leucogranite samples are 1.79–1.78 Ga. The age slightly postdates the culmination of the regional metamorphism (1.84–1.80 Ga). As the leucogranite (magma layer) represents the lowest horizontal rock unit, it has – during crustal exhumation – crystallized slightly after the peak of the regional metamorphism.

The northern extent of the Scandinavian Caledonides includes the Skibotn Nappe Complex of still debated structural position. This paper is focused on part of this complex and presents new U–Th–total Pb monazite dating results for the migmatitic gneiss of the Kåfjord Nappe. The rocks show mineral assemblage of garnet + plagioclase + biotite + white mica + kyanite + rutile ± K-feldspar ± sillimanite. Thermodynamic modelling suggests that garnet was stable at P–T conditions of ca. 680–720 °C and 8–10 kbars in the stability field of kyanite and the rocks underwent partial melting during exhumation following a clockwise P–T path. This episode is dated to 444 ± 12 Ma using chemical Th–U–total Pb dating of the Y-depleted monazite core. Second episode highlighted by growth of secondary white mica resulted from subsequent overprint in amphibolite and greenschist facies. Fluid assisted growth of the Y-enriched monazite rim at 419 ± 8 Ma marks the timing of the nappe emplacement. Age of migmatization and thrusting in the Kåfjord Nappe is similar to the Kalak Nappe Complex, and other units of the Middle Allochthon to the south. Nevertheless, the obtained results do not allow for unambiguous definition of the tectonostratigraphic position of the Skibotn Nappe Complex.

The southern basement of the Cuddapah Basin comprises the Dharwar Batholith and greenstone belt complex. Granitoids of the batholith exhibit extensive variation in terms of geomorphology, age, mineralogy, and micro/meso scale structures. The eastern part of Dharwar Craton along 13°50′ to 14°8′N latitude and 78°45′ to 79°05′E longitude was studied to enlighten the rheological influence on crustal evolution. Frequent occurrences of migmatites of restricted dimension are observed in the south of 14°10′N latitude. The granite‐migmatite contacts are not sharp in general. Different types of migmatite complex and their relationships with granitoids as well as older country rocks represent an exhumed segment of the crustal catazone. The widespread group of migmatitic rocks are classified in a composite manner on the basis of morphology and structure. Furthermore, genetic implication vis‐a‐vis anatexis history is also evaluated. Static and dynamic modes of migmatites are recognized with reference to geothermal gradient and tectonics. Based on the degree of anatexis, two categories of migmatites are identified in the field, that is, metatexites and diatexites. In addition, metatexites are classified into four sub‐types (viz, patch, dilatant, net, and stromatic) and diatexites are also sub‐divided into two categories (viz, schollen or raft and schlieren). The hybrid nature of migmatitic rocks with both metamorphic and igneous characteristics are used to analyse pre‐ and post‐anatectic events. The preserved evidences of partial melting are marked as leucocratic patches. In situ stagnation of the melt or subsequent separation from the remaining solid provides different morphology of static mode. Importance of dihedral angle at solid–liquid contacts is also considered in the present context to describe the grain boundary penetration by partial melt. Folds, veins, and boudins of different styles and generations played significant role in dynamic mode migmatitization. The syn‐ and post‐metamorphic deformation events and granite melt generation from migmatites are schematically defined. Spatial and temporal relationships of schist‐gneiss‐migmatites of both static as well as dynamic mode reveal initiation of the crustal development by vertical accretion of ultramafic‐mafic lava and TTG. Cyclic partial remelting of the metabasic lava and TTG and underplating led to development of the lithospheric plate. Later upwelling material at convergent plate and associated heat transfer led to generation of granitic magma. The established prograde and retrograde cycle of metamorphism were possibly interrupted by crustal reworking events. This study confirms about the crustal catazone segment (with >15 km depth and >500°C) in which physical processes control generation, segregation, ascent, and emplacement of juvenile granite from migmatites. [ABSTRACT FROM AUTHOR]

The gamma dose rate exposure levels from different brands of building materials at commercial distribution stores/shops in two major cities in Ondo State, Nigeria, were measured using a well calibrated Inspector 1000 scintillator detector. The results showed that the different brands of building materials which are "Corrugated iron sheet, Aluminum roofing sheets, Conduit pipes, Paints, Cement, PVC pipes, Wash hand basin, Bath tub, Water closet, Kitchen zinc, Asbestos, Floor tiles, Wall tiles, Bullet proof door, Binding wire, rings and rods, Red bricks, Galvanized pipes, Copper pipes, Water tanks" contributed excess annual effective doses of 0.332 mSv/y and 0.311mSv/y to store keepers in Ikare Akoko and Akure cities respectively. The indoor and outdoor annual effective dose of each of the investigated two cities are correlated using simple linear regression equations. The results of the modeling and experiment show that annual effective dose received by the occupants of these shops/stores was about 12 % higher than what could be received in a typical natural radiation environment in the two cities because the building materials acts as a source of radiation indoor. The research indicated that the typical habit of using poorly ventilated and confined space as stores/shops by the sales men might subject them to internal exposure through inhalation of radon gas and its short-lived decay products. Implementation of the developed equations would definitely promote rapid determination of outdoor annual effective dose through indoor annual effective dose and ultimately save time and other valuable resources. [ABSTRACT FROM AUTHOR]

In the Southern Ribeira Belt (Brazil), the Itatins Complex, composed of ortho- and para-derived migmatites record granulite facies metamorphism. Our work focuses on the ortho-derived migmatite, which displays features indicative of partial melting ranging from in-situ melting (cm-thick lenses and veins) to accumulations of melt as leucosomes and patches of diatexite. The unit comprises a biotite felsic granulite (metagranodiorite) with a residual neosome and a leucocratic neosome, generally referred to as leucosome. Phase equilibria modelling using a modified bulk composition from the geochemical standard JG-1 (granodiorite) was carried out to evaluate whether a protolith of granodiorite bulk composition could produce the mineral assemblages observed in the residual neosome and the compositions of melt and residue produced by the partial melting. Isopleth thermobarometry of plagioclase, biotite and orthopyroxene points to P-T conditions of 0.7–1.0 GPa and 845–872 ºC. The modified granodiorite bulk composition generated just 10 mol % melt at these conditions, far lower than the amount estimated from outcrops (around 32 %). A T-XH2O pseudosection shows that increasing H2O content enhances the fertility of the bulk composition and it can become capable of producing melt volumes similar to that observed in outcrop. The melt compositions determined for partial melting of the modified granodiorite bulk composition in open- and closed-systems using THERMOCALC are granitic, and peraluminous. The melts have SiO2 contents between 52.02 mol % and 77.27 mol. % and show XFe values of 0.68 and 0.86. In K2O vs. Na2O+CaO, K2O vs. XFe and K2O-(FeO+MgO)-(Na2O+CaO) space natural samples (5 from the residual neosome and 2 from leucosome) from the Itatins Complex plot in the direction of the trends for melt and residue compositions obtained from modelling of the modified granodiorite bulk composition. The differences between modeled compositions and real rocks are interpreted to result from the interaction of melt with its residual counterpart. Chondrite normalized REE patterns from the residual neosome shows considerably greater depletion of HREE than geochemical standard JG-1 (granodiorite), and the two analyzed leucosomes show lower HREE contents. Zircon rims have REE patterns interpreted to indicate metamorphic recrystallization. U-Pb zircon Concordia ages indicate that the protolith formed during the Paleoproterozoic (2137 Ma) but that metamorphic recrystallization is Neoproterozoic (between 632 and 601 Ma). The metamorphic age pre-dates the intense granitic magmatism that affected the Southern Ribeira Belt between 600 and 570 Ma. [ABSTRACT FROM AUTHOR]

Lithological characterization and structural assessments of basement rocks around Guga, Katsina State was carried out to understand their geologic evolution and deformational history better. Field and petrographic studies were utilized in characterizing macrostructural, textural, and mineralogical components. Migmatite, banded and augen gneisses, schist, quartzite, and granite constitute the major lithologic units in the study area. Migmatite and the closely related banded gneiss are recognized as igneous-derived metamorphic rocks of Eburnean to early Pan African. In contrast, the augen gneisses are metamorphosed analogues of earlier banded gneiss that were intensely deformed within a ductile shear zone during the middle stages of the Pan African. Similarly, the schist and interbedded quartzite were emplaced during this period, subsequently forming part of the Malumfashi supracrustal cover, related to simple ensialic graben-like structural development. The granitic intrusions represent the youngest rock units in the mapped area, resulting from the magmatic activity of the Pan-African orogeny. Structural analysis suggests the mapped area was affected by two-phase deformation events (D1 and D2). The D1 deformation represents a regional, fabric-forming compressional event, while D2 is a localized deformational event associated with the development of a local shear zone linked to the Kalangai fault system (KFS). [ABSTRACT FROM AUTHOR]

To understand the crustal growth of the Qinling orogenic belt and the Mesozoic continental interaction between the North China and Yangtze blocks, it is critical to study the South Qinling accretionary complex belt, which is an important part of the Qinling orogen. Based on detailed zircon U–Pb geochronology and Hf isotopic compositional analyses of the Madao complex, this study presents constraints on the migmatization and tectonic evolution of the South Qinling orogenic belt during the Mesozoic. Zircons from leucosome samples of migmatites were found to have weak oscillatory zoning, and one sample yielded a weighted mean age that reflects the time at which the regional tectono‐thermal event initiated the anatexis (210–217 ± 2 Ma). The Hf isotopic compositions indicate that the Madao migmatites were derived from the ancient middle–Late Palaeoproterozoic crust. Zircons from mesosome samples of the migmatites that varied in age from the Palaeozoic to Neoproterozoic exhibited core‐rim textures with magmatic cores (256–1,329 Ma), indicating that they were derived from multiple sources with sedimentary protoliths. Of the 55 analysis spots on the overgrowth rims that yielded 206Pb/238U ages of 200–233 Ma, 40 analyses yielded a weighted age of 211.5 ± 1.0 Ma, indicating the time of anatexis due to the regional tectono‐thermal event. Combined with previously reported Mesozoic data from the South Qinling belt, these results suggest that the migmatites were probably controlled by post‐orogenic extension driven by Mesozoic orogenesis and a prolonged melting episode (from ~200 to 233 Ma). This study reinforces the interpretation that the continental crust in the South Qinling belt may have experienced complex interactions with asthenospheric mantle material during the Mesozoic. [ABSTRACT FROM AUTHOR]

Abstract As seismic data from the lower crust becomes more readily available, it is important to link seismic properties to the ongoing processes within lower crustal evolution. This includes high temperature, pre‐ and post‐migmatization solid state deformation as well as melt‐present deformation. We selected two tonalitic migmatites with variable former melt content (one metatexite and one diatexite) from the lower crustal Daqingshan area, northern North China Craton to assess the link between seismic properties and rock structure and rheology. Field observation along with microstructural features suggest that the characteristics of hornblende and plagioclase within the residuum of the metatexite can be used to derive information on the pre‐melt deformation. Residuum's plagioclase CPO (crystallographic preferred orientations) is consistent with high temperature dislocation creep as the main deformation mechanism; similarly, hornblende shows a strong CPO related to dislocation creep. During syn‐melt (melt present) conditions, phenocrysts of plagioclase in the metatexite's neosome and K‐feldspar and peritectic hornblende in the diatexite's neosome are present. The rheology of the rock was dominated by melt; hence is inferred to follow Newtonian flow. After melt crystallization deformation is minor but again dominated by dislocation creep. The seismic properties (seismic velocity, anisotropy, Vp/Vs ratio, etc.) for pre‐ and post‐melt have similar values expected values for solid mafic rocks, whilst the syn‐melt seismic velocities are generally lower and Vp/Vs ratios and seismic anisotropies are higher.

The Swartoup and Polisiehoek plutons in the Swartoup Hills (South Africa) formed during an episode of significant magma emplacement in the Mesoproterozoic Namaqua Sector of the Namaqua Metamorphic Province. They intruded into mid-crustal metasedimentary rocks of the metapelitic Koenap and mafic to carbonate-bearing Bysteek Formations during and shortly after the ∼1,200–1,220 Ma regional metamorphic peak that reached ultrahigh temperatures. Subsequent to pluton emplacement, the crust underwent regional high-temperature deformation during slow near-isobaric cooling. A further episode of pluton emplacement associated with fluid circulation truncated the first-order regional tectonic structures at ∼1,100 Ma. Based on their petrography, the Swartoup pluton is subdivided into leuco-granitoids with biotite as the sole mafic phase, pyroxene granitoids, and garnet-bearing granitoids, which may contain significant biotite. These subgroups display distinctive geochemical variations from one another, and from the Koenap Formation migmatites and the Polisiehoek granites, which are exposed nearby. Incompatible trace element distributions suggest that the Swartoup and Polisiehoek granitoids represent modified A-type granite magma, consistent with derivation from partial melting of quartzo-feldspathic crust. The magmas incorporated significant amounts of juvenile mantle-derived magma (εNd1200 of ∼−5, and LREE-depleted), but do not require older, early to late Paleoproterozoic crust. Particularly close to contacts to the calcic Bysteek Formation, localized contamination of the Swartoup granites by supracrustal carbonates is evident. A relatively pervasive alkali metasomatic effect is manifested strongly in the initial 87Sr/86Sr and LILE profiles of the Polisiehoek granites in particular, as well as in some of the Swartoup pyroxene granitoids, which could be either a symptom of CO2 metasomatism related to the Bysteek Formation carbonates, or to post-magmatic fluid metasomatism, perhaps linked to regional shearing. The comparison of our results with literature data suggests that similar sources, A-type granitic, Meso- to Paleoproterozoic crustal, and enriched mantle, have contributed, in locally differing proportions, to granites in most parts of the Namaqua Sector. Most likely, these plutons were generated during crustal and mantle melting in a long-lived hot continental back-arc environment.

Leucosome sizes in migmatites has been shown to follow power-law distribution, which is indicative of self-organized criticality governing accumulation and transport of partial melts in anatexis. In our measurements of leucosome widths in the Olkiluoto migmatite in western Finland, we found double power-law distributions in addition to single power-law distributions. We divided the double power-law behaviors into those with positive and negative kinks separating the two power-law regimes. We propose that double power-law distributions in migmatites result from impediments on the bottom-up self-organized criticality that melt transport processes commonly display. These impediments can be caused by some leucosomes solidifying before others, in which case the leucosomes were effectively formed in two distinct events or phases. We also consider the emergence of double power-laws as a result of melt accumulation in and sudden melt removal from conduits of a specific size.

In the Hamedan region, migmatitic rocks occur with various structures. In the Simin area (South Hamedan) stromatic and in the Darreh-Omar (Toyserkan) area ophtalmitic structures are abundant. Migmatites have been developed in a poly-metamorphic region. At least one regional metamorphism and two contact metamorphism by mafic and felsic intrusions occurred in the area. It seems that in the Darreh-Omar area contact metamorphism of mafic body leading to migmatization, But in the Simin area previous regional metamorphism and development of shear zones followed by contact metamorphism by felsic body. Therefore, in some areas, such as the Simin area, the migmatization may have occurred in more than one stage. These are consistent with recent geochronological studies of the Alvand plutonic body and surrounding metamorphic rocks. Index minerals of metapelites such as garnet (almandine), biotite (siderophyllite), staurolite, andalusite, sillimanite, kyanite, fibrolite, cordierite, plagioclase (andesine) and spinel (hercynite) are existing in these rocks. Field geology, petrographic and geochemical evidences suggest that different generations of staurolite, biotite and cordierite exist in metamorphic rocks of different grades in the Hamadan area. These minerals sometimes have been formed by progressive reactions and some other times from retrogressive reactions. A number of these phases have been formed at the peak of metamorphism and some others in later time. Based on thermometric cation-exchange method of garnet-biotite pair, using different calibrations, the obtained temperature using first-generation of biotites is 655 °C and temperature range of 529 °C for second-generation biotites. Cordierite-garnet thermometry indicates a temperature of 637 °C for related migmatitic rocks. In barometry with GPBQ system, calculated pressure for first-generation biotite is estimated to be about 3.9 kbar and for the second-generation biotite around 3.6 kbar.

Migmatite in the Sulu ultra‐highpressure (UHP) terrane is an ideal sample to provide information on anatexis during the exhumation of the deeply subducted continental crust. The studied migmatite is composed of the leucosome and melanosome with strongly ductile shear deformation. Petrographic observations clearly show an anatexis process, for example, cuspate and triangular K‐feldspars in triple junction and along grain boundaries, felsic veinlets and pockets mainly consisting of K‐feldspar + quartz + plagioclase ± biotite. The zircon grains of the migmatite have a core‐rim structure: the inherited magmatic core and the anatectic overgrowth rim. The inherited cores exhibit oscillatory zonings in the cathodoluminescence (CL) images and display strong heavy rare earth element (HREE) enrichment with clearly positive Ce and negative Eu anomalies. The inherited cores have an upper intercept U‐Pb age of 814 ± 45 Ma with εHf(t) values of −5.6 to ‐10.6 (mean = −8.5 ± 0.8, n = 16). Thus, protolith of the migmatite is a mid‐Neoproterozoic granitic rock. The overgrowth rims exhibit a typical anatexis genesis, that is, a bright homogeneous luminescence in the CL images, very low Th/U ratios (<0.02) with low U (<100 ppm) and Th (<1 ppm) contents, and lower total REE and Y contents with lower (Gd/Lu)N ratios and higher Hf/Y ratios than the inherited cores. They are Late Triassic with ages ranging from 211 to 234 Ma (mean = 223 ± 8 Ma), which, combined with previous studies on the Sulu UHP terrane, suggests that the anatexis occurred during the early exhumation stage. They have higher Ti‐in‐zircon temperatures ranging from 760 to 813°C (mean = 791 ± 16°C) than the pre‐anatexis zircon (244 ± 5 Ma and 739°C), suggesting a 'hot' exhumation. They have εHf(t) values of −17.6 to −14.5 (mean = −15.5 ± 0.6) which are lower than the estimated value (~12.0) on the crustal evolution array, suggesting an addition of crustal fluid during the anatexis. The anatexis also dramatically affected the zircon Lu–Hf isotopic system, that is, 176Yb/177Hf and 176Lu/177Hf isotopic ratios are markedly decreased but initial 176Hf/177Hf ratios are increased from the inherited magmatic cores to the anatectic rims. Thus, we propose that the anatexis plays a critical role in the exhumation of the UHP metamorphic rocks. The anatexis could lubricate the subducted slices and further facilitate their buoyant rise from the mantle depth to the crustal level. [ABSTRACT FROM AUTHOR]